Tailo ed silicon nanos uc u es in hyd ogel-de i ed conduc i e binde s:
Role o size, s uc u e, and su ace chemis y in enhancing Li-ion
ba e y pe o mance
Gab iela Soukupo ´
a
a
, Filip Ma ˇ
ejka
a,b
, Zuzana Vlˇ
cko ´
a ˇ
Zi co ´
a
c
, Abdelghani Laachachi
d
,
Pa el Gal´
aˇ
b
, Milosla Lho ka
e
, O aka F ank
c
, Jiˇ
í ˇ
Ce enka
b
, Fa ima Hassouna
a,*
a
Facul y o Chemical Enginee ing, Uni e si y o Chemis y and Technology, P ague, Technick´
a 5, 166 28, P ague 6, Czech Republic
b
FZU - Ins i u e o Physics o he Czech Academy o Sciences, Cuk o a nick´
a 10/112, 162 00, P ague 6, Czech Republic
c
J. Hey o sky Ins i u e o Physical Chemis y, Czech Academy o Sciences, Dolejsko a 2155/3, 182 00, P ague 8, Czech Republic
d
Luxembou g Ins i u e o Science and Technology, 5, ue Bommel, L-4940, Hau cha age, Luxembou g
e
Facul y o Chemical Technology, Uni e si y o Chemis y and Technology, P ague, Technick´
a 5, 166 28, P ague 6, Czech Republic
HIGHLIGHTS GRAPHICAL ABSTRACT
•La ge Si nanoc ys als (100 nm) achie e
highe ini ial capaci y in LIB anodes.
•Smalle Si nanoc ys als (6 nm) imp o e
cycling s abili y.
•Amo phous Si nanopa icles ou pe o m
c ys alline Si in cycling s abili y.
•3D c osslinked PPy accommoda es Si
olume expansion, enhancing anode
pe o mance.
•Op imal Si size (6–20 nm) in PPy ne -
wo ks imp o es elec ochemical
pe o mance.
ARTICLE INFO
Keywo ds:
Li-ion ba e y
Si nanopa icles
Elec ically conduc i e polyme
3D ne wo k
Elec ochemical p ope ies
ABSTRACT
Silicon (Si) is a p omising anode ma e ial o Li-ion ba e ies (LIBs), bu i s p ac ical applica ion is limi ed by
olume expansion du ing li hia ion/deli hia ion, leading o poo cycling s abili y. While Si nanos uc u ing
mi iga es his issue, i emains only a pa ial solu ion.
This s udy sys ema ically in es iga es he e ec s o Si pa icle size (6, 20, 55, o 100 nm), su ace chemis y
( ype and deg ee o oxida ion), and solid-s a e p ope ies (amo phous s. c ys alline) on he elec ochemical
pe o mance o Si-based anodes using a h ee-dimensional (3D) c osslinked polypy ole (PPy) binde . In si u PPy
polyme iza ion a ound Si nanopa icles o ms a 3D in e connec ed conduc i e ne wo k wi hin he PPy/Si an-
odes, e ec i ely accommoda ing olume changes and main aining elec ical con ac du ing he gal anos a ic
cycling. The pa icle size dependence shows ha la ge Si nanopa icles p o ide highe ini ial cha ge capaci y
(2975 mAh/g), whe eas smalle ones imp o e cycling s abili y (85 % capaci y e en ion a e 100 cycles).
* Co esponding au ho .
E-mail add ess: [email p o ec ed] (F. Hassouna).
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Jou nal o Powe Sou ces 661 (2026) 238620
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Amo phous Si exhibi s signi ican ly lowe speci ic capaci y bu supe io capaci y e en ion (~100 % a e 100
cycles) compa ed o c ys alline Si. Cyclic ol amme y and elec ochemical impedance spec oscopy demons a e
ha in eg a ing 6 o 20 nm Si nanoc ys als in o a 3D c osslinked PPy enhances anode pe o mance. These
indings highligh he impo ance o op imizing Si p ope ies in designing conduc i e hyd ogel-de i ed anodes
o high-pe o mance LIBs.
1. In oduc ion
In ecen yea s, he demand o cos -e ec i e, high-pe o mance
echa geable ba e ies wi h ex ended cycle li e has g own signi ican ly,
d i en by hei applica ions in elec onic de ices, elec ic ehicles, and
la ge-scale ene gy s o age sys ems. Among all, Li-ion ba e ies (LIB)
ha e a ac ed signi ican a en ion due o hei excep ional ene gy
densi y, high powe densi y, and long cycle li e [1–4]. The comme cially
used g aphi ic anode o e s only a limi ed heo e ical speci ic capaci y
(~370 mAh/g) [2,5–7], which has p omp ed ex ensi e esea ch in o
al e na i e anode ma e ials. Si is conside ed one o he mos p omising
anode ma e ials o LIB due o i s high heo e ical speci ic li hia ion
capaci y (~3579 mAh/g o Li
15
Si
4
), low discha ge po en ial (~0.4 V s
Li/Li
+
), en i onmen al sus ainabili y, and high elemen al abundance [1,
8–10]. Howe e , he p ac ical applica ion o Si as an anode ma e ial in
LIB is signi ican ly limi ed due o i s poo elec ical conduc i i y and
subs an ial olume expansion (~300 % o Li
15
Si
4
[11]) du ing li h-
ia ion. This expansion leads o se e e issues such as ma e ial c acking,
anode pul e iza ion, o e g ow h o a solid elec oly e in e phase (SEI),
and capaci y ading [7–9,12,13].
To add ess hese challenges, se e al s a egies ha e been explo ed.
