Ca ageenans as Sus ainable Wa e -P ocessable Binde s o High-
Vol age NMC811 Ca hodes
Ana Cla a Rolandi, C is ina Pozo-Gonzalo, I a xe de Mea za, Ne ea Casado, Ma ia Fo sy h,*
and Da id Mece eyes*
Ci e This: ACS Appl. Ene gy Ma e . 2023, 6, 8616−8625
Read Online
ACCESS Me ics & Mo e A icle Recommenda ions *
sı Suppo ing In o ma ion
ABSTRACT: Poly( inylidene luo ide) (PVDF) is he mos
common binde o ca hode elec odes in li hium-ion ba e ies.
Howe e , PVDF is a luo ina ed compound and equi es oxic N-
me hyl-2-py olidone (NMP) as a sol en du ing he slu y
p epa a ion, making he elec ode ab ica ion p ocess en i on-
men ally un iendly. In his s udy, we p opose he use o
ca ageenan biopolyme s as a sus ainable sou ce o wa e -
p ocessable binde s o high- ol age NMC811 ca hodes. Th ee
ypes o ca ageenan (Ca ) biopolyme s we e in es iga ed, wi h
one, wo, o h ee sul ona e g oups (SO3−), namely, kappa, io a,
and lambda ca ageenans, espec i ely. In addi ion o he na u e o
ca ageenans, his a icle also epo s he op imiza ion o he
ca hode o mula ions, which we e p epa ed by using be ween 5 w
% o he binde o a lowe amoun o 2 w %. P ocessing o he aqueous slu ies and he na u e o he binde , in e ms o he
mo phology and elec ochemical pe o mance o he elec odes, we e also in es iga ed. The Ca binde wi h 3SO3−g oups (3SO3−
Ca ) exhibi ed he highes discha ge capaci ies, deli e ing 133.1 mAh g−1a 3C and 105.0 mAh g−1a 5C, which was simila o he
o ganic-based PVDF elec ode (136.1 and 108.7 mAh g−1, espec i ely). Fu he mo e, 3SO3−Ca eached an ou s anding capaci y
e en ion o 91% a e 90 cycles a 0.5C, which was a ibu ed o a homogeneous NMC811 and a conduc i e ca bon pa icle
dispe sion, supe io adhesion s eng h o he cu en collec o (17.3 ±0.7 N m−1 s 0.3 ±0.1 N m−1 o PVDF), and educed
cha ge- ans e esis ance. Pos mo em analysis un eiled good p ese a ion o he NMC811 pa icles, while he 1SO3−Ca and
2SO3−Ca elec odes showed damaged mo phologies.
KEYWORDS: biopolyme , ca ageenans, NMC811 ca hodes, aqueous p ocessing, wa e -soluble binde s, li hium-ion ba e ies
■INTRODUCTION
In o de o ma ch he wo ldwide expansion o elec omobili y
and ene gy s o age om enewable sou ces, massi e esea ch
e o s ha e been unde aken o e he pas ew decades o
de elop a new gene a ion o li hium-ion ba e ies (LIBs). The
goal is o s o e mo e ene gy and ope a e o ex ended pe iods
wi hou deg ading o posing sa e y isks. Despi e he binde
being only a small componen o he ba e y elec ode
s uc u e (app ox. 5 w %),
1
i plays key oles in he ba e y
pe o mance, such as assu ing a good dis ibu ion o ac i e and
conduc i e ma e ials o op imal li hium di usion and
main aining he mechanical in eg i y o he elec ode.
Howe e , o maximize he ba e y capaci y o he ba e y,
he binde con en should be as low as possible (less han 3 w
% o he elec ode) while s ill ul illing he unc ions men ioned
abo e.
2
Un o una ely, he ab ica ion o ca hodes s ill elies on he
use o poly( inylidene luo ide) (PVDF) as a binde . Alongside
he d awback o he luo opolyme disposal once eaching he
end o li e o he cell, PVDF has o be dissol ed in N-me hyl-2-
py olidone (NMP), which is a oxic and e a ogenic sol en ,
3
and equi es ele a ed empe a u es o d ying; none o hose
a e ideal om an en i onmen al pe spec i e. These ac s
u he inc ease he cos o ba e y p ocessing since an
expensi e eco e y sys em is needed o a oid he elease o
NMP in he a mosphe e.
4
The e o e, aqueous elec ode
p ocessing has eme ged as an op imis ic al e na i e o educe
he en i onmen al impac s and ene gy consump ion since
wa e is no oxic and e apo a es a lowe empe a u es han
NMP.
5,6
Fo his eason, many esea che s ha e explo ed wa e -based
binde sys ems o he ab ica ion o ca hodes o LIBs,
7−13
especially biopolyme s, whe e sodium ca boxyme hyl cellulose
Recei ed: July 5, 2023
Accep ed: Augus 2, 2023
Published: Augus 14, 2023
A iclewww.acsaem.o g
© 2023 The Au ho s. Published by
Ame ican Chemical Socie y 8616
h ps://doi.o g/10.1021/acsaem.3c01662
ACS Appl. Ene gy Ma e . 2023, 6, 8616−8625
Downloaded ia UNIV DEL PAIS VASCO on Decembe 22, 2023 a 14:46:47 (UTC).
See h ps://pubs.acs.o g/sha ingguidelines o op ions on how o legi ima ely sha e published a icles.
(Na-CMC) is he mos widely used.
14−16
Biopolyme s a e
appealing al e na i es due o hei na u al a ailabili y,
unabili y, and ela i ely lowe cos compa ed o he widely
used binde , PVDF. Ano he in e es ing biopolyme amily is
ca ageenans, which a e wa e -soluble and linea sul ona ed
polysaccha ides ha ha e been ex ensi ely u ilized in ood and
medical applica ions.
17
Ca ageenans a e comme cially a ail-
able as kappa, io a, and lambda ca ageenans wi h one, wo, o
h ee sul ona e (3SO3−) g oups, espec i ely,
18
being ob ained
om ed seaweeds (Euchema co oni,Chond us c ip us, and
Euchema spisosum). The occu ence o he sul ona e g oups in
ca ageenan is na u al, unlike Na-CMC whe e ca boxylic
g oups a e in oduced by subs i u ion.
8
The ac ha he
sul ona e g oups a e na u ally p esen in he s uc u e may lead
o a mo e uni o m dis ibu ion along he chains, po en ially
p o iding an enhanced o ma ion o pa hways o li hium
anspo .
