Advances, challenges, and environmental impacts in metal-air battery electrolytes

Author: Salado, Manuel,Lizundia Fernández, Erlantz

Publisher: Elsevier

Year: 2022

DOI: 10.1016/j.mtener.2022.101064

Source: https://addi.ehu.eus/bitstream/10810/57918/1/1-s2.0-S2468606922001228-main.pdf

Ad ances, challenges, and en i onmen al impac s in me aleai
ba e y elec oly es
Manuel Salado
a
,
**
, E lan z Lizundia
a
,
b
,
*
a
BCMa e ials, Basque Cen e o Ma e ials, Applica ions and Nanos uc u es, UPV/EHU Science Pa k Leioa, 48940, Spain
b
Li e Cycle Thinking G oup, Depa men o G aphic Design and Enginee ing P ojec s, Uni e si y o he Basque Coun y (UPV/EHU), Plaza Ingenie o To es
Que edo 1 Bilbao, Biscay, 48013, Spain
a icle in o
A icle his o y:
Recei ed 14 Ma ch 2022
Recei ed in e ised o m
25 May 2022
Accep ed 26 May 2022
A ailable online 2 June 2022
Keywo ds:
Me aleai ba e ies
Elec oly e
Gel polyme elec oly e
En i onmen al impac
Li e cycle assessmen
abs ac
E ﬁcien ene gy s o age echnologies a e i al in he cu en e o s owa ds deca bonisa ion. Ba e ies, as
one o he mos e sa ile elec ochemical ene gy s o age sys ems, ha e he po en ial o shape he
ansi ion om he cu en clima e c isis scena io o a ca bon neu al and sus ainable u u e. In
pa icula , me aleai ba e ies a e gaining scien iﬁc and indus ial in e es as p omising con ende s o
he ubiqui ous li hium-ion ba e ies. The elec oly e plays a c i ical ole in me aleai ba e ies as i
de e mines he ba e y pe o mance, i s sa e y and he ope a ing li espan. The low-densi y, ease o
p ocessing, good he mal and elec ochemical s abili y, mechanically s i bu duc ile cha ac e , elec i-
cally insula ing p ope ies and ailo -made chemis y make polyme s singula ly in e es ing o be applied
as a sepa a o /liquid elec oly e pai , gel-elec oly es o solid-elec oly es. Acco dingly, in his wo k he
cu en bo lenecks and challenges in me aleai ba e ies a e p esen ed, wi h pa icula emphasis on he
elec oly e design. The implemen a ion o aqueous liquid elec oly es, o ganic liquid elec oly es, poly-
me memb anes soaked in liquid elec oly es, gel-like elec oly es and solid-s a e elec oly es is dis-
cussed and he en i onmen al impac s associa ed wi h me aleai ba e ies a e analysed wi hin a Ci cula
Economy pe spec i e. We expec his wo k can guide u u e e o s in he de elopmen o po en ially
sus ainable nex gene a ion me al-ai ba e ies.
©2022 The Au ho (s). Published by Else ie L d. This is an open access a icle unde he CC BY license
(h p://c ea i ecommons.o g/licenses/by/4.0/).
1. In oduc ion
Nowadays, li hium-ion ba e ies (LIBs) a e he p e e ed com-
me cial echnology a ailable o ulﬁll he demanded equi emen s
(e.g ene gy- o-weigh a ios, high open ci cui ol age, low sel -
discha ge a e, no memo y e ec and a slow loss o cha ge when
no in use) [1]. Howe e , his echnology p esen s di e en limi-
a ions such as cos and sa e y issues (e.g. he mal unaway due o
elec oly e deg ada ion/e apo a ion) [2]. Al hough LIBs ha e been
a ailable o many yea s, his echnology s ill has se e al d awbacks
o o e come h ough di e en s a egies (e.g. solid-s a e elec o-
ly e) [3]. I is indeed expec ed ha he u u e expansion o elec ic
ehicles (EVs) will mul iply by a ac o o nine he li hium (Li) de-
mand o he p oduc ion o LIBs in he nex en yea s [4].
Consequen ly, i will be a no able inc emen in he consump ion o
some ce ain ma e ials (e.g. cobal , manganese, nickel…) used in
hei ab ica ion, especially o he ca hode [5].
In his scena io, me aleai ba e ies (MABs) a e conside ed as a
iable u u e al e na i e o LIBs. Howe e , se e al challenges and
d awbacks need o be aced o hei p ac ical implemen a ion [6].
Fo ins ance, high cha ge ol ages and eac i e oxygen in-
e media es such as supe oxide and single oxygen can lead o he
decomposi ion o he ca hode ma e ial and he elec oly e [7].
The e o e, a ca e ul selec ion o he elec oly e is o cen al
impo ance gi en i s pi o al ole in he ba e y cell sa e y and i s
elec ochemical p ope ies.
I should be conside ed ha he eac i i y o he me al anode
inﬂuences he na u e o he elec oly e (aqueous o non-aqueous);
ne e heless, ca bon dioxide (CO
2
) ni ogen (N
2
), and oxygen (O
2
)
p esen as dissol ed species in he liquid elec oly e, s ongly
a ec ing he discha ge mechanism and he s abili y o he me al
anode. Sun e al. [8], in es iga ed he e ec o Li anode deg ada ion
by in-si u X- ay and neu on omog aphy. As summa ised in Fig.1a,
he species in he elec oly e induce he o ma ion o an i e e sible
*Co esponding au ho .
** Co esponding au ho .
E-mail add esses: [email p o ec ed] (M. Salado), e lan z.
[email p o ec ed] (E. Lizundia).
Con en s lis s a ailable a ScienceDi ec
Ma e ials Today Ene gy
jou nal homepage: www.jou nals.else ie .com/ma e ials- oday-ene gy/
h ps://doi.o g/10.1016/j.m ene .2022.101064
2468-6069/©2022 The Au ho (s). Published by Else ie L d. This is an open access a icle unde he CC BY license (h p://c ea i ecommons.o g/licenses/by/4.0/).
Ma e ials Today Ene gy 28 (2022) 101064
Li po ous-s uc u alised ansi ion laye unde a ious chemical
condi ions. Mo e speciﬁcally, Fig. 1b and c depic as he li hium
anode su e s p og essi ely a se e e mo phological deg ada ion
(e.g. a la ge olume expansion) when i is exposed o en cha ge-
discha ge cycles.
This signiﬁcan co osion o deg ada ion is no a pa icula case
o Li me al. Indeed, sodium (Na), po assium (K), and zinc (Zn)
me als ha e also shown his beha iou in hei co esponding MAB
conﬁgu a ions [9e11]. The e o e, he excellen heo e ical ene gy
densi y o he me al anode canno be ully exploi ed i i su e s
om a as deg ada ion du ing cycling. On he o he hand, he as-
sembly o a desi ed MAB es ing esul s a complex ask. Pa icula ly
challenging is he de elopmen o new ca hode ma e ials ( o he
h ee componen s: a ca alys laye , a cu en collec o and a gas
di usion laye ) o e ﬁcien ly inc ease he O
2
di usion. Among he
h ee componen s, he de elopmen o no el mo phology and
composi ion o a ca alys ma e ial has a ac ed he a en ion o
esea che s. Recen ly, a co e-shell CuMo
2
ON@NG nanohyb id
ca hode has been designed h ough a simple, scalable, cos -
e ec i e, and eco- iendly py olysis s a egy o Zn-ai ba e ies
[12]. A speciﬁc capaci y o 736 mAh$g
1
Zn
and a ema kable ene gy
densi y o 800.75 Wh$kg
1
we e achie ed. Ano he me hod p o-
posed [13] consis ed in FeNi alloy nanopa icles (NPs) encapsula ed
in N-doped ca bon nano ubes (NCNT) g own on o a co on pad
(FeNi@NCNT-CP) by a sel -je apou -phase g ow h app oach. This
me hod p o ided a be e peak powe densi y (200 mW$cm
2
)
compa ed o he p e ious py olysis p ocess (176.3 mW$cm
2
).
Al hough, ex ensi e esea ch has been done in his a ea [14], he
esea ch communi y has been awa e o he impo ance o elec-
oly e chemis y in he ﬁnal pe o mance o he ba e ies. In his
di ec ion, a dual-sol en sys em has been ecen ly s udied by
mixing ﬂuo ina ed 1,6-dime hoxyhexane (FDMH) and 1,2-
dime hoxye hane (DME) [15]. In his sys em, he FDMH p o ides
elec oly e oxida i e s abili y (6 V) while he co-sol en DME en-
ables imp o ed ionic conduc i i y and educed in e acial esis-
ance (~75
U
$cm
1
). Besides, he de elopmen o no el elec oly es
can allow he supp ession o me al dend i es. Fo ins ance, p e-
ﬁxed CO
2
in a poly( inyl alcohol) (PVA) elec oly e ia ionisa ion
o a oid he poisoning e ec o CO
2
as well as signiﬁcan ly supp ess
he Zn dend i e g ow h and ZnO deposi ion [16]. As a esul , e en
wi h a concen a ion o CO
2
o 22.7% in he a mosphe e, he ba e y
wi h he modiﬁed elec oly e was wel e imes mo e s able han
he one con aining a nea PVA elec oly e.
Taking in o accoun hese concep s, he scope o his e iew
comp ises ﬁ s ly a b ie desc ip ion o he main issues ha limi he
ull implemen a ion o MABs and secondly, he di e en s a egies
ha could be conside ed du ing he design o no el elec oly es o
o e come hese p oblems.
2. Me aleai ba e ies: S uc u e and mechanism
Cu en pos Li-ion echnologies ollow a simila wo king p in-
ciple o me al ba e ies o Li-ion/me al, wi h hesubs i u ion o o he
alkali me als (e.g. Na
þ
,K
þ
), di alen (Ca
2þ
,Mg
2þ
) o i alen me als
(Al
3þ
)[3,17]. Howe e , he sluggish ionic anspo o he poo ly
e e sible me al pla ing/s ipping a he anode o mul i alen ba -
e ies a e in sha p con as wi h he ea u es usually ound in LIBs,
mainly due o he lack o sui able elec oly es [18]. In con as o he
physically closed sys em o a LIB [19], he MAB is ea u ed wi h an
open cell s uc u e as shown in Fig. 2. Basically, he cell conﬁgu a ion
possess he same s uc u e han a LIB (a me al anode, a sepa a o and
an elec oly e), bu wi h a po ous ca hode [20]. The p esence o O
2
and elec oly e impu i ies yield side eac ions (e.g. edox eac ions
ha p oduce educed oxygen species such as supe oxides) on he
Fig. 1. Mechanisms o Li anode deg ada ion in a Lieai ba e y. (a) Li anode ans o ma ion in he p esence o an e he -based elec oly e, ha is, he chemical pa h as indica ed by
①and he elec ochemical pa h indica ed by ②. (b) and (c) Illus a ion o he mo phological e olu ion du ing long- e m elec ochemical cycling condi ions [8]. Copy igh ©2019,
Ame ican Chemical Socie y.
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
2
me al elec ode, which usually esul in he co osion o he me al
anode by he elec oly e, elec oly e deg ada ion, o blockage o
ca hode eac ion si es because o elec oly e decomposi ion [21]. As
a consequence, me al elec odes in MABs su e om me al dend i e
g ow h, shape change, co osion and su ace passi a ion [22]. In he
case o non-aqueous ba e ies, gene ally a solid elec oly e in e -
phase (SEI) is o med on he anode su ace inhibi ing u he elec-
oly e decomposi ion. Howe e , o aqueous ba e ies, he li hium
me al is isola ed a oiding sel -discha ge eac ion wi h he oxygen
and allowing he applica ion o acidic o neu al elec oly es ha a e
no suscep ible o ca bona ion p ocesses.
Among he di e en anode me als p e iously desc ibed, Li-ai
ba e ies a e he mos s udied ba e ies wi hin he MAB echnol-
ogy because o hei high ene gy densi y o abou 3458 Wh$kg
1
,
which is se e al imes highe han ha o con en ional LIBs
(250e300 Wh$kg
1
)[23]. Due o he high eac i i y o Li in aqueous
elec oly es, Zn me al has been deeply s udied as an anode choice
in MABs. As a esul , enhanced sa e y and lowe cos s a e achie ed
a expenses o a lowe ene gy densi y o 1084 Wh$g
1
. Ne e he-
less, o he me al-ai sys ems ha e also been de eloped as sum-
ma ised in Fig. 3a. Among hem and bea ing in mind he
( heo e ical) ene gy densi y, he good a ailabili y o he aw
ma e ial and i high sa e y, Al can be conside ed a p omising me al
anode o eplace bo h Zn-ai and Li-ai ba e ies. Ne e heless, up-
o-da e only Zn-ai ba e ies can be elec ically echa ged in
aqueous elec oly e. In he case o he Al- o Mg-ai ba e ies, as
hey canno be di ec ly educed om ions o me als, a mechanical
me hod has o be used o change he me al anodes.
To ensu e an e ﬁcien ionic anspo be ween elec odes and
a oid he sho -ci cui o he ba e y a hin elec ically insula ing
physicalsepa a o isused.Typically, hisconsis son asingle-o mul i-
laye o polye hylene (PE), polyp opylene (PP) o glass-ﬁb e ma s
[25]. In his sense, enewable polyme -based compounds ha e been
p omising used as a sepa a o in Li-ion ba e ies [26], o Na-ion
ba e ies [27], and MABs [28]. O he app oaches such as he modiﬁ-
ca ion o comme cial sepa a o s by changing hei su ace chemical
p ope ies and po e s uc u e [29] ha e been also pu sued. Lee e al.
ca ied ou a modiﬁca ion o he sepa a o using edox media o s
(5,10-dihyd o5,10-dime hylphenazine), achie ing a ound- ip e ﬁ-
ciencyo 90% in a LieO
2
ba e y o e 20 cycles [30]. Recen ly, Hu e al.
summa ised he s a e-o - he-a bi-dimensional (2D) ma e ials o
sepa a o s [31]. Among hose ma e ials, an ul a hin laye o g a-
phene nanoshee supp essed dend i e o ma ion as well as imp o ed
he dimensional s abili y a ele a ed empe a u es [32].
Fig. 2. Gene al conﬁgu a ion o a me aleai ba e y, highligh ing he main issues associa ed o he ca hode and he anode and he chemical eac ions depending on he ype o
liquid elec oly e.
Fig. 3. Ene gy densi y in ba e ies. (a) Compa ison be ween g a ime ic and olume ic capaci ies, s anda d educ ion po en ial and Ea h's c us abundance o me al nega i e
elec odes used o p oposed o applica ion in elec ochemical s o age sys ems. Fig. ep oduced wi h pe mission om Leisegang e al. [24] Copy igh ©2019. (b) Theo e ical ene gy
densi ies o di e en ypes o me alai ba e ies. Fig. ep oduced wi h pe mission om Li e al. [22]. Copy igh ©2017, Royal Socie y o Chemis y.
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
3
Rega ding he ca hode, an ai -ca hode is desi ed o beneﬁ om
he abundan oxygen in he ai as an elec on accep o . Ne e he-
less, H
2
O oge he wi h some ace o CO
2
in ambien ai con ib-
u es o he o ma ion o ca bona es in he ﬁ s ew cycles and
consequen ly, accele a es he a o emen ioned deg ada ion p o-
cesses. Since he o ma ion o hese ca bona es occu s mainly in
s ong alkaline elec oly es, he use o acidic elec oly es based on
Leclanch
e elec oly es can mi iga e he p oblem [33e35]. Ne e -
heless, low pH elec oly es en ail he appea ance o o he issues
(e.g. he lack o o ma ion o ZnO in he case o Zn-ai ba e ies o
physical de e io a ion o he cell). Consequen ly, neu al elec o-
ly es a e p e e ed e en i he ca hode s abili y is a ec ed. In any
case, eaching a comp omise be ween capaci y and elec ode s a-
bili y is o pa amoun ele ance o de elop e ﬁcien MABs [36,37].
Ex ensi e esea ch has been ocused on he op imisa ion o he ai
ca alys and ca hode a chi ec u e as i plays a decisi e ole in
imp o ing ba e y pe o mance. Cu en ly, he use o noble-me al-
ee ca alys en ails dissolu ion, sin e ing, and agglome a ion p o-
cesses du ing he ope a ion o he ca hode [38]. Besides, o a
echa geable ba e y, di e en s a egies need o be de eloped o
an e ﬁcien oxygen elec ode wi h dual ca aly ic ac i i y o oxygen
educ ion eac ion (ORR) and oxygen e olu ion eac ion (OER).
Among hem, ansi ion-me al-based elec oca alys s exhibi ela-
i ely sa is ac o y bi- unc ional pe o mances in compa ison o
hei alloy coun e pa s wi h me al- ee ca bon-based ca alys s. Fo
ins ance, Yang e al. de eloped Fe
2
N/Fe
3
C NPs nanopa icles o
imp o e he ORR pe o mance in acidic media while keeping good
s abili y and high cu en densi y. As a esul , a hal -wa e po en ial
o 0.764 V ( s. RHE) and high cu en densi y in acidic elec oly es
we e achie ed [39].
ORR and OER a e deﬁned as he basic elec ochemical eac ions
a he ai ca hode, which co espond o he discha ging and
cha ging p ocess, espec i ely. Al hough he eac ion pa h depends
on di e se pa ame e s such as he ca alys used [40], gene ally ORR
can be di ided in o a ou -elec on ans e p ocess and 2-plus-2
elec on ans e p ocess. The wo-elec on ans e p ocess e-
qui es a lowe o e po en ial compa ed o ou -elec on ans e
p ocess, and he in e media e HO

