Jou nal o Ene gy S o age 54 (2022) 105367
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Resea ch pape s
Su ace modi ica ion o ac i a ed ca bon wi h sil e nanopa icles o
elec ochemical double laye capaci o s
Am i a Jain
a
,
*
, Monika Michalska
b
, Angelika Zaszczy´
nska
a
, Pio Denis
a
a
Ins i u e o Fundamen al Technological Resea ch, Polish Academy o Sciences, Pawi´
nskiego 5B, 02-106 Wa saw, Poland
b
Depa men o Chemis y and Physico-Chemical P ocesses, Facul y o Ma e ials Science and Technology, Vˇ
SB-Technical Uni e si y o Os a a, 17. lis opadu 2172/15,
708 00 Os a a-Po uba, Czech Republic
ARTICLE INFO
Keywo ds:
Supe capaci o
Ac i a ed ca bon-sil e composi e
Gel polyme elec oly e
Elec ochemical s udies
ABSTRACT
In he p esen wo k, we epo he syn hesis o su ace modi ied ac i a ed ca bon (AC). The su ace o he
ac i a ed ca bon ha e been modi ied by using sil e nanopa icles. The syn hesis p ocess is simple, cos e ec i e
and en i onmen iendly. The modi ied-AC powde s ha e been cha ac e ized by using X- ay di ac ion, scan-
ning elec on mic oscopy and su ace a ea and po e size measu emen s. The elec ochemical pe o mance o he
p epa ed ma e ials ha e been es ed by ab ica ing symme ic con igu a ion o EDLC by using magnesium-ion
based polyme elec oly es. The cells ha e been es ed by using cyclic ol amme y, elec ochemical imped-
ance spec oscopy and gal anos a ic cha ge-discha ge echnique. AC wi h 3 w % o sil e p esen s bes esul s
wi h speci ic capaci ance o he o de o 398 F g
−1
ene gy densi y and powe densi y o 55 Wh kg
−1
and 2.4 kW
kg
−1
making i an in e es ing ma e ial o supe capaci o applica ion.
1. In oduc ion
Conside ing he high powe densi y, quick echa ge ime, and long
li e, supe capaci o s (SCs) ha e a ac ed a lo o a en ion in ecen
yea s [1–4]. They ha e been u ilized in a wide ange o a eas, such as
po able and comme cial/household elec onics, g id ins alla ions, and
di e en o ms o anspo a ion (buses, ams, olleybuses, e c.) [1–4].
The con igu a ion o a supe capaci o de ice is as simple as con en ional
capaci o s [5,6]. An elec oly e (liquid/solid/gel) is sandwiched be-
ween wo elec oac i e elec odes o ab ica e a supe capaci o cell
[5,6]. On he basis o he ypes o elec ode ma e ials used and he
cha ge s o age mechanism, i is classi ied in o wo ypes; (a) elec o-
chemical double laye capaci o s (EDLCs) in which la ge su ace a ea
ca bonaceous ypes o ma e ials a e used and he cha ge s o age
mechanism is elec os a ic in na u e; and (b) pseudocapaci o s, in which
conduc ing polyme s and elec oac i e oxides a e used and as a adic
cha ge ans e eac ion gi es ise o pseudocapaci ance [1–8].
Ca bon-based ma e ials ha e been applied as a i s ma e ials in
elec odes in li hium-ion ba e ies and supe capaci o s due o hei
na u al abundance, low cos , high elec ical conduc i i y, and signi i-
can capaci ance ela ed o hei high speci ic su ace a ea [9–12].
Di e en o ms o ca bon ha e been es ed as elec ode ma e ials in SCs
such as: ca bon nano ubes (CNT), g aphene, ca bon ae ogel, ca bon
nano ibe s (CNF) and ac i a ed ca bon (AC) [9–22]. Up o now, ac i-
a ed ca bons a e a ac i e elec ode ma e ials o an EDLC capaci o
om he economic poin o iew and he possibili y o ob aining a well-
de eloped speci ic su ace a ea o ca. 2500 m
2
g
−1
wi h a con olled po e
size dis ibu ion and also because o i s su ace chemis y which can be
easily modi ied o imp o e i s pe o mance by su ace modi ica ion ia;
pos ea men o ca bon ma e ials wi h eac i e he e oa om sou ces o
by making composi es o ca bon wi h ei he me al oxide ma e ials o
conduc ing polyme s [21–25]. Yumak e al. [23] p epa ed he com-
posi es o ac i a ed ca bon wi h MnO
2
as well as wi h NiO using hy-
d o he mal and p ecipi a ion echniques. The au ho s disco e ed ha
adding MnO
2
and NiO o ac i a ed ca bon-based supe capaci o s
inc eased hei speci ic capaci ance by 50 % and 150 %, espec i ely
[23]. This beha io was asc ibed o he pseudocapaci i e e ec o MnO
2
and NiO, as well as he e ec o oxygen-con aining su ace unc ional
g oups de i ed om he composi e syn hesis p ocess [23]. The au ho s
also claimed ha he su ace unc ional g oups, su ace a ea, and he -
mal s abili y o achie ed composi e ma e ials, as well as he elec o-
chemical pa ame e s o ab ica ed supe capaci o s, we e all a ec ed by
he syn hesis p ocedu e [23]. Vijayan and co-au ho s [26] p oposed he
easy echnique o modi y ac i a ed ca bon ma e ial wi h hin
* Co esponding au ho .
E-mail add ess: [email p o ec ed] (A. Jain).