19
Ca ageenans ha e been s udied as binde s in
li hium−sul u ba e ies (Li−S),
20
showing good s abili y
agains polysul ide dissolu ion in he elec oly e, a majo
issue o Li−S ba e ies ha causes elec ode deg ada ion and
capaci y ading. Sul ona e g oups in ca ageenan binde s a e
able o cap u e he polysul ides, a oiding he high-capaci y
d op and low cycle li e obse ed when PVDF is used as a
binde . Fu he mo e, a ecen s udy applied lambda ca a-
geenan as a binde o silicon anodes,
21
whe e he au ho s
epo ed enhanced adhesion s eng h, li hium-ion di usion,
and elec ochemical pe o mance compa ed wi h o he
common wa e -soluble binde s such as sodium algina e and
Na-CMC. The imp o ed beha io was a ibu ed o he
numbe o sul ona e g oups in he s uc u e o he biopolyme
binde , which e ec i ely accommoda ed he huge olume
changes ha silicon su e s du ing cycling and hus main ained
he mechanical in eg i y o he elec ode.
In his a icle, ca ageenans con aining a di e en numbe o
sul ona e g oups in hei s uc u e a e in es iga ed as binde s
o NMC811 ca hodes. A he ou se , a ypical wa e -based
o mula ion o 90 w % o NMC811, 5 w % o conduc i e
ca bon, and 5 w % o biopolyme binde was explo ed,
compa ing i s pe o mance wi h PVDF and Na-CMC, which
a e p ocessed in NMP and wa e , espec i ely. In e es ingly,
since ca ageenans p o ide high iscosi y o he slu y, he
o mula ion could be op imized down o 2 w % o binde and
consequen ly he p opo ion o ac i e ma e ial in he inal
elec ode inc eased. As men ioned p e iously, his is impo an
om an indus ial pe spec i e o educe cos s. Finally, he
elec ochemical pe o mance o he wa e -based NMC811
ca hodes wi h ca ageenan binde s was es ed using elec odes
wi h a loading o 2.1−2.2 mAh cm−2, assessing he impac o
he numbe o sul ona e g oups in he s uc u e o he
biopolyme .
■EXPERIMENTAL SECTION
Ma e ials: Sou ce and Cha ac e iza ion. LiNi0.8MnCo0.1O2
(NMC811, T81RX, Ta g ay), conduc i e ca bon C-NERGY Supe
C45 (C45, Ime ys), and ca bon-coa ed aluminum cu en collec o
(CC-Al, Gelon) we e used as ecei ed. Th ee ca ageenan
biopolyme s we e s udied: kappa-ca ageenan (1SO3−Ca ), io a-
ca ageenan (2SO3−Ca ), and lambda ca ageenan (3SO3−Ca )
pu chased om Sigma-Ald ich. Fo compa a i e pu poses, poly-
( inylidene luo ide) (PVDF, 534 kDa molecula weigh , Sigma-
Ald ich) was used as a binde wi h 1-me hyl-2-py olidone (NMP,
≥99%, Sigma-Ald ich) as he sol en . As a coun e elec ode, g aphi e
anode was p epa ed o ull cell assessmen : g aphi e (HE3, Hi achi)
was used as ecei ed, and as a binde , a blend o sodium
ca boxyme hyl cellulose (Na-CMC, 250 kDa molecula weigh ,
Sigma-Ald ich) and s y ene bu adiene ubbe (SBR, BM451B,
Zeon) was employed. All o he ma e ials we e used as ecei ed.
The he mal s abili y o he ca ageenan biopolyme s was assessed
by he mog a ime ic analysis (TGA) using a Q500 analyze (TA
ins umen s) unde a ni ogen a mosphe e a a a e o 10 °C min−1
om 25 o 800 °C. Also, he elec ochemical s abili y o he
ca ageenans was s udied by cyclic ol amme y (CV) in he po en ial
ange o 2.0−4.5 V s Li/Li+a a scan a e o 0.1 mV s−1, using a
VMP-3 Biologic Ins umen . Fo his, coin cells we e assembled using
li hium oil as he coun e and e e ence elec odes, which we e
p epa ed ollowing he p ocedu e desc ibed in he Ca hode Elec ode:
P epa a ion and Cha ac e iza ion sec ion. The wo king elec ode
composi ion was 50 w % o ca ageenans and 50 w % o conduc i e
ca bon and was ee o ac i e ma e ial o check o any edox eac ions
occu ing in he binde .
Ca hode Elec ode: P epa a ion and Cha ac e iza ion.
Ca hode slu ies o 50 g o solids we e p epa ed using wa e o
NMP as he sol en , depending on he binde (ca ageenans/Na-
CMC o PVDF, espec i ely). Fi s , he binde was dissol ed in he
sol en and hen he conduc i e and ac i e ma e ial we e mixed o 4
h in a mechanical blade mixe a 700 pm. The inal solid- o-liquid
a io was be ween 1 and 0.9 in all cases (53% solid con en ).
As men ioned in he In oduc ion sec ion, apa om explo ing
di e en binde s, he o mula ion o he ca hode was a ied. As
ou lined in Table 1, he ela i e amoun o binde was dec eased,
while he ac i e ma e ial inc eased. The p opo ion o conduc i e
ca bon was kep equal o all o mula ions o a oid u he a iables
unde analysis. In he case o he g aphi e anode, a single composi ion
was employed (94 w % g aphi e, 2 w % conduc i e ca bon, 2 w %
Na-CMC, and 2 w % SBR la ex).
Figu e 1. Simpli ied scheme o he aqueous p ocessing o ca hodes o li hium-ion ba e ies.