2
o ma ion en ails a as deg a-
da ion o he ca hode. OER p esen s a complex mechanism ha
simila ly o ORR, equi es a high o e po en ial in p ac ical appli-
ca ion o b eak he O]O bond (which is b oken du ing discha ge).
The s eps o ORR and OER a e shown below:
Oxygen educ ion eac ion:
1: 4-elec on eac ion p ocess:
O2þ2H
2Oþ4e
/4OH
E0¼0:401 V(1)
2: 2-plus-2 elec on eac ion p ocess
O2þH2Oþ2e
/HO
2þOHE0¼0:065 V(2)
HO
2þH2Oþ2e
/3OH
E0¼0:867 V(3)
Oxygen e olu ion eac ion
4OH
/O2þ2H
2Oþ4e
E0¼0:401 V(4)
In his ega d, me aleo ganic amewo ks (MOFs)-based ma e-
ials a e p omising ca alys s o p omo e he ORR and OER a he ai
elec ode, hus educing he o e po en ial o cha ge/discha ge e-
ac ion and inc easing he ci cula ion s abili y o he ba e y. The
syne gis ic e ec be ween he la ge su ace a ea, he la ge a ie y o
chemically a ailable linke s and he hollow amewo k mo phology
o he me al- ee ca bon-based elec o-ca alys imp o es he O
2
adso p ion. This kind o mo phology also boos s he elec onic
conduc i i y and mass anspo , causing enhanced ca aly ic ac i -
i y and s abili y o he ca alys s. Fo ins ance, Sindhe e al. s udied
he use o a hexaiminobenzene-based MOF (Mn/FeeHIB-MOF) as a
bi- unc ional oxygen elec o-ca alys in ﬂexible Zneai ba e y wi h
unc ionalised cellulose elec oly es [41]. Supe io bi unc ional ox-
ygen elec oca aly ic ac i i y (0.627 V s. RHE) o oxygen educ ion
and o e po en ial (280 mV a 10 mA$cm
2
) o oxygen e olu ion
eac ions we e ob ained. Recen ly, Kundu e al. also eplica ed he
na u al shape o bamboo o syn hesise ni ogen-doped ca bon
nano ube-encapsula ed Co
0.25
Ni
0.75
alloy elec oca alys (Co
0.25
N-
i
0.75
@NCNT) and i s bi unc ional oxygen elec oca aly ic pe o -
mance owa d oxygen educ ion and oxygen e olu ion eac ions
[42]. When he ca hode ma e ial was applied o Zneai ba e y, a
peak powe densi y o 167 mW cm
2
was achie ed wi h a high
open-ci cui ol age o 1.53 V.
Con a ily o MOFs, co alen o ganic amewo ks (COFs)
consis o po ous polyme s assembled by ligh weigh o ganic
building blocks h ough s able co alen bonds o p oduce highly
c oss-linked ne wo ks wi h pe iodic skele ons and o de ed po es
[43]. The e o e, i is possible o uni o mly dispe se single-me al
si es and unique o de ed channels. As an example, po phy in-
based COF as an e ﬁcien ca hode ca alys was syn hesised ac-
co ding o he demand o a high-pe o mance LieCO
2
ba e y [44].
Taking in o accoun he complexi y o ob ain excellen s abili y,
wi h his app oach 180 cycles a 300 mA$g
1
wi h a ﬁxed
1000 mAh$g
1
capaci y was achie ed. In his sense, elec ospun
ca bon nanoﬁb es deco a ed wi h ZIF-67 se e as e ﬁcien bi unc-
ional oxygen ca alys s o Zneai ba e ies. The applica ion o a
supe -assembly me hod educes he need o elec ochemical ca -
alys s based on p ecious me als, ob aining a Zneai ba e y wi h a
speciﬁc capaci y o 1635 mAh$g
1
a 20 mA$cm
2
[45]. These
p omising s a egies could pa e he way o he de elopmen o
COF and MOF-de i ed ca bon-based bi unc ional oxygen elec o-
ca alys s o comme cial applica ions in MABs.
Gene ally, MABs can be di ided in o ollowing ypes acco ding
o he elec oly e cha ac e is ics. Depending on he in e ac ions
be ween he anode and he elec oly e (Fig. 3b), aqueous elec o-
ly es a e applied in o Fee,Zne,Aleo Mgeai ba e ies, while
non-aqueous elec oly es a e used in o Lie,Naeo Keai ba e ies.
Aqueous MABs a e conside ed mo e en i onmen al iendly, cos -
e ec i e and e ﬁcien . Meanwhile, non-aqueous elec oly es p e-
sen a wide elec ochemical window [46]. Besides, solid-s a e
elec oly es allow he implemen a ion o a wide ange o me al
anodes as well as o o e come he cu en isk o liquid-base
elec oly es (e.g. leakage and igni ion) [47]. A g ea e o has
been ca ied ou o imp o e he pe o mance o he di e en pa s
o he MABs, indica ing ha he na u e o he elec oly e a ec s he
o ma ion o he passi a ing SEI laye on he nega i e me al. In
addi ion, he by-p oduc s o med du ing he eac ion wi h he
elec oly es can block he ai -ca hode, limi ing he exploi a ion o
emaining me al, as well as he s o age cha ac e is ics o he MABs.
Acco dingly, Sec ion 3is ocused on he di e en kinds o elec o-
ly es aimed o o e come he cu en issues.
In pa icula , deﬁning an app op ia e elec oly e composi ion
is one o he mos impo an choices ha MAB designe s ace.
The elec oly e mus be chemically and he mally s able, ioni-
cally conduc i e, and should acili a e he eac ions a bo h he
anode and he ca hode. Fu he mo e, elec oly e composi ion
plays a c i ical ole du ing he cell ageing p ocess. Al hough, only
p ima y Zneai ba e ies ha e been comme cialised o daily li e
applica ions [48], he de elopmen o no el bi- unc ional ca a-
lys s capable o ca alysing bo h he oxygen educ ion (ba e y
discha ge) and oxygen e olu ion (ba e y echa ge) eac ions as
well as sui able elec oly es ha b oaden he me al anodes, ha e
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
4
pa ed he pa h o c ea e p ac ically iable echa geable MABs
(e.g Nan Ene gy, EOS Ene gy En e p ises). Zneai conﬁgu a ion
o e s a heo e ical ene gy densi y o 1353 Wh$kg
1
, howe e
he p ac ically a ainable ene gy densi y o Zneai is usually
be ween 350 and 500 Wh$kg
1
. Comme cialised Zneai ba e ies
p esen ela i ely poo a e capabili y limi ed by he ine ﬁciency
o ai ca alys s, and hus a e mos ly in ended o low powe
applica ions such as minia u e hea ing aids (e.g. Phine gy, Is ael)
[49]. Fu he mo e, echa geable Zneai ba e ies su e om
poo ene gy e ﬁciency (<60%) caused by he se e e deg ada ion
ela ed o mo phology changes o he anode, he p ecipi a ion
o ca bona es in he ca hode and addi ional elec oly e
deg ada ion.
3. Elec oly es
In his sec ion, he modelling ools cu en ly a ailable o design
and op imise elec oly es o MABs a e discussed o smoo h he
de imen al e ec s p e iously a o emen ioned (Table 1). Acco ding
o he na u e o he elec oly es, MABs a e di ided in o wo ypes.
F om one side, a cell sys em using an aqueous elec oly e ha is no
sensi i e o mois u e is ound. The main d awback o his conﬁg-
u a ion is i s ol age window limi a ion. On he o he side, a wa e -
sensi i e sys em based on an elec oly e wi h ap o ic sol en s is
used. In e es ingly, Zneai ba e y e ﬁciency can be signiﬁcan ly
inc eased using ionic liquids (ILs) as elec oly es [50]. Howe e ,
ﬁnding he bes IL o a ce ain sys em is di ﬁcul wi hou a ho -
ough unde s anding o he elec ochemical eac ions occu ing in
IL-based zinc cells [51].
Aqueous elec oly es ei he on hei own o as pa o hyb id
sys ems a e widely used in he a ious me aleai chemis ies [65].
The mos common elec oly es a e alkaline (e.g., KOH, NaOH),
which a e economically a o dable and allow high pe o mance
de ices. Howe e , when hey a e exposed o ai , dissol ed CO
2
e-
ac s wi h he excess OH

o o m ca bona e ions, CO
2
3
. This
pa asi ic eac ion educes he conduc i i y o he elec oly e, slows
Table 1
Summa y o he main d awbacks o MABs depending on he na u e o he elec oly e.
Me al anode Elec oly e Main d awbacks Re
Aqueous Fo ma ion o ZnðOHÞ
2
4
and p ecipi a ion o ZnO in alkaline elec oly es
Shape changes and dend i e o ma ion
P ecipi a ion o insoluble ca bona es
Hyd ogen e olu ion eac ion (HER) due o wa e elec olysis ha changes he ca hode/elec oly e dis ibu ion
[52,53]
Fo ma ion o a passi a ing oxide laye
High co osion a es in s ongly alkaline elec oly es
[24,54]
Hyd ogen eleasing
Anode passi a ion by i on oxide ﬁlms
[55,56]
Co osion o he Mg anode
The sluggish kine ics o he ORR in he ai ca hode
[57,58]
Non-aqueous Poo cyclabili y
The sluggish educ ion o O
2
o o m elec ochemically ac i e oxygen
Mois u e om ai
[59e61]
The complexi y o discha ge p oduc iden iﬁca ion and discha ge mechanism
Na co osion
Poo conduc i i y and deposi ion o non-conduc i e NaO
2
and Na
2
O
2
(discha ge p oduc s) on o he po ous ca hode
[61,62]
K dend i e o ma ion
Mois u e om ai
[63]
The ORR on he supe oxide has no been demons a ed
Oxygen educ ion is s ill a he i e e sible
[64]
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
5

he eac ion kine ics, and can lead o unwan ed p ecipi a ion o he
ca bona e sal s wi hin he cell. On he o he hand, nea -neu al
elec oly es (e.g. NH
4
Cl, NaCl) a e less suscep ible o he o ma-
ion o ca bona es and a e a g owing a ea o in e es o MABs.
Finally, acidic elec oly es a e usually a oided due o he inc eased
isk o co osi e sel -discha ge o he me al elec ode. Unde -
s anding he equilib ium p ope ies o he elec oly e is he ﬁ s
s ep o imp o e he pe o mance o MABs in he dynamic ba e y
en i onmen . To acili a e he eading o he con en in Sec ion 3,
Scheme 1 summa ises he di e en ca ego ies ega ding he used
elec oly e.
3.1. Po ous memb anes soaked in o liquid elec oly es
The basic unc ion o he sepa a o is o physically sepa a e he
anode and he ca hode o p e en sho -ci cui . To accomplish i s
unc ion, he ideal sepa a o is a we able po ous memb ane ha is
elec ically insula ing bu ionically conduc i e; i is mechanically,
dimensionally and elec o-chemically s able ac oss di e en en i-
onmen condi ions. In addi ion o hese basic unc ions, sepa a o s
can also limi he mig a ion o speciﬁc ions o molecules [7].
Polyme ic memb anes soaked in o an ionically conduc ing liquid
elec oly e ep esen a common o m o sepa a o in MABs. This
laye physically sepa a es he anode and he ca hode o a oid sho -
ci cui while enables an adequa e ion-di usion be ween he elec-
odes. As occu s wi h con en ional LIBs, mic opo ous polyoleﬁn
memb anes based on PP o PE (mainly comme cialised by Cel-
ga d®)[66], o glass mic oﬁb e sepa a o s (comme cialised unde
Wha man®)[67], a e applied. These ma e ials o e easy
p ocessing, mechanical/elec ochemical s abili y and good ionic
conduc i i ies a oom empe a u e (12.8 mS$cm
1
in 6 M KOH o
Celga d®3501) [68].
The seminal wo k by Ab aham and Jiang in 1996 showed a
LieO
2
ba e y wi h a poly(ac yloni ile)-based polyme elec oly e
eaching a speciﬁc ene gy o 250e350 Wh$kg
1
[69]. Howe e ,
ce ain ins abili y issues we e iden iﬁed esul ing om he i e-
e sible decomposi ion o li hium hexaﬂuo ophospha e (LiPF
6
)in
o ganic elec oly es, as non-ionised LiPF
6
dissocia es o PF
5
and LiF
in o ganic sol en s [70]. Following his wo k, Amanchukwu e al.
s udied he s abili y o di e en polyme s widely used as sepa a-
o s in LIBs and concluded ha poly(ac yloni ile),
poly( inyl chlo ide), poly( inylidene ﬂuo ide) (PVDF), and poly(-
inylpy olidone) (PVP) show eac i i y and s abili y issues in he
p esence o Li
2
O
2
[71]. On he con a y, Naﬁon, poly( e aﬂuo o-
e hylene) (PFTE) and poly(me hyl me hac yla e) (PMMA) showed
good s abili y agains he nucleophilic Li
2
O
2
a ack (summa ised in
Fig. 4a) [71]. Howe e , he po e size o hese memb ane based on
hose polyme s is o en la ge han he size o sol a ed zinca e ions
(Zn(OH)
4
2
), so undesi ed species gene ally di use ac oss he
sepa a o o he ai ca hode. The c osso e o zinca e ions in Zneai
ba e ies o he c osso e o H
2
O and O
2
om he ai eca hode o
he Li me al, oge he wi h he p esence o edox media o s is
conside ed some o he main bo lenecks acing MABs.
As demons a ed in Fig. 4b, a po e-less polyu e hane sepa a o
soaked in 1 M li hium pe chlo a e (LiClO
4
)/TEGDME e ec i ely
supp esses he c osso e o wa e and oxygen om he ai eca hode
side o he Li me al in LieO
2
ba e ies, which is in con as wi h he
pe o mance p o ided by a con en ional PE sepa a o (an imp o ed
elec oly e we ing is achie ed and he conduc i i y is enhanced by
34%) [72]. The polyu e hane memb ane also p o ec s Li me al anodes
om edox media o s used o enhance he ba e y e e sibili y,
esul ing in a capaci y o 600 mAh$g
1
o mo e han 200 cycles.
Simila ly, o ace his issue and enable longe las ing echa geable
Zneai ba e ies, Kim e al. designed an anion- epelling ma e ial
wi h selec i e ion anspo channels based on elec ospun PVA/
polyac ylic acid nanoﬁb e ma imp egna ed wi h Naﬁon [68]. Naﬁon
p e en s Zn(OH)
4
2
c osso e ia he Donnan exclusion e ec , while
Scheme 1. Elec oly e ypes ( anging om liquid o solid-s a e) aiming o imp o e he ene gy densi y and sa e y in me aleai ba e ies.
Widely used in con en ional LIBs, he con igu a ion based
on po ous memb anes soaked in o a liquid elec oly e e-
sul s in bulky ba e ies wi h se ious sa e y issues associa ed
o elec oly e leakage and combus ion isks
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
6
he nanoﬁb e ma ensu e an OH

conduc ion (6.6 mS$cm
1
in 6 M
KOH). As a esul cycling s abili y is inc eased om 900 min (con-
en ional PP sepa a o ) o 2500 min. O he s uggling issue acing
MBAs is he pa asi ic co osion o Al when in physical con ac wi h
he liquid elec oly e. This e ec o ms a passi e oxide/hyd oxide
laye limi ing he elec ochemical pe o mance o Al-ai ba e ies. A
PP sepa a o was applied in he o m o mic oﬂuidic channels being
able o deli e he liquid elec oly e ia capilla y ac ion, enabling a
compac cell design. A maximum discha ge capaci y o 375 mAh$g
1
was achie ed a a cu en o 30 mA using a 1 M KOH elec oly e [73].
I was ound ha s ong alkaline solu ions inc ease he co osion a e
(Al eac s wi h OH

o o m Al(OH)
3
) and lead o poo anode u i-
lisa ion, educing he deli e ed capaci y o nea ly 80 mAh$g
1
.A
sulphona ion ea men can be applied o mic opo ous PP mem-
b anes o enhance hei su ace hyd ophilici y (con ac angle d op
om 85 o 66