One p omising app oach is he nanos uc u ing o Si (e.g., nanowi es o
nanopa icles), which helps accommoda e he olume changes, he eby
enhancing he mechanical s abili y o he ma e ial and imp o ing i s
cycling pe o mance [14–18]. I has been epo ed ha when he pa -
icle size is educed below a c i ical h eshold o 150 nm, he c acking o
he ma e ial is signi ican ly educed [19–22]. Al hough nanos uc u ing
imp o es he mechanical p ope ies o Si anodes, se e al signi ican
challenges emain. These include he highe su ace ac i i y o Si, which
can lead o pa icle agglome a ion, he o ma ion o a hicke SEI laye ,
and he high cos associa ed wi h he p epa a ion p ocess [17,19,
22–24]. To o e come he poo elec ical conduc i i y o nanos uc u ed
Si and acili a e mo e e icien Li-ion di usion, conduc i e ca bon (C)
addi i es such as ca bon black (Supe P), ca bon nano ubes, and g a-
phene a e commonly inco po a ed. The addi ion o hese C ma e ials no
only helps o bu e he olume expansion du ing li hia ion bu also
imp o es he o e all conduc i i y, he eby p o iding an e ec i e elec-
onic pa hway o elec on ans e [8,17,23]. Gene ally, polyme
binde s such as ca boxyme hyl cellulose, polyamide imide, o poly
(ac ylic acid) (PAA) a e inco po a ed wi h Si/C o enhance mechanical
s abili y and hence, he cycling pe o mance o he anode ma e ial [7,8,
10,25]. E ec i e binde s o Si-based anodes mus mee se e al c i ical
equi emen s. They mus be capable o o ming uni o m mix u es wi h Si
and C, es ablishing s ong binding in e ac ions wi h bo h Si and C o
ensu e s able elec ical pa hways o he cu en collec o , and demon-
s a ing elec ochemical s abili y wi hin he ope a ional po en ial win-
dow. Mo eo e , hey should exhibi high elas ic modulus alues o
accommoda e he signi ican olume expansion o Si, esis excessi e
swelling in he elec oly e, acili a e he o ma ion o a s able and hin
SEI laye , and ensu e a obus connec ion be ween he anode ma e ial
and he cu en collec o h oughou cycling. In addi ion o hese ech-
nical cha ac e is ics, an ideal binde should also be economically
easible, s aigh o wa d o manu ac u e in la ge quan i ies, a o dable,
and compa ible wi h exis ing p oduc ion echniques [25,26]. The use o
he a o emen ioned insula ing polyme binde s may esul in a weak
in e ace be ween Si and C, leading o con ac loss du ing cycling [25,
27]. In his con ex , eplacing he insula ing con en ional binde s wi h
elec ically conduc i e polyme s p esen s a p omising al e na i e, as i
would elimina e he Si/C in e ace issues. The conduc i e polyme
would no only se e as a binde bu also enhance he conduc i i y o he
anode ma e ial, he eby imp o ing o e all elec ochemical pe o -
mance. This app oach was clea ly demons a ed by Li e al. [1], who
compa ed he elec ochemical pe o mance o Si-based anodes
employing ei he an insula ing binde (PAA) o a conduc i e polyme
binde . Thei s udy e ealed ha conduc i e polyme binde s signi i-
can ly enhance cycling s abili y and a e capabili y compa ed o hei
insula ing coun e pa s. Conduc i e polyme s, such as polyaniline
(PANI), polypy ole (PPy), and poly(3,4-e hylenedioxy hiophene)
(PEDOT), o e se e al ad an ages, including mechanical lexibili y,
cos -e ec i eness, ease o syn hesis and p ocessing, en i onmen al
iendliness, high elec ical conduc i i y, and in insic elec ochemical
ac i i y [28–30]. Each polyme , howe e , p esen s unique s eng hs and
limi a ions. Fo ins ance, PPy binde s exhibi enhanced Li-ion di usion
bu su e om con inuous deg ada ion; PANI binde s p o ide good
adhesion bu a e p one o olume expansion du ing cycling; PEDOT
binde s o e chemical s abili y and sel -healing p ope ies bu equi e
op imiza ion o balance conduc i i y and mechanical lexibili y
[31–33].
Al hough conduc i e polyme s ha e ecei ed signi ican in e es o
hei applica ion in LIB, ela i ely limi ed esea ch has been conduc ed
on in eg a ing hem wi h Si nanos uc u es o de elop comme cially
iable anodes o LIB [1,2,5]. A iable and p omising s a egy o in e-
g a ing Si nanos uc u es in o conduc i e polyme binde s in ol es a
hyd ogel-based p epa a ion echnique. In his app oach, in si u poly-
me iza ion and c osslinking o he conduc i e polyme ake place in he
p esence o Si, o en accompanied by an addi ional elec ically
conduc i e addi i e. The p ocess esul s in he o ma ion o a
h ee-dimensional (3D) ne wo k, whe ein Si is uni o mly coa ed and
in e connec ed by he conduc i e polyme ma ix [1,2,5,9,14,25,34,
35]. This 3D in e connec ed ne wo k imp o es elec ochemical pe o -
mance h ough se e al bene icial ea u es. The 3D amewo k unc ions
as bo h a conduc i i y enhance and a conduc i e binde , imp o ing he
pa icle- o-pa icle con ac . I s po ous s uc u e helps bu e he olume
changes o Si du ing li hia ion [35], while he 3D conduc i e ne wo k
acili a es imp o ed elec on and ion di usion [14]. Fu he mo e,
embedding Si wi hin he amewo k p omo es he o ma ion o a mo e
s able SEI du ing li hia ion by be e isola ing Si om he elec oly e
[34]. Despi e hei impo ance, he impac o key ac o s such as he size,
su ace chemis y, and solid-s a e p ope ies o Si on he elec ochemical
pe o mance o esul ing anodes emains poo ly unde s ood and has no
been sys ema ically in es iga ed in Si/conduc i e polyme -based an-
odes, including hose p epa ed using hyd ogel-based app oaches.
P e ious s udies in es iga ing he size e ec o Si nanopa icles in
anode ma e ials ha e p ima ily ocused on physical blending me hods,
whe e Si pa icles o ca bonized co e-shell Si pa icles ( anging in size
om 30 nm o 5
μ
m) we e mechanically mixed wi h a binde and ca bon
addi i e [20,24,36–38], o p epa ed ia gas deposi ion echniques [39].
The s udies on Si-based anodes using 3D c osslinked conduc i e poly-
me ic binde s ha e used di e en ypes and sizes o Si nanopa icles,
including nanopa icles wi h a e age diame e s anging om 40 o 300
nm [1,5,9,14,25,35,40,41], mic o-sized po ous Si pa icles [42], o Si
dend i es [34]. Howe e , he selec ion o Si ype and size has o en been
a bi a y, lacking a sys ema ic me hodology. Fu he mo e, hese s udies
ha e p edominan ly used comme cial Si ma e ials wi h poo ly
con olled su ace chemis y. This lack o sys ema ic in es iga ion also
applies o he eme ging class o Si quan um do s (SiQD), which, despi e
G. Soukupo ´
a e al.
Jou nal o Powe Sou ces 661 (2026) 238620
2
o e ing ad an ages, such as high su ace a ea, sho e di usion pa h-
ways, and educed olume expansion, ha e ecei ed only limi ed
a en ion in he con ex o LIB anodes [43–50]. P ac ical implemen a ion
o SiQD emains challenging due o di icul ies in syn hesizing mono-
dispe se pa icles and mi iga ing undesi able side eac ions a ising om
hei high su ace eac i i y due o hei signi ican ly cu ed su ace and
p esence o hyd ogen su ace e mina ion.
To he bes o ou knowledge, no comp ehensi e s udy has sys em-
a ically examined he combined in luence o Si pa icle size, su ace
chemis y, and in insic solid-s a e p ope ies on he elec ochemical
pe o mance o Si-based anodes inco po a ing 3D c osslinked conduc-
i e polyme ic binde s in LIB. The p esen s udy aims o add ess his
impo an knowledge gap by p o iding a undamen al unde s anding o
s uc u e-p ope y ela ionships ha go e n he beha io o such
ad anced and complex anode sys ems.