Table 1. Di e en Ca hode Fo mula ions Explo ed in he
P esen S udy
5 w %
binde 2 w %
binde 1 w %
binde
ac i e ma e ial�NMC811 (w
%) 90 93 94
conduc i e ca bon�CB (w %) 5 5 5
binde (w %) 5 2 1
ACS Applied Ene gy Ma e ials www.acsaem.o g A icle
h ps://doi.o g/10.1021/acsaem.3c01662
ACS Appl. Ene gy Ma e . 2023, 6, 8616−8625
8617
Be o e cas ing, he inal slu ies we e subjec ed o heology es s
using a heome e AR 200ex (TA ins umen s) in pa allel pla e
geome y, wi h a 40 mm diame e and a 1 mm gap se ing. The
dynamic heological measu emen s we e pe o med a 25 °C o e a
shea a e ange o 0.1−1000 s−1. Then, he slu ies we e coa ed on a
ca bon-coa ed cu en collec o wi h a doc o -blade echnique a 120
mm min−1. The hickness was a ied o ob ain a loading o 12−13 mg
cm−2(2.1−2.2 mAh cm−2). A e d ying he elec odes in a
con ec ion o en a 60 °C, hey we e compac ed using a oll-p ess
(DMP solu ions) un il a po osi y o 40% was ob ained. The loading o
he anodes was balanced o assemble ull cells wi h a nega i e- o-
posi i e capaci y a io (N/P) o 1.1 (mass loading o anodes 13.2−
14.3 mg/cm−2).
Peel es s we e pe o med wi h he calenda ed elec odes o
compa e he adhesion s eng h be ween di e en binde s and
composi ions. Fo his, elec ode s ips o 2 cm ×9 cm we e s uck
on o me hac yla e pla es wi h a no malized o ced and pulled a a 90°
angle. The s eng h alue (N m−1) is ob ained by ca ying ou he peel
es in ambien condi ion a a c osshead speed o 20 mm min−1.
Coin Cells: P epa a ion and Elec ochemical Cha ac e -
iza ion. Ca hode and anode disks o 16.6 mm and 17.7 mm,
espec i ely, we e d ied a 120 °C o 16 h unde acuum. The
CR2025 cell co e s we e washed wi h e hanol in an ul asonic ba h
o 15 min and hen d ied o 1 h a 60 °C. The coin cells we e
subsequen ly assembled in a d y oom (−40 °C dew poin ) using he
NMC811 ca hodes and g aphi e anodes. As he elec oly e, 100 μL o
1 mol L−1li hium hexa luo ophospha e in (1:1 ol %) e hylene
ca bona e:dime hyl ca bona e + 2% inylene ca bona e −99.9% (1 M
LiPF6in EC:DMC + 2% VC (1:1)) was used. The sepa a o s we e
glass ibe ype (Wha man GF/A) ha had been d ied a 60 °C o 1
h.
Using a BaSyTec CTS ba e y es sys em, gal anos a ic cha ging
and discha ging cycles we e pe o med on he NMC811|g aphi e coin
cells in he ange o 2.8−4.3 V. A e 8 h a open ci cui po en ial, a
i s cycle o o ma ion a 0.1C was ca ied ou and hen he
elec ochemical esponse was e alua ed a a ious C- a es pe o ming
3 cycles a 0.5, 1, 2, 3, and 5C. Finally, a long- e m cycling o 90 cycles
a 0.5C was pe o med. The supplie -p o ided heo e ical capaci y o
he NMC811 ac i e ma e ial (200 mAh g−1) was used o de e mine
he C- a e.
Wi h a ol age ampli ude o 10 mV and a equency ange o 1
mHz o 1 MHz, elec ochemical impedance spec oscopy (EIS)
measu emen s we e ca ied ou wi h a VMP-3 po en ios a (Biologic
Science Ins umen ). The EIS was ca ied ou bo h a e he i s
o ma ion cycle (p is ine) and a e he long- e m cycling (aged) o
he ull coin cells (NMC811 ca hode and g aphi e anodes).
Fu he mo e, he EIS esul s allow us o de i e he Wa bu g ac o
(σ) by plo ing he eal pa o he o al impedance (Z′) agains he
in e se o squa e oo o he angula eloci y (ω−0.5), ollowing he
Randles eq 1
22
Z R R
e con ac
0.5
= + +
(1)
F om he Wa bu g ac o , he li hium-ion di usion can be ound by
he A henius eq 2
Figu e 2. (a) Pic u es o he 5 w % ca ageenan in wa e samples and hei chemical s uc u es, showing he di e en numbe o sul ona e g oups
pe epea ing uni o he 1SO3−,2SO3−and 3SO3−Ca ; (b) he mog a ime ic analysis (TGA) o he ca ageenan biopolyme s; and (c) cyclic
ol amme y o he po en ial window o he ca ageenan binde s. The wo king elec ode is composed o 50 w % o ca ageenans and 50 w % o
conduc i e ca bon, using li hium as he coun e and e e ence elec odes (0.1 m s−1be ween 2.0 and 4.5 V s Li/Li+a oom empe a u e).
ACS Applied Ene gy Ma e ials www.acsaem.o g A icle
h ps://doi.o g/10.1021/acsaem.3c01662
ACS Appl. Ene gy Ma e . 2023, 6, 8616−8625
8618
DR T
A F C2
Li
2 2
2 4 2 2
=
+
(2)
whe e Ris he gas cons an (8.314 J K−1mol−1), T is he absolu e
empe a u e, Ais he su ace a ea o he elec ode, Fis he Fa aday
cons an (96,500 C mol−1), and Cis he mola concen a ion o
li hium ions. Since he ac i e ma e ial is no en i ely uni o m and he
elec ode con ains oids and po es, bo h Aand Ca e complex ac o s.
Fo his s udy, cons an alues o A(2.16 cm2) and C(1 mol cm−3)
a e assumed and he esul s o DLi+will be compa ed quali a i ely.
Mic os uc u al Cha ac e iza ion. The coin cells we e dis-
assembled inside a glo ebox a e he gal anos a ic cycling, and he
ca hodes we e hen washed wi h dime hyl ca bona e (DMC) o ge
id o any esidual sal s on he su ace. Th ough he use o a ield
emission scanning elec on mic oscope (FESEM, ULTRA plus
ZEISS), he componen dis ibu ion in bo h p is ine and aged
elec odes was obse ed.