) and anionic conduc i i y in alkaline elec oly es om
1.52 10
2
S$cm
1
o 3.5210
2
S$cm
1
[74]. Al hough he o iginal
po es o abou 400 nm 50 nm in size o he o iginal PP memb ane
in Fig. 4c p o ide channels o he anspo o elec oly es, sulpho-
na ion enhances he Zneai ba e y powe densi y om
20 mW$cm
2
o 38 mW$cm
2
. A he same ime, he anionic
anspo numbe was inc eased om 0.79 o 0.89 in 1 M KOH [74].
Memb ane coa ing is also a commonly ollowed app oach o
enhance ope a ing pe o mance. Hwang e al. coa ed a comme cial
PP memb ane wi h a polyme ised IL and applied his ma e ial in o a
Zneai ba e y (6 M KOH elec oly e) [75]. As schema ically depic ed
in Fig. 4d, his app oach keeps he anionic ans e h ough he
sepa a o and minimises he mig a ion o zinca e ions o he ca hode
compa men du ing cha ge/discha ge by 96%, keeping high elec-
oly e conduc i i y and a oiding he de e io a ion o he ca aly ic
ac i i y by he o ma ion o ZnO on he su ace o he ca alys laye .
As a esul , he du abili y o he ba e y li e was inc eased by 281% in
compa ison wi h he pu e comme cial PP memb ane.
Polyoleﬁns a e cha ac e ised by ela i ely low mel ing empe -
a u es ( heo e ical uppe limi s o 171

C o pe ec ly iso ac ic PP
and 146

C o PE), so he isk o he mal unaway emains la en .
Fig. 4. Po ous polyme ic memb anes soaked in o liquid elec oly es. (a) Summa y o he s abili y o di e en polyme s when applied as Lieai ba e y sepa a o s. Rep oduced wi h
pe mission [71]. Copy igh ©2015, Ame ican Chemical Socie y. (b) Compa a i e schema ic illus a ion o LieO
2
ha ing a con en ional po ous polye hylene sepa a o and po e-less
polyu e hane sepa a o . Rep oduced wi h pe mission [72]. Copy igh ©2016, Royal Socie y o Chemis y. (c) Scanning elec on mic oscope (SEM) mic og aphs o sulphona ed poly-
p opylene memb anes: i) be o e he sulphona ion, ii) a e 128 h. Rep oduced wi h pe mission [74]. Copy igh ©2008, Else ie . (d) Schema ic showing he dis inc i ely ion anspo
cha ac e o polyme ised ionic liquid/PP sepa a o , whe e zinca e ion would be p ohibi ed and solely OH

is anspo ed du ing cha ge/discha ge. Rep oduced wi h pe mission [75].
Copy igh ©2016, Ame ican Chemical Socie y. Pape -based Aleai ba e y: (e) Schema ic illus a ion o he whole ba e y; ( ) schema ic c oss-sec ion showing he O
2
- ich/low elec oly e
dis ibu ion in Aleai ba e ies wi h pape based and (g) non-pape based (bo om) sepa a o . Rep oduced wi h pe mission [76]. Copy igh ©2019, Royal Socie y o Chemis y.
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
7
Addi ionally, sepa a o s based on PVP o PVDF can eac wi h su-
pe oxide/pe oxide and eac i e in e media es o o m undesi ed
side p oduc s. To add ess hese issues, na u ally-de i ed polyme ic
memb anes o ino ganic sepa a o s ha e been used. A mic oﬂuidic
Aleai ba e y was cons uc ed using a cellulosic ﬁl e pape soaked
in o a 1.5 M KOH elec oly e [28]. The po osi y and hyd ophilici y o
cellulose enabled he ﬂuidic anspo o he liquid elec oly e ia
capilla y ac ion [77], o e ing a maximum cu en o 17.4 mA wi h a
powe o 3.0 mW (3 3cm
2
ba e y). The design has been
imp o ed o a ain an open-ci cui ol age o 1.45 V and
28 mW$cm
2
using a echnical g ade comme cial Al-6061 anode
and a MnO
2
-loaded ca bon clo h ca hode [78]. In his app oach, as
schema ically shown in Fig. 4e, Shen e al. cons uc ed an Aleai
ba e y composed o an Al anode, a ca alys loaded g aphi e ca h-
ode, and a cellulosic pape ac ing as bo h sepa a o and mic oﬂuidic
channel able o ca y he elec oly es o elec ode su aces [76].
Flowing elec oly es can mi iga e he elec ochemical issues ela ed
o oxygen mass ans e p o iding su ﬁcien mass ans e o O
2
o
ca hode. Acco dingly, in his example he pape ac s as a capilla y
anspo sys em o make he elec oly e ﬂow along he pape
channel in a lamina and con inuous way o he ca hode ca alys
laye wi h a ﬂow a e o 24
m
L$min
1
(Fig. 4 ). This way he as
deple ion o O
2
nea he su aces o he ca hode cha ac e is ic o
con en ional MABs is p e en ed (Fig. 4g). In addi ion, no ex e nal
auxilia ies such as pumps a e needed o ci cula e he elec oly e. In
addi ion, he elec oly e ﬂow emo es he insoluble p oduc s
gene a ed du ing ope a ion, p e en ing elec ode su ace passi -
a ion. Howe e , he a eal powe densi y is lowe ed om ~22 o
~13 mW$cm
2
when inc easing he elec ode ac i e a ea om 40 o
120 mm
2
. This beha iou sugges s a deple ion o O
2
a he elec ode
due o he ac ha he ac i e cen es educe he O
2
amoun in he
elec oly e a esul . Impo an ly, in con as o egula Aleai ba -
e ies which ha e a p e-loaded elec oly e, he designed ba e y
p o ec s he Al anode om he elec oly e be o e use hanks o he
po ous pape ha allows he ﬂow o he elec oly e h ough
capilla i y and e ﬁcien ly anspo s O
2
o he ca hode side. As a
esul , he pa asi ic co osion e ec s du ing s o age a e a oided,
limi ing he sel -discha ge o enla ge ba e y sel -li e, which is
conside ed as one o he mos p essing sho comings o adi ional
Aleai ba e ies.
Gene ally, biopolyme s ensu e la ge elec oly e up ake and good
ionic conduc i i y alues [79]. Howe e , he s eng h weakening
beha iou o biopolyme s soaked in elec oly es should be
conside ed om he sa e y poin o iew as i ma kedly educes
bo h Young's modulus and ensile s eng h [80]. As a good ﬁlm-
o ming cellulose de i a i e, he 3e10 nm po e-s uc u e and he
nega i ely cha ged su ace o cellophane o e s la ge OH

con-
duc i i y alues and excludes he nega i ely cha ged Zn(OH)
4
2
ions, enabling a lowe zinca e c osso e han ha o Celga d®3501
in 45% KOH (po e size o 64 nm) [81]. Biopolyme s ha e also been
used in MABs as addi i es. A wa e -soluble cellulose de i a i e such
as ca boxyme hyl cellulose (CMC), in conjunc ion wi h ZnO, has
been p o en e ﬁcien o mi iga e he co osion o he aluminium
anode (4 M NaOH elec oly e) [82]. The ca boxyl g oups adso bed
on o Al su ace a o d a s able p o ec ing laye o med ia he
in e ac ion be ween CMC and Zn
2þ
ions. As a esul , he anode
u ilisa ion inc eases om 91.1% o 94.1%, which is ansla ed in o a
capaci y inc ease om 2710 mAh$g
1
o 2824 mAh$g
1
.
Ino ganic sepa a o s gene ally o e a good elec oly e adso p-
ion oge he wi h he subsequen e en ion o elec oly es hanks
o hei highly po ous s uc u e. Ce amic sepa a o s ha e a be e
s abili y agains oxida i e agen s in compa ison o polyme ic
memb anes. In ac , he wo k o B uce e al. in 2006 used a glass
ﬁb e sepa a o soaked in o 1 M LiPF
6
in p opylene ca bona e [67].
Howe e , he use o comme cial glass ﬁb e sepa a o s has no able
limi a ions due o he p esence o edox media o s. Fig. 5a shows a
simpliﬁed mechanism whe e upon he use o glass ﬁb e sepa a o
he o e po en ial du ing cha ging is educed (p omo ing Li
2
O
2
oxida ion), also esul ing in Li me al anode deg ada ion due o
pa asi ic eac ions [30]. In his sense, he inhe en cha ac e is ics o
po ous ino ganic ma e ials se e o ace he shu le o edox
media o molecules in LieO
2
. As shown in Fig. 5b, a sepa a o
ha ing a 15
m
m hick MOF laye was exploi ed as a edox media o
molecula sie e o educe he elec on shu ling be ween he
ca hode and anode [83]. Speciﬁcally, he h ee-dimensional (3D)
channel s uc u e ha ing highly o de ed po es o 6.9e9 Å enable
Li
þ
c ossing, while edox media o molecules a e blocked. In ha
way, he incomple e Li
2
O
2
decomposi ion and Li anode deg ada ion
in ap o ic LieO
2
cell is minimised, deli e ing a capaci y o
5000 mAh$g
1
a e 100 cycles a 1 A$g
1
. In a syn he ically simple
app oach, a hin polypy ole could be in oduced be ween a glass
ﬁb e sepa a o and he ai ca hode o supp ess he edox shu le
e ec in LieO
2
cells, enhancing he cycling li e ou imes [84].
Fu he mesopo ous ma e ials such as he hyd ophilic MCM-41
(Mobil C ys alline Ma e ial nº41), a one-dimensional hexagonally
o de ed amo phous silica ha ing a speciﬁc su ace a ea o nea ly
1000 m
2
$g
1
and hie a chically a anged in o hexagonally o de ed
na ow po e s uc u es, ha e been applied in o o he me al ai
chemis ies. Fo example, a 5
m
m hick MCM-41 ﬁlm was placed
be ween a Zn anode and a Ni mesh ca hode o p o ide ion exchange
channels and ac as a elec oly e ma ix when soaked in KOH
(maximum powe densi y o 32 mW$cm
2
, olume ic ene gy
densi y o 300 Wh$L
1
)[87]. As ano he example o an ino ganic
memb ane soaked in o a liquid elec oly e, li hium phospho us
oxyni ide (LiPON, gene al o mula o Li
x
PO
y
N
z
), an amo phous
glassy ma e ial, can wo k as an elec oly e ma e ial in a Li-ai
ba e y as pa en ed o e 15 yea s ago [88]. LiPON is soaked in o
p opylene ca bona e/LiPF
6
o ganic elec oly e o ac as a p o ec i e
ba ie agains mois u e and oxygen co osion, educing he apid
co osion o Li anodes. A 40
m
m hick ees anding LISICON sepa-
a o was applied in o Lieai ba e ies ha ing a 2 M LiOH aqueous
elec oly e [85]. This memb ane esul ed su ﬁcien ly hin o mini-
mise ohmic losses in an aqueous Lieai cell while o e ing a
wa e igh p o ec ion o he Li anode o p e en i s oxida ion by he
wa e . Addi ionally, as shown in Fig. 5c, o limi Li me al a ack, a
LiPON coa ing was applied on he anode side o he sepa a o .
Howe e , i s poo ionic conduc i i y o 1.6 10
3
mS$cm
1
caused
a ele an ohmic loss, esul ing in ela i ely poo ene gy densi y
and powe densi y alues.
Simila ly, o ex end he li e o LieO
2
ba e ies, edox-media o
(RM)-sie ing g aphene oxide (GO) memb anes we e ab ica ed
deposi ing a z200 nm hin GO laye on o a hyd ophilic and po ous
43
m
mpoly e aﬂuo oe hylene ﬁl e [86]. Gi en he ma ginal esis-
ance o he GO laye a negligible o e po en ial in o LieO
2
cells was
obse ed. Impo an ly, he nano-channels p o ided by GO selec-
i ely ejec 5,10-dihyd o-5,10-dime hylphenazine (DMPZ) while
enable Li
þ
anspo . Mo eo e , he nega i ely cha ged GO su aces
epel nega i e ions ia Donnan exclusion, con ibu ing o la ge Li
þ
ans e ence numbe s. As a esul , he e e sibili y o he oxida ion
and educ ion eac ion be ween DMPZ and DMPZ
þ
in LieO
2
ba e y
sys ems was no ably imp o ed as shown by CV cu es in Fig. 10d.
This is ansla ed in o a ound- ip e ﬁciency o e 90% a e 10 cycles
as compa ed o he sho cyclabili y when no GO is used (Fig. 5e).
3.1.1. Aqueous-based elec oly es
3.1.1.1. Con en ional wa e -based elec oly es. Me als such as Zn, Fe,
Al, and Mg a e he modynamically uns able in he aqueous me-
dium and su e om c i ical issues including elec ode co osion,
passi a ion, hyd ogen e olu ion, and dend i e o ma ion [89]. The
elec oly e ma e ial design can passi a e hei su aces by di e en
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
8
elec oly e addi i es, and hus makes hem compa ible wi h
aqueous elec oly es o some ex en .
In his con ex , he applica ion o zinc sulpha e (ZnSO
4
) and
sodium algina e (SA) as elec oly e addi i es o 4 M NaOH was
in es iga ed wi h he aim o slow down he sel -co osion o o Al
[90]. As esul , no only an imp o emen o he s abili y o he Al
anode was achie ed, bu also an inc ease o discha ge capaci y by
64.6% ( om 162.46 o 267.41 mAh$cm
2
) when compa ed wi h
elec oly es wi h o wi hou addi i es. In addi ion, Hosseini e al.
s udied he inﬂuence o sulphu eoxygen g oup addi i es in a 4 M
Fig. 5. Po ous memb anes soaked in o liquid elec oly es bea ing ino ganic ma e ials. (a) Redox media o s p omo e he oxida ion o Li
2
O
2
by educing he o e po en ial in he cha ging
p ocess, also esul ing in side eac ions a he Li me al anode side: i) scena io using a comme cial glass ﬁb e sepa a o and ii) coa ed glass ﬁb e sepa a o o a oid undesi ed edox
media o e ec s. Rep oduced wi h pe mission [30]. Copy igh ©2017, Wiley. (b) Scheme depic ing he concep o a MOF-based sepa a o ac ing as a physical laye inhibi ing he shu le
o edox media o molecules as opposed o he mechanisms in he p esence o a glass mic oﬁb e sepa a o . Rep oduced wi h pe mission [83]. Copy igh ©2018, Ame ican Chemical
Socie y. (c) Scheme o an aqueous Lieai ba e y showing: a: O
2
educ ion a he ca hode, b: O
2
e olu ion elec ode (s ainless s eel g id); c: a LiSICON sepa a o ; d: a p o ec i e li hium
phospho us oxyni ide (LiPON) laye ; e: cu en collec o . Rep oduced wi h pe mission [85]. Copy igh ©2012, Else ie . (d) CV cu es in he ol age ange o 2.5e3.8 V unde wi h a ba e
PTFE memb ane and a GO-coa ed PTFE memb ane. (e) Elec ochemical pe o mance o LieO
2
cells wi h 0.2 M 5,10-dihyd o-5,10-dime hyl phenazine o DMPZ a a capaci y o limi o
0.75 mAh$cm
2
showing ound- ip e ﬁciency e sus cycle numbe . Rep oduced wi h pe mission [86]. Copy igh ©2018, Wiley.
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
9
4.1 10
7
cm
2
$min
1
. As a esul , ba e y li espan was inc eased
om he 900 min o he con en ional PP sepa a o o >2500 min o
he pe mselec i e GPE. Recen ly, gel elec oly es ha e been ob-
ained by he dispe sion o umed silica in he aqueous elec oly e
(whe e Li
2
SO
4
and ZnSO
4
a e p esen ). The p esence o Li
2
SO
4
a-
cili a es he gel o ma ion while ZnSO
4
hinde s gelling. Upon
op imisa ion, he discha ge capaci y e en ion (a e 300 cha ge-
discha ge cycles a 4C) was 10% enhanced o e he liquid elec o-
ly e [150].
GPEs also enable he de elopmen o mul i unc ional ba e ies
use ul o wea able elec onics, anspa en sc eens o sma
windows [151]. An op ically anspa en Zn-ai ba e y (see
Fig. 12b) ope a ing o mo e han 100 cycles and ha ing a
maximum powe densi y o 9.77 mW$cm
2
was ab ica ed using a
6 M KOH poly(ac ylic acid) gel elec oly e [148]. In e es ingly, he
gel elec oly e a oids ﬂooding he ai elec ode, and a he same
ime educes he di ec exposu e o he ca hode o he elec oly e
sa u a ed wi h zinc ions, which in u n could o m an oxide
coa ing which poisons he ac i e ca alys . Lee e al. epo ed a
seconda y Zneai ba e y wi h imp o ed mechanical ﬂexibili y
and s able cycling up o 1500 min using a c oss-linked PVA/PAA
(6 M KOH) gel polyme elec oly e [149]. The pe mselec i e GPE
supp essed he zinca e ion c osso e by 3 imes in compa ison o
ha shown by he comme cial polyoleﬁn sepa a o . As shown by
he ene gy dispe si e X- ay spec oscopy and SEM images in
Fig. 12c, his was ansla ed in o a ZnO con amina ion- ee ai
ca hodes. Thanks o i s design, he ba e y was able o wi hs and
bending, wis ing and e en c umpling (Fig. 12d). In sea ch o
enhanced mechanical unc ionali ies, a ﬂexible and s e chable
ﬁb e-shaped Aleai ba e y ha ing GEP and deli e ing a speciﬁc
capaci y o 935 mAh$g
1
and an ene gy densi y o 1168 Wh$kg
1
was epo ed [152]. No only he mechanical pe o mance and
ionic conduc i i y (180 mS$cm
1
) is ema kable, bu also he
co osion o he Al anode was educed by inco po a ing ZnO and
Na
2
SnO
3
o he PVA/polye hylene oxide in KOH elec oly e.
3.3. Solid-s a e elec oly es
The conﬁgu a ion based on a po ous memb ane soaked in o a
liquid elec oly e esul s in bulky ba e ies wi h se ious sa e y is-
sues associa ed o elec oly e leakage and combus ion isks. T an-
si ioning om liquid-based elec oly es o solid-like elec oly es
may simpli y he design and ab ica ion p ocess o he ba e ies and
lowe gas c osso e [153]. Howe e , he applica ion o solid elec-
oly es has been limi ed by he ionic conduc i i ies o one o de
lowe han hose o liquid elec oly es. Addi ionally, he chemical
and elec ochemical s abili y o solid elec oly es is ela i ely poo ,
which coupled wi h hei b i leness and poo in e acial adhesion
o me allic anode p e en hem om being implemen ed in p ac-
ical applica ions. To o e come hese bo lenecks, he e o s ha e
been mainly di ec ed o de elop polyme ic (ei he in he o m o
mono-ma e ial o composi e), solid ino ganic and composi e
polyme elec oly es. Con en ionally, polyme -con aining solid
elec oly es a e achie ed by c oss-linking. The deg ee o c oss-
linking no ably inﬂuences he physico-mechanical and elec o-
chemical pe o mance o polyme ic elec oly es. An ex ended
c oss-linking es ic s chain mobili y o he ma ix and usually e-
duces he c ys allini y o he elec oly e [154,155]. A educed
c ys allini y ypically esul s in inc eased ion anspo numbe s
and ionic conduc i i ies, while a educed mac omolecula mobili y
inc eases he mechanical s abili y (wi h shea modulus inc eases),
imp o ing i s esis ance agains dend i ic g ow h. Howe e , i
Fig. 12. Mechanically de o mable gel polyme elec oly es in me aleai ba e ies. (a) Scheme depic ing he ab ica ion o he PVA-based nanocomposi e GPE. Rep oduced wi h
pe mission [147]. Copy igh ©2019, Else ie . (b) Op ical pho og aph o a bended anspa en Zneai cell. Rep oduced wi h pe mission [148]. Copy igh ©2019, Sp inge -Na u e. (c)
Pos -mo em su ace ene gy-dispe si e X- ay spec oscopy images (SEM a inse ) o he ai ca hodes o he GPE and Celga d memb ane soaked in o a liquid elec oly e. Rep oduced
wi h pe mission [149]. Copy igh ©2018, Ame ican Chemical Socie y. (d) In si u analysis o he gal anos a ic discha ge/cha ge cycling p oﬁles upon bending (5 mm adius) and
wis ing ( o a ion angle o 100a 30$s
1
). Rep oduced wi h pe mission [149]. Copy igh ©2018, Ame ican Chemical Socie y.
Solid-s a e elec oly es ha e he po en ial o ci cum en he
complex wa e managemen and po en ial leakage issues.
Howe e , he elec ochemical pe o mance is somewha
poo due o low ionic conduc i i ies and poo in e acial
adhesion
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
16