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Jou nal o Ene gy S o age 54 (2022) 105367
2
manganese oxide and hey e ealed ha he bes esul s o a wo- old
inc ease in he speci ic capaci ance in 1 M Na
2
SO
4
elec oly e deli -
e ed ma e ial o composi ion: 10 w % Mn
2
O
3
@AC [26]. The au ho s
es ed hei ma e ial as a symme ic supe capaci o wi h 1 M Na
2
SO
4
elec oly e and he ma e ial had an ene gy densi y o 31 Wh kg
−1
, powe
densi y o 4.8 kW kg
−1
[26]. A edox eac ion was u ilized o deposi he
RuO
2
nanopa icles on he mic opo ous ca bon su aces by Y. Zhang and
S.-J. Pa k [27]. The ma e ial o composi ion 9 w % RuO
2
@AC had a
speci ic capaci ance o 510 Fg
−1
, a a cu en densi y o 1 Ag
−1
, and he
capaci ance e en ion was 87 % a a cu en densi y o 1 Ag
−1
a e 3000
cycles [27]. A hin me allic cobal ilm was deposi ed on po ous ca bon
(PC) by Vijayan e al. [28]. The modi ied ma e ial (10 w % Co@PC) was
examined as an elec ode o aqueous alkaline supe capaci o s in 1 M
Na
2
SO
4
and li hium-ion capaci o s using an ionic liquid (1 M LiPF
6
). The
speci ic ene gy and speci ic powe o he aqueous alkaline supe -
capaci o buil wi h he Co-modi ied po ous ca bon elec ode we e
nea ly 10 imes highe han hose p epa ed wi h he pu e po ous ca bon
elec ode [28]. The composi e made o oid-size-ma ched hie a chical
3D i ania lowe s in po ous ca bon (TiO
2
@AC) was syn hesized by he
hyd o he mal me hod [29]. The composi e ma e ial was es ed in 1 M
Na
2
SO
4
elec oly e and he cons uc ed elec ode in SCs deli e ed 143 F
g
−1
a 1 A g
−1
, ene gy densi y o 28 W h kg
−1
, powe densi y o 4.8 kW
kg
−1
, and he s abili y was 95 % a a cu en densi y o 1 Ag
−1
a e
5000 cycles [29]. Hyd o he mal syn hesis was u ilized by Mohamed
e al. [30] o ob ain composi e o ZnO@ac i a ed ca bon. The ma e ial
was examined as supe capaci o elec ode ma e ial in acidic (H
2
SO
4
)
and alkaline (KOH) elec oly es [30]. The speci ic capaci ance o 667
Fg
−1
o ZnO@ac i a ed ca bon composi e showed be e capaci ance
pe o mance when compa ed o p is ine AC (355 Fg
−1
) [30]. A e 3000
cycles, he ma e ial main ained 90 % o i s speci ic capaci ance [30].
The goal o as-p esen ed wo ks was o show ha each modi ica ion wi h
me allic, me al oxide pa icles, o conduc i e polyme s o o he ca bon
ma e ials posi i ely a ec he elec ochemical pe o mances while he
ma e ial was es ed as supe capaci o elec ode ma e ial. Mo eo e , he
esea che s also claimed ha a e he modi ica ion he achie ed com-
posi es ma e ials possessed highe speci ic su ace a ea and po osi y
which esul ed o inc ease desi ed pa ame e s o SC applica ions, like
speci ic capaci ance, ene gy, and powe densi y. Conside ing he abo e-
men ioned ac s in he p esen wo k, he su ace o he ac i a ed ca bon
has been modi ied by using sil e (Ag) pa icles, hese pa icles will
enhance he elec ical cha ge ans e which inally imp o es he elec-
ochemical pe o mance. Kim e al. epo ed he e ec o modi ying he
g aphi e nano ibe s and PANI elec ode wi h Ag nanopa icles and
ound ha sil e signi ican ly imp o ed he speci ic su ace a ea along
wi h he elec ochemical u iliza ion o elec odes [31].
Along wi h he elec ode ma e ials, elec oly es a e also he impo -
an componen o ene gy s o age de ice like li hium-ion ba e ies o
supe capaci o s [32–35]. Because o hei di e en physical and chem-
ical p ope ies, hey play di e en ly a he in e ace wi h di e en
elec odes and hence hey possess di e en elec ochemical cha ac e -
is ics o he de ice. Though aqueous elec oly es like KOH, H
2
SO
4
, NaCl
e c. ha e ad an ages like high ionic conduc i i y, en i onmen ally
iendly, cos e ec i e, non- lammabili y e c. bu he main d awback is
i s limi ed elec ochemical s abili y ange and unsa e handling [35]. In
o de o ind a mid-way, gel polyme elec oly es (GPEs) a e excellen
subs i u e due o hei accep able ionic conduc i i y and solid like
dimensional s abili y. The mos commonly used polyme s o en ap he
liquid elec oly es a e poly( inyl alcohol) (PVA) [36,37], poly( inyl
py olidone) (PVP) [38], poly(me hyl me hac yla e) (PMMA) [39], poly
( inylidene luo ide-co-hexa luo op opylene) (PVdF-HFP) [40,41] e c.
Ou o hese polyme s, PVdF-HFP is used abundan ly because o i s good
mechanical s abili y, he mal s abili y and chemical esis i i y.
In he p esen wo k, su ace modi ied ac i a ed ca bon wi h di e en
weigh pe cen age o sil e pa icles we e used as an elec ode ma e ial
and ee s anding gel polyme elec oly e using PVdF-HFP as hos
polyme and magnesium pe chlo a e (Mg(ClO
4
)
2
) as sal we e used.