■RESULTS AND DISCUSSION
In his wo k, h ee ca ageenan biopolyme s wi h a di e en
numbe o sul ona e g oups in hei s uc u e, namely, kappa-
ca ageenan (1SO3−Ca ), io a-ca ageenan (2SO3−Ca ),
and lambda ca ageenan (3SO3−Ca ), we e in es iga ed as
aqueous binde s o NMC811 ca hodes. The i s s ep o he
elec ode ab ica ion (Figu e 1) is he slu y p epa a ion, whe e
a mechanical mixe is used o o m a homogeneous slu y. In
compa ison o he con en ional o ganic sys em, aqueous
ca hode p ocessing is a mo e en i onmen ally iendly and
cos -e ec i e p ocess. Du ing he coa ing and d ying s eps,
using wa e as he sol en would subs an ially educe he
ope a ion cos s, compa ed wi h he cos s associa ed wi h he
use o NMP as he sol en . This is mainly due o he
equi emen s o a en ila ion and eco e y sys em when using
NMP, which includes condensa ion and/o dis illa ion o
NMP o a oid i s dispe sion in he a mosphe e. Besides, wa e
is a much cheape sol en han NMP and has a as e a e o
e apo a ion, educing he empe a u e o he d ying s ep and
he e o e i s cos .
23
As explained in he Expe imen al Sec ion, he i s s ep o he
slu y p epa a ion p ocedu e is o dissol e he binde in he
app op ia e sol en . The e o e, he h ee ypes o ca ageenans
(1, 2, o 3SO3−g oups) we e dissol ed in wa e un il a
concen a ion o 5 w % was ob ained (Figu e 2a). The
cha ac e is ics o he solu ions a ied, wi h he solu ions
p epa ed wi h 1SO3−and 2SO3−Ca o ming a dense mix u e,
while he one wi h 3SO3−Ca was less iscous and able o
low. The 3SO3−Ca p esen s mo e sul ona e g oups pe uni
and, he e o e, la ge nega i e cha ge. The e o e, o compen-
sa e hem, i may ha e a la ge in e ac ion wi h wa e han he
o he wo and a e mo e p one o o m helix s uc u es.
Be o e es ing he ca ageenans as binde s, wo impo an
pa ame e s needed o be assessed, namely, he he mal and
elec ochemical s abili y. Fo his, he mal g a ime ic analysis
(TGA) was pe o med, and he co esponding p o iles a e
shown in Figu e 2b. The i s weigh loss o a ound 10−13 w
% a low empe a u e (below 100 °C) is a ibu ed o he
deso p ion o wa e om he polysaccha ide s uc u e,
24,25
and
his was mo e p onounced o he 3SO3−Ca in acco dance
wi h i s highe wa e up ake. The onse o he decomposi ion
s a ed a 189 °C o 1SO3−Ca and a ound 240 °C o he
2SO3−Ca and 3SO3−Ca biopolyme s. The e o e, he TGA
esul s p o ed ha all biopolyme s a e he mally s able a he
elec ode p ocessing empe a u e (d ying a 120 °C).
Figu e 3. (a) Images o elec odes p epa ed wi h he slu ies con aining he di e en ca ageenan biopolyme s wi h 1, 2, and 3SO3−g oups pe
epea ing uni ; (b) heology esul s o he binde slu ies s PVDF, showing he iscosi y as a unc ion o shea a e (0.1 and 200 s−1) a 25 °C; and
(c) peel es s o elec odes coa ed om he di e en binde slu ies. All samples om he slu ies p epa ed wi h he 2 w % binde o mula ions.
ACS Applied Ene gy Ma e ials www.acsaem.o g A icle
h ps://doi.o g/10.1021/acsaem.3c01662
ACS Appl. Ene gy Ma e . 2023, 6, 8616−8625
8619
Mo eo e , Figu e 2c shows he cyclic ol amme y (CV)
da a o he cells assembled wi h a wo king elec ode made o
binde and conduc i e ca bon (wi hou NMC811), wi h
li hium oil as he coun e and e e ence elec odes. Fi e
consecu i e scans we e pe o med o each binde , be ween 2.0
and 4.5 V s Li/Li+, o check hei elec ochemical s abili y in
he ol age ange used o cycling. No signi ican di e ences
we e obse ed be ween he 1s and 5 h cycles, demons a ing
he elec ochemical s abili y o he binde s upon cycling.
Howe e , we no iced ha he 1SO3−Ca and 2SO3−Ca
biopolyme s exhibi ed a mo e p onounced oxida ion peak a
4.5 V s Li/Li+ han he 3SO3−Ca . Al hough he no malized
cu en alues a e small, 3SO3−Ca may be mo e elec o-
chemically s able han he o he wo ca ageenan biopolyme s.
A e ha , 5 w % o binde slu ies was p epa ed (Table 1),
which is he ypical elec ode o mula ion used in lab scale
expe imen s. The inal slu ies a e shown in Figu e S1. As
expec ed, he consis ency o he binde s a ec ed he
heological p ope ies o he elec ode slu ies. In ac , he 5
w % 1SO3−Ca - and 2SO3−Ca -based slu ies could no be
used o coa ings since hey we e oo dense o low o e he
cu en collec o . The e o e, o mula ions wi h 2 w % o
binde we e p epa ed, e ec i ely inc easing he ac i e ma e ial
con en o 93 w % o NMC811. This app oach is p e e able
since maximiza ion o he amoun o ac i e ma e ial in he
o mula ion is one o he main goals o he ba e y
op imiza ion and manu ac u ing p ocess. Following he same
p ocedu e o he elec ode p epa a ion as desc ibed abo e,
coa ings wi h each o he 2 w % o ca ageenan binde slu ies
we e success ully coa ed on o he cu en collec o (Figu e 3a),
excep o he 2 w % o Na-CMC, which led o a slu y wi h
agg ega es and i was disca ded o lack o p ocessabili y. Also,
he inal elec ode coa ed wi h he slu y con aining 1SO3−
Ca appea ed inhomogeneous, while he o he wo (2SO3−
Ca and 3SO3−Ca ) ga e imp o ed coa ing p ope ies in
e ms o homogenei y and dispe sion o ac i e ma e ial and
conduc i e ca bon in he slu y. In he case o he 1SO3−Ca
binde , only a eas showing uni o m coa ing we e selec ed o
es ing. Following he same p ocedu e, 1 w % o binde
o mula ion o ca hodes was p epa ed (Table 1). Un o u-
na ely, he slu ies wi h only 1 w % o polyme binde we e
unable o dispe se he ac i e and conduc i e ma e ial pa icles,
gene a ing agglome a es in he coa ing (Figu e S2). Liu e al.
26
explained ha when he binde con en is oo low, he e is
insu icien polyme o o m a ully s able laye on he pa icle
su ace, causing agglome a ion and sedimen a ion, as obse ed
Figu e 4. (a) Gal anos a ic cycling o ull coin cells p epa ed om he 2 w % binde ca hode o mula ion (loading 2.1 mAh cm−2) using di e en
binde s; ol age p o iles a (b) 5C, cycle 15 and (C) 0.5C, cycle 80. Po en ial ange: 2.8−4.3 V a 25 °C.
