Ionogel-based solid-state supercapacitor operating over a wide range of temperature

HAL Id: hal-01466246

https://hal.archives-ouvertes.fr/hal-01466246

Submitted on 13 Feb 2017

HAL is a multi-disciplinary open access

archive for the deposit and dissemination of

sci-entific research documents, whether they are

pub-lished or not. The documents may come from

teaching and research institutions in France or

abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est

destinée au dépôt et à la diffusion de documents

scientifiques de niveau recherche, publiés ou non,

émanant des établissements d’enseignement et de

recherche français ou étrangers, des laboratoires

publics ou privés.

Ionogel-based solid-state supercapacitor operating over a

wide range of temperature

Léo Nègre, Barbara Daffos, Viviane Turq, Pierre-Louis Taberna, Patrice

Simon

To cite this version:

Léo Nègre, Barbara Daffos, Viviane Turq, Pierre-Louis Taberna, Patrice Simon. Ionogel-based

solid-state supercapacitor operating over a wide range of temperature. Electrochimica Acta, Elsevier, 2016,

vol. 206, pp. 490-495. �10.1016/j.electacta.2016.02.013�. �hal-01466246�

O

pen

A

rchive

T

OULOUSE

A

rchive

O

uverte (

OATAO

)

OATAO is an open access repository that collects the work of Toulouse researchers and

makes it freely available over the web where possible.

This is an author-deposited version published in :

http://oatao.univ-toulouse.fr/

Eprints ID : 16651

To link to this article : DOI:10.1016/j.electacta.2016.02.013

URL :

http://dx.doi.org/10.1016/j.electacta.2016.02.013

To cite this version :

Nègre, Léo and Daffos, Barbara and Turq,

Viviane and Taberna, Pierre-Louis and Simon, Patrice

Ionogel-based solid-state supercapacitor operating over a wide range of

temperature. (2016) Electrochimica Acta, vol. 206. pp. 490-495.

ISSN 0013-4686

Any correspondence concerning this service should be sent to the repository

administrator:

staff-oatao@listes-diff.inp-toulouse.fr

Ionogel-based

solid-state

supercapacitor

operating

over

a

wide

range

of

temperature

L.

Negre

a,b

_,

_B.

_Daffos

a,b

_,

_V.

_Turq

a

_,

_P.L.

_Taberna

a,b

_,

_P.

_Simon

a,b,

_*

a_{CIRIMAT,UniversitédeToulouse,CNRS,UT3,118routedeNarbonne,31062ToulouseCedex,France} b_{RéseausurleStockageElectrochimiquedel’Energie(RS2E),FRCNRS3459,France}

ABSTRACT

Aninorganicgelpolymerelectrolytebasedontheconfinementofanionicliquidmixture(1:1byweight ormolarratio)ofN-methyl-N-propylpiperidiniumbis(fluorosulfonyl)imide(PIP13FSI)and N-butyl-N-methylpyrrolidiniumbis(fluorosulfonyl)imide(PYR14FSI)intoaSiO2matrixpreparedfromasol-gel

methodwaspreparedandfurtherusedaselectrolyteinanallsolid-statesupercapacitor.Thesynthetized ionogelexhibitsahighionicconductivityoverawidetemperaturerange(from0.2mScm!1_at!40"_Cup

to10mScm!1_at60"_{C).Theionogel-basedsupercapacitorusingtwoactivatedcarbonelectrodescanbe}

operatedover3Vcellvoltagewindow.Moreoverthisallsolid-supercapacitorshowsacapacitanceupto 90Fg!1_{atroomtemperature.Theseencouragingresultsshowtheinterestofdevelopingsuchdevices,}

includingnon-toxicandsaferelectrolytes,packagingissuesandflexibledevicesdevelopment.