Modi ied ac i a ed ca bon has been cha ac e ized by using di e en
echniques like BET, XRD and SEM, EDLC cell has been ab ica ed by
using su ace modi ied ac i a ed ca bon and GPE. The pe o mance
cha ac e is ics o EDLC cells ha e been e alua ed by impedance spec-
oscopy, cyclic ol amme y (CV) and gal anos a ic cha ge-discha ge
measu emen s.
2. Expe imen al de ails
2.1. P epa a ion o su ace modi ied ac i a ed ca bon
The nanocomposi es o ac i a ed ca bon (AC) (Ac i a ed cha coal
pu e p.a., CHEMPUR) wi h 1, 3 and 5%w . Ag we e ab ica ed by a acile
chemical low- empe a u e ou e. In he i s s ep, AgNO
3
(used as a Ag
sou ce, pu chased as a pu e om Lachema) was dissol ed in e hanol
solu ion (E OH, 96 %, Me ci) in he weigh a io Ag/AC: 0.01, 0.03, and
0.05, espec i ely. This p ocess was ca ied ou a oom empe a u e. In
he second s ep, he AC powde was added o he AgNO
3
-E OH-H
2
O
solu ion. The as-p epa ed mix u e was magne ically s i ed o a ew
hou s o ob ain a black homogeneously dispe sed suspension. A e -
wa ds, he suspension was kep in an ul asonic wa e ba h cleane o 1
h om 25 o 60 ◦C. Each suspension was o e nigh ai -d ied a 60 ◦C and
hen a 150 ◦C o a ew hou s. To ob ain a ine powde , he AC/n-Ag (n-
deno es: 1, 3 and 5%w . Ag) nanocomposi es we e g inded in an aga e
mo a o 1 h. The p epa ed samples om he ea e called as ACAG1,
ACAG3, ACAG5.
The s uc u e o he p epa ed ca bon ma e ial composi es we e
cha ac e ized by using X-Ray powde di ac ion (XRD) by using B uke
D8 Disco e Di ac ome e equipped wi h CuK
α
(λ
XRD
=1.542 Å) a-
dia ion sou ce and by he con ocal Raman spec ome e (Renishaw
inVia) equipped wi h a cha ge-coupled de ice (CCD) came a and a
con inuous wa e diode pumped Nd:YAG lase wo king a λ =532 nm,
espec i ely. Mo phological s udies o ACAG1, ACAG3 and ACAG5 we e
ca ied ou by ield emission scanning elec on mic oscopy using he
ins umen SEM/FIB-Zeiss C ossbeam 350, Ge many. A he mal
analyze DSC SDTQ600, DSC TGA Ins umen was used o s udy he
he mal s abili y o ACAG composi e ma e ials om 30
C o 900
C wi h a
hea ing a e o 10
 C min
−1
unde A gon low 20 ml min
−1
. The speci ic
su ace a eas o he ca bon ma e ials we e measu ed wi h he Au oSo b
IQ, Quan ach ome, USA unde ni ogen low. The po e size dis ibu ion
cu es we e ob ained by using DFT model.
2.2. Fab ica ion and cha ac e iza ion o EDLC cells
GPE ilms we e p epa ed by using s anda d solu ion cas echnique.
The de ails o he p epa a ion and cha ac e iza ion o he polyme ic
ilms we e desc ibed elsewhe e [42]. The capaci o elec odes we e
p epa ed in he o m o lexible elec odes. All he h ee ac i a ed ca bon
powde s (ACAG1, ACAG3, ACAG5) we e g inded o 30 min indi idu-
ally in pes le mo a o ge a uni o m and ine powde . PVdF is used as a
binde in he a io o 90:10 (w/w). PVdF and ace one (sol en ) was
magne ically s i ed o 30 min and la e a slu y was pe o med. The
slu y was cas ed o e ca bon clo h (A Ca b, USA). The p epa ed elec-
odes we e ai d ied a 80 ◦C be o e using hem o ab ica e he EDLC
cells. The mass loading o ac i e ma e ial was in be ween 0.39 and 0.43
mg cm
−2
. To ab ica e he EDLC cell, GPE we e sandwiched be ween he
symme ical elec odes. Th ee EDLC cell (Cell A-C) we e ab ica ed by
using ACAG1, ACAG3, ACAG5 espec i ely. All he cells we e elec o-
chemically cha ac e ized by using Biologic VMP3 (Seyssine -Pa ise ,
F ance) elec ochemical wo ks a ion.
A. Jain e al.
Jou nal o Ene gy S o age 54 (2022) 105367
3
3. Resul s and discussion
3.1. S uc u al s udies and mo phology da a (XRD, Raman spec oscopy,
SEM, BET and TGA)
The XRD pa e n o ac i a ed ca bon (AC) ma e ial, pu e and deco-
a ed wi h 1, 3 and 5 % w . Ag is p esen ed in Fig. 1. The AC amo phous
peaks a e si ua ed a a ound 26◦and 43◦[12]. The e a e also isible
c ys al peaks o pu e AC, coming om g aphi e o o he hexagonal
ca bon s uc u es. As shown in Fig. 1, he di ac og ams o ma e ials
wi h Ag p esen , ea u e wo cha ac e is ic peaks a 2θ angles o : 38.1,
and 44.3◦ o CuK
α
adia ion (λ =1.542 Å), co esponding o he c ys al
planes (111) and (200), espec i ely. Tha wo e lec ions ep esen he
me allic Ag phase (COD 9008459). C ys al peak a 32.1
o
can be asc ibed
o he nanoc ys alline sil e , (122) plane [43]. The peaks in ensi y
g ow h wi h he inc ease o Ag con en om 1 o 5 % w . was obse ed
and indica ed ha me allic Ag nanopa icles we e success ully deposi ed
on he su ace o ac i a ed ca bon ma e ial. These esul s we e u he
con i med by SEM analysis as well as ha e ound posi i e e ec while
elec ochemical pe o mances we e e alua ed. Acco ding o he Ag
single c ys alli es size analysis, hey a e supposed o be below 1 nm, and
he Ag pa icles obse ed in SEM, consis ing o many c ys alli es, ha e
an a e age size o 10 nm.