ACS Applied Ene gy Ma e ials www.acsaem.o g A icle
h ps://doi.o g/10.1021/acsaem.3c01662
ACS Appl. Ene gy Ma e . 2023, 6, 8616−8625
8620
in he slu ies wi h 1 w % o binde ca hodes. The
epe cussions will be ha li hium conduc i i y will be hinde ed
and he elec ochemical pe o mance diminished. As a
conclusion, we es ablished ha in he p esen wo k, 2 w %
o binde is he op imal o mula ion since i is he minimum
amoun ha can be applied while s ill assu ing he mechanical
and dispe sion p ope ies.
Figu e 3b shows he heology esul s o he 2 w % binde
slu ies. As isually obse ed in Figu e 2a, he solu ions o
1SO3−Ca and 2SO3−Ca polyme s in wa e a 5 w % a e
mo e dense han he 3SO3−Ca dissolu ion. This beha io
had a clea impac on he heological p ope ies o he slu ies
since he 1SO3−Ca - and 2SO3−Ca -based slu ies
mani es ed highe iscosi ies a all shea a es. Fu he mo e,
hese wo slu ies p esen ed mo e shea - hinning beha io ,
whe e he iscosi y a ies no iceably wi h he shea a e. In
con as , PVDF and 3SO3−Ca su e ed a huge d op in
iscosi y a low shea a es and hen he iscosi y was ela i ely
cons an as he shea a e inc eased.
A e d ying and calenda ing he elec odes, peel es s we e
pe o med o e alua e he e ec o he sul ona e g oups on he
adhesion s eng h o he coa ings o he cu en collec o .
Figu e 3c depic s he o ce (N) as a unc ion o he dis ance
(mm). To calcula e he adhesion s eng h (N m−1), an a e age
o he o ce alues is conside ed. The da a indica e ha he
adhesion s eng h o all o he coa ings con aining he 2 w %
binde was g ea e han he e e ence PVDF binde elec ode
(0.3 ±0.1 N m−1) and, he e o e, he coa ing de ached om
he cu en collec o as obse ed in Figu e 3c. As a
compa ison, he peel s eng h o he 5 w % PVDF binde
was measu ed (8.6 ±0.9 N m−1) and he coa ing did no
de ach. Hence, he amoun o binde in he 2 w % PVDF
binde elec ode was oo low o ul ill i s unc ion o assu ing
he mechanical in eg i y o he elec ode. No wi hs anding, he
2 w % ca ageenan binde elec odes exhibi enhanced
mechanical p ope ies. The adhesion s eng h o he 2 w %
1SO3−Ca -, 2SO3−Ca -, and 3SO3−Ca -based elec odes
esul ed in 5.7 ±1.5, 13.6 ±3.5, and 17.32 ±1.7 N m−1,
espec i ely. The eason why he peel s eng h o 1SO3−Ca
was no ably lowe compa ed wi h he o he wo Ca binde s
may be due o he inhomogenei ies obse ed du ing he d ying
and calenda ing s eps o he elec ode ab ica ion. On he o he
hand, 2SO3−Ca and 3SO3−Ca binde s yielded imp o ed
coa ings han achie ed wi h 1SO3−Ca , wi h be e adhesion
s eng hs. Fu he mo e, he sul ona ed g oups a e expec ed o
es ablish s onge bonds wi h he ac i e and conduc i e
pa icles, enhancing he adhesion be ween hem and wi h he
cu en collec o . The e o e, he imp o ed mechanical s eng h
o he 3SO3−Ca elec ode can be a ibu ed o he la ge
numbe o ee pola unc ional and sul ona e g oups.
The elec ochemical pe o mance o NMC811 ca hodes
p epa ed om 2 w % o binde mix u es was assessed, and he
esul s a e shown in Figu e 4. In all cases, ull coin cells we e
assembled using g aphi e anodes and 1 M LiPF6in EC:DMC +
2% VC (1:1) as he elec oly e. To be e assess and compa e
he esul s, he mos ele an da a is summa ized in Table 2.
P ima ily, du ing he i s cycle o o ma ion a 0.1C, all cells
deli e ed simila discha ge capaci ies (be ween 195 and 200
mAh g−1) wi h a Coulombic e iciency o 88−89% (Figu e S3),
including he 2 and 5 w % binde ca hodes. This is a ibu ed
o he solid elec oly e o ma ion on he anode side
27
and
he e o e seems o be independen o he binde choice o he
ca hode. Howe e , when inc easing he C- a es (Figu e 4a),
he elec ode wi h 2 w % o he 3SO3−Ca binde
ou pe o med he o he ca ageenan binde s, being close o
he pe o mance o he PVDF-based elec ode p ocessed in
o ganic sol en (NMP). The di e ence be ween he discha ge
capaci ies was no majo , as e iden om he ol age p o iles
shown in Figu e 4b, al hough a end o imp o ed C- a e
pe o mance is disce ned wi h he inc easing amoun o
sul ona e g oups.
Fo compa ison, Figu e S4 depic s he elec ochemical
pe o mance o se e al coin cells using he NMC811 ca hodes
wi h 5 w % o di e en binde s: 3SO3−Ca , PVDF, and Na-
CMC. The esul s o 5 w % o 1SO3−Ca and 2SO3−Ca
a e no shown since, as men ioned be o e, he slu ies could
no o m a coa ing. The discha ge capaci y deli e ed (Figu e
S4a) by he PVDF-based cell was highe a all C- a es since i is
known ha NMC811 is e y sensi i e owa d wa e .