should be conside ed ha an excessi e c oss-linking can also lowe
he ionic conduc i i y by es ic ing oo much chain mobili y.
3.3.1. Solid polyme elec oly es (SPEs)
Simila ly o GPEs, polyme ic solid elec oly es a e ypically
complexes o a sal and a high-molecula -weigh polyme , bu wi h
heo e ically absence o sol a ing liquids. Howe e , many epo s
do no s ic ly dis inguish gel o solid polyme elec oly es as SPEs
may ha e mo e o less liquid as he conduc ion medium o ions o
ob ain sa is ac o y conduc i i ies. To a oid misunde s anding, his
sec ion does no p o ide an exhaus i e lis o SPEs bu i ies o
b ieﬂy summa ise he s a e-o - he-a in he ﬁeld. Gene ally, due o
he absence o sol a ing liquids, SPEs ha e low conduc i i ies a
oom empe a u e (~10
2
mS$cm
1
), and hei elas ic modulus is in
he o de o se e al MPa, o e ing an insu ﬁcien p o ec ion agains
dend i e g ow h in compa ison o ino ganic solid elec oly es.
Howe e , hei ela i ely so cha ac e enables an easy ba e y
handling and an in ima e con ac wi h he elec odes, which is
ansla ed in o longe li espans.
In spi e o he widesp ead use o PEO as SPE o LIBs, he use o
his polye he o ab ica e SPEs o Lieai ba e ies has been some-
how limi ed. In his ega d, Balaish e al. sol ed he inhe en limi-
a ions o PEO ( ela i ely poo in e acial p ope ies and high
c ys allini y) by ope a ing a 80

C, a empe a u e ~10

C abo e he
mel ing poin o he polyme i sel , eaching accep able ionic
conduc i i y alues o a PEO-li hium iﬂa e SPE [156]. In compa -
ison oLieO
2
ba e iesha ingliquidelec oly es(cha ging ol ageo
4e4.2 V), he cha ging ol age was lowe ed o 3.6 V, indica ing a
lowe cha ging-o e -po en ial. Addi ionally, as a liquid- ee solu-
ion, his app oach aces he long- e m s abili y issues due o he
au oxida ion o liquid elec oly es unde oxygena ed adicals ha
a e o med upon ope a ion. In compa ison o PEO, PVA o e s
imp o ed liquidabso p ion hanks oi s eOHg oupsa ached o he
ca bon chain. An ionic conduc i i y o 47 mS$cm
1
a oom em-
pe a u e has been epo ed o a PVA elec oly e, which inc eased
discha ge capaci y o 792 mAh o he PE/PP sepa a o o 1475 mAh
when assembled in o a Zneai ba e y (pe cen age o u ilisa ion
inc ease om 49.5% o 92%) [157]. PVA can be u he gelled in an
aqueous10w %glu a aldehydesolu ion( u he addi iono ace one
and HCl) o ob ain imp o ed mechanically ﬂexible elec oly es,
al hough he ionic conduc i i y d opped o 15 mS$cm
1
[158].
Poly(ac ylic acid) gene ally o e s highe ionic conduc i i ies
hanks o i s low c ys allini y and hyd ophilic domains, al hough i s
mechanical p ope ies can be poo . Fo example, an ionic conduc-
i i y as high as 288 mS$cm
1
a oom empe a u e has been e-
po ed o a poly(ac ylic acid)-based elec oly e ob ained a e he
c oss-linking (in KOH) o ac ylic acid wi h N,N'me hylene-bisac y-
lamide and K
2
S
2
O
8
as a polyme isa ion ini ia o [159]. Syn hesised
elec oly e showed a e y simila elec ochemical s abili y as he
nea alkaline solu ion. As schema ically depic ed in Fig. 13a, he
Fig. 13. S uc u e o solid polyme elec oly es used in me aleai ba e ies. (a) Diag am depic ing he high comp essibili y o a polyac ylamide hyd ogel elec oly e. The inse is he
molecula o mula o polyac ylamide; (b) SEM image o a eeze-d ied polyac ylamide hyd ogel. Rep oduced wi h pe mission [160]. Copy igh ©2018, Ame ican Chemical Socie y. (c)
Op ical pho og aph o he bac e ial cellulose/PVA elec oly e highligh ing i s ﬂexibili y and diag am, o he assembled Zneai ba e y. Rep oduced wi h pe mission [164]. Copy igh ©
2019, Ame ican Chemical Socie y. (d) c oss-sec ion SEM image o he eeze-d ied PANa-cellulose elec oly e; (e) syn he ic p ocedu e o he sodium polyac yla e-cellulose hyd ogel
elec oly e using he N,N0-Me hylenebisac ylamide (MBAA) c oss-linke , ac yla e monome and cellulose. Rep oduced wi h pe mission [165]. Copy igh ©2019, Wiley.
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
17
e e sible in e molecula hyd ogen bonds o med in poly-
ac ylamide elec oly es polyme ised by N,N
0
-me hyl-
enebis(ac ylamide) enable he polyac ylamide chains o
dynamically b eak and ecombine o dissipa e he applied ene gy,
hinde ing he o ma ion and p opaga ion o c acks [160]. The
in e connec ed mac opo es shown in Fig. 13b allow ee ion
ans e wi hin he elec oly e. As a esul , hese elec oly es enable
Zn-ai ba e ies wi hs anding comp essions up o 54% s ain and
bending up o 90

wi hou losses in cha ge/discha ge pe o mance
and ou pu powe . O he polyme s such as poly(e hylene ca bon-
a e), poly( ime hylene ca bona e), poly(p opylene ca bona e),
PVDF-HFP, o PMMA a e good candida es o de elop SPEs as hey
ypically p esen good sal dissocia ion, and hus, la ge ionic
conduc i i ies [161].
Biopolyme s ha e also been used o de elop SPEs o MABs. In
his sense, Fu e al. epo ed he syn hesis o an alkaline-exchange
elec oly e memb ane based on qua e na y ammonia- unc ional-
ised cellulose nanoﬁb es o solid-s a e Zneai ba e ies [162]. The
memb ane wi h po e sizes o 25e300 nm acili a es he hyd oxide
ion hopping (21.2 mS$cm
1
in 1 M KOH), o e s a la ge wa e
e en ion capaci y o a oid elec oly e loss by e apo a ion and is
mechanically ﬂexible. As a esul , he speciﬁc capaci y and he
cycling s abili y o he ba e y imp o ed in compa ison o he
comme cial alkaline anion-exchange memb ane, which showed a
p og essi e wa e loss and ionic conduc i i y decay. In ano he
example, a cellulose-based SPE has been ab ica ed using sodium
polyac yla e, 10 M NaOH and a po ous pape skele on o s o e he
gelled alkaline elec oly e [163]. When applied in o an Al-ai ba -
e y, a capaci y up o 901 mAh$g
1
was ob ained wi h an open
ci cui ol age o 1.5 V and a peak powe densi y o 3.8 mW$cm
2
.
Impo an ly, biopolyme s show syne ge ic p ope ies when
blended wi h o he pe oleum-based polyme s. A ﬂexile solid-s a e
Zneai ba e y was de eloped using bac e ial cellulose, PVA, KOH,
and Zn(CH
3
COO)
2
[164]. Thanks o he achie ed mic opo ous dual-
ne wo k s uc u e o igina ing om he ﬁb e-like shape o bac e ial
cellulose, ionic conduc i i ies up o 80.8 mS$cm
1
we e obse ed,
and a load-bea ing pe cola ing dual ne wo k is o med due o he
hyd ogen bonding be ween bo h elec oly e cons i uen s. In e -
es ingly, he solid elec oly e could old and ben in any angle and
es o es i s o iginal size once mechanical s esses a e emo ed,
enabling ﬂexible Zneai ba e ies (Fig. 13c). The Zneai ba e y
could ope a e o mo e han 440 h wi h no no able capaci y
dec ease. Ma e al. ecen ly epo ed he ab ica ion o a highly-
s e chable Zneai ba e y comp ising a sodium polyac yla e/cel-
lulose elec oly e [165]. C oss-sec ion SEM images o he eeze-
d ied solid elec oly es in Fig. 13d e eal a hie a chical s uc u e
wi h o de ed po ous channels dis ibu ed be ween laye s. These
basal spaces a e expec ed o inc ease he wa e - e en ion and ionic
conduc i i y o he hyd ogel. As shown in Fig. 13e, he elec oly e
was syn hesised ia ee adical polyme isa ion o ac ylic acid
neu alised by a NaOH solu ion in he p esence o cellulose and
MBAA c oss-linke s. A co alen c oss-linking is o med be ween
sodium polyac yla e/eOH g oups o cellulose and PANa/MBAA,
u he ein o ced by hyd ogen bonds be ween sodium poly-
ac yla e and cellulose chains. The syne gy a ising om chemical
and physical c oss-linking p o ides a s eng hened mechanical
obus ness and s e chabili y o he elec oly e. Addi ionally, he
elec oly e showed an enhanced alkaline ole ance, holding 6 M
KOH which ende s a conduc i i y o 280 mS$cm
1
.
3.3.2. Solid ino ganic elec oly es (SIEs)
Di e en ypes o SIEs ha e been epo ed, whe e sulﬁde-, ox-
ide-, ni ide- and phospha e-based ones a e he mos commonly
ound examples in li hium-me al ba e ies [166]. Gene ally, ino -
ganic solid elec oly es exhibi sa is ac o y ionic conduc i i ies
Fig. 14. Ce amic-based solid elec oly es in me al-ai ba e ies. (a) S uc u e o a bulk- ype all solid s a e ba e y and he esis ance o igina ed om solid elec oly es. AM: ac i e
ma e ials; SE: solid elec oly e. Rep oduced wi h pe mission [169]. Copy igh ©2019, Else ie . (b) A schema ic ep esen a ion o a Lieai ba e y con aining a LISICON SIE.
Rep oduced wi h pe mission [171]. Copy igh ©2010, Else ie . (c) Schema ic showing he imp o ed we abili y o he ga ne -based SIE agains Li me al using Li-me al alloy.
Rep oduced wi h pe mission [178]. Copy igh ©2017, Ame ican Associa ion o he Ad ancemen o Science.
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
18
when compa ing wi h polyme ic solid elec oly es. Thei elas ic
modulus is also highe , al hough su ace adhesion wi h elec odes
is comp omised gi en hei o en igid cha ac e , esul ing in
inc eased in e acial esis ances upon cycling. The chemical and
elec ochemical s abili y o SIEs is also a conce n. Fo example,
some sulﬁdes ha e good ionic conduc i i y p ope ies, al hough
hey a e uns able when exposed o mois u e o oxygen, gene a ing
highly oxic H
2
S.
Oxides p esen a gene ally imp o ed esis ance o oxida ion
o e sulﬁdes. In ac , NASICON oxide elec oly es ha e been e-
po ed o be s able when exposed o ai mois u e, al hough hei
poo elec ochemical s abili y a low ol ages is a conce n [3]. In
2004 Visco e al. p oposed a Li
þ
conduc ing NASICON- ype solid
elec oly e o p o ec he Li anode in a Lieai ba e y [167]. This
concep o e s he ad an age ha he discha ge eac ion p oduc
(eg. LiOH) is soluble in wa e . Following his app oach, Li-ai ba -
e ies wi h aqueous elec oly es sepa a ed by a wa e s able Li
þ
conduc ing glass ce amics ha e been epo ed [168]. Li hium i a-
nium aluminium phospha e (LATP) in he composi ion o
Li
1þx
Al
x
Ti
2x
(PO
4
)
3
a e a p omising g oup o solid-s a e elec oly e
ma e ials hanks o hei high-ionic conduc i i y and low-
manu ac u ing cos [169]. As he bulk ionic conduc i i y o LATP
ce amic is gene ally an o de o magni ude g ea e han ha o he
g ain bounda y in e ace, he con ol o he g ain bounda ies on
LATP enables enhancing he Li
þ
mobili y. To ha end, as shown in
Fig. 14a, a high- empe a u e sin e ing p ocess was applied o
densi y he solid-s a e elec oly e and emo e he po es/ oids/
c acks.
A200
m
m hick solid elec oly e sepa a o o Li
1.3
Al
0.5
Nb
0.2
-
Ti
1.3
(PO
4
)
3
p epa ed by a ape-cas ing app oach ha ing a bending
s eng h o 100 MPa and ionic conduc i i y o 0.91 mS$cm
1
a
25