Raman spec oscopy was u ilized o ge mo e in o ma ion abou he
s uc u al ea u es o p is ine AC ma e ial and one selec ed sample o AC
modi ied wi h 3%w . Ag. The ob ained esul s a e p esen ed in Fig. 2.
The c ys al s uc u e o AC powde s emained unchanged a e Ag
modi ica ion, as expec ed. The Raman spec a ea u e ou well-de ined
bands a 1340, 1580, 2690, and 2942 cm
−1
, which co espond o he D,
G, 2D, and D +G bands o ypical g aphi ic ma e ials, espec i ely [12].
A ibu ed o he p e alence o sp
3
hyb idiza ion in he ca bon s uc u e
and he E
2g
phonon ib a ions o he sp
2
ca bon a oms, he D and G
bands a e ela ed wi h he A
1g
ib a ional mode o he diso de ed ca bon
s uc u e [12,44]. The sca e ing o phonons a he zone bounda y (K
poin ) causes he 2D mode, which is a second-o de ib a ion o he G
mode [12,43]. The combina ion o D and G peaks can be induced by he
p esence o a ious de ec s in he g aphi ic s uc u e [12,44]. I is also
possible o es ablish he “deg ee o g aphi iza ion”, which in o ms on
he c ys allini y le el o ca bon ma e ials, by compa ing he in ensi y
a ios o he D o G bands (I
D
/I
G
) [12,44]. Fo he AC and ACAG3
samples, he es ima ed I
D
/I
G
alues a e 1.100 and 1.093, espec i ely.
These calcula ions o he in ensi y a ios e ealed ha bo h o he ca bon
s uc u es s udied: p is ine AC and AC modi ied wi h 3%w . Ag ma e-
ials a e qui e diso de ed. The AC ma e ial modi ied wi h 3%w . Ag has
a li le highe deg ee o g aphi iza ion in compa ison o p is ine AC
ma e ial.
The su ace mic og aphs o sil e modi ied ac i a ed ca bon
(ACAG1, ACAG3, ACAG5) a e illus a ed in Fig. 3. As can be seen om
he mo phologies ha deposi ion o sil e nanopa icles we e con i med
and hey we e obse ed as a small balls (less han 10 nm). Owing o
special mo phology which ep esen ac i a ed ca bon ma e ial we could
suppose ha he small balls o me allic Ag a e placed be ween he ca -
bon nanoshee s. Also, om he mo phology o ACAG3 i can be seen ha
he small po es a e de eloped which p o ides he acile accessibili y o
elec oly e ions, which a e bene icial in o ming capaci i e in e ace
wi h gel polyme elec oly es.
The he mal beha io s o ACAG1, ACAG3, and ACAG5 samples we e
examined om 30 o 900 ◦C wi h a hea ing a e 10 ◦C min
−1
in a gon
a mosphe e (Fig. 4). The h ee-s age loss o weigh is obse ed o all
analyzed samples. Fi s occu s om he empe a u e 30 o ca. 150 ◦C and
is ela ed o he e apo a ion o he esidual wa e (ca. 9 %) as well as
accompanies he decomposi ion p ocesses o ca bon ma e ial in o non-
condensable gases such as CO, CO
2
, CH
4
, H
2
, and o he s [45]. The
weigh loss obse ed in he second s age, be ween ca. 200 ◦C and 600 ◦C,
is a ibu able o he hea deg ada ion o aw ma e ials. These eac ions
a e accompanied by u he chemical changes such as dehyd a ion,
deg ada ion, and condensa ion, all o which esul in he loss o alipha ic
cha ac e , inc easing a oma ici y and eleasing gases simul aneously
[45]. A he hi d-s age he signi ican e ec o weigh loss o 35 %, 25
%, and 45 % was obse ed in he empe a u e ange om 600 ◦C o
900 ◦C o samples: ACAG1, ACAG3, and ACAG5, espec i ely. Tha
s age displays he inal weigh loss, which indica es ha he ac i e si es
ha e comple ely eac ed as well as being a measu e o he syn hesized
ma e ial's he mal s abili y [45].
N
2
adso p ion-deso p ion iso he ms ha e been eco ded o ACAG1,
ACAG3 and ACAG5 powde s and a e ypically shown in Fig. 5(a–c). As
can be seen om he iso he ms, all he samples shows an ini ial N
2
up ake ollowed by a g adual inc ease. All iso he ms shows ype II
pa e n (IUPAC nomencla u e) in which a e y low p essu es, he mi-
c opo es a e ill wi h he ni ogen gas. A he knee, o ma ion o
monolaye s a s and mul ilaye o ma ion akes place a he medium
p essu e. A he highe p essu es, usually capilla y condensa ion akes
place [46]. Table 1 summa izes he alues o a ious pa ame e s es i-
ma ed om his s udies. The 45 mic opo e olumes (V
mic o
) o all he
samples a e es ima ed om -plo me hod and a e abula ed in Table 1.