28
Ne e heless, he elec odes p epa ed wi h 3SO3−Ca as a
binde s ill deli e ed an adequa e pe o mance wi h only 5%
loss o capaci y a e 30 cycles a 0.5C discha ge a e, while he
Na-CMC-based cell p esen ed a la ge loss o capaci y in he
same condi ions (8%). Conside ing ha he aqueous ou e is a
mo e en i onmen ally iendly me hod o he p ocessing o
high-ene gy ca hodes, he ou come o he 3SO3−Ca is
sa is ac o y and, mo eo e , an imp o emen in compa ison o
he Na-CMC binde . Du ing he cha ge−discha ge cycling a
di e en C- a es, he 3SO3−Ca binde deli e ed 120.3 and
86.0 mAh g−1a 3C and 5C, while o PVDF, he discha ge
capaci ies we e 140.4 and 110.8 mAh g−1a he same C- a es,
espec i ely. This may be due o a highe pola iza ion in he
case o he ca ageenan binde , which is e iden om he
ol age p o iles a 5C (Figu e S4c). These p o iles indica e ha
he 3SO3−Ca binde elec ode has highe pola iza ion han
he PVDF elec ode and could ye be op imized by
modi ica ion o he ca hode o mula ion. Howe e , 3SO3−
Ca once again ou pe o med he Na-CMC-based cell ha
only achie ed 109.9 and 65.1 mAh g−1a 3C and 5C,
espec i ely.
The e o e, be ween he di e en o mula ions (5 and 2 w %
binde s), a no able imp o emen occu ed o he 3SO3−Ca
binde . A 3C, he discha ge capaci y was inc eased om 120.3
o 133.1 mAh g−1when dec easing he amoun o binde om
5 o 2 w %. Simila ly, a 5C, i enla ged om 86.0 o 105 mAh
g−1. This de i ed o a capaci y inc ease o 10 and 22% a 3C
Table 2. Elec ochemical Pa ame e s o he Gal anos a ic
Cycling Using Elec odes wi h 2 and 5 w % o Binde
Fo mula ions
DC
a
cycle 1
0.1C
DC
a
cycle 12
3C
DC
a
cycle 15
5C DC
a
cycle
17 0.5C
CR
b
90
cycles
0.5C
5 w % PVDF 200.5 140.4 110.8 188.7
5 w %
3SO3−Ca 195.2 120.3 86.0 177.7
5 w %
Na-CMC 196.1 109.9 65.1 170.1
2 w % PVDF 196.9 136.1 108.7 176.7 95
2 w %
1SO3−Ca 195.3 128.3 102.9 173.1 81
2 w %
2SO3−Ca 196.4 129.5 104.1 171.4 87
2 w %
3SO3−Ca 199.6 133.1 105.0 173.4 91
a
DC, speci ic discha ge capaci y (mAh g−1NMC811).
b
CR, capaci y
e en ion90 cycles (%) = [DCCycle 107]×[DCCycle 17]−1×100.
ACS Applied Ene gy Ma e ials www.acsaem.o g A icle
h ps://doi.o g/10.1021/acsaem.3c01662
ACS Appl. Ene gy Ma e . 2023, 6, 8616−8625
8621
and 5C, espec i ely. The e o e, he educ ion in he binde
p opo ion no only allowed an enla gemen o he p opo ion
o ac i e ma e ial in he ca hode o mula ion bu also enhanced
he elec ochemical pe o mance. In con as , when dec easing
he amoun o PVDF binde om 5 o 2 w %, he discha ge
capaci y dec eased. Al hough he loss was mino , an imp o e-
men did no occu as i did o he 3SO3−Ca binde . The
capaci y e en ion a e 90 cycles a 0.5C e ealed di e se
beha io o he cells using di e en binde s. As e iden in
Table 2 and Figu e 4a, he aqueous elec odes su e ed la ge
capaci y decay han he PVDF binde using NMP since
NMC811 is highly sensi i e when p ocessed wi h wa e .
Howe e , he capaci y e en ion o he PVDF and 3SO3−Ca
binde s was no ha a apa (95 and 91%, espec i ely),
whe eas he o he wo ca ageenans deli e ed capaci y
e en ions lowe han 90%. Vol age p o iles o he di e en
elec odes a cycle 80 (0.5C) a e depic ed in Figu e 4c. The
3SO3−Ca and 2SO3−Ca binde s deli e ed less discha ge
capaci y han he 3SO3−Ca and PVDF ca hode cells a 0.5C,
as a consequence o he inc eased pola iza ion esis ance
du ing he discha ge s ep. The imp o ed pe o mance o he
3SO3−Ca binde -based cell can be a ibu ed o he highe
peel s eng h and be e dispe sion p ope ies. Fu he mo e,
he sul ona e g oups can be ac ing as li hium ca ie s du ing
he cha ge and discha ge o he ba e y. The e o e, by ha ing a
highe numbe o sul ona e g oups in he s uc u e, he li hium
mobili y may be boos ed h ough ionic pa hways.
29
In
addi ion, he la ge numbe o sul ona e g oups p esen in
he 3SO3−Ca binde may con ibu e o he p o ec ion o he
NMC811 pa icles agains wa e , achie ing a mo e s able
cycling han he 1SO3−Ca and 2SO3−Ca . This e ec could
be simila o he one obse ed by Heidbuchel e al.
30
ha ha e
ecen ly epo ed he posi i e impac o he addi ion o Li2SO4
du ing he aqueous p ocessing o NMC811 ca hodes since a
p o ec i e coa ing a ound he ac i e ma e ial was obse ed by
XPS measu emen s.
EIS measu emen s we e conduc ed on he ull coin cells (2
w % binde o mula ion NMC811 ca hodes s g aphi e
anodes) a e he o ma ion cycle and a e cycling (C- a e and
90 cycles a 0.5C). The co esponding Nyquis plo s a e
p esen ed in Figu e 5a,b, espec i ely, i ed wi h he equi alen
ci cui as shown on op o he igu e. To be e unde s and he
a iabili y in he elec ochemical beha io , he mos ele an
da a is p esen ed in Table S1. The elec oly e esis ance (Re) is
ep esen ed by he in e sec ion o he cu e wi h he Z′axis,
which is alike o all Nyquis cu es (a ound 1−3Ω). The
ollowing semici cle is assigned o he double laye p ocess o
he cha ge- ans e esis ance (Rc ), whe e signi ican di e -
ences can be obse ed. A e he o ma ion cycle, he Rc shows
he lowes alue o he PVDF cell (79.7 ±4.2 Ω) and hen he
Rc dec eased when inc easing he numbe o sul ona e g oups:
435.8 ±5.6, 205.9 ±13.5, and 190.3 ±8.1 Ω o he 1SO3−
Ca -, 2SO3−Ca -, and 3SO3−Ca -based cells, espec i ely.