C was applied in o a Lieai ba e y [170]. Howe e , a polyme ic
po ous sepa a o wi h 4 M LiFSI in e hylene glycol dime hyl e he
was used o sol e he s abili y issues o he solid elec oly ewhen in
con ac wi h he Li anode, educing he ene gy densi y o he cell.
Al hough less a en ion in compa ison o NASICON SIEs has been
paid, LISICON (Li
þ
supe ionic conduc o ) SIEs a e p omising can-
dida es o MABs gi en hei high ionic di usion in he mobile ion
sub-la ice a oom empe a u e. A LISICON solid elec oly e was
implemen ed in o Li-ai ba e ies o sepa a e o ganic and aqueous
Fig. 15. Composi e polyme elec oly es in me aleai ba e ies. (a) Gal anos a ic cha ge-discha ge cycles o LLZTO-based CPE in symme ic 2032 coin cells a 10.0 mA$cm
2
and 3.33
mAh$m
2
. Red line ep esen s he CPE, while black line accoun s o he ba e LLZTO. Rep oduced wi h pe mission [183]. Copy igh ©2020, Else ie . (b) Op ical pho og aph o he
ﬂexible g aphene oxide/CNF CPE. (c) Syn he ic p ocedu e o he syn hesis o he g aphene oxide/CNF CPE in ol ing unc ionalisa ion, ﬁl a ion, c oss-linking, and hyd oxide-
exchange. Rep oduced wi h pe mission [184]. Copy igh ©2016, Wiley.
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
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M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
20
elec oly es ob ain enhanced cycling s abili ies [171]. In his sys em,
he ca aly ic educ ion o O
2
occu s in an alkaline aqueous elec-
oly e, while Li emains in con ac wi h a non-aqueous elec oly e
(Fig. 14b). This design enables he con inuous educ ion o O
2
om
ai o deli e ene gy.
NASICON- ype LAGP solid elec oly es such as Li
1.5
Al
0.5
-
Ge
1.5
(PO
4
)
3
ha e been used o inhibi he c osso e o soluble
p oduc s in LieO
2
ba e ies, al hough a Li
þ
conduc ing in e ace
be ween he Li me al and he solid elec oly e is gene ally equi ed
o p e en he di ec educ ion o he solid elec oly e [172]. In spi e
o his p o ec ing laye , inc eased impedances a e obse ed upon
cycling due o localised educ ion. Kamaya e al. epo ed a solid
Li
10
GeP
2
S
12
elec oly e eaching an ionic conduc i i y as high as
12 mS$cm
1
a oom empe a u e, e en hough he ma e ial was
no es ed in o a MAB [173].
Apa om NASICON and LISICON solid elec oly es, he e a e
also u he ma e ials sui able o MABs. In his con ex , Pe o ski e-
ype solid elec oly es a e in e es ing gi en hei high bulk ionic
conduc i i ies eaching se e al mS$cm
1
a oom empe a u e
[174]. Howe e , hese ma e ials p esen a low decomposi ion
ol age agains me allic Li and he g ain bounda y e ec no ably
educes he esul ing ionic conduc i i y by one o de o magni ude.
To sol e hese issues, Inaguma and Nakashima p epa ed a
lan hanum li hium i ana e (LLTO) ce amic elec oly e
(La
0.57
Li
0.29
TiO
3
) wi h a maximum conduc i i y o 0.57 mS$cm
1
a
27

C elimina ing he esis i e g ain-bounda y by g ain g ow h
[175]. When applied as a sepa a o in o a Lieai ba e y ha ing
a 0.5 M LiOH aqueous and a Li o ganic elec oly e, one week s a-
bili y was ob ained, unde lying he po en ial o LLTO ce amics in
MABs.
Ano he ema kable example o oxide SIEs a e ga ne - ype
ma e ials, which o e high ionic conduc i i ies, adequa e
chemical s abili ies wi h Li me al, and wide elec ochemical
po en ial windows [176]. Sue e al. showed he applica ion o a
ga ne - ype SIE ha ing he nominal composi ion o Li
7
La
3
Z
2
O
12
(LLZO) in o a LieO
2
ba e y [177]. A cu o capaci y o 1000
mAh$g
1
ca bon a 20
m
A$cm
2
was achie ed. Howe e , he
ope a ing empe a u e was 80

C o imp o e he Li-SIE and he
ca hode-SIE in e acial con ac . To modi y he su ace we abili y
o a ga ne (Li
7
La
2.75
Ca
0.25
Z
1.75
Nb
0.25
O
12
) SIE om li hiophobic
o li hiophilic, an in e media y Li-me al alloy could be applied
be ween he SIE and he me allic Li as schema ically depic ed in
Fig. 14c[178]. Thanks o he imp o ed con ac o he ga ne SIE
wi h me allic Li, a hyb id solid-liquid LieO
2
cell could be cycled
o e 10 imes.
In addi ion o hese ma e ials wi h ema kable p ope ies, o he
ino ganic ma e ials a e also being explo ed o de elop solid elec-
oly es o MABs. An in eg a ed solid-s a e Lieai ba e y ha ing an
ul a hin, high-ion-conduc i e zeoli e-based solid elec oly e has
been ecen ly epo ed by Chi e al. [179]. The inhe en mic opo ous
c ys alline s uc u e o zeoli es acili a es he mass anspo p o-
cess while he good con ac be ween he ca hode and he zeoli e-
based solid elec oly e minimises he in e acial esis ance o he
cell. Mo eo e , he Gu ley imes ( he ime needed o 100 cm
3
ai o
pass h ough a sepa a o unde an ai p essu e o 0.862 kg $cm
2
)
o he zeoli e-elec oly e we e oo long o be wi hin he de ec ion
ange, in compa ison wi h he 1410 s and 1s measu ed o he
Celga d and he glass ﬁb e sepa a o s, espec i ely. This much
slowe pe meabili y sugges s a no ably educed di usion o O
2
,N
2
o H
2
O o he anode, limi ing i s co osion. As a esul , an ex ended
li ecycle o 149 cycles a 1000 mAh$g
1
was ob ained, in
compa ison o he 12 cycles ob ained o a Li-ai ba e y based on
li hium aluminium ge manium phospha e elec oly es and he 102
cycles o he ba e y bea ing o ganic elec oly es.
3.3.3. Composi e polyme elec oly es (CPEs)
Composi e polyme elec oly es (CPEs) a e o med by a polyme
ma ix inco po a ing chemically ine ino ganic ﬁlle s ha assis
ion conduc i i y [180,181]. CPEs a e de eloped o combine he
ad an ages o solid polyme elec oly es and ion conduc i e ino -
ganic ce amics. Al hough CPEs ha e been mainly applied in o o he
echnologies such as sodium-ion ba e ies (NIBs) o li hium-me al
ba e ies (LMBs), some examples could also be ound in MABs. Fo
ins ance, a PVDF-HFP plas icised by a hyd ophobic IL was used as a
ma ix o hos 1e6 w % hyd ophobic silica nanopa icles [138]. The
ionic conduc i i y inc eased om 1.19 mS$cm
1
up o a maximum
o 1.83 mS$cm
1
wi h 3 w % silica and designed CPE e ec i ely
s abilised he Li/CPE in e ace and diminish Li co osion by wa e .
Polydopamine-coa ed MOFs (CAU-1-NH
2
) we e inco po a ed in o a
PMMA ma ix o ob ain an O
2
selec i e memb ane hanks o he
high su ace a ea, con olled po osi y and adjus able chemical
unc ionali y o he MOF [182]. The eNH
2
g oups in he MOF, eOH
in polydopamine, and he eC]O double bond in PMMA p e e ably
in e ac wi h CO
2
and p e en i s in e ac ion wi h Li
2
O
2
o o m
Li
2
CO
3
, while he hyd ophobici y o he CPE limi s he ing ess o
wa e in o he cell. As a esul , when he e minal discha ge ol age
is se a 2 V, he Lieai ba e y li ecycle was ex ended om 6 o 66
cycles ha ing he CPE. In ano he example, a CPEs con aining
89.6 w % LLZTO ga ne was included in a polye he sul one ma ix
o ob ain a ‘polyme -in-ce amic’CPE ha ing an ionic conduc i i y o
0.69 mS$cm
1
a 20

C[183]. As depic ed by gal anos a ic cha ge/
discha ge cycles in symme ic Li cells in Fig. 15a, an imp o ed
compa ibili y wi h Li me al and accep able capabili y agains Li
dend i e was ob ained ( ed line o he CPE, black line o ba e
LLZTO). Mo eo e , he discha ge-cha ge ol age gap was educed o
0.6 V in compa ison wi h he nea ly 1.5 V obse ed o he ba e
LLZTO solid elec oly e.
A highly ﬂexible lamina e-s uc u ed unc ionalised GO/CNF
memb ane ha ing highly hyd oxide-conduc i e qua e na y
ammonium g oups was de eloped o a s e chable Zneai ba e y
(Fig. 15b) [184]. As summa ised in Fig. 15c, he CPE was ob ained
a e a mul i-s ep p ocess in ol ing chemical unc ionalisa ion,
laye -by-laye ﬁl a ion, c oss-linking, and ion-exchange p o-
cesses. The wo aldehyde unc ional g oups o glu a aldehyde e-
ac s wi h he hyd oxyl g oups on o GO and CNFs o o m an ace al
s uc u e wi h a c oss-linked laye ed-s uc u ed memb ane wi h
hyd oxide-conduc ing p ope ies. CNFs o e an in e connec ed
amewo k in eg a ing g aphene oxide in o a ﬂexible memb ane
wi h high wa e abso p ion abili y. Ionic conduc i i ies as high as
39.0 mS$cm
1
(58.8 mS$cm
1
a 70

C) a e achie ed as a esul o
he high mobili y o hyd oxide ions dissocia ed om he g a ed
qua e na y ammonium g oups. Those beneﬁ s a e mani es ed in o
a peak powe densi y o 44.1 mW$cm
2
as opposed o he
33.2 mW$cm
2
o he A201 memb ane, while no pe o mance
loss a e 600 h was obse ed (A201-based ba e y has la ge
cha ge/discha ge pola isa ions a e 300 min). O e all, he wo k
di ec ed o he sea ch o solid-s a e elec oly es o be imple-
men ed in MABs is no ably lowe when compa ing wi h o he
ba e y conﬁgu a ions such as solid-s a e LMBs. Ne e heless,
he e a e ple ho a o lessons ha can be lea ned om hese p e-
ious e o s.
Fig. 16. En i onmen al impac s o me al-ai ba e ies. (a) The sha e o he di e en Zneai ba e y subassemblies o he ou een impac ca ego ies analysed acco ding o he
In e na ional Re e ence Li e Cycle Da a Sys em (ILCD) me hodology. Rep oduced wi h pe mission [196]. Copy igh ©2020, Else ie . (b) En i onmen al impac s o se en LieO
2
ba e ies no malised o 1 kWh o s o age capaci y based on li e cycle assessmen . Rep oduced wi h pe mission [198]. Copy igh ©2021, Ame ican Chemical Socie y.
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
21