This s udy sys ema ically in es iga es he e ec s o size (6, 20, 55,
and 100 nm), su ace chemis y (oxide ype and deg ee) and solid-s a e
p ope ies (amo phous e sus c ys alline) using bo h comme cial and
labo a o y-syn hesized Si nanopa icles, including highly monodispe se
6 and 20 nm pa icles, on he s uc u al, mo phological, and elec o-
chemical pe o mance o he esul ing anodes. The anode ma e ials we e
p epa ed ia he in si u polyme iza ion o a conduc i e PPy hyd ogel,
se ing as a model c osslinked conduc i e polyme binde , using an
en i onmen ally iendly, wa e bo ne me hod pe o med a nea -ze o
empe a u es. Phy ic acid (PhA), a na u ally occu ing molecule, was
employed as a c osslinking agen o he PPy chains, while PAA se ed as
a s abilizing agen o he Si nanopa icles. The esul ing 3D c osslinked
PPy ne wo k unc ioned as a high-pe o mance conduc i e binde ,
con o mally coa ing he Si nanopa icles. This in eg a ion o he 3D
c osslinked PPy ne wo k wi h he Si nanopa icles was achie ed a low
empe a u es, elimina ing he need o high- empe a u e ca boniza ion,
which is commonly employed o c ea e s able conduc i e ma ices. A
clea ela ionship was es ablished be ween he Si nanopa icle size,
su ace chemis y, solid-s a e p ope ies, and hei collec i e impac on
he elec ochemical pe o mance o he esul ing anodes. These insigh s
p o ide a ounda ion o he a ional design and op imiza ion o Si-based
anodes o enhanced elec ochemical pe o mance.
2. Expe imen al pa
2.1. Ma e ials
Two ypes o Si nanoc ys als (SiNC
100
wi h 100 nm a e age diam-
e e , s ock keeping uni NG04CO28095; SiNC
55
wi h 55 nm a e age
diame e , s ock keeping uni NG04EO1804) we e pu chased om
Nanog a i. Two o he ypes o SiNC (SiNC
6
wi h 6 nm a e age diame e ;
SiNC
20
wi h 20 nm a e age diame e ) and one ype o amo phous Si
nanopa icles (SiNA
20
wi h 20 nm a e age diame e ) we e syn hesized
in he ame o his s udy. Dilu ed silane (1 % in a gon, Linde, A 5.0,
SiH
4
5.0, UN1954), hyd ogen (H
2
7.0, Linde, UN1049), a gon (A , A
6.0, UN1006), and pu e silane (SiH
4
, UN2203) we e used o he Si
syn hesis. Conduc i e ca bon ille Supe P (40 nm a e age diame e )
was kindly dona ed by Ime ys S.A. Py ole monome ( eagen g ade, 98
%, M
w
=67.09), phy ic acid solu ion (PhA, 50 % (w/w) in H
2
O, M
w
=
660.04), poly(ac ylic acid) (PAA, M
w
=450,000), ammonium pe sul a e
(APS, ≥98.0 %, M
w
=228.20), li hium hexa luo ophospha e solu ion in
e hylene ca bona e and dime hyl ca bona e (1.0 M LiPF
6
in EC/DMC =
50/50 ( / ), ba e y g ade), and Li-me al oil ( hickness: 0.6 mm, 99.9
%) we e pu chased om Me ck. Cu en collec o coppe oil ( hickness:
25
μ
m, 99.8 %) was pu chased om The mo Fishe . Deionized (DI)
wa e was used as an aqueous medium in all he expe imen s.
2.2. Ma e ials p epa a ion
2.2.1. Syn hesis o SiNC
SiNC
20
, SiNC
6
, and SiNA
20
we e syn hesized using a non-comme cial
non- he mal plasma low- h ough eac o ope a ed unde low p essu e.
The sys em was c ea ed by adap ing he appa a us o Ko s hagen e al.
[51]. The ope a ional p essu es we e wi hin 10 Pa in he s andby mode
and lowe han 500 Pa in he syn hesis mode. The plasma was gene a ed
wi h a adio equency (RF) powe sou ce (RFG 600W, Coaxial Powe
Sys ems) ope a ing a 13.56 MHz equipped wi h au oma ic ma ch box
(Coaxial Powe Sys ems). Fo he syn hesis o 6 mm c ys alline pa icles
(SiNC
6
), a na ow glass ube eac o was used, wi h an in e nal diame e
o 0.8 cm. The plasma discha ge was gene a ed using plana elec odes
(dimensions 5 cm–12 cm). The ou pu RF powe was 150 W, and he
SiNCs we e syn hesized using a 1 % dilu ed silane in a gon mixed wi h
hyd ogen. Fo he syn hesis o he 20 nm c ys alline pa icles (SiNC
20
), a
glass eac o wi h an in e nal diame e o 2.1 cm, equipped wi h ing
elec odes (heigh 2.7 cm), was used. The eac ion mix u e was
composed o a gon and pu e silane, and he ou pu RF powe was se o
107 W. The 20 nm amo phous pa icles (SiNA
20
) we e syn hesized using
a wo-s age eac o . The i s s age consis ed o a na ow glass ube
eac o wi h an in e nal diame e o 0.8 cm and a leng h o 50 cm. Plana
elec odes (measu ing 5 cm by 12 cm) we e a ached o he eac o . A
low o dilu ed silane was in oduced in o his s age, and he RF ou pu
powe was se o 150 W. The second s age was implemen ed using a
b oad glass ube wi h an in e nal diame e o 2.1 cm and a leng h o 50
cm. Double-helix elec odes we e a ached o he ube, wi h one elec-
ode g ounded, and he wi es spaced 1 cm apa . Du ing his s age,
lows o pu e silane and a gon we e in oduced, and he second RF
powe ou pu was se o 250 W.
2.2.2. Syn hesis o PPy hyd ogel-based Si composi es and anode
p epa a ion
PPy hyd ogel-based composi es we e p epa ed ia in si u oxida i e
polyme iza ion o py ole monome using APS in he p esence o Si
nanopa icles (SiNC o SiNA). The composi es we e p epa ed acco ding
o he ollowing p ocedu e. Fi s ly, 11
μ
l o py ole monome was
ans e ed o a small glass ial wi h 35.4
μ
l o PhA and DI wa e . The
solu ion was mixed using a magne ic s i e . Nex , 38.4 mg o Si nano-
pa icles we e g ound in a mo a o 10 min. Subsequen ly, 15.9 mg o
Supe P was added and mixed wi h he Si nanopa icles o an addi ional
10 min. Then, 15.4 mg o PAA was inco po a ed in o he Si and Supe P
mix u e and blended o ano he 10 min. The esul ing powde mix u e
was ans e ed in o a small glass ial, and DI wa e was added. The
powde mix u e was dispe sed in DI wa e using a sonica ion ba h (PS
3000, Powe Sonic) and u he mixed wi h a magne ic s i e o achie e
a homogeneous dispe sion. Once he powde s we e ully dispe sed and a
uni o m ink was ob ained, he solu ion o py ole wi h PhA and DI wa e
was added o he ink. This mix u e was s i ed o 10 min wi h a mag-
ne ic s i e , and he ial was labeled as solu ion A. In pa allel, an APS
solu ion was p epa ed by dissol ing 11 mg o APS in DI wa e . Bo h
solu ions, solu ion A and APS solu ion, we e cooled sepa a ely in an ice
ba h o 10 min. Finally, he APS solu ion was pou ed in o solu ion An
unde con inuous s i ing in he ice ba h, ini ia ing he in si u poly-
me iza ion o he py ole monome . A e 4 h, he esul ing ink was cas
on o coppe oil and allowed o d y a oom empe a u e. The ob ained
hin ilms we e hen p essed o 1 min a 60 kPa and d ied in a acuum
o en a 60 ◦C o e nigh . The p epa ed anodes we e labeled as PPy/Si,
speci ying he ype o Si used, i.e., SiNC o SiNA.