The e o e, he 3SO3−Ca binde p esen ed he lowes alue
o all o he ca ageenan binde s, which is in ag eemen wi h
he gal anos a ic cycling esul s. This is likely a consequence o
he highe numbe o sul ona e g oups, such ha he li hium-
ion conduc i i y was boos ed and he Rc educed. Su p isingly,
he Rc dec eased o he ca ageenan cells ollowing he cycling
(i.e., he semici cle educed i s diame e ), showing alues o
171.2 ±20.2, 169.5 ±15.7, and 93.1 ±4.6 Ω o he 1SO3−
Ca -, 2SO3−Ca -, and 3SO3−Ca -based cells, espec i ely.
Howe e , he Rc o he PVDF cell inc eased signi ican ly o e
cycling. Tang e al.
31
also no iced a educ ion o he Rc p ocess
when using chi osan oligosaccha ides o Li2ZnTi3O8elec o-
des. The educ ion o he impedance was a ibu ed o he
o ma ion o mo e cha ge- ans e si es du ing cycling and
he e o e he imp o emen in he di usion pa ame e s. Finally,
a high equencies, he di usion p ocesses ake place,
desc ibed by he spike line ha ollows he semici cle; a
s eepe slope o he cu e means ha he di usion o li hium
ions is mo e e ec i e. Following bo h he o ma ion s ep and
he cycling s ages, he 3SO3−Ca yielded he la ges slope.
Figu e 5. Nyquis plo s esul ing om he EIS measu emen s on ull coin cells (NMC811|g aphi e) (a) a e he o ma ion s ep and (b) a he end
o cycling (C- a e cycling and 90 cycles a 0.5C).
ACS Applied Ene gy Ma e ials www.acsaem.o g A icle
h ps://doi.o g/10.1021/acsaem.3c01662
ACS Appl. Ene gy Ma e . 2023, 6, 8616−8625
8622
To explo e mo e in de ail he di usion p ocesses ha ake
place a low equencies, he EIS da a was i ed using he
Randles equa ion. The eal pa o he o al impedance (Z′)
was ep esen ed as a unc ion o he angula eloci y (ω−0.5)
(Figu e S5), whe e he slope ep esen s he Wa bu g ac o (σ)
and he alues a e exhibi ed in Table S1. Wi h he A henius
equa ion, he coe icien o li hium ions (DLi+) can be ob ained.
The DLi+ o he a e - o ma ion s eps (Figu e S5a) esul ed in
3.0 ×10−13, 1.4 ×10−14, 8.0 ×10−15, and 8.5 ×10−14 cm2s−1
o PVDF, 1SO3−Ca , 2SO3−Ca , and 3SO3−Ca ,
espec i ely. The PVDF elec ode showed he highes di usion
o li hium ions, ollowed by he 3SO3−Ca cell, which is in
ag eemen wi h he gal anos a ic cycling esul s. The di e ence
be ween he PVDF and he ca ageenan cells is p obably due
o he deg ada ion o he NMC811 ac i e ma e ial when in
con ac wi h wa e . Howe e , a e he cycling (Figu e S5b),
he cells showed he ollowing DLi+ alues: 1.2 ×10−14, 1.4 ×
10−14, 1.7 ×10−14, and 2.3 ×10−13 o PVDF, 1SO3−Ca ,
2SO3−Ca , and 3SO3−Ca , espec i ely. While he o ganic
PVDF, 1SO3−Ca , and 2SO3−Ca exhibi ed simila alues o
li hium di usion, he 3SO3−Ca e ealed a DLi+one o de o
magni ude highe . This s iking ou come e idenced he
enhanced li hium di usion con e ed by he 3SO3−Ca
binde , a ibu ed o he la ge amoun o sul ona e g oups in
he elec ode ha can ac as li hium ca ie s, boos ing he
conduc i i y. In conclusion, he educed Rc and enhanced
li hium di usion o he 3SO3−Ca binde led o he
imp o emen in elec ochemical pe o mance and his may
also be ela ed o he imp o ed mechanical and heological
p ope ies.
Finally, o u he explain he e ec o di e en binde s on
he ba e y pe o mance, he coin cells we e opened o
isualize he elec ode condi ions a e cycling. Figu e 6 shows
he mo phology o he elec odes using di e en binde s a
1000×and 3000×magni ica ions. Fo he PVDF elec odes,
he NMC811 pa icles p esen ed a sphe ical shape and no
agglome a es we e obse ed. On he o he hand, he 1SO3−
Ca and 2SO3−Ca elec odes showed deg ada ion wi h
Figu e 6. FESEM c oss-sec ional images o aged elec odes using di e en binde s a 1000×(le ) and 3000×( igh ) magni ica ions.
ACS Applied Ene gy Ma e ials www.acsaem.o g A icle
h ps://doi.o g/10.1021/acsaem.3c01662
ACS Appl. Ene gy Ma e . 2023, 6, 8616−8625
8623
deposi ion p oduc s and p o usions all along he elec odes.
This can lead o an inc eased esis ance inside he cell, leading
o he capaci y ading obse ed in he gal anos a ic cycling.
Unlike he less sul ona ed ca ageenans, he 3SO3−Ca
p o e ed a smoo h pa icle su ace wi h educed deg ada ion
and simila appea ance as seen o he o ganic PVDF coa ings,
e en hough he 3SO3−Ca coa ing was p ocessed in wa e .
Also, c oss-sec ional FESEM images we e acqui ed o he
p is ine elec odes, i.e., a e he calenda ing wi h no cycling
(Figu e S6), whe e no majo di e ences we e no ed compa ed
wi h he aged elec odes. The 1SO3−and 2SO3−Ca ca hodes
depic ed a damaged mo phology, while he 3SO3−Ca looked
mo e like he o ganic-based PVDF elec ode.
■CONCLUSIONS
In his wo k, ca ageenan biopolyme s we e applied as wa e -
soluble binde s o NMC811 ca hodes, possessing 1, 2, o
3SO3− unc ionali ies pe uni o he biopolyme . In addi ion o
analyzing he e ec o he numbe o sul ona e g oups, we also
explo ed di e en o mula ions o binde con en s: 5, 2, and 1
w %. Dec easing he amoun o binde gi es he ad an age o
inc easing he ac i e ma e ial and he e o e he capaci y o he
elec ode. Wi h 5 w % o binde , he slu ies wi h 1SO3−and
2SO3−binde s could no be used o o m coa ings; he slu ies
we e oo dense. Consequen ly, he 2 w % binde o mula ion
ensu ed op imal coa ing o he elec odes. Finally, in he 1 w
% case, he binde con en was oo low o gene a e elec os a ic
epulsion be ween pa icles, and agglome a es we e obse ed.