4. En i onmen al impac s
The de elopmen o sus ainable ene gy s o age sys ems is an
inexcusable ask ha scien is and indus y mus unde ake,
pa icula ly gi en he ac ual conce ns o e he deple ion o non-
enewable esou ces, global wa ming and ba e y was e manage-
men issues. Nowadays, LIB echnology s ill has ecognised en i-
onmen al sus ainabili y issues, mos ly a ising om he use o
highly oxic and sca ce ma e ials [185]. In he sus ainable ene gy
s o age landscape, MABs o e en i onmen al beneﬁ s o igina ing
om hei high ene gy e ﬁciency ha is 5e30 imes g ea e han
con en ional LIBs. In addi ion, as opposed o LIBs o NIBs which use
conside able amoun s o ma e ials ound in he CRM lis (Co, Mn, V,
Ni, o g aphi e), MABs a ely use hese ma e ials, and when hey do,
small quan i ies a e needed [186]. Fo example, he e oa om-doped
hie a chical ca bon wi h honeycomb s uc u es unc ion well as
me al- ee elec oca alys o ORR [187], opening he doo o design
sus ainable me al-ai ba e ies ee o ca alys s such as P /C. These
s a egies can lessen he p essu es o e he ex ac ion o CRMs o
he ba e y indus y, which encompasses se ious en i onmen al
p essu es, as o example,1900 ons o H
2
O (di e ed om essen ial
ag icul u al ac i i ies) a e consumed by e apo a ion o he
ex ac ion o 1 Li one [188]. Howe e , i should be conside ed ha
he ca alys s in MAB a e o en composed by noble me als subjec ed
o supplychain bo lenecks and en i onmen al conce ns (in spi e o
he ela i ely small quan i y o me als equi ed as opposed o LIBs/
NIBs). Ba e y ecycling is a plausible app oach o eco e
hose sca ce ma e ials as he ne impac o LIB p oduc ion can be
educed when he ma e ials a e eco e ed a e ba e y end-o -li e
(EoL) [189].
Apa om hese concep s, he ull unde s anding he sus ain-
abili y o MABs equi es he de e mina ion o hei en i onmen al
impac s. I he en i onmen al bu dens o pu e me als a e consid-
e ed, Caeai , Zneai , and Mgeai ba e ies should be a p io i
p e e ed. Indeed, he p oduc ion o pu e Li has a global wa ming
po en ial (GWP) o 7.1 kg CO
2
$equi $kg
1
, being he impac s o he
o he me als as ollows: 8.2 kg CO
2
$equi $kg
1
o Al, 5.4 kg
CO
2
$equi $kg
1
o Mg, 3.1 kg CO
2
$equi $kg
1
o Zn, and 1.0 kg
CO
2
$equi $kg
1
o Ca [190]. Mo eo e , calcium is widely p esen in
Ea h's c us . Rega ding ca hode ma e ials, pu e cobal shows a
GWP o 8.3 kg CO
2
$equi $kg
1
, while anadium encompasses
33.1 kg CO
2
$equi $kg
1
, manganese 1.0 kg CO
2
$equi $kg
1
,i on
1.5 kg CO
2
$equi $kg
1
, o nickel 6.5 kg CO
2
$equi $kg
1
[190].
The ab ica ion o ene gy s o age sys ems is subjec ed o la ge
amoun s o aw ma e ials and ene gy consump ion, oge he wi h
he emission o di e en was es [191]. Acco dingly, ba e y sus-
ainabili y should go beyond he me e de e mina ion o he global
wa ming in ol ed du ing he use o aw ma e ials, and should
co e he di e en li e cycle s ages. In ac , he wo ldwide g een-
house gas emissions o igina ing om ba e y manu ac u ing a e
es ima ed o be 182 M CO
2
$equi alen s (a uni o measu emen
applied o s anda dise he clima e e ec s o g eenhouse gases)
[192]. In his sense, a c adle- o-g a e ( he ull li e cycle, co e ing
om esou ce ex ac ion o c adle, manu ac u ing, dis ibu ion, use
and end-o -li e o g a e), o a leas c adle- o-ga e ( om aw ma-
e ial ex ac ion o he p ocessing, manu ac u ing and p oduc
ab ica ion o ac o y ga e) app oach needs o be conside ed o ge
he bigge pic u e [193]. Using he li e cycle assessmen (LCA)
me hodology, i is possible o quan i y o en i onmen al impac o a
p oduc o se ice h ough i s li e cycle, co e ing om he ex ac-
ion and p ocessing o he aw ma e ials o he EoL and aking in o
accoun he manu ac u ing, dis ibu ion and use [194]. A p io i, he
main en i onmen al bu dens o MABs a ise om he na u e o
ca hode ca alys s (which o en equi e highly oxic and sca ce el-
emen s). Aqueous elec oly es a e en i onmen ally p e e ed o e
ap o ic sol en s, which en ail no able en i onmen al bu dens in
e ms o CO
2
emissions and oxici y.
Zn-based ba e ies a e s able owa ds mois u e, so no ine a -
mosphe e is equi ed du ing ba e y manu ac u ing. This simpliﬁes
he p oduc ion p ocess and esul s in lowe ene gy and ma e ial
(a gon) consump ion ypically needed o ensu e a mois u e- ee
ine a mosphe e du ing cell assembly o con en ional LIBs o
NIBs (ensu ing hese condi ions equi es he 29.4% o he o al
ene gy o he p oduc ion o a 32-Ah LMO/g aphi e cell) [195]. On
his basis, San os e al. s udied he c adle- o-ga e en i onmen al
impac s o a Zneai ba e y bea ing a PVA-KOH hyd ogel elec oly e
( e med as memb ane in he s udy) and a ca bon black/MnO
2
ca hode [196]. A cumula i e ene gy demand (CED) o
590.8 MJ$kg
1
was ob ained (whe e he ca hode ai , he mem-
b ane, he Zn anode and he elec oly e accoun ed o he 56, 39, 3
and 2%, espec i ely) as compa ed wi h he a e age o
152.9 MJ$kg
1
( alues anging om 19.6 o 1416.0 o 76 di e en
s udies) co esponding o LIBs [197]. In spi e o such la ge alue,
he elec ici y consump ion could be lowe han ha o a LIB gi en
he labo a o y-scale p oduc ion o analysed Zn-ai ba e y. An
embedded emission o 61.2 kg CO
2
$equi pe 1 kWh o s o ed en-
e gy was ob ained, whe e he ca hode accoun ed o 50%, he
memb ane he 38%, he Zn anode 8% and he elec oly e solely 4%.
As shown in Fig. 16a, his is he gene al end excep o he
esou ce deple ion ca ego y, whe e he Zn powde anode has he
la ges con ibu ion. O e all, no able impac s in human oxici y
(cance and non-cance e ec s), eshwa e eco oxici y and
esou ce deple ion a e achie ed. I should be no ed ha cu en
LCA s udies a e mainly pe o med o labo a o y-scale ba e ies, so
small lab-scale conﬁgu a ions a e analysed and no da a ega ding
comme cial cells is a ailable.
Zack isson e al. pe o med a c adle- o-g a e analysis (including
p oduc ion,use and ecycling) on Lieai ba e ycell o EVs[199].The
ba e y has a Li oil anode,a PP sepa a o soaked inLiClO
4
inTEGDME,
aCNT/Co
3
O
4
ca hode, coppe cu en collec o s and PP housing. The
ca hodehada ela i ep oduc ion- ela edCO
2
impac o 37%, ollowed
by he 28% o he assembly ene gyand he 23% o he Li oil. A no able
abio ic esou ce deple ion (89% con ibu ion) and eco oxici y (67%
con ibu ion) du ing p oduc ion a ising om coppe was obse ed.
In e es ingly,10%e30% o p oduc ion ela ed en i onmen al impac s
could be a oided conside ing a ecycling scena io. Al hough a com-
ple e sus ainabili y-d i en compa ison wi h ma u e ba e y ech-
nologies is somehow di ﬁcul gi en he di e en echnology
eadiness le els, Wang e al. compa ed he c adle- o-g a e en i on-
men al impac s o a 63.5 kWh LieO
2
ba e y (Li anode, CNT/MoS
2
ca hode, LiClO
4
in TEGDME elec oly e) wi h a NMC- ype LIB [200].
The nega i e elec ode (Li oil) akes he la ges sha e in mos o he
ca ego ies, la gely a ibu ed o he coppe cu en collec o used. On
he con a y, hanks o i s high po osi y and ligh ness, he ca hode
con ibu es by less han 7% in mos o he ca ego ies. O e all, wi h
149 g$CO
2
$equi $km
1
, heLieO
2
ba e y sys em showed a 9.5%
educ ion in li e cycle clima e change due o he a oidance o man-
ganese,nickel,andcobal in heca hode.Anaddi ionalen i onmen al
beneﬁ when implemen edin oanelec ic ehiclemaya ise om he
weigh o LieO
2
ba e ies, whe e dec eases om 531 o 267 kg ha e
been es ima ed by eplacing a NMC (nickel, manganese, and cobal )
LIB [200]. Such weigh sa ing can p o ide di ec en i onmen al
beneﬁ s when implemen ed in o an elec ic ehicle independen ly o
he elec ici y g id ype [201]. Howe e , ou o de s o magni ude
la ge impac s o e es ial eco oxici y po en ial and 8 imes la ge
o ozonedeple ionpo en iala eachie ed,highligh ing he need o a
holis ic design o he ba e y.
Finally, I u ondobei ia e al. analysed he c adle- o-ga e impac s
o 7 labo a o y-scale ap o ic LieO
2
ba e y ca hode chemis ies
ha ing 60 kWh [198]. As shown in Fig.16b, he impac s la gely a y
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
22
depending on he ba e y ype due o he a ie y o ma e ials
including nickel, MnO
2
, u henium, g aphene, cobal , MOFs, ca bon
nano ubes, Co
3
O
4
, Ag o AuNi. On a e age, he ca hode is he majo
con ibu o o he GWP wi h a ela i e weigh o 44.5%, ma ching
he conclusions d awn by San os e al. [196]. LieO
2
ba e ies p e-
sen an a e age alue o 55.8 kg$CO
2
$equi pe 1 kWh, which e-
mains below he 146.4 kg$CO
2
$equi o NIBs, 146.4 kg$CO
2
$equi
o NIBs, he 58.4 kg$CO
2
$equi o LIBs, o he 130.6 kg$CO
2
$equi
o LieS (ha ing a simila ene gy densi y). The impac s ela ed o
oxicological isks can be also educed hanks o he simplici y/e -
ﬁciency o he ca hode ab ica ion, he use o abundan and sa e
ma e ials, and limi ed amoun s o elec oly e. O e all, epo ed LCA
s udies highligh he po en ial o MABs as a p omising choice o
ab ica e sus ainable ene gy s o age sys ems, pa icula ly gi en he
low echnical ma u i y.
I is impo an o bea in mind ha ba e y pe o mance
(deli e ed ene gy) and li e ime a e impo an a iables de e -
mining he ull sus ainabili y. En i onmen ally sus ainable MABs
should be designed o a oid he phenomena esul ing in ea ly
ailu e o he cell, such as hose including dend i e o ma ion,
cu en collec o co osion, componen olume ic changes, anode
de achmen om he cu en collec o , and loss o elec ode's
elec onic conduc i i y o elec oly e con amina ion o decompo-
si ion. This would a oid he ex ac ion o new esou ces equi ed
o a new ba e y, would limi he CO
2
emission o igina ing om
ba e y manu ac u ing and would delay he en e ing o he ba e-
ies in he was e s eam.
5. Summa y and ou look
MABs a e conside ed as one o he mos signiﬁcan con ende s
wi hin he nex -gene a ion elec ochemical ene gy s o age sys-
ems. Gi en i s pa icula ele ance, ill he da e many e o s ha e
been di ec ed o he de elopmen o new ca hode ma e ials and
designs (oxygen elec oca alys s). Howe e , MABs should be s ud-
ied om a holis ic poin o iew, paying a en ion o he o he
ba e y componen s. In his sense, he applica ion o polyme s o
de elop elec oly es o MABs can ce ainly help o ace he
inhe en d awbacks associa ed wi h he o ma ion o undesi ed by-
p oduc s [7], he ORR/OER o e po en ial, he e e sibili y o he
me al elec ode o he low ound- ip e ﬁciency. Mic opo ous
polyoleﬁn memb anes such as Celga d 2325 o 2500 e olu ionised
he comme cial liquid elec oly e based LIBs hanks o hei ease o
ab ica ion, low cos , scalabili y and shu down p ope y [25].
Howe e , he pe o mance o hese ma e ials when implemen ed
in o MABs is a om p ac icabili y. In any case, i should be
conside ed ha gi en he e sa ili y o polyme s o ob ain ailo ed
chain s uc u es, unc ional g oups and physico-mechanical p op-
e ies, hese ma e ials hold a b igh u u e o imp o e he s a e-o -
he-a ene gy s o age sys ems bo h a undamen al and applied
science le el.
Gelepolyme elec oly es and solidepolyme elec oly es show
ela i ely poo ionic conduc i i ies in a simila way o hei ana-
logues applied in con en ional LIBs o NIBs. In his sense, gel-
polyme elec oly es bea ing aqueous elec oly es should be
explo ed in he nea u u e gi en hei po en ial o each ionic
conduc i i ies up o ew mS$cm
1
a oom empe a u e upon
p ope design, al hough poo ans e ence numbe alues may s ill
be ound. IL elec oly es p o ide wide elec ochemical s abili y
windows and o e an en i onmen ally benign al e na i e o con-
en ional ca bona e-based elec oly es. Howe e , ob ained ionic
conduc i i ies canno compe e wi h he alues ob ained wi h
con en ional ca bona e o wa e -based elec oly es. Solid polyme
elec oly es ha e he beneﬁ o p o iding enhanced mechanical
p ope ies while p e en ing undesi ed liquid elec oly e leakage.
Addi ionally, na u ally-de i ed polyme s such as cellulose hold a
b igh u u e o MAB elec oly es wi h enhanced elec ochemical
pe o mance gi en hei po en ial o dissol e sal s, ich a ie y o
unc ional g oups including eNH
2
,eOH, eCONH
-
,eCONH
2
, and
eSO
3
H, and abili y o de elop gel-like po ous s uc u es [79]. In
addi ion, hei inhe en biodeg adabili y, lack o oxici y and
biocompa ibili y o e addi ional ad an ages ha could no be
igno ed.
As he esea ch on MABs is s ill in i s in ancy, hei en i on-
men al sus ainabili y and end-o -li e scena ios ha e been la gely
neglec ed. In addi ion, ce ain unding agencies encou age he
implemen a ion ci cula economy and en i onmen al impac
me ics in p ojec p oposals. Acco dingly, u he wo ks a e needed
o unequi ocally quan i y he en i onmen al impac s du ing MAB
p oduc ion and use-phase. Me hodologies such as li e cycle