As can be seen om he alues, ACAG3 shows he highes su ace a ea
wi h low po e size, bu as he pe cen age o sil e inc eases, i leads o
dec ease in mic opo osi y and inc ease o mesopo osi y which leads o
dec ease in he speci ic su ace a ea as well. All he ma e ial shows small
hys e esis in deso p ion b anch which con i ms he p esence o small
amoun o mesopo es along wi h mic opo es. This end is well-
Fig. 1. XRD spec a o AC ma e ials modi ied wi h 1, 3 and 5%w . Ag.
Fig. 2. Raman spec a o p is ine AC ma e ial and modi ied wi h 3%w . Ag.
A. Jain e al.
Jou nal o Ene gy S o age 54 (2022) 105367
4
connec ed wi h elec ochemical s udies (discussed la e ) as well. The
po e size dis ibu ion o each sample is shown in he inse o he
espec i e igu es, i has been calcula ed by using Ba e -Joyne -
Halenda (BJH) me hod analysis o deso p ion b anch [47–50]. I has
been obse ed ha he p epa ed composi ions show he highes con-
cen a ion o po es in be ween 0.5 nm o 2.3 nm bu in case o ACAG5,
he po e wid h is b oade as compa ed o o he wo composi ions and
hence his la ge po es c ea ed was blocked by sil e pa icles. These
esul s a e also in synch oniza ion wi h elec ochemical esul s. O e all,
we obse ed he ACAG3 has he maximum su ace a ea wi h good and
op imized po e size dis ibu ion.
3.2. Elec ochemical s udies
Symme ical con igu a ion o he EDLC cells wi h ou ypes o
elec ode ma e ials wi h polyme gel elec oly es a e gi en below:
Cell#A: ACAG1|GPE|ACAG1
Cell#B: ACAG3|GPE|ACAG3
Cell#C: ACAG5|GPE|ACAG5
Cell#Re : Pu e AC|GPE| Pu e AC
As men ioned abo e, ou kind o EDLC cells we e ab ica ed by
using su ace modi ied ac i a ed ca bon ma e ials and he esul s has
been compa ed wi h p is ine ac i a ed ca bon as well. GPE in he p e-
sen s udy is PVdF-HFP-PC-Mg(ClO
4
)
2
. Compa a i e impedance mea-
su emen s, CV and GCD measu emen s ha e been ca ied ou and
discussed in his sec ion.
Fig. 6a shows he oom empe a u e cyclic ol ammog ams ob ained
o cell #A-#C, he CV plo o Cell#Re is shown in supplemen a y
ma e ial (Fig. S1). The esul s shows he signi ican con ibu ion o sil e
pa icles. A non-symme ic cha ge discha ge p o ile o CV o he elec-
ochemical double laye is also e i ied. Ideally he cyclic ol ammo-
g ams o he elec ochemical double laye cell is in he o m o
symme ical ec angula shape [51]. As can be seen om he cu es ha
wi h he inc ease in he pe cen age o sil e , he e is he loss in he
symme y and i migh be due o he e e sible pseudo- a adic eac ions
and he edox peak becomes p ominen in case o 3 and 5 w % and in he
case o pu e and 1 w % o sil e he edox peaks a e almos absen .
In e es ingly he e is an inc ease o he elec ic double laye capaci ance
in he ol ame ic p o iles om 0 w % o 3 w % and a e ha he e is
sha p deg ada ion o he capaci ance alues. I migh be due o he
blockage o po es because o he inc eased amoun o sil e pa icles,
also BET s udies con i ms ha he su ace a ea o 5 w % o sil e
modi ied ma e ial is low and po e size is la ge as compa ed o es o he
ma e ials. The end is consis en wi h GCD and impedance s udies also
and a e discussed in he ollowing sec ion. Up o 3 w % sil e
Fig. 3. SEM images ob ained a 20.000 magni ica ion o : (a) ACAG1, (b) ACAG3, (c) ACAG5 samples.
Fig. 4. TGA cu e o ACAG composi es modi ied wi h 1, 3 and 5%w . Ag.
A. Jain e al.
Jou nal o Ene gy S o age 54 (2022) 105367
5
nanopa icles plays a posi i e ole by enhancing he exposed su ace
a ea so ha he mos e ec i e elec ochemical double laye p ocess
akes place. The CV cu es we e eco ded a he scan a e o 5 mV s
−1
in
he po en ial ange o 0 V o 1.0 V. The capaci ance alues calcula ed by
using CV echnique (Eq. (1)) [49] o cell #A-#C a e 231.5 F g
−1
, 362.5
F g
−1
and 59.6 F g
−1
espec i ely.
Cs=∫IdV/s×ΔV×m(1)
whe e, s is he scan a e, V is he ol age ange and m is he mass o he
ac i e ma e ial used in single elec ode.
As can be seen ha he e is a signi ican d op o capaci ance alue o
cell #C in which 5 w % Ag is used o su ace modi ica ion. Fig. 6b
depic s he a ia ion o capaci ance as a unc ion o scan a e o
capaci o cell #A-#C. As can be seen om he plo , a lowe scan a e
he e is a sligh dec ease in he alues o capaci ance, a e ha almos
Fig. 5. N
2
adso p ion-deso p ion iso he ms and inse ; po e size dis ibu ion spec a o : (a) ACAG1, (b) ACAG3, (c) ACAG5.