2.3. Cha ac e iza ion me hods
The chemical s uc u e o all Si nanopa icles was analyzed by
Raman spec oscopy (633 nm, 1.96 eV, objec i e 100x, He-Ne lase ;
Ho iba LabRAM HR spec ome e in eg a ed wi h an Olympus mic o-
scope) and Fou ie - ans o m in a ed spec oscopy (FTIR, Nicole iS50
ABX). The su ace chemis y was examined using X- ay pho oelec on
spec oscopy (XPS, X- ay beam Al K
α
wi h E =1486.6 eV and powe o
60 W, pho oelec on emission ake-o angle o 0◦; The mo ishe Nexsa
G2). The ob ained XPS spec a we e decon olu ed using he CasaXPS
G. Soukupo ´
a e al.
Jou nal o Powe Sou ces 661 (2026) 238620
3
so wa e. The mic o/nanos uc u e was isualized using scanning elec-
on mic oscopy (SEM, Mi a3 LMH, Tescan, seconda y elec ons a 3 kV)
and high- esolu ion ansmission elec on mic oscopy (TEM, EFTEM
Jeol 2200 FS, coppe mesh). The image analysis was pe o med using
Image J so wa e. Ene gy-dispe si e X- ay spec oscopy (EDS) analysis
was conduc ed on he composi es using SEM Mi a 3 LMH (Tescan) and
B uke XFlash 6|10 de ec o wi h so wa e Esp i 2.1. The c ys allini y o
he Si nanopa icles was cha ac e ized using X- ay di ac ion (XRD, Cu
lamp; PANaly ical X’Pe PRO wi h PIXcel1D_1D de ec o ). The speci ic
su ace a ea was analyzed using he ni ogen physiso p ion echnique on
a 3Flex analyze (Mic ome i ics, No c oss).
To assemble Li-ion hal -coin cell ba e ies, he anode ma e ials p e-
pa ed in his wo k we e d ied a 80 ◦C in a acuum o en o 12 h and cu
in o 1.5 cm diame e ci cles. Each cu ci cle was weighed and ans-
e ed o an A - illed glo ebox o he ba e y assembly. Li me al oil was
used as he e e ence and coun e elec ode, and 1.0 M LiPF
6
in EC/DMC
se ed as he elec oly e.
The elec ochemical pe o mance o he anodes was e alua ed
h ough gal anos a ic cha ge/discha ge (GCD) cycling wi hin he po-
en ial ange o 0.05–1 V e sus Li/Li
+
. This was pe o med using a
ba e y es e (Newa e BTS-4008-5V50mA) a a cha ging a e o 0.1C
(0.4 A/g), calcula ed o each sample indi idually based on he mass o
Si. Fu he cha ac e iza ion in ol ed cyclic ol amme y (CV) using a
po en ios a (
μ
Au olab, Me ohm), and elec ochemical impedance
spec oscopy (EIS) in he discha ged s a e (0.05 V), wi h equencies
anging om 80 kHz o 0.03 Hz (I ium Compac S a , I ium Tech-
nologi d B. V.).
3. Resul s and discussion
The 3D c osslinked PPy-based anodes we e syn hesized h ough a
s aigh o wa d in si u oxida i e polyme iza ion p ocess in an aqueous
medium (Fig. 1). This me hod acili a es he o ma ion o a 3D in e -
connec ed ne wo k, whe ein he conduc i e polyme embeds, connec s,
and s abilizes Si nanopa icles and Supe P. PPy was selec ed due o i s
excellen elec ical conduc i i y, mechanical lexibili y, and i s abili y o
o m a conduc i e, 3D c osslinked ne wo k when combined wi h a
c osslinking agen such as PhA. Di e en ypes o Si nanopa icles wi h
a ying sizes and physicochemical p ope ies we e in eg a ed wi hin he
anodes o examine he e ec o Si pa icle size, su ace chemis y, and
in insic solid-s a e p ope ies on he elec ochemical pe o mance o Si-
based anodes wi h conduc i e polyme ic binde in LIB.
3.1. Chemical and physical p ope ies o s udied Si nanopa icles and
mic o-s uc u e o anodes
The chemical and physical p ope ies o all Si nanopa icles we e
analyzed and compa ed. The XRD di ac og ams, shown in Fig. 2a,
e ealed he c ys alline na u e o all SiNC (SiNC
6
, SiNC
20
, SiNC
55
, and
SiNC
100
) and he amo phous s a e o SiNA
20
. No ably, a sligh shi in all
peaks owa d highe 2θ alues is obse ed in he di ac og am o SiNC
55
compa ed o o he SiNC, indica ing a s uc u al di e ence [52]. In
addi ion, he SiNC
55
di ac og am exhibi s a small peak a 22.34◦,
which is a ibu ed o he p esence o SiO
2
[53–55]. Va ia ions in peak
shape and sha pness ac oss he SiNC a e associa ed wi h he size o he
nanoc ys als, wi h peak b oadening indica i e o smalle nanoc ys als,
speci ically in he case o SiNC
6
[56]. In con as o SiNC, he di -
ac og am o SiNA
20
displays wo b oad bands, con i ming i s amo -
phous na u e. A simila pa e n has been p e iously epo ed in s udies
o amo phous Si and SiO
2
[57].
Fig. 2b depic s he Raman spec a o he SiNC and SiNA. The Raman
spec a o SiNC exhibi he cha ac e is ic sha p c ys alline Si peak in he
ange o 508–516 cm
−1
, i.e., 516 cm
−1
o SiNC
6
and SiNC
20
, 508 cm
−1
o SiNC
55
, and 511 cm
−1
o SiNC
100
. These peaks a e clea ly dis in-
guishable om he b oad band o SiNA
20
cen e ed a 498 cm
−1
, which is
cha ac e is ic o amo phous Si [58,59]. The Raman spec a u he
co obo a e he indings o he XRD analysis.
The FTIR spec a o he SiNC and SiNA a e p esen ed in Fig. 2c. All
spec a exhibi abso p ion bands cha ac e is ic o Si. The bands obse ed
a 3355 cm
−1
and 1625 cm
−1
a e asc ibed o Si-OH s e ching and
bending ib a ions, espec i ely [60–62], indica ing he p esence o
su ace oxida ion in all he Si nanopa icles. A shoulde a 2246 and a
band a 975 cm
−1
a e associa ed wi h he Si-H ib a ions in O
y
-Si-H
x
[63]. The bands in he anges o 2000–2200, and 600–700 cm
−1
a e
assigned o Si-H ib a ions, speci ically, Si-H s e ching a 2076 cm
−1
,
Si-H
2
s e ching a 2103 cm
−1
, and Si-H
3
s e ching a 2134 cm
−1
, and
Si-H bending and/o Si-H
2
wagging a 655 cm
−1
[64]. Bands a 902 and
851 cm
−1
can be asc ibed o Si-H
3
de o ma ion modes o o Si-H
2
i-
b a ions [64]. No ably, he band a 1042 cm
−1
, co esponding o Si-O-Si
s e ching, u he con i ms he su ace oxida ion o Si nanopa icles
[61,63]. Si-O-Si s e ching is also ep esen ed by ano he shoulde a
794 cm
−1
[60,65], suppo ing he obse a ions. The spec um o SiNC
55
displays an addi ional band a 1230 cm
−1
, a ibu ed o Si-O-Si
s e ching, con i ming he p esence o SiO
2
impu i ies [66,67]. This
inding aligns wi h he XRD esul s, whe e only SiNC
55
exhibi ed a SiO
2
peak, sugges ing a highe deg ee o oxida ion. In e es ingly, he spec-
um o SiNC
100
also e eals a shi ed band a 1206 cm
−1
, which may
indica e ei he he p esence o C [68] o SiO
2
impu i ies.