assessmen o e he means o do so by ocusing on he whole li e
cycle [199]. The echno-economic assessmen o MABs may o e
in e es ing in o ma ion o add ess he economic easibili y o new
ba e ies, especially conside ing he capi al-in ensi e ma e ials and
manu ac u ing equipmen equi ed some imes [196]. In addi ion,
he deg ada ion o he ma e ials building up he ba e ies, and hei
po en ial ecycling should be conside ed in he coming yea s. This
would no only lowe he en i onmen al oo p in o ba e ies bu
also would help secu ing he access o c i ical aw ma e ials,
g a ing he es ablishmen o mo e esilien supply chains o ba -
e ies ma e ials. The conse a ion o na u al esou ces and sol ing
ba e y end-o -li e issues a e now being in ensi ely s udied in he
LIB ﬁeld due o he la ge amoun o spen ba e ies being gene a ed.
The e o e, u he esea ch is needed in hese neglec ed aspec s in
he de elopmen o MABs [202].
CRediT au ho ship con ibu ion s a emen
Manuel Salado: Concep ualiza ion; Da a cu a ion; Fo mal
analysis; In es iga ion; P ojec adminis a ion; Valida ion; Visual-
iza ion; W i ing - o iginal d a ; W i ing - e iew &edi ing. E lan z
Lizundia: Concep ualiza ion; Da a cu a ion; Fo mal analysis;
In es iga ion; P ojec adminis a ion; Valida ion; Visualiza ion;
W i ing - o iginal d a ; W i ing - e iew &edi ing.
Decla a ion o compe ing in e es
The au ho s decla e ha hey ha e no known compe ing
ﬁnancial in e es s o pe sonal ela ionships ha could ha e
appea ed o inﬂuence he wo k epo ed in his pape .
Re e ences
[1] J. Deng, C. Bae, A. Denlinge , T. Mille , Elec ic ehicles ba e ies: e-
qui emen s and challenges, Joule 4 (2020) 511e515, h ps://doi.o g/10.1016/
j.joule.2020.01.013.
[2] J. Wen, Y. Yu, C. Chen, A e iew on li hium-ion ba e ies sa e y issues:
exis ing p oblems and possible solu ions, Ma e . Exp ess. 2 (2012) 197e212,
h ps://doi.o g/10.1166/mex.2012.1075.
[3] S. Fe a i, M. Falco, A.B. Mu~
noz-Ga cía, M. Bonomo, S. B u i, M. Pa one,
C. Ge baldi, Solid-s a e pos Li me al ion ba e ies: a sus ainable o hcoming
eali y? Ad . Ene gy Ma e . 11 (2021), 2100785 h ps://doi.o g/10.1002/
aenm.202100785.
[4] M. Ga side, Global P ojec ion o To al Li hium Demand 2016-2030, A alaible
a : h ps://Www.S a is a.Com/S a is ics/452025/P ojec ed-To al-Demand-
o -Li hium-Globally/. (accessesed on May 2022).
[5] I. O e, I.O. Pigmen s, P. Rock, Q. C ys al, R. Ea hs, S. Ash, Mine al Commodi y
Summa ies 2020, A ailable a : h ps://pubs.usgs.go /pe iodicals/mcs2020/
mcs2020.pd (accessesed on May 2022).
[6] Y. Li, J. Lu, Me al-ai ba e ies: u u e elec ochemical ene gy s o age o
choice? ACS Ene gy Le . 2 (2017) 1370e1377.
[7] H.F. Wang, Q. Xu, Ma e ials design o echa geable me al-ai ba e ies,
Ma e 1 (2019) 565e595, h ps://doi.o g/10.1016/j.ma .2019.05.008.
[8] F. Sun, R. Gao, D. Zhou, M. Osenbe g, K. Dong, N. Ka djilo , A. Hilge ,
H. Ma k€
o e , P.M. Bieke , X. Liu, I. Manke, Re ealing hidden ac s o Li anode
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
23
in cycled li hiumeoxygen ba e ies h ough X- ay and neu on omog aphy,
ACS Ene gy Le . 4 (2019) 306e316, h ps://doi.o g/10.1021/acsene gy
le .8b02242.
[9] D.D. Macdonald, K.H. Lee, A. Mocca i, D. Ha ing on, E alua ion o alloy an-
odes o aluminum-ai ba e ies: co osion s udies, Co osion 44 (1988)
652e657.
[10] Y.N. Jo, K. P asanna, S.H. Kang, P.R. Ilango, H.S. Kim, S.W. Eom, C.W. Lee, The
e ec s o mechanical alloying on he sel -discha ge and co osion beha io
in Zn-ai ba e ies, J. Ind. Eng. Chem. 53 (2017) 247e252.
[11] Y. He, W. Shang, M. Ni, Y. Huang, H. Zhao, P. Tan, In-si u obse a ion o he
gas e olu ion p ocess on he ai elec ode o Zn-ai ba e ies du ing cha ging,
Chem. Eng. J. 427 (2022), 130862.
[12] J. Balamu ugan, T.T. Nguyen, N.H. Kim, D.H. Kim, J.H. Lee, No el co e-shell
CuMo-oxyni ide@N-doped g aphene nanohyb id as mul i unc ional ca a-
lys s o echa geable zinc-ai ba e ies and wa e spli ing, Nano Ene gy 85
(2021), 105987, h ps://doi.o g/10.1016/j.nanoen.2021.105987.
[13] X. Zheng, X. Cao, K. Zeng, J. Yan, Z. Sun, M.H. Rümmeli, R. Yang, A sel -je
apo -phase g ow h o 3D FeNi@NCNT clus e s as e ﬁcien oxygen elec o-
ca alys s o zinc-ai ba e ies, Small 17 (2021), 2006183, h ps://doi.o g/
10.1002/smll.202006183.
[14] Q. Liu, Z. Pan, E. Wang, L. An, G. Sun, Aqueous me al-ai ba e ies: unda-
men als and applica ions, Ene gy S o age Ma e . 27 (2020) 478e505, h ps://
doi.o g/10.1016/j.ensm.2019.12.011.
[15] H. Wang, Z. Yu, X. Kong, W. Huang, Z. Zhang, D.G. Mackanic, X. Huang, J. Qin,
Z. Bao, Y. Cui, Dual-sol en Li-ion sol a ion enables high-pe o mance Li-
me al ba e ies, Ad . Ma e . 33 (2021), 2008619, h ps://doi.o g/10.1002/
adma.202008619.
[16] Y. Zhou, J. Pan, X. Ou, Q. Liu, Y. Hu, W. Li, R. Wu, J. Wen, F. Yan, CO
2
ionized
poly( inyl alcohol) elec oly e o CO
2
- ole an Zn-ai ba e ies, Ad . Ene gy
Ma e . 11 (2021), 2102047, h ps://doi.o g/10.1002/aenm.202102047.
[17] F. Du ne , N. K onemeye , J. Tübke, J. Leke , M. Win e , R. Schmuch, Pos -
li hium-ion ba e y cell p oduc ion and i s compa ibili y wi h li hium-ion
cell p oduc ion in as uc u e, Na . Ene gy 6 (2021) 123e134.
[18] D. Mon i, A. Pon ouch, R.B. A aujo, F. Ba de, P. Johansson, M.R. Palacín,
Mul i alen ba e iesdp ospec s o high ene gy densi y: Ca ba e ies, F on .
Chem. 7 (2019) 79, h ps://doi.o g/10.3389/ chem.2019.00079.
[19] T. Kim, W. Song, D.-Y. Son, L.K. Ono, Y. Qi, Li hium-ion ba e ies: ou look on
p esen , u u e, and hyb idized echnologies, J. Ma e . Chem. A. 7 (2019)
2942e2964, h ps://doi.o g/10.1039/C8TA10513H.
[20] S. Cla k, A. La z, B. Ho s mann, A e iew o model-based design ools o
me al-ai ba e ies, Ba e ies 4 (2018) 5.
[21] G. Houchins, V. Pande, V. Viswana han, Mechanism o single oxygen p o-
duc ion in Li-ion and me aleai ba e ies, ACS Ene gy Le . 5 (2020)
1893e1899.
[22] Y. Li, J. Lu, Me aleai ba e ies: will hey be he u u e elec ochemical en-
e gy s o age de ice o choice? ACS Ene gy Le . 2 (2017) 1370e1377, h ps://
doi.o g/10.1021/acsene gyle .7b00119.
[23] Y. Son, N. Kim, T. Lee, Y. Lee, J. Ma, S. Chae, J. Sung, H. Cha, Y. Yoo, J. Cho,
Calende ing-compa ible mac opo ous a chi ec u e o siliconeg aphi e
composi e owa d high-ene gy li hium-ion ba e ies, Ad . Ma e . 32
(2020), 2003286.
[24] T. Leisegang, F. Meu zne , M. Zscho nak, W. Münchgesang, R. Schmid,
T. Nes le , R.A. E emin, A.A. Kabano , V.A. Bla o , D.C. Meye , The aluminum-
ion ba e y: a sus ainable and seminal concep ? F on . Chem. 7 (2019) 268,
h ps://doi.o g/10.3389/ chem.2019.00268.
[25] P. A o a, Z. Zhang, Ba e y sepa a o s, Chem. Re . 104 (2004) 4419e4462,
h ps://doi.o g/10.1021/c 020738u.
[26] C. H€
ansel, E. Lizundia, D. Kundu, A single Li-ion conduc o based on cellulose,
ACS Appl. Ene gy Ma e . 2 (2019) 5686e5691, h ps://doi.o g/10.1021/
acsaem.9b00821.
[27] X. Casas, M. Niede be ge , E. Lizundia, A sodium ion ba e y sepa a o wi h
e e sible ol age esponse based on wa e -soluble cellulose de i a i es,
ACS Appl. Ma e . In e aces 12 (2020) 29264e29274, h ps://doi.o g/
10.1021/acsami.0c05262.
[28] A. A oundjian, V. Gal an, F.A. Gomez, An inexpensi e pape -based
aluminum-ai ba e y, Mic omachines 8 (2017), h ps://doi.o g/10.3390/
mi8070222.
[29] X.-B. Cheng, R. Zhang, C.-Z. Zhao, Q. Zhang, Towa d sa e li hium me al anode
in echa geable ba e ies: a e iew, Chem. Re . 117 (2017) 10403e10473,
h ps://doi.o g/10.1021/acs.chem e .7b00115.
[30] S.H. Lee, J.-B. Pa k, H.-S. Lim, Y.-K. Sun, An ad anced sepa a o o LieO
2
ba e ies: maximizing he e ec o edox media o s, Ad . Ene gy Ma e . 7
(2017), 1602417, h ps://doi.o g/10.1002/aenm.201602417.
[31] Y. Hu, X. Zhu, L. Wang, Two-dimensional ma e ial- unc ionalized sepa a o s
o high-ene gy-densi y me alesul u and me al-based ba e ies, Chem-
SusChem 13 (2020) 1366e1378, h ps://doi.o g/10.1002/cssc.201902758.
[32] W.-K. Shin, A.G. Kannan, D.-W. Kim, E ec i e supp ession o dend i ic
li hium g ow h using an ul a hin coa ing o ni ogen and sul u codoped
g aphene nanoshee s on polyme sepa a o o li hium me al ba e ies, ACS
Appl. Ma e . In e aces 7 (2015) 23700e23707, h ps://doi.o g/10.1021/
acsami.5b07730.
[33] J. Jind a, J. M ha, M. Musilo 
a, Zinc-ai cell wi h neu al elec oly e, J. Appl.
Elec ochem. 3 (1973) 297e301, h ps://doi.o g/10.1007/BF00613036.
[34] F.W. Thomas Goh, Z. Liu, T.S.A. Ho , J. Zhang, X. Ge, Y. Zong, A. Yu, W. Khoo,
A nea -neu al chlo ide elec oly e o elec ically echa geable zinc-ai
ba e ies, J. Elec ochem. Soc. 161 (2014) A2080eA2086, h ps://doi.o g/
10.1149/2.0311414jes.
[35] A. Sumboja, X. Ge, G. Zheng, F.W.T. Goh, T.S.A. Ho , Y. Zong, Z. Liu, Du able
echa geable zinc-ai ba e ies wi h neu al elec oly e and manganese oxide
ca alys , J. Powe Sou ces 332 (2016) 330e336, h ps://doi.o g/10.1016/
j.jpowsou .2016.09.142.
[36] A. Kube, N. Wagne , K.A. F ied ich, Inﬂuence o o ganic addi i es o zinc-ai
ba e ies on ca hode s abili y and pe o mance, J. Elec ochem. Soc. 168
(2021), 050531, h ps://doi.o g/10.1149/1945-7111/ab 63.
[37] S. Cla k, A.R. Maina , E. I uin, L.C. Colmena es, J.A. Bl
azquez, J.R. Tolcha d,
Z. Jusys, B. Ho s mann, Designing aqueous o ganic elec oly es o zinceai
ba e ies: me hod, simula ion, and alida ion, Ad . Ene gy Ma e . 10
(2020), 1903470, h ps://doi.o g/10.1002/aenm.201903470.
[38] C.-X. Zhao, J.-N. Liu, J. Wang, D. Ren, B.-Q. Li, Q. Zhang, Recen ad ances o
noble-me al- ee bi unc ional oxygen educ ion and e olu ion elec o-
ca alys s, Chem. Soc. Re . 50 (2021) 7745e7778.
[39] C. L , Y. Zhu, W. Zhang, W. Xu, J. Ren, H. Liu, X. Yang, R. Cai, S. Jin, D. Li,
D. Yang, In e acial enhancemen o O*p o ona ion on Fe
2
N/Fe
3
C nano-
pa icles o boos oxygen educ ion eac ion and he uel cell in acidic
elec oly e, Ma e . Today Ene gy 21 (2021), 100834, h ps://doi.o g/10.1016/
j.m ene .2021.100834.
[40] Y. Wu, S. Naga a, Y. Nabae, Genuine ou -elec on oxygen educ ion o e
p ecious-me al- ee ca alys in alkaline media, Elec ochim. Ac a 319 (2019)
382e389, h ps://doi.o g/10.1016/j.elec ac a.2019.06.174.
[41] S.S. Shinde, C.H. Lee, J.-Y. Jung, N.K. Wagh, S.-H. Kim, D.-H. Kim, C. Lin,
S.U. Lee, J.-H. Lee, Un eiling dual-linkage 3D hexaiminobenzene
me aleo ganic amewo ks owa ds long-las ing ad anced e e sible Zneai
ba e ies, Ene gy En i on. Sci. 12 (2019) 727e738, h ps://doi.o g/10.1039/
C8EE02679C.
[42] A. Kundu, A. Saman a, C.R. Raj, Hie a chical hollow MOF-de i ed bamboo-
like N-doped ca bon nano ube-encapsula ed Co
0.25
Ni
0.75
alloy: an e ﬁcien
bi unc ional oxygen elec oca alys o zinceai ba e y, ACS Appl. Ma e .
In e aces 13 (2021) 30486e30496, h ps://doi.o g/10.1021/acsami.1c01875.
[43] J. Xu, Y. Xu, C. Lai, T. Xia, B. Zhang, X. Zhou, Challenges and pe spec i es o
co alen o ganic amewo ks o ad anced alkali-me al ion ba e ies, Sci.
China Chem. 64 (2021) 1267e1282.
[44] Y. Zhang, R.-L. Zhong, M. Lu, J.-H. Wang, C. Jiang, G.-K. Gao, L.-Z. Dong,
Y. Chen, S.-L. Li, Y.-Q. Lan, Single me al si e and e sa ile ans e channel
me ged in o co alen o ganic amewo ks acili a e high-pe o mance Li-CO
2
ba e ies, ACS Cen . Sci. 7 (2021) 175e182, h ps://doi.o g/10.1021/
acscen sci.0c01390.
[45] J. Cao, H. Gong, L. Xie, Y. Li, N. Zhang, W. Tian, R. Zhang, J. Zhou, T. Wang,
Y. Zhai, N. Li, M. Luo, K. Liang, P. Chen, B. Kong, Supe -assembled ca bon
nanoﬁbe s deco a ed wi h dual ca aly ically ac i e si es as bi unc ional ox-
ygen ca alys s o echa geable Zn-ai ba e ies, Ma e . Today Ene gy 20
(2021), 100682, h ps://doi.o g/10.1016/j.m ene .2021.100682.
[46] A.R. Maina , E. I uin, L.C. Colmena es, A. K asha, I. de Mea za, M. Bengoechea,
O. Leone , I. Boyano, Z. Zhang, J.A. Blazquez, An o e iew o p og ess in
elec oly es o seconda y zinc-ai ba e ies and o he s o age sys ems based
on zinc, J. Ene gy S o age 15 (2018) 304e328, h ps://doi.o g/10.1016/
j.es .2017.12.004.
[47] C.-S. Yang, K.-N. Gao, X.-P. Zhang, Z. Sun, T. Zhang, Recha geable solid-s a e
Li-ai ba e ies: a s a us epo , Ra e Me . 37 (2018) 459e472.
[48] J. Zhang, Q. Zhou, Y. Tang, L. Zhang, Y. Li, Zinceai ba e ies: a e hey eady
o p ime ime? Chem. Sci. 10 (2019) 8924e8929, h ps://doi.o g/10.1039/
C9SC04221K.
[49] S.P. Pen eado, R.F. Ben o, Pe o mance analysis o en b ands o ba e ies o
hea ing aids, In . A ch. O o hinola yngol. 17 (2013) 291e304.
[50] Z. Liu, S.Z. El Abedin, F. End es, Elec odeposi ion o zinc ﬁlms om ionic
liquids and ionic liquid/wa e mix u es, Elec ochim. Ac a 89 (2013)
635e643, h ps://doi.o g/10.1016/j.elec ac a.2012.11.077.
[51] F. Ilyas, M. Ishaq, M. Jabeen, M. Saeed, A. Ihsan, M. Ahmed, Recen ends in