Table 1
Pa ame e s es ima ed om N
2
adso p ion-deso p ion measu emen s.
Sample SSA (BET) m
2
g
−1
V
mic o
(cm
3
g
−1
) D
a g
(nm)
ACAG1 743.2 0.60 0.6
ACAG3 824.7 0.49 0.5
ACAG5 679.9 0.53 0.7
Fig. 6. (a) Compa a i e cyclic ol ame ic cu es o cell #A-#C eco ded a a scan a e o 5 mV s
−1
and (b) Va ia ion o speci ic capaci ance o cell #A-#C as a
unc ion o scan a e.
A. Jain e al.

Jou nal o Ene gy S o age 54 (2022) 105367
6
s able and cons an capaci ance alues has been obse ed e en o
highe scan a es like 100 mV s
−1
which shows he as ion swi ching
beha io a he in e ace o he elec ode and elec oly e. This con i ms
he sui abili y o gel polyme elec oly e o he applica ion o EDLCs.
Impedance spec oscopy also called as elec ochemical impedance
spec oscopy (EIS) s udies a e ca ied ou o ind insigh in o ma ion
abou he capaci o cells such as bulk esis ance, cha ge- ans e esis-
ance, di usion phenomenon a he elec ode and elec oly e in e aces
and inally he cha ge s o age in e ms o speci ic capaci ance [50].
Fig. 7a shows he impedance (Nyquis ) plo s o he cells #A-#C wi h he
magnesium ion based gel polyme elec oly e eco ded in he equency
ange om 200 kHz o 1 mHz a oom empe a u e (25 ◦C).
The EIS plo o Cell#Re is p o ided in he Supplemen a y ma e ial
(Fig. S2) o compa ison. Impedance plo s o any supe capaci o cells a e
di ided in o h ee egions, capaci ance a lowe equencies, esis ance
a high equencies and ion pene a ion e ec o elec ode ma e ials in
he middle equency egion. The e ical line pa allel o he imagina y
axis o he impedance plo shows he ideal capaci o beha io . I can be
seen om he plo s ha all he cells shows s eep ising in he lowe
equency egion which con i ms he capaci i e na u e o all cells. In he
high/middle equency ange, he semici cula spu is also obse ed
om which he in o ma ion o bulk esis ance, cha ge ans e esis ance
a he elec ode elec oly e in e ace can be ob ained. The di e ence in
he diame e o he semici cles may be associa ed o he unc ional g oup
o he in luence o sil e pa icles on he su ace o ac i a ed ca bon.
Simila o CV esul s, impedance esul s also shows he same pa e n, up
o 3 w % o sil e pa icles, he alues o capaci ance inc eased and o 5
w % i signi ican ly d opped and he esis ance alue inc eased which
clea ly con i ms he blockage o po es o ma e ial when i is modi ied
wi h 5 w %. The alues o bulk esis ance R
b
, cha ge ans e esis ance
R
c
, o e all esis ance R and capaci ance C measu ed a a equency o 1
mHz a e summa ized in Table 2. The capaci ance alues we e calcula ed
by using Eq. (2) [49].
C=2
2
π
mZ˝
(2)
whe e, m is he mass o he single elec ode, is he equency and Z" is
he alue o imagina y impedance ypically a 1 mHz.
The a e pe o mance o he capaci o cell B has been e alua ed om
impedance analysis ollowing he Mille 's app oach [51] by plo ing he
Bode plo s o impedances (Z' and Z" s. equency) which a e illus a ed
in Fig. 7b. F om hese plo s, he alue o he cha ac e is ic esonan
equency (
0
) can be ob ained, i is ha in e sec ing poin whe e eal
and imagina y alues a e equal. This equency is also known as
esponse equency whe e eal and imagina y pa s o impedance has a
phase di e ence o ~45◦and he ecip ocal o his equency is called as
esponse ime (
τ
0
). Response ime is basically he ime which is aken by
elec oly e ions o adso b and deso b in he po es o he elec ode ma-
e ial (ACAG in he p esen case). Fu he , he esponse equency o he
Fig. 7. (a) EIS plo s o EDLC cell #A-#C. Expanded ep esen a ion o EIS plo in high/mid equency egion is shown in inse , (b) eal and imagina y impedances
e sus equency (c) eal and imagina y capaci ances e sus equency.
Table 2
Elec ical pa ame e s o Cell #A-#C om impedance analysis.
Cells R
c
(Ω cm
2
) R
b
(Ω cm
2
) 1 mHz
R (Ω cm
2
) C
(mF cm
−2
)
a
(F g
−1
)
b
#A 4.2 42.4 600.8 188.7 180
#B 3.1 31.5 124.3 344.3 229.6
#C 5.5 52.5 453.1 112.6 56.3
a
O e all capaci ance o cell.
b
Single elec ode speci ic capaci ance o he cell.
A. Jain e al.
Jou nal o Ene gy S o age 54 (2022) 105367
7
cell B eco ded om Mille Bode plo s has also been es ima ed by using
Tabe na plo ( eal and imagina y capaci ance s. equency) and is
shown in Fig. 7c. I has been obse ed ha he esponse equencies and
hence esponse imes a e in good alignmen wi h he alues ob ained
om Mille plo s. The esonan equency o cell B is 0.01 Hz and
esponse ime (
τ
0
) is 14.2 s. The cell has lowe esponse equency and
highe esponse ime due o he p esence o sil e ions a he in e ace o
he cell.