1.Introduction

Electrochemicaldoublelayercapacitors(EDLCs),alsoknownas supercapacitors, storeenergy by ion electrosorption onporous electrodes,mostlyactivatedcarbons[1].ThekeyfeatureofEDLCs compared to Li-ion batteries is their highpower delivery (full chargeordischargedcanbeachievedwithinfewsecondsortensof seconds) and high cyclability. Despite abounding research on pseudocapacitive materials with promising performance [2–4], conventionalEDLCsusinghighsurfaceareacarbonelectrodesand non-aqueousliquidelectrolytesrepresentthestateoftheart[5]. However, thecurrent liquid electrolytesusedin supercapacitor devices sufferfromseveral drawbacks.Conventional supercapa-citorsemploytheuseofsolvent-basedelectrolyteswhichallowion conduction at sub-zerotemperatures, e.g NEt4BF4 in propylene carbonate (PC)or acetonitrile (AN). Nevertheless,theseorganic solventsreducethevoltagewindowofthedeviceandANcanpose securityissuesduetoitsflammabilityandlowflashpointof2"_C.

Electrolyteleaks,whichcanoccurbecauseofinternalgasrelease,is also animportantconcern.Since themaximumspecific energy increases with squared of the voltage window (EmaxðinWhÞ¼1

2&CðinFÞ&DV2maxðinVÞ

.

[1]),thetypeofelectrolyteused is important indetermining theenergydensity andsafety ofa device.Astrategytotackletheseissuesistoreplaceliquidbysolid

–orgelified–electrolytes.Severalmaterialshavebeenutilizedas solidpolymerelectrolytes,suchasNafion[6], poly(etheretherke-tone)[7],polybenzimidazole[8],poly(methylmethacrylate) [9]

andpoly(ethyleneoxide)[10]arepromisingcandidatesofferingas welleasyassembly,lowcost,andflexiblepackaging.However,the operatingvoltageislimitedtolessthan2Vbecauseoftheuseof protonor proton-like conductingpolymers[11].More recently, ionogels,whicharesolidorquasi-solidelectrolytesbasedonthe trappingofroomtemperatureionicliquids(RTILs)inasilicamatrix havebeenproposed[12–14]becausetheycanreachhighvoltage, up to 4V [15]. However, based on ionic liquid salt, the ionic conductivityat low temperatureis still anissuefor developing solid-state supercapacitors operating with a wide range of temperature.

Inthispaper,weproposetodevelopasolid-stateelectrolyte basedonaionicliquidmixturetrappedintoaninorganicsilica network. Following previous work [16], we used an mixture composed of (1:1 by weight or molar ratio) N-methyl-N-propylpiperidinium bis(fluorosulfonyl) imide(PIP13-FSI) and N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl) imide (PYR14-FSI).Inthesemixtures,cationshavethesamemolecularweight andthesamenumberofatomsofthesamenature,withtheonly differencebeingtheircationmolecularstructure:afive-member (piperidinium)orsix-member(pyrrolidinium) heterocycle.Asa result,theincreasingdisorderandasymmetryamongthecations hinderslatticeformation,thustoloweringthemeltingpointwhile maintaininggoodmiscibilityandconductivity[17].Theliquidstate ofthisILmixturecanbemaintainedattemperaturesseveraltens

*Correspondingauthor.

E-mailaddress:simon@chimie.ups-tlse.fr(P.Simon).

ofdegreeslowerthantheindividualILs.Ionicliquidmixture-based ionogelhavebeendesignedforenlargingtheoperating tempera-ture range of these solid state electrolytes, thus offering new opportunitiesforsolid-statesupercapacitors.

2.Experimental

Ionogel synthesis procedure was described elsewhere [14]. Basically,asolidionogel-basedelectrolytewassynthetizedusing two different sol-gel agents: TMOS (TetraMethyl Ortho Silicate 98%,fromSigma–Aldrich)andTEOS(TetraEthylOrthoSilicate98%, fromSigma–Aldrich)underacidicconditions(Methanoicacid98%, fromVWR).TheTEOS:TMOS:MAvolumetric ratiowas 2:2:5.All reactantsweremixedtogetherundermoderatestirring(300rpm)