The XPS spec a u he con i m su ace oxida ion ac oss all Si
Fig. 1. Schema ic illus a ion o he p epa a ion o 3D c osslinked PPy-based anodes.
G. Soukupo ´
a e al.
Jou nal o Powe Sou ces 661 (2026) 238620
4
nanopa icles, which is consis en wi h he indings om he FTIR
analysis. Table S1 summa izes he elemen al a omic composi ion o he
su ace o each sample, e ealing peaks a binding ene gies o app oxi-
ma ely 532, 285, 154, and 100 eV, co esponding o he O(1s), C(1s), Si
(2s), and Si(2p) co e le els. The su ey spec a, combined wi h he
decon olu ion o he Si(2p) and C(1s) co e-le el peaks (Table S1,
Fig. S1), e eal dis inc di e ences be ween he comme cial and lab-
syn hesized Si nanopa icles. The comme cial Si nanopa icles exhibi
a highe su ace O con en and lowe C con en compa ed o he lab-
syn hesized coun e pa s. The decon olu ion o he Si co e-le el
spec a e eals se e al dis inc peaks: Si 2p
3/2
(99.4 eV) and Si 2p
1/2
(100.0 eV), bo h cha ac e is ic o elemen al Si, along wi h peaks co -
esponding o oxidized species, i.e., Si
4+
(103.5 eV), Si
3+
(102.5 eV),
Si
2+
(101.6 eV),and Si
+
(100.6 eV). The p esence o hese oxidized
species is a ibu ed o oxygen e mina ion esul ing om a mosphe ic
exposu e [69]. The spec a o he comme cial Si nanopa icles exhibi a
highe p opo ion o Si
4+
, o igina ing in SiO
2
, compa ed o hei
lab-syn hesized coun e pa s. This obse a ion con i ms di e ences in
he su ace chemis y and indica es a g ea e deg ee o oxida ion, and
hus a highe SiO
2
amoun , in he comme cial samples. This inding is
u he co obo a ed by FTIR spec a, which lack he peak a 2246 cm
−1
,
co esponding o Si-H s e ching ib a ions, in bo h SiNC
100
and SiNC
55
.
The absence o his peak p o ides addi ional e idence o he oxida ion
o hese Si nanopa icles. The na u e o C on he su ace o Si nano-
pa icles was analyzed h ough he decon olu ion o he C co e-le el
spec a, e ealing i e dis inc peaks: C-(C, H) (285.0 eV), C-(O,N)
(286.5 eV), C=O/O-C-O (287.9 eV), O=C-O (289.2 eV), and C-COO
(285.4 eV). These indings closely align wi h p e iously epo ed XPS
spec a o ad en i ious C [70], which ises om con amina ion by C
compounds p esen in he ai . The highe C con en in he
lab-syn hesized Si nanopa icles can be asc ibed o hei highly cu ed
su aces, which a e mo e suscep ible o su ace con amina ion. Upon
exposu e o ai du ing analysis, he highly eac i e Si nanopa icle
su ace eadily adso bs a mosphe ic C, leading o he o ma ion o
su ace-bound C species. The exac condi ions o he p epa a ion p ocess
o he comme cial Si nanopa icles is no known. Howe e , he p esence
o SiO
2
sugges s di e ences in syn hesis and handling p ocedu es, likely
in ol ing mo e ex ensi e su ace oxida ion.
The TEM and SEM images o he Si nanopa icles a e p esen ed in
Fig. 3a – e and Fig. S2, espec i ely. The TEM images e eal a sphe ical
mo phology o all Si nanopa icles. Image analyses o he TEM da a
indica e ha he lab-syn hesized SiNC
20
, SiNA
20
, and SiNC
6
exhibi a
monodispe se size dis ibu ion, wi h minimal s anda d de ia ions (6 ±
1 nm o SiNC
6
, and 20 ±5 nm o SiNC
20
and SiNA
20
), con i ming he
uni o mi y o he nanopa icle o ma ion. In con as , he comme cial
SiNC
100
and SiNC
55
display a signi ican ly b oade size dis ibu ion wi h
la ge s anda d de ia ions (100 ±45 nm o SiNC
100
and 55 ±30 nm o
SiNC
55
). The co esponding pa icle size dis ibu ion cu es a e p e-
sen ed in Fig. S3.
The SEM images o he anodes a e shown in Fig. 3 –i and Fig. S4. The
images e eal good dispe sion and embedding o Si nanopa icles and
Supe P wi hin he 3D po ous, oam-like ne wo k composed o in e -
connec ed dend i ic nano ibe s. No mo phological di e ences we e
obse ed be ween PPy/SiNC
20
and PPy/SiNA
20
, as bo h SiNC
20
and
SiNA
20
ha e simila sizes and su ace chemis ies (side-by-side com-
pa ison o SiNC
20
and SiNA
20
, along wi h Si- ee anode is shown in
Fig. S4). No ably, owing o he QD size o SiNC
6
, he SEM image o he
PPy/SiNC
6
anode shows clus e s o SiNC
6
and Supe P embedded wi hin
PPy ne wo k (Fig. 3i), while he o he anodes exhibi uni o mly
dispe sed, well-de ined, and in e connec ed nano ille s.
Fig. 2. Physico-chemical p ope ies o he Si nanopa icles: a) XRD di ac og ams, b) Raman spec a (* he Raman spec um o SiNC
6
was mul iplied by ac o 2),
and c) FTIR spec a.
G. Soukupo ´
a e al.
Jou nal o Powe Sou ces 661 (2026) 238620
5
The EDX elemen al maps shown in Fig. S5 e eal a homogeneous
dis ibu ion o PPy h oughou he anode c oss-sec ions, as indica ed by
he uni o m p esence o ni ogen, which is speci ic o he PPy s uc u e.
Phospho us is also de ec ed due o he use o PhA as a c oss-linking agen
du ing binde syn hesis, while coppe o igina es om he Coppe oil
used as he cu en collec o . These esul s con i m he e ec i e and
uni o m inco po a ion o he PPy binde wi hin he elec ode s uc u e.
The EDX maps u he demons a e he homogeneous dis ibu ion o Si
ac oss all anode ma e ials, ega dless o nanopa icle size.