To supplemen he esul s ob ained om EIS and CV, gal anos a ic
cha ge-discha ge (GCD) s udies we e also pe o med o e alua e he a e
pe o mance o he su ace modi ied ca bon ma e ials. Fig. 8(a) depic s
he GCD cu e o cell #A-#C a he cu en densi y o 1.0 mA cm
−2
and
in a po en ial window o 0 o 1.0 V. All he h ee cells shows he cu ed
na u e o cha ge-discha ge pa e ns. The non-linea pa e n in GCD
cu es while cha ging and discha ging a e owing o he edox peaks
which was obse ed in CV s udies as well. The e e sible edox eac ions
a he in e ace because o which pla eau egions appea s du ing cha ge-
discha ge a e esponsible o highe alues o capaci ance [52]. The
capaci ance was calcula ed using he discha ge b anch excluding he
ohmic d op. Fo compa ison GCD cu e o Cell#Re is p o ided as
Fig. S3 in supplemen a y in o ma ion. In GCD s udies also, same end
has been obse ed capaci ance alues we e g adually inc eased om 0
w % o 3 w % o sil e pa icles and la e i sha ply dec eased in case o
5 w %. The discha ge speci ic capaci ance C
d
om non-linea discha ge
p o ile has been calcula ed by using he Eq. (3) [49]:
Cd=4i∫Vd
m×V2∣V
Vi
(3)
whe e, i is he cu en densi y, m is he mass o ac i e ma e ial o single
elec ode, ∫Vd is he a ea unde he discha ge cu e, V is he maximum
ope a ing ol age and V
i
and V
a e he ini ial and inal alues o ol ages
on he GCD cu es. Long e m cycling e iciency is ano he s udies by
which s abili y o cells a e es ima ed [50]. Con inuous cha ge-discha ge
cycles we e ca ied ou o 10,000 cycles a he cu en densi y o 1 mA
cm
−2
be ween 0 and 1.0 V. The cyclic es ing was pe o med o he bes
cell (cell B in he p esen case) and is shown in Fig. 8b. As can be seen
om he igu e, he e is a dec ease in ea ly s age o cycling, i may be
because o he loss o cha ges esul ing om adso p ion o ions a he
elec ode-elec oly e in e ace o accumula ion o ions o o m ion pai s
in he cha ge-discha ge cycling p ocess [53]. Ne e heless, he cell B
was s able up o 10,000 cycles a e ini ial dec ease in he capaci ance
alues. As can be seen om pa e n he capaci ance alues o cell B
shows ~2 % o ading in he beginning is possibly because o he i e-
e sible s o age componen s o elec oly e and la e i is consis en
because o he p ope accessibili y o and non-modi ied po e each-
abili y o elec ochemical edox eac ions. The esul s shows he s able
cyclic pe o mance o he capaci o cell B. The a ia ion o speci ic
discha ge capaci ance o he cell as a unc ion o applied cu en densi y
by using GCD echnique is shown in he inse o Fig. 8b. As can be seen
om he igu e ha capaci ance g adually inc eased ill 1.4 mA/cm
2
bu
la e i s a ed dec easing wi h inc easing cu en densi y which con-
i ms he mode a e a e capabili y o he cell.
To ge u he insigh , SEM images wi h EDX pa e n o cycled
ACAG3 elec odes a e also ca ied ou and a e shown in Fig. 8(c) and
EDX pa e n a e shown in inse o Fig. 8c. I can be ha e en a e
10,000 cycles he e is no appa en di e ence be ween he mo phology
o be o e cycling samples (Fig. 3b) and a e cycling samples (Fig. 8c)
indica ing he s abili y o ACAG samples. Howe e , in he images, we
can see some sphe es which may be a e om elec oly e ma e ials, may
Fig. 8. (a) GCD cu es o cell #A-#C eco ded a cu en densi y o 1 mA cm
−2
in be ween 0 and 1.0 V, (b) Speci ic capaci ance o cell #B e sus cha ge discha ge
cycles measu ed a cons an cu en densi y o 1 mA cm
−2
(c) SEM image and EDX spec a o ACAG3 elec ode a e cycling.
A. Jain e al.
Jou nal o Ene gy S o age 54 (2022) 105367
8
be some aces o Mg sal o polyme . F om EDX spec a, i is also clea ed
ha he ACAG sample a e cycling con ains aces o Mg, F, O e c. which
a e because o he in e ac ion o elec ode and elec oly e ma e ial
du ing elec ochemical es ing leading o he dec ease in he numbe o
mobile ions wi hin he elec oly e and deme i ing he pe o mance o
de ice [53].
To make i mo e clea , he epe i ion o he speci ic capaci ance a e
cycling, ac impedance was also ca ied ou a e 10,000 cycles and he
plo is shown in supplemen a y Fig. S4. Be o e cycling, he alues o bulk
esis ance, cha ge ans e esis ance a e only 31.5 and 3.1 Ω cm
2
espec i ely showing he high conduc i i y and good compa ibili y be-
ween elec ode and elec oly e ma e ial bu a e cycling bulk esis-
ance is same 31.6 Ω cm
2
bu cha ge ans e esis ance inc eased o
24.4 Ω cm
2
, his con i ms ha decay in he capaci ance s o age is due o
cha ge ans e esis ance, elec oly e ions migh s uck in o elec ode
leading o dec ease in numbe o ee ions, addi ionally his s uck ions
migh also p oduce epulsi e o ce among o he ions hinde ing he ion
adso p ion in elec ode elec oly e in e ace and hence inc easing R
c
[53].