The e o e, he assessmen o he ype o ca ageenan and he
e ec o he numbe o sul ona e g oups in i s s uc u e was
pe o med wi h he 2 w % binde o mula ions. O pa icula
no ice was he educ ion in he cha ge- ans e esis ance o e
cycling, which was a ibu ed o he o ma ion o mo e eac ion
si es. Among hese biopolyme s, he lambda ca ageenan
binde , ha ing 3SO3−g oups, demons a ed signi ican ly
imp o ed dispe sion p ope ies, adhesion s eng h, and
p ese a ion o he NMC811 ac i e ma e ial when exposed
o wa e . The highe con en o sul ona e g oups in he
s uc u e boos ed he di usion kine ics, enabling he 3SO3−
Ca -based elec ode o deli e highe and mo e s able
discha ge capaci ies. I was able o deli e 133.1 mAh g−1a
3C and 105.0 mAh g−1a 5C, which was simila o he o ganic-
based PVDF elec ode (136.1 and 108.7 mAh g−1,
espec i ely), while p o iding a mo e sus ainable ou e o
ca hode elec ode p epa a ions using a wa e -soluble, en i on-
men ally iendly, and na u al polyme . Mo eo e , he 3SO3−
ca ageenan binde enabled highe ene gy densi ies by he
educ ion o binde amoun o 2 w %, consequen ly inc easing
he amoun o NMC811 loading, in con as o PVDF, whe e 2
w % o binde dec eased he pe o mance capabili y compa ed
o he 5 w % binde con en .
■ASSOCIATED CONTENT
*
sı Suppo ing In o ma ion
The Suppo ing In o ma ion is a ailable ee o cha ge a
h ps://pubs.acs.o g/doi/10.1021/acsaem.3c01662.
Slu ies wi h 5 w % o binde p epa ed wi h 1SO3−
Ca , 2SO3−, and 3SO3−Ca ; gal anos a ic cycling o 5
w % o binde elec odes; slu y p epa ed wi h 1 w % o
binde o mula ion; i ing alues o he EIS spec a; and
FESEM c oss sec ions o p is ine elec odes using
di e en binde s (PDF)
■AUTHOR INFORMATION
Co esponding Au ho s
Ma ia Fo sy h −Ins i u e o F on ie Ma e ials, Deakin
Uni e si y, Melbou ne 3125, Aus alia; POLYMAT,
Uni e si y o he Basque Coun y UPV/EHU, Donos ia-San
Sebas ián 20018, Spain; IKERBASQUE, Basque Founda ion
o Science, Bilbao 48011, Spain; o cid.o g/0000-0002-
4273-8105; Email: [email p o ec ed]
Da id Mece eyes −POLYMAT, Uni e si y o he Basque
Coun y UPV/EHU, Donos ia-San Sebas ián 20018, Spain;
IKERBASQUE, Basque Founda ion o Science, Bilbao
48011, Spain; o cid.o g/0000-0002-0788-7156;
Email: [email p o ec ed]
Au ho s
Ana Cla a Rolandi −Ins i u e o F on ie Ma e ials, Deakin
Uni e si y, Melbou ne 3125, Aus alia; CIDETEC Basque
Resea ch and Technology Alliance (BRTA), 20014 Donos ia-
San Sebas ian, Spain; POLYMAT, Uni e si y o he Basque
Coun y UPV/EHU, Donos ia-San Sebas ián 20018, Spain
C is ina Pozo-Gonzalo −Ins i u e o F on ie Ma e ials,
Deakin Uni e si y, Melbou ne 3125, Aus alia
I a xe de Mea za −CIDETEC Basque Resea ch and
Technology Alliance (BRTA), 20014 Donos ia-San
Sebas ian, Spain
Ne ea Casado −POLYMAT, Uni e si y o he Basque
Coun y UPV/EHU, Donos ia-San Sebas ián 20018, Spain;
IKERBASQUE, Basque Founda ion o Science, Bilbao
48011, Spain; o cid.o g/0000-0003-0799-5111
Comple e con ac in o ma ion is a ailable a :
h ps://pubs.acs.o g/10.1021/acsaem.3c01662
Au ho Con ibu ions
A.C.R.: w i ing�o iginal d a and in es iga ion. C.P.-G.,
I.d.M., N.C., and M.F.: e iew and edi ing, supe ision.
D.M.: e iew and edi ing, alida ion, supe ision, and
concep ualiza ion.
No es
The au ho s decla e no compe ing inancial in e es .
■ACKNOWLEDGMENTS
The au ho s acknowledge he Aus alian Resea ch Council
(ARC) Cen e o T aining Cen e o Fu u e Ene gy S o age
Technologies (s o Ene gy) (IC180100049) o unding. The
au ho s would like o hank he Eu opean Commission o
inancial suppo h ough unding om he Eu opean Union’s
Ho izon 2020 esea ch and inno a ion p og am unde he
Ma ie Sklodowska-Cu ie g an ag eemen No 823989 and
Spanish AEI-MINECO o unding h ough p ojec PID2020-
119026 GB-I00.
■REFERENCES
(1) Li, J.; Wu, Z.; Lu, Y.; Zhou, Y.; Huang, Q.; Huang, L. Wa e
Soluble Binde , an Elec ochemical Pe o mance Boos e o
Elec ode Ma e ials wi h High Ene gy Densi y. Ad . Ene gy Ma e .
2017,1701185, No. 1701185.
(2) Zou, F.; Man hi am, A. A Re iew o he Design o Ad anced
Binde s o High-Pe o mance Ba e ies. Ad . Ene gy Ma e . 2020,10,
No. 200250.
(3) Wang, M.; Dong, X.; Escoba , I. C.; Cheng, Y. T. Li hium Ion
Ba e y Elec odes Made Using Dime hyl Sul oxide (DMSO) - A
G een Sol en . ACS Sus ainable Chem. Eng. 2020,8, 11046−11051.
ACS Applied Ene gy Ma e ials www.acsaem.o g A icle
h ps://doi.o g/10.1021/acsaem.3c01662
ACS Appl. Ene gy Ma e . 2023, 6, 8616−8625
8624