3.2. Pe o mance- ela ed cha ac e is ics o he anodes
To e alua e he elec ochemical pe o mance o PPy/SiNC and PPy/
SiNA anodes in hal coin-cell LIB, GCD cycling es s we e conduc ed in
he po en ial window o 0.05–1 V s. Li/Li
+
(PPy decomposes abo e 1V)
a a cu en densi y o 0.4 A/g. Fig. 4a shows he GCD cycling pe o -
mance up o 500 cycles, while Fig. 4b p o ides a zoomed-in iew o he
i s 100 cycles. A co ela ion be ween SiNC size and ini ial speci ic
capaci y is obse ed, wi h he capaci y inc easing as he a e age pa icle
size inc eases. Acco ding o Fig. 4c and Table S2, he highes ini ial
cha ge capaci y o 2975 mAh/g (discha ge capaci y 4732 mAh/g) is
displayed by he PPy/SiNC
100
, while he lowes , 1013 mAh/g (discha ge
capaci y 3291 mAh/g), is obse ed o PPy/SiNC
6
. Fig. 4c also shows
ha SiNC wi h sizes below 100 nm exhibi lowe ini ial e e sible Li
s o age capaci y. The eason can be ound in hei highe su ace a ea
(Table S3), which leads o a ela i ely mo e p ominen i e e sible SEI
o ma ion despi e pa ial p o ec ion by PPy [19,20]. In addi ion, hei
educed ac i e olume can limi Li alloying capaci y, and he s ong
Si–PPy in e ace can ap Li o hinde di usion, lowe ing e e sibili y
[71]. To e alua e he in luence o Si solid-s a e p ope ies (c ys alline s.
amo phous) on elec ochemical pe o mance, he speci ic capaci ies o
PPy/SiNC
20
and PPy/SiNA
20
composi es, bo h con aining Si nano-
pa icles o iden ical a e age size and compa able speci ic su ace a ea,
we e compa ed. PPy/SiNA
20
exhibi s ema kable capaci y e en ion o
78 % a e 500 cycles. This enhanced cycling s abili y is consis en wi h
p e ious epo s and is p ima ily a ibu ed o he iso opic, diso de ed
s uc u e o amo phous Si, which accommoda es olume changes du ing
li hia ion/deli hia ion mo e uni o mly han c ys alline Si [72]. In
Fig. 3. TEM images o Si nanopa icles: a) SiNC
100
, b) SiNC
55
, c) SiNC
20
, d) SiNA
20
, and e) SiNC
6
. SEM images o he anodes: ) PPy/SiNC
100
, g) PPy/SiNC
55
, h) PPy/
SiNC
20
, and i) PPy/SiNC
6
.
G. Soukupo ´
a e al.
Jou nal o Powe Sou ces 661 (2026) 238620
6
con as , c ys alline Si unde goes sha p phase ansi ions (e.g., o
Li
15
Si
4
), leading o localized mechanical s ess and e en ual ac u ing.
The g adual Li
+
inse ion in amo phous Si, wi hou dis inc phase
bounda ies, educes in e nal s ess and helps p ese e s uc u al in eg-
i y o e long- e m cycling. Despi e i s s abili y ad an age, PPy/SiNA
20
deli e s a signi ican ly lowe ini ial cha ge speci ic capaci y (247
mAh/g) han PPy/SiNC
20
, highligh ing he ole o Si c ys allini y in
achie ing highe capaci ies. In e es ingly, wi h ex ended cycling, he
capaci y o PPy/SiNC
20
g adually con e ges owa d ha o PPy/SiNA
20
,
likely due o he p og essi e amo phiza ion o c ys alline Si unde
epea ed li hia ion.
In gene al, all in es iga ed anodes exhibi a capaci y d op du ing he
i s cycle, asc ibed o he o ma ion o he SEI laye , which esul s om
he decomposi ion o he elec oly e [73,74]. Al hough he o ma ion o
he SEI laye leads o i e e sible capaci y loss, i s p esence is bene icial,
as a s able SEI laye subdues ongoing side eac ions wi h he elec oly e
ha would o he wise con ibu e o Li consump ion [74]. The capaci y
loss du ing he ini ial cycles can be co ela ed wi h he size and he
speci ic su ace a ea o he SiNC, as summa ized in Table S3. Ni ogen
physiso p ion measu emen s con i m ha he speci ic su ace a ea
Fig. 4. Elec ochemical pe o mance in po en ial window 0.05–1 V a cu en densi y 0.4 A/g o anodes con aining SiNC o SiNA: a) GCD cycling o 500 cycles, b)
zoom o he GCD cycling up o 100 cycles, c) gal anos a ic ol age p o iles om he 1s cycle, d) coulombic e iciency; e) capaci y e en ion a e 100 cycles and
ini ial speci ic capaci y (measu ed a 2nd cycle) o anodes con aining SiNC, and ) e olu ion o capaci y e en ion du ing he cycling o each PPy/SiNC
anode ma e ial.
G. Soukupo ´
a e al.
Jou nal o Powe Sou ces 661 (2026) 238620
7
inc eases as he pa icle size dec eases. Fo ins ance, PPy/SiNC
6
, which
con ains SiNC
6
wi h he smalles pa icle size and he highes speci ic
su ace a ea (509.4 m
2
/g), displays he mos subs an ial ini ial capaci y
loss. As epo ed by Kong e al. [74], while Si nanos uc u ing educes
olume expansion, i also inc eases he o ma ion o he SEI laye due o
he inc eased speci ic su ace a ea, leading o enhanced Li consump ion.
Simila ly, he coulombic e iciency (CE) (Fig. 4d) in he i s cycle is
signi ican ly below 100 % o all anodes due o he SEI laye o ma ion.
Among hem, PPy/SiNC
100
exhibi s he highes ini ial CE (63 %), while
PPy/SiNC
6
shows he lowes (31 %). Ne e heless, in subsequen cycles,
he CE inc eases o nea ly 100 % o all anodes. This end o inc easing
capaci y loss in he i s cycle wi h dec easing SiNC pa icle size aligns
wi h he indings o Nadimpalli e al. [75], who epo ed ha a highe
speci ic su ace a ea leads o g ea e ini ial capaci y d op, ul ima ely
educing ene gy densi y in la e cycles. The e olu ion o capaci y
e en ion du ing GCD cycling is shown in Fig. 4e– and Table S2.
PPy/SiNC
100
exhibi s he lowes capaci y e en ion (24 % a e 100 cy-
cles), while PPy/SiNC
6
shows he highes e en ion (85 % a e 100
cycles). All anode ma e ials expe ience capaci y ade du ing epea ed
cha ge/discha ge cycling, p ima ily due o he deg ada ion o SiNC,
which is linked o he olume expansion o SiNC and he o ma ion o an
uns able SEI [74]. A e 500 cycles, PPy/SiNC
100
e ains only 3 % o i s
capaci y, whe eas PPy/SiNC
6
main ains a capaci y e en ion o 44 %.