at40"_{Cduring18min.Thesecondstepwastheadditionof60%by}

volumeof ionic liquidmixture(PIP13-FSI):(PYR14-FSI):50:50 in weight.Comparedtoourpreviouswork using1-ethyl-3-methyl imidazolium bis(trifluoromethanesulfonylimide) EMITFSI-based ionogel[14],ILcontentwasdecreasedfrom70%downto60%vol toimprovethemechanicalpropertiesofthegel.Then,theresulting solutionwascastedinsealedcylindricalcontainersandkeptfor 24hoursatroomtemperatureforgelationandthendriedat50"_C

during4 days.Allthecells used forconductivitymeasurement wereassembledina

MBraüngloveboxoperatingunderargonatmosphere(O2and H2Ocontents lower than 0.1ppm) toavoid any contamination. Samplespreparedforfurthermechanicalcharacterizationswere injectedintostainlesssteelmolds,whichensuredgood reproduc-ibilityofmeasurements.

2.1.Supercapacitorcellassembly

Activematerialwasmadeof95wt%ofPICACTIFSC,astandard highspecificsurfaceareaactivatedcarbon(2300m2_g!1_)[18],and 5wt%ofPTFE(60wt%PTFEinwaterDuPontNemours,France)[19]. Carbonelectrodesweredriedoutinavacuumovenduring2hours then 250

m

L of silane-ILmixture was spread ontoan electrode whichwaslaidinanappropriatemould,thenanotherelectrode

Fig.1.ConductivityvariationversustemperatureofneatIlsmixture(PIP13-PYR14/ FSI)andionogelbetween!50"_Cand80"_{C.Conductivitieswerecalculatedfrom}

high frequency intercept with real axis of the Nyquist plotsobtained from ElectrochemicalImpedanceSpectroscopy(EIS)measurements.

wasdepositedontothesurfaceoftheliquidSilane-ILsmixture.The gel formation was obtained following procedure previously described. The resulting Carbon-Ionogel-Carbon sandwich was placed between two gold current collectors in a RHD cell for furtherelectrochemicaltests.Thistechniqueoffersawaytowork

with a large amount of active material (from few mg up to 15mgcm!2_).

Electrochemicaltestswerecarried outusingan Autolab PG-STAT128N(Metrohm,Switzerland).ARHDCell(RHD,Germany) wasusedforprecisecontrolofthecelltemperaturefrom!40"_Cto

+60"_{C.Prioranymeasurement,thecellwasmaintainedattheset}

temperature for 2h until equilibration. After sandwiching the samplesbetweentwogoldcurrentcollectors,ionicconductivity measurementsoftheionogelwereperformedbyElectrochemical ImpedanceSpectroscopy(EIS)for each temperature;a biascell voltageof0Vwithafrequencyrangefrom25kHzdownto0.01Hz wereapplied.Conductivitieswerecalculatedfromhighfrequency interceptwiththerealaxisoftheNyquistPlots.Allelectrochemical testsof the supercapacitors wereperformed withan electrode massloadingof5mgcm!2_.

Mechanical characterizations of theionogel wereconducted using an UltraNanoHardness Tester from CSM Instruments (Switzerland).Young’smodulusEandhardnessHandpercentage of elastic recovery were measured with a modified Berkovich three-sidedpyramiddiamondindenter.Themaximalnormalforce was 200

m

N; the maximum force was keptduring 60s before discharge.Theloadingratewas400

m

Nmin!1_{andthemaximum} penetrationdepthwas12

m

m(valuelowerthanthetenthofthe sample thickness (1.5mm) thus the mechanical answer of the substratewasneglected).ThePoissonratioofthehybridcoatings wastakenatamediumvalueof

y

=0.3(valuebetweenthePoisson ratioofamorphoussilica(0.17)andthatofconventionalpolymeric materials(0.5)).Experimentswereperformedatambient temper-ature.InallCSMnano-indentationtests,atotalofthreeindents wereaveragedtodeterminethemeanYoung'smodulusand nano-hardness.Theanalysis proceduresuggestedbyOliver andPharr

[20]wereusedtocalculatethehardnessandelasticmodulus. 3.Resultsanddiscussions

3.1.Ionogelconductivity

Fig.1shows thechangeof theionogelandneat ILsmixture conductivitieswithtemperature(Arrheniusplot) between80"_C

and!50"_{C.AscanbeseeninFig. 1,theionogelconductivityisclose}

tothatof theneatIL mixturein the!20"_{C +60}"_{C temperature} Fig.3. CyclicVoltammetryofan ionogel-basedsupercapacitorusingactivated

carbonelectrodes,at5mVs!1_{atvarioustemperatures(from}

!40to60"_C).