The speci ic ene gy o he cell #A-#C has been calcula ed by using
he exp ession E=
1
/
2
CdV2, and he powe densi y o he cells we e
calcula ed by using P =E/Δ , whe e Δ is he discha ge ime in he cells
[42]. The alues o discha ge capaci ance, ene gy densi y and powe
densi y a e summa ized in Table 3. The Ragone plo ( a ia ion o spe-
ci ic ene gy E e sus e ec i e powe densi y) o cell B has been e alu-
a ed a di e en cu en densi ies; 1.0 mA/cm
2
o 1.8 mA/cm
2
and is
shown in Fig. 8(d). The ene gy and powe densi y lies in be ween 3.0
and 5.8 Wh kg
−1
and 18.0 o 21.5 kW kg
−1
espec i ely. These alues a e
ound o be compa able han o he ca bon-based supe capaci o s which
a e epo ed in he li e a u e [54–58].
Simila ly like cyclic ol amme y and elec ochemical impedance
spec oscopy, GCD also showed he same pa e n, he capaci ance
alues, ene gy densi y and powe densi y g adually imp o ed om 0 w
% o 3 w % and o 5 w % o sil e pa icles i signi ican ly d opped, i
migh be because o he blockage o he po es o he incompa ibili y o
po es o elec ode ma e ial wi h e e ence o elec oly e.
4. Conclusions
Su ace modi ied ac i a ed ca bon in which he modi ica ion was
done by sil e pa icles we e success ully syn hesized and in es iga ed
as elec ode ma e ials o elec ochemical double laye capaci o s by
using magnesium ion based gel polyme elec oly es. The p ocess o
su ace modi ica ion was simple, cheap and sa e as well. The modi ica-
ion me hod allowed he deposi ion o me allic sil e in nano-size
dimension. The modi ica ion was con i med by SEM, XRD, Raman,
and BET analyses. F om he elec ochemical s udies, modi ica ion wi h
3 w % o sil e was op imized o ene gy s o age applica ion. This
in e es ing and inimi able a chi ec u e o highly po ous ca bon ma e-
ials p o ides a acile and low cos oppo uni y o de eloping elec o-
chemical double laye cells. Despi e o low quan i y o sil e deposi ed
he e was signi ican inc ease in he p ope ies o he ma e ial. Elec-
ochemical s udies o ACAG3 shows excellen esul s ha ing speci ic
capaci ance o 398 F g
−1
wi h ene gy densi y and powe densi y o 55
Wh kg
−1
and 2.4 kW kg
−1
. The cell showed he s able pe o mance up o
1500 GCD cycles. Combining all he abo e esul s, ACAG3 can be
conside ed as a po en ial candida e o supe capaci o applica ions.
CRediT au ho ship con ibu ion s a emen
Am i a Jain: Concep ualiza ion, Me hodology, Valida ion, In es i-
ga ion, Resou ces, Da a cu a ion, W i ing—o iginal d a p epa a ion,
W i ing— e iew and edi ing, Supe ision, P ojec adminis a ion,
Funding acquisi ion. Monika Michalska: Me hodology, Valida ion,
Fo mal analysis, In es iga ion, W i ing—o iginal d a p epa a ion,
W i ing— e iew and edi ing, Visualiza ion, P ojec adminis a ion,
Funding acquisi ion. Angelika Zaszczy´
nska: In es iga ion, W i-
ing— e iew and edi ing. Pio Denis: W i ing— e iew and edi ing,
In es iga ion, Expe imen s.
Decla a ion o compe ing in e es
The au ho s decla e he ollowing inancial in e es s/pe sonal e-
la ionships which may be conside ed as po en ial compe ing in e es s:
Am i a Jain epo s inancial suppo was p o ided by Na ional
Cen e o Resea ch and De elopmen . Monika Michalska epo s a
ela ionship wi h Minis y o Educa ion You h and Spo s o he Czech
Republic ha includes: employmen .
Da a a ailabili y
Da a will be made a ailable on eques .
Acknowledgmen s
Au ho s a e hank ul o M . M. Milcza ek and D . Kamil Bochenek
IPPT PAN o SEM measu emen s. We a e also hank ul o D . Łukasz
Rogal, Ins i u e o Me allu gy and Ma e ials Science, Polish Academy o
Science, K ak´
ow o TGA measu emen s.
This wo k was inancially suppo ed by he Na ional Cen e o
Resea ch and De elopmen (NCBR, Poland); P ojec numbe : V4-Japan/
2/17/A omDeC/2022 and he Minis y o Educa ion, You h and Spo s,
Czech Republic (con ac no. 8F21007) unde he Viseg ad G oup-Japan
2021 Join Call on Ad anced Ma e ials in coope a ion wi h he In e -
na ional Viseg ad Fund.
Appendix A. Supplemen a y da a
Supplemen a y da a o his a icle can be ound online a h ps://doi.
o g/10.1016/j.es .2022.105367.
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Table 3
Cha ge-discha ge cha ac e is ics o EDLC cell #A-#C a cons an cu en densi y
o 1 mA cm
−2
.
Cells Discha ge capaci ance
(C
d
) [F g
−1
]
Ene gy Densi y (E
d
)
[Wh kg
−1
]
Powe Densi y (P
d
)
[kW kg
−1
]
A 237.5 32.9 2.5
B 398.1 55 2.4
C 40.1 5.6 2.2
A. Jain e al.
Jou nal o Ene gy S o age 54 (2022) 105367
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