In o de o de e mine whe he he imp o emen in cycling s abili y is
solely a ibu ed o he dec easing size o SiNC, a PPy hyd ogel-de i ed
anode ee o SiNC was p epa ed using he same expe imen al p oced-
u e. Al hough he measu ed capaci y (Fig. S6) was inhe en ly low, gi en
ha SiNC is he p ima y ac i e ma e ial in his sys em, no capaci y
deg ada ion was obse ed o e 500 cycles. Ins ead, he capaci y g ad-
ually inc eased. This emphasizes he signi ican ole o SiNC on he
o e all capaci y decay. To u he con i m he bene icial ole o he 3D
in e connec ed PPy s uc u e in combina ion wi h SiNC, an anode ma-
e ial composed o non-c osslinked PPy and SiNC
20
(a ep esen a i e
ype o SiNC) was p epa ed. The GCD cycling o he esul ing anode,
labeled as PPy
non-c osslinked
/SiNC
20
(Fig. S7), e eals poo cycling s a-
bili y, wi h he speci ic capaci y d opping om app oxima ely 800
mAh/g o nea ly 0 mAh/g a e 300 cycles. These indings highligh he
impo ance o combining small SiNC wi h a 3D c osslinked PPy ma ix o
achie e good capaci y e en ion. The SiNC se es as he p ima y ac i e
ma e ial in he anode, while he c osslinked PPy ma ix bu e s me-
chanical s ess and enhances elec ical conduc i i y. I is wo h no ing
ha he p onounced capaci y ade obse ed in he PPy/SiNC
100
could
also be pa ially a ibu ed o he size he e ogenei y o SiNC
100
[76,77].
The GCD p o iles we e measu ed a a ious cu en densi ies
(Fig. S8) o 0.4, 0.7, 1.8, and 3.6 A/g and compa ed o wo selec ed
ep esen a i e anodes, PPy/SiNC
20
and PPy/SiNC
100
. The cha ge ca-
paci y o PPy/SiNC
20
anges om ~1280 o 165 mAh/g, demons a ing
good s abili y and e e sibili y, especially a lowe cu en a es. A e
e u ning o 0.4 A/g, i eco e s i s p e ious capaci y alues. In con as ,
he cha ge capaci y o PPy/SiNC
100
a ies om 2698 o 69 mAh/g.
In e es ingly, his anode does no show he same le el o e e sibili y
and s abili y as he one wi h a smalle SiNC
20
. While he e e sibili y o
PPy/SiNC
100
emains ai ly high, i does no ully eco e i s p e ious
capaci y upon e u ning o 0.4 A/g. This beha io could be pa ially
ela ed o he b oade size dis ibu ion o SiNC
100
, which may lead o
une en li hia ion and non-uni o m SEI o ma ion. O e all, hese obse -
a ions emphasize he bene icial ole o small, mo e uni o m SiNC (20
nm) in enhancing cycling s abili y and capaci y e en ion.
To in es iga e he s uc u al and mo phological e olu ion o he
anode ma e ials a e he GCD cycling, ep esen a i e anodes we e
analyzed by Raman spec oscopy and SEM be o e and a e cycling. SEM
images (Fig. S9) o he anode ma e ials on hei c oss-sec ions a e he
cycling show a loss o he s uc u e and/o he buildup o he SEI;
howe e , his migh also be caused by he elec oly e emnan s. The
Raman spec a o PPy/SiNC
100
and PPy/SiNC
20
be o e and a e he
cycling a e compa ed o hose o PPy/SiNA
20
(Fig. S10). All anodes
display he cha ac e is ic peaks o PPy (e.g., he peak a 970 cm
−1
,
co esponding o he in-plane ing de o ma ion o he pola on s a e, and
he peak a 938 cm
−1
, assigned o bipola on s a e) [78,79] along wi h
he dis inc Si peak. P io o cycling, he Si peak appea s a 515 cm
−1
o
bo h PPy/SiNC
100
and PPy/SiNC
20
, co esponding o he c ys alline Si.
Howe e , a e cycling, a no iceable downshi o he SiNC peak (~472
cm
−1
), along wi h an asymme y owa ds lowe wa enumbe s, is
obse ed, aligning wi h he peak shape and posi ion o PPy/SiNA
20
.
These changes con i m he amo phiza ion o SiNC a e cycling.
Table S4 p esen s he elec ochemical pe o mance o ou de eloped
anodes con aining SiNC
6
and SiNC
20
(i.e., PPy/SiNC
6
and PPy/SiNC
20
)
in compa ison wi h he mos ele an hyd ogel-de i ed conduc i e
polyme binde /Si anodes epo ed in he li e a u e. I is wo h
men ioning ha wo key ac o s mus be conside ed be o e making any
di ec compa ison. Fi s o all, he Si used in hose s udies a ies
signi ican ly in e ms o pa icle size and su ace chemis y. In many
cases, p ope ies such as c ys allini y and su ace chemis y a e nei he
analyzed no discussed. O en, comme cially a ailable Si is selec ed
wi hou ho ough examina ion and used as is, which can in oduce
signi ican a iabili y in he esul s. As demons a ed in ou s udy, any
su ace modi ica ion, p onounced oxida ion, o al e a ion in he c ys-
alline s uc u e can ha e a emendous impac on he esul ing elec-
ochemical p ope ies. Secondly, he condi ions unde which he
elec ochemical measu emen s a e pe o med, such as he po en ial
window, cu en a e, elec oly e used, and he numbe o cycles, also
a y ac oss s udies. In addi ion, impo an de ails, such as whe he he
epo ed ini ial speci ic capaci y e e s o discha ge o cha ge capaci y o
whe he he s a ed capaci y e en ion is ela ed o he 1s , 2nd, o la e
cycles, a e no always clea ly speci ied. The e o e, di ec compa isons o
hese esul s should be made wi h cau ion, as hey may conceal se e al
po en ial pi alls. Bo h anodes (PPy/SiNC
6
and PPy/SiNC
20
) p esen ed
in his s udy exhibi p omising cha ac e is ics and p ope ies ac oss
a ious pa ame e s. The p epa a ion p ocedu e was conduc ed in an
aqueous medium using a conduc ing polyme as a binde , bo h o which
a e en i onmen ally iendly. As shown in Table S4, hese anodes ach-
ie ed ini ial discha ge capaci ies o 3291 mAh/g o PPy/SiNC
6
and
2978 mAh/g o PPy/SiNC
20
, which a e among he highes alues e-
po ed o 3D c osslinked conduc i e polyme ic binde /Si anode ma e-
ials. Al hough hei ini ial cha ge capaci ies a e ela i ely modes (1014
mAh/g o PPy/SiNC
6
and 1273 mAh/g o PPy/SiNC
20
), hey emain
signi ican and a e compa able o hose epo ed in he li e a u e [5,9,
35]. Fu he mo e, he ob ained capaci y e en ions o his wo k a e
sa is ac o y and compa able wi h p e iously epo ed esul s (Table S4).