Fig.4.EISplotof(A)supercapacitorusingtwocarbonglasselectrodesandanionogelsoakedseparatorbetween1MHzand200Hz(B)supercapacitorusingtwoactivated carbonelectrodesandanionogelsoakedseparatorbetween1MHzand0.1Hz.BiasVoltage:0V.Signalamplitude:5mVRMS.

Table1

Gravimetricandarealcapacitancecalculatedfromthe5mVs!1_CVsduringthe

dischargeatdifferenttemperatures.

Temperature !40"_{C !20}"_{C 0}"_{C 20}"_{C 40}"_{C 60}"_C

Gravimetriccapacitance(Fg!1_{) 34 68 89 91 94 96}

range,whichevidencesasmallimpactofthepresenceofthesilica matrix.Theroomtemperatureconductivity(20"_{C)wasmeasured}

at5.5mScm!1_{forboththeneatILmixtureandtheionogel,which} iscomparabletoconventionalpropylenecarbonate-basedliquid electrolytes[21]andmatcheswiththestandardsneededforuseas electrolytein supercapacitordevices. However,for temperature below!20"_{C,thelimitedmobilityoftheelectrolyteduetothe}

confinementeffectinsidethesilicamatrixisassumedtolimitthe conductivity.A conductivity upto0.2 mS.cm!1_{was still} main-tained at !40"_{C. Such high conductivity values at such low}

temperature,toourknowledge,haveneverbeenreportedinthe literature for ionogel electrolyte. Nevertheless, these kind of electrolytes have been intended to suit to mechanical stress experiencesinceagoodmechanicalstabilityhastobe.Mechanical

tests were carried out using a nano-indentation technique to assessthemechanicalpropertiesofasmadeionogels.

3.2.Mechanicalcharacterizations

Mechanical properties of ionogels were measured by nano-indentation.Fig.2showstheloadasafunctionofthepenetration depth plotfor a 1.5mm-thick ionogelpellet usinga Berkovitch indenter.IonogelsexhibitratherlowvaluesofbothVickersHardness (0.11' 0.02MPa) and elastic modulus (0.935'0.114 MPa) as comparedto other gelelectrolytes: 26MPafor PMMA [22] and 35–50MPaforPVdF-basedpolymer[23].Theelasticcontributionto theloadingcanbeobtainedfromFig.2,bysubtractingtheplastic displacement to the total displacement normalized to the total

Fig.5.EISPlotofionogel-basedsupercapacitoratdifferenttemperature(a)!40"_C,!20"_Cand0"_C(b)20"_C,40"_Cand60"_{C.Biasvoltage:0V.Signalamplitude:150mVRMS.}

Fig.6.Evolutionofcapacitanceversuspotentialscanrateofionogel-basedsupercapacitorwithin3Vatdifferenttemperatures(A)!40"_C,!20"_Cand0"_C(B)20"_C,40"_Cand

displacement.Anelasticrecoveryof45%wasmeasured,thathasto becomparedto14%forpureTEOSandTMOSsilicagel.Thetrapped ionicliquidisactingasaplasticizerintheresultingionogel. 3.3.Ionogelassolid-stateelectrolyteforsupercapacitor

An all-solid supercapacitor was assembled using porous PICACTIF activated carbon based electrodes stacked with the ionogelaselectrolyte(seeexperimental).InFig.3arepresented CyclicVoltammogramsobtained(CV)at5mVs!1_between0and 3Vatvarioustemperatures(from!40to60"_C).Downto!20"_C

theelectrochemicalsignaturesarequietdecentsincea rectangu-lar-shape characteristicwas achievedwhich was expectedfora capacitive behaviour based on charging/discharging of the electricaldoublelayer.