he benign-by-design elec oly es o zinc ba e ies, J. Mol. Liq. 343 (2021),
117606, h ps://doi.o g/10.1016/j.molliq.2021.117606.
[52] C. Wang, J. Li, Z. Zhou, Y. Pan, Z. Yu, Z. Pei, S. Zhao, L. Wei, Y. Chen,
Recha geable zinc-ai ba e ies wi h neu al elec oly es: ecen ad ances,
challenges, and p ospec s, Ene gyChem 3 (2021), 100055, h ps://doi.o g/
10.1016/j.enchem.2021.100055.
[53] X. Zhao, X. Liang, Y. Li, Q. Chen, M. Chen, Challenges and design s a egies o
high pe o mance aqueous zinc ion ba e ies, Ene gy S o age Ma e . 42
(2021) 533e569, h ps://doi.o g/10.1016/j.ensm.2021.07.044.
[54] R. Buckingham, T. Asse , P. A anasso , Aluminum-ai ba e ies: a e iew o
alloys, elec oly es and design, J. Powe Sou ces 498 (2021), 229762, h ps://
doi.o g/10.1016/j.jpowsou .2021.229762.
[55] R.D. McKe ache , C. Ponce de Leon, R.G.A. Wills, A.A. Shah, F.C. Walsh,
A e iew o he i oneai seconda y ba e y o ene gy s o age, Chem-
pluschem 80 (2015) 323e335, h ps://doi.o g/10.1002/cplu.201402238.
[56] W.K. Tan, G. Kawamu a, H. Mu o, A. Ma suda, Chap e 3 - Cu en P og ess in
he De elopmen o Fe-Ai Ba e ies and hei P ospec s o Nex -Gene a ion
Ba e ies, Else ie , 2021, pp. 59e83, h ps://doi.o g/10.1016/B978-0-12-
820628-7.00003-4.
[57] L. Li, H. Chen, E. He, L. Wang, T. Ye, J. Lu, Y. Jiao, J. Wang, R. Gao, H. Peng,
Y. Zhang, High-ene gy-densi y magnesium-ai ba e y based on dual-laye
gel elec oly e, Angew. Chem. In . Ed. 60 (2021) 15317e15322, h ps://
doi.o g/10.1002/anie.202104536.
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
24
[58] T.Zhang, Z.Tao,J.Chen,Magnesiumeai ba e ies: omp inciple oapplica ion,
Ma e . Ho iz. 1 (2014) 196e206, h ps://doi.o g/10.1039/C3MH00059A.
[59] J.-S. Lee, S. Tai Kim, R. Cao, N.-S. Choi, M. Liu, K.T. Lee, J. Cho, Me aleai
ba e ies wi h high ene gy densi y: Lieai e sus Zneai , Ad . Ene gy Ma e .
1 (2011) 34e50, h ps://doi.o g/10.1002/aenm.201000010.
[60] L. Liu, H. Guo, L. Fu, S. Chou, S. Thiele, Y. Wu, J. Wang, C i ical ad ances in
ambien ai ope a ion o nonaqueous echa geable Lieai ba e ies, Small 17
(2021), 1903854, h ps://doi.o g/10.1002/smll.201903854.
[61] K. Chen, G. Huang, X.-B. Zhang, E o s owa ds p ac ical and sus ainable Li/
Na-ai ba e ies, Chin. J. Chem. 39 (2021) 32e42, h ps://doi.o g/10.1002/
cjoc.202000408.
[62] X. Bi, R. Wang, Y. Yuan, D. Zhang, T. Zhang, L. Ma, T. Wu, R. Shahbazian-
Yassa , K. Amine, J. Lu, F om sodiumeoxygen o sodiumeai ba e y: enabled
by sodium pe oxide dihyd a e, Nano Le . 20 (2020) 4681e4686, h ps://
doi.o g/10.1021/acs.nanole .0c01670.
[63] W. Wang, Y.-C. Lu, The po assiumeai ba e y: a om a p ac ical eali y?
Accoun s Ma e . Res. 2 (2021) 515e525, h ps://doi.o g/10.1021/accoun s
m .1c00061.
[64] Y.-T. Lu, A.R. Neale, C.-C. Hu, L.J. Ha dwick, Di alen nonaqueous me al-ai
ba e ies, F on . Ene gy Res. 8 (2021) 357, h ps://doi.o g/10.3389/
en g.2020.602918.
[65] P. Chen, K. Zhang, D. Tang, W. Liu, F. Meng, Q. Huang, J. Liu, Recen p og ess
in elec oly es o Zneai ba e ies, F on . Chem. 8 (2020) 372, h ps://
doi.o g/10.3389/ chem.2020.00372.
[66] M. He, P. Zhang, L. Liu, B. Liu, S. Xu, Hie a chical po ous ni ogen doped
h ee-dimensional g aphene as a ee-s anding ca hode o echa geable
li hium-oxygen ba e ies, Elec ochim. Ac a 191 (2016) 90e97, h ps://
doi.o g/10.1016/j.elec ac a.2016.01.026.
[67] T. Ogasawa a, A. D
eba , M. Holzap el, P. No 
ak, P.G. B uce, Recha geable
Li
2
O
2
elec ode o li hium ba e ies, J. Am. Chem. Soc. 128 (2006)
1390e1393, h ps://doi.o g/10.1021/ja056811q.
[68] H.-W. Kim, J.-M. Lim, H.-J. Lee, S.-W. Eom, Y.T. Hong, S.-Y. Lee, A iﬁcially
enginee ed, bicon inuous anion-conduc ing/- epelling polyme ic phases as a
selec i e ion anspo channel o echa geable zinceai ba e y sepa a o
memb anes, J. Ma e . Chem. A. 4 (2016) 3711e3720, h ps://doi.o g/10.1039/
C5TA09576J.
[69] K.M. Ab aham, Z. Jiang, A polyme elec oly e-based echa geable li hium/
oxygen ba e y, J. Elec ochem. Soc. 143 (1996) 1e5, h ps://doi.o g/10.1149/
1.1836378.
[70] T. Kawamu a, S. Okada, J. Yamaki, Decomposi ion eac ion o LiPF
6
-based
elec oly es o li hium ion cells, J. Powe Sou ces 156 (2006) 547e554,
h ps://doi.o g/10.1016/j.jpowsou .2005.05.084.
[71] C.V. Amanchukwu, J.R. Ha ding, Y. Shao-Ho n, P.T. Hammond, Unde s anding
he chemical s abili y o polyme s o li hiumeai ba e ies, Chem. Ma e . 27
(2015) 550e561, h ps://doi.o g/10.1021/cm5040003.
[72] B.G. Kim, J.-S. Kim, J. Min, Y.-H. Lee, J.H. Choi, M.C. Jang, S.A. F eunbe ge ,
J.W. Choi, A mois u e- and oxygen-impe meable sepa a o o ap o ic Li-O
2
ba e ies, Ad . Func . Ma e . 26 (2016) 1747e1756, h ps://doi.o g/10.1002/
ad m.201504437.
[73] W.C. Tan, L.H. Saw, M.C. Yew, D. Sun, Z. Cai, W.T. Chong, P.-Y. Kuo, Analysis o
he polyp opylene-based aluminium-ai ba e y, F on . Ene gy Res. 9 (2021)
32, h ps://doi.o g/10.3389/ en g.2021.599846.
[74] G.M. Wu, S.J. Lin, J.H. You, C.C. Yang, S udy o high-anionic conduc ing sul-
ona ed mic opo ous memb anes o zinc-ai elec ochemical cells, Ma e .
Chem. Phys. 112 (2008) 798e804, h ps://doi.o g/10.1016/j.ma chemphys.
2008.06.058.
[75] H.J. Hwang, W.S. Chi, O. Kwon, J.G. Lee, J.H. Kim, Y.-G. Shul, Selec i e ion
anspo ing polyme ized ionic liquid memb ane sepa a o o enhancing
cycle s abili y and du abili y in seconda y zinceai ba e y sys ems, ACS
Appl. Ma e . In e aces 8 (2016) 26298e26308, h ps://doi.o g/10.1021/
acsami.6b07841.
[76] L.-L. Shen, G.-R. Zhang, M. Biesalski, B.J.M. E zold, Pape -based mic oﬂuidic
aluminumeai ba e ies: owa d nex -gene a ion minia u ized powe sup-
ply, Lab Chip 19 (2019) 3438e3447, h ps://doi.o g/10.1039/C9LC00574A.
[77] E. Lizundia, C.M. Cos a, R. Al es, S. Lance os-M
endez, Cellulose and i s de-
i a i es o li hium ion ba e y sepa a o s: a e iew on he p ocessing
me hods and p ope ies, Ca bohyd . Polym. Technol. Appl. 1 (2020), 100001,
h ps://doi.o g/10.1016/j.ca p a.2020.100001.
[78] P. Ka souﬁs, M. Ka sai i, C. Mou elas, T.S. And ade, V. D acopoulos, C. Poli is,
G. A gou opoulos, P. Lianos, S udy o a hin ﬁlm aluminum-ai ba e y, En-
e gies 13 (2020), h ps://doi.o g/10.3390/en13061447.
[79] E. Lizundia, D. Kundu, Ad ances in na u al biopolyme -based elec oly es
and sepa a o s o ba e y applica ions, Ad . Func . Ma e . 31 (2021),
2005646, h ps://doi.o g/10.1002/ad m.202005646.
[80] W. Xie, W. Liu, Y. Dang, A. Tang, T. Deng, W. Qiu, In es iga ion on elec oly e-
imme sed p ope ies o li hium-ion ba e y cellulose sepa a o h ough
mul i-scale me hod, J. Powe Sou ces 417 (2019) 150e158, h ps://doi.o g/
10.1016/j.jpowsou .2019.02.002.
[81] D.E. Tu ney, J.W. Gallaway, G.G. Yada , R. Rami ez, M. Nyce, S. Bane jee,
Y.K. Chen-Wiega , J. Wang, M.J. D'Amb ose, S. Kolheka , J. Huang, X. Wei,
Recha geable zinc alkaline anodes o long-cycle ene gy s o age, Chem. Ma e .
29 (2017) 4819e4832, h ps://doi.o g/10.1021/acs.chemma e .7b00754.
[82] J. Liu, D. Wang, D. Zhang, L. Gao, T. Lin, Syne gis ic e ec s o ca boxyme hyl
cellulose and ZnO as alkaline elec oly e addi i es o aluminium anodes
wi h a iew owa ds Al-ai ba e ies, J. Powe Sou ces 335 (2016) 1e11,
h ps://doi.o g/10.1016/j.jpowsou .2016.09.060.
[83] Y. Qiao, Y. He, S. Wu, K. Jiang, X. Li, S. Guo, P. He, H. Zhou, MOF-based
sepa a o in an LieO
2
ba e y: an e ec i e s a egy o es ain he shu ling
o dual edox media o s, ACS Ene gy Le . 3 (2018) 463e468, h ps://doi.o g/
10.1021/acsene gyle .8b00014.
[84] N. Togasaki, R. Shibamu a, T. Na use, T. Momma, T. Osaka, P e en ion o
edox shu le using elec opolyme ized polypy ole ﬁlm in a
li hiumeoxygen ba e y, APL Ma e . 6 (2018), 47704, h ps://doi.o g/
10.1063/1.5011135.
[85] L. Puech, C. Can au, P. Vina ie , G. Toussain , P. S e ens, Elabo a ion and
cha ac e iza ion o a ee s anding LiSICON memb ane o aqueous
li hiumeai ba e y, J. Powe Sou ces 214 (2012) 330e336, h ps://doi.o g/
10.1016/j.jpowsou .2012.04.064.
[86] S.H. Pa k, T.H. Lee, Y.J. Lee, H.B. Pa k, Y.J. Lee, G aphene oxide sie ing
memb ane o imp o ed cycle li e in high-e ﬁciency edox-media ed LieO
2
ba e ies, Small 14 (2018), 1801456, h ps://doi.o g/10.1002/smll.
201801456.
[87] H. Sapu a, R. O hman, A.G.E. Su jip o, R. Muhida, MCM-41 as a new sepa-
a o ma e ial o elec ochemical cell: applica ion in zinceai sys em,
J. Memb . Sci. 367 (2011) 152e157, h ps://doi.o g/10.1016/j.memsci.
2010.10.061.
[88] Jody Klaassen, Li hium/ai Ba e ies wi h LiPON as Sepa a o and P o ec i e
Ba ie and Me hod, US20050095506A1, 2005.
[89] S. Huang, P. Pei, Z. Wang, Anode co osion o Zn-ai uel cell: mechanism and
p o ec ion, J. Elec ochem. Soc. 167 (2020), 90538.
[90] L. Yang, Y. Wu, S. Chen, Y. Xiao, S. Chen, P. Zheng, J. Wang, J.-E. Qu,
A p omising hyb id addi i e o enhancing he pe o mance o alkaline
aluminum-ai ba e ies, Ma e . Chem. Phys. 257 (2021), 123787, h ps://
doi.o g/10.1016/j.ma chemphys.2020.123787.
[91] S. Hosseini, Z.-Y. Liu, C.-T. Chuan, S.M. Sol ani, V.V.K. Lanjapalli, Y.-Y. Li, The
ole o SO-g oup-based addi i es in imp o ing he echa geable aluminium-
ai ba e ies, Elec ochim. Ac a 375 (2021), 137995, h ps://doi.o g/10.1016/
j.elec ac a.2021.137995.
[92] T. Phusi ananan, W. Kao-Ian, M.T. Nguyen, T. Yonezawa,
R. Po np ase suk, A.A. Mohamad, S. Kheawhom, E hylene glycol/e hanol
anoly e o high capaci y alkaline aluminum-ai ba e y wi h dual-
elec oly e conﬁgu a ion, F on . Ene gy Res. 8 (2020) 189, h ps://doi.o g/
10.3389/ en g.2020.00189.
[93] D. Snihi o a, L. Wang, S.V. Lamaka, C. Wang, M. Deng, B. Vagheﬁnaza i,
D. H€
oche, M.L. Zheludke ich, Syne gis ic mix u e o elec oly e addi i es: a
ou e o a high-e ﬁciency Mgeai ba e y, J. Phys. Chem. Le . 11 (2020)
8790e8798, h ps://doi.o g/10.1021/acs.jpcle .0c02174.
[94] R.D. McKe ache , H.A. Figue edo-Rod iguez, K. Dimogiannis, C. Aleg e,
N.I. Villanue a-Ma inez, M.J. L
aza o, V. Baglio, A.S. A ic
o, C. Ponce de Leόn,
E ec o 1-oc ane hiol as an elec oly e addi i e on he pe o mance o he
i on-ai ba e y elec odes, J. Solid S a e Elec ochem. 25 (2021) 225e230,
h ps://doi.o g/10.1007/s10008-020-04738-4.
[95] L. Suo, O. Bo odin, T. Gao, M. Olguin, J. Ho, X. Fan, C. Luo, C. Wang, K. Xu,
“Wa e -in-sal ”elec oly e enables high- ol age aqueous li hium-ion
chemis ies, Science 350 (2015), h ps://doi.o g/10.1126/science.aab1595,
938 LP e943.
[96] Y. Zhang, E.J. Maginn, Wa e -in-sal LiTFSI aqueous elec oly es (2): anspo
p ope ies and Liþdynamics based on molecula dynamics simula ions,
J. Phys. Chem. B (2021), h ps://doi.o g/10.1021/acs.jpcb.1c07581.
[97] L. Chen, J. Zhang, Q. Li, J. Va amanu, X. Ji, T.P. Polla d, C. Cui, S. Hou, J. Chen,
C. Yang, L. Ma, M.S. Ding, M. Ga aga, S. G eenbaum, H.-S. Lee, O. Bo odin,
K. Xu, C. Wang, A 63 m supe concen a ed aqueous elec oly e o high-
ene gy Li-ion ba e ies, ACS Ene gy Le . 5 (2020) 968e974, h ps://doi.o g/
10.1021/acsene gyle .0c00348.
[98] L. Suo, O. Bo odin, Y. Wang, X. Rong, W. Sun, X. Fan, S. Xu, M.A. Sch oede ,
A.V. C esce, F. Wang, C. Yang, Y.-S. Hu, K. Xu, C. Wang, “Wa e -in-Sal ”
elec oly e makes aqueous sodium-ion ba e y sa e, g een, and long-las ing,
Ad . Ene gy Ma e . 7 (2017), 1701189, h ps://doi.o g/10.1002/
aenm.201701189.
[99] D. Rebe , R. Figi, R.-S. Kühnel, C. Ba aglia, S abili y o aqueous elec oly es
based on LiFSI and NaFSI, Elec ochim. Ac a 321 (2019), 134644, h ps://
doi.o g/10.1016/j.elec ac a.2019.134644.
[100] D. Rebe , R. G issa, M. Becke , R.-S. Kühnel, C. Ba aglia, Anion selec ion
c i e ia o wa e -in-sal elec oly es, Ad . Ene gy Ma e . 11 (2021),
2002913, h ps://doi.o g/10.1002/aenm.202002913.
[101] J. Hwang, A.N. Si asenga an, H. Yang, H. Yamamo o, T. Takeuchi,
K. Ma sumo o, R. Hagiwa a, Imp o emen o elec ochemical s abili y using
he eu ec ic composi ion o a e na y mol en sal sys em o highly
concen a ed elec oly es o Na-ion ba e ies, ACS Appl. Ma e . In e aces 13
(2021) 2538e2546.
[102] S. Wu, S. Hu, Q. Zhang, D. Sun, P. Wu, Y. Tang, H. Wang, Hyb id high-
concen a ion elec oly e signiﬁcan ly s eng hens he p ac icabili y o
alkaline aluminum-ai ba e y, Ene gy S o age Ma e . 31 (2020) 310e317,
h ps://doi.o g/10.1016/j.ensm.2020.06.024.
[103] T. Zhang, R. Amine, X. Bi, Y. Qin, M. Li, S. Al-Hallaj, F. Huo, J. Lu, K. Amine,
Explo ing he cha ge eac ions in a LieO2 sys em wi h li hium oxide ca h-
odes and nonaqueous elec oly es, J. Ma e . Chem. A. 7 (2019) 15615e15620,
h ps://doi.o g/10.1039/C9TA03763B.
M. Salado and E. Lizundia Ma e ials Today Ene gy 28 (2022) 101064
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