Fo deepe unde s anding o he elec ochemical pe o mance, CV
was conduc ed on coin hal -cell ba e ies (Fig. 5 and Fig. S11). Mea-
su emen s we e pe o med in he po en ial window o 0.05–1 V a a scan
a e o 0.1 mV/s. Fig. 5a–c compa es 1s , 3 d, and 10 h cycles o all he
anodes and Fig. S11 p esen s CV o each anode sepa a ely. In he 1s
cycle, a educ ion peak appea s a 0.4 V o PPy/SiNC
20
, 0.5 V o PPy/
SiNC
6
, and app oxima ely 0.6 V o PPy/SiNC
100
and PPy/SiNC
55
. This
peak disappea s in subsequen cycles and co esponds o he i e e sible
eac ion o elec oly e decomposi ion on he anode su ace, and o he
o ma ion o he SEI laye [80–82]. In he PPy/SiNA
20
, anode, he
cha ac e is ic educ ion peak associa ed wi h SEI o ma ion is no
dis inc ly obse ed du ing he i s cycle o CV. When amo phous Si is
used as he anode ma e ial, he absence o a p onounced educ ion peak
a e he i s cycle, despi e a signi ican capaci y loss, could be a ib-
u ed o he na u e o Li inse ion in o amo phous Si [83–85]. Unlike
c ys alline Si, which unde goes a clea phase ans o ma ion du ing
ini ial li hia ion [86], amo phous Si accommoda es Li ia a g adual,
solid-solu ion mechanism wi hou sha p phase ansi ions [83–85]. This
esul s in b oad, indis inc elec ochemical ea u es a he han
well-de ined educ ion peaks. The capaci y ade obse ed in GCD mea-
su emen s (Fig. 4b) is p ima ily due o i e e sible SEI o ma ion, me-
chanical s ess, and Li becoming apped in elec ochemically inac i e
phases, a he han al e a ions in he undamen al Li mechanism.
G. Soukupo ´
a e al.
Jou nal o Powe Sou ces 661 (2026) 238620
8
Ne e heless, SEI o ma ion is e iden , as indica ed by he capaci y
decline in GCD cycling (Fig. 4b) and he impedance inc ease obse ed in
EIS (Fig. 6d).
In e es ingly, PPy/SiNC
55
exhibi s a b oad educ ion peak a a ound
0.9 V, which is signi ican ly mo e in ense han he peak a 0.6 V, sug-
ges ing he occu ence o ano he i e e sible eac ion. This peak
(a ound 0.9 V and highe ) has been p e iously connec ed wi h he
i e e sible eac ion be ween SiO
2
and Li
+
, esul ing in he con e sion o
SiO
2
o Si and li hium silica es (e.g., Li
4
SiO
4
) and li hium oxide (e.g.,
Li
2
O) [87,88]. This obse a ion aligns well wi h he ea lie analysis o
SiNC
55
, which showed a highe SiO
2
con en . Du ing con inued CV
cycling, ou peaks eme ged [50]. Reduc ion ca hodic peaks a 0.17 V
and 0.05 V a e linked o he con e sion o c ys alline Si o amo phous
Li-Si phases (a-Li
x
Si) du ing he li hia ion and he subsequen c ys alli-
za ion and o ma ion o c-Li
3.75
Si [8,81]. Oxida ion anodic peaks a 0.35
V (a-Li
3.5
Si o a-Li
2
Si) and 0.5 V (a-Li
2
Si o a-Si) co espond o he
ansi ion o c ys alline o an amo phous phase, ollowed by a dealloying
eac ion [8,89,90]. Howe e , PPy/SiNC
6
and PPy/SiNA
20
(Fig. S11d–e)
ini ially showed only one educ ion and one oxida ion peak. This
beha io can be expec ed o PPy/SiNA
20
as i con ains amo phous Si,
meaning he e is no ansi ion om c ys alline o amo phous Si, and
only alloying and dealloying p ocesses occu . As CV cycling con inues, a
educ ion peak a ound 0.1 V s a s o appea , indica ing a g adual
ac i a ion o li hia ion si es. In he case o PPy/SiNC
6
, only one educ-
ion and one oxida ion peak a e obse ed un il he 7 h cycle, when he
educ ion peak a 0.17 V i s appea s. The anodic peak a 0.35 V e-
mains ba ely no iceable h oughou he 10 cycles. These obse a ions
sugges ha he li hia ion connec ed wi h phase ans o ma ion o bo h
PPy/SiNC
6
and PPy/SiNA
20
is slowe compa ed o hose o PPy/SiNC
20
.
The posi ions o bo h educ ion and oxida ion peaks emain s able
h oughou cycling o all he s udied anodes, indica ing good e e s-
ibili y o he Si-Li eac ions [89]. CV cycling es s o PPy/SiNC
20
,
PPy/SiNC
6
, and PPy/SiNC
55
e eal inc easing peak in ensi ies o e
ime, a phenomenon p e iously epo ed in he li e a u e and asc ibed o
he ac i a ion p ocess o he anode ma e ial [89]. This ac i a ion p ocess
is acili a ed by he amo phiza ion o Si, which enhances li hia ion ca-
paci y wi h each cycle [91]. No ably, his e ec is less p onounced o
PPy/SiNC
100
, whe e peak in ensi ies ini ially inc ease bu begin o
decline a e 5 cycles. This beha io can be a ibu ed o he la ge size o
SiNC
100
, as well as i s size he e ogenei y, and a limi ed li hia ion ime,
which es ic s he dep h o li hia ion and s ess buildup o he
sub-su ace egions in he la ge nanopa icles. This localized s ess can
cause nanopa icle ac u e, deac i a ion, and a subsequen dec ease in
peak in ensi y [91]. In con as , he peak in ensi ies o PPy/SiNC
55
(Fig. S11b) inc ease sligh ly o e cycling, as a esul o he smalle size o
SiNC
55
.
Among all he anodes, PPy/SiNC
20
demons a es he bes CV pe -
o mance, which can be linked o he op imal size o he SiNC
20
, which
balances su ace a ea, Li
+
di usion, and mechanical s abili y. In
con as , PPy/SiNC
6
exhibi s lowe peak in ensi ies, e lec ing educed
elec ochemical ac i i y and co ela ing wi h i s ini ially lowe speci ic
capaci y (Fig. 4a). This diminished pe o mance is likely a esul o
nanopa icle agglome a ion, which nega es he ypical ad an ages o
ul asmall pa icle sizes (<20 nm) [92]. Indeed, as p e iously obse ed,
SEM images o PPy/SiNC
6
(Fig. 3i) e eal signi ican agglome a ion o
SiNC
6
, a ea u e unique o his anode.
Meanwhile, PPy/SiNC
55
shows lowe elec ochemical ac i i y
consis en wi h he highe deg ee o oxida ion exhibi ed by SiNC
55
(i.e.,
g ea e SiO
2
con en ). Since SiO
2
is la gely elec ochemically inac i e, i
con ibu es minimally o e e sible Li s o age and can hinde pe o -
mance by o ming insula ing byp oduc s du ing li hia ion. As no ed
abo e, du ing li hia ion, SiO
2
can unde go an i e e sible eac ion wi h
Li
+
o o m li hium silica es and li hium oxide [93], which consume Li
+
wi hou con ibu ing o e e sible capaci y. These eac ion p oduc s a e
ypically elec ically insula ing and can block Li di usion pa hways,
u he educing he ac i e use o su ounding Si [94]. In addi ion, SiO
2
on he su ace o SiNC
55
can hinde he o ma ion o Li–Si alloys by
ac ing as a ba ie laye , educing bo h Li accessibili y and o e all
Fig. 5. CV measu emen s a a scan a e 0.1 mV/s o all he anodes in a) 1s , b) 3 d cycle, and c) 10 h cycles.
G. Soukupo ´
a e al.
Jou nal o Powe Sou ces 661 (2026) 238620
9