Aspecificcapacitanceof91Fg!1_{(pergramofactivatedcarbon)} havebeenobtainedat20"_{Cwithacellvoltageof3V,whichisvery}

similar to that was measured in conventional organic liquid electrolyte [19]. Table 1 summarizes gravimetric and areal capacitancescalculatedfromtheCVsatapotential scanrateof 5mVs!1_{between0and3Vfrom!40to60}"_C.

Asobservedinthistable,thecapacitivebehaviouriskeptdown totemperatureaslowas!20"_{C;withonly25%capacitancelossat}

!20"_{C.TheseresultsareconsistentwithFig.1thatshowedthat}

ionogelionicconductivitywasstilldecent(0.2mScm!1_)atsuch lowtemperature.At!40"_{C,thecrystallizationoftheILconfinedin}

pores of thecarbon structure is assumed to occur. Despite an electrochemicalkineticsmainlycontrolledbyohmicdrop,40%of thecapacitanceobtainedat20"_{Cwaspreserved.Interestinglythe}

electrochemicalbehaviourofall-solidsupercapacitorwasfoundto beveryclosetoliquid-basedsupercapacitors.Suchperformance couldbeexplainbyawettingcarbonmicroporebytheILthatcan movefreelywiththesiliciumnetwork.Tocheckthehypothese,we carriedouttodesignanadditionalexperimentusinganon-porous carbon(carbonglass)forcomparisonprupose.

Intheexperiment,an(EMITFSI)-basedionogelsoakedseparator wasusedtoobservethecarbon/ionogelinterface;EISmeasurements were madeeach30minbetween 1MHz–200Hz to measurethe change of theimpedance with time. Fig. 4A shows thesoaked separatorbetweentwocarbonglasselectrodes.Sameexperiment wasconductedwithtwoactivatedcarbonelectrodeplacedbetween thesameseparatorsoakedwithionogel(Fig. 4B).

While the impedance is kept constant for the non porous electrode(Fig.4B),therealpartoftheimpedanceincreaseswith timewhenusingporouscarbonelectrode.Thisisassumedtobe linked tothehydrophobicityof thecarbonwhichattracts ionic liquid (hydrophobic) from the silica host network (which is hydrophilic)intothecarbonpores;besides,capillarityforcecan alsocontributetoattractILinthepores.Thisbehaviourallowsa (partial) filling of the carbon microporous structure with ions leadingtosuchhighcapacitance.

In Fig.5 arepresentedtheNyquist plotsof acarbon-carbon ((PIP13-FSI)0.5(PYR14-FSI)0.5) ionogelbased supercapacitorata biascellvoltageof0V.

In the 20"_{C ! 60}"_{C temperature range (Fig. 5A), the high}

frequencyseriesresistance,whichistheionicbulkresistance,was measured at 20

V

cm2 _{for thewholecell at roomtemperature}

(20"_{C), which is comparable to our previous work [14]. As}

expected,whenthetemperatureincreasesfrom0"_Cupto60"_C,

thehighfrequencyresistancedecreasesfrom52to9.2

V

cm2_.The sharp increase of the imaginary partof theimpedance at low frequencies ischaracteristic ofthesystem capacitivebehaviour. Evenfor sub-zerotemperatures,EIS measurementsstill showa capacitivebehaviour,despitethepresenceofagrowingsemi-circle athighfrequency,attributedtotheonsetofgelationthatisrelated

to decreased mobility of the electrolyte ions at such low temperatures.

Fig. 6showsthechangeofthearealandgravimetriccapacitance (derivedfromtheslopeoftheQ-Vcurveduringcelldischarge)of theactivatedcarbonelectrodesversusthepotentialscanrateat various temperatures. The capacitance of the ionogel-based supercapacitor decreases with increasing scan rate, since the ohmicdropincreaseswiththescan rate. Temperatureplaysan importantrole,sincealreadymentionedseriesresistanceincrease at low temperaturewhile a fastdecrease of thecapacitance is observedathigherscanrate.

Inhere,itwasexpectedsincecapacitancelimitationispurely due to ohmicdrop. The effective accessible surface is strongly dependentonthescanrate[17].

4.Conclusion

Thepresentpaperpresentssomeresultsobtainedwitha carbon-carbonsolid-statesupercapacitorusing((PIP13-FSI)0.5(PYR14-FSI) 0.5)-basedionogelasbothelectrolyteandseparator.Thankstohigh ionicconductivityoftheionogel,ionsfromthegelareabletofulfil porosityofthecarbonelectrodesleadingtosuchhighcapacitance (95Fg!1_{at room temperature). Anall solid supercapacitor with} attractiveareal capacitance up to 100mFcm!2 _{per electrodeat}

!40"_Cfor5mVs!1_{scanrateupto 3Vcellvoltagecouldbewas}

assembled.Suchdevicescouldefficientlymatchmultiplecriteria (high capacitance, good power density and high cell potential window)neededforsolidsupercapacitorapplications.

References

[1]P.Simon,Y.Gogotsi,Materialsforelectrochemicalcapacitors,Nat.Mater.7 (2008)845–854.

[2]P.Simon,Y.Gogotsi,B.Dunn,WhereDoBatteriesEndandSupercapacitors Begin,Science343(2014)1210–1211.

[3]V.Augustyn,P.Simon,B.Dunn,Pseudocapacitiveoxidematerialsforhigh-rate electrochemicalenergystorage,EnergyEnviron.Sci.7(2014)1597. [4]T.Brousse,P.-L.Taberna,O.Crosnier,R.Dugas,P.Guillemet,Y.Scudeller,etal.,

Long-termcyclingbehaviorofasymmetricactivatedcarbon/MnO2aqueous electrochemicalsupercapacitor,J.PowerSources173(2007)633–641. [5]J.R.Miller,P.Simon,MaterialsScience:ElectrochemicalCapacitorsforEnergy

Management,Science321(2008)651–652.

[6]B.C.Kim,J.S.Kwon,J.M.Ko,J.H.Park,C.O.Too,G.G.Wallace,Preparationand enhancedstabilityofflexiblesupercapacitorpreparedfromNafion/polyaniline nanofiber,Synth.Met.160(2010)94–98.

[7]P.Sivaraman,V.R.Hande,V.S.Mishra,C.S.Rao,A.B.Samui,All-solid supercapacitorbasedonpolyanilineandsulfonatedpoly(etheretherketone), J.PowerSources.124(2003)351–354.

[8]D.Rathod,M.Vijay,N.Islam,R.Kannan,U.Kharul,S.Kurungot,etal.,Designof anallsolid-statesupercapacitorbasedonphosphoricaciddoped

polybenzimidazole(PBI)electrolyte,J.Appl.Electrochem.39(2009)1097– 1103.

[9]M.Schroeder,P.Isken,M.Winter,S.Passerini,A.Lex-Balducci,A.Balducci,An InvestigationontheUseofaMethacrylate-BasedGelPolymerElectrolytein HighPowerDevices,J.Electrochem.Soc.160(2013)A1753–A1758. [10]C.V.SubbaReddy,G.P.Wu,C.X.Zhao,Q.Y.Zhu,W.Chen,R.R.Kalluru,

CharacterizationofSBA-15doped(PEO+LiClO4)polymerelectrolytesfor electrochemicalapplications,J.Non-Cryst.Solids353(2007)440–445. [11]A.A.Łatoszy!nska,G.Z. _Zukowska,I.A.Rutkowska,P.-L.Taberna,P.Simon,P.J.

Kulesza,etal.,Non-aqueousgelpolymerelectrolytewithphosphoricacid esteranditsapplicationforquasisolid-statesupercapacitors,J.PowerSources 274(2015)1147–1154.

[12] D.Membreno,L.Smith,K.-S.Shin,C.O.Chui,B.Dunn,Ahigh-energy-density quasi-solid-statecarbonnanotubeelectrochemicaldouble-layercapacitor withionogelelectrolyte,Transl.Mater.Res.2(2015)015001.

[13]M.Brachet,T.Brousse,J.LeBideau,AllSolid-StateSymmetricalActivated CarbonElectrochemicalDoubleLayerCapacitorsDesignedwithIonogel Electrolyte,ECSElectrochem.Lett.3(2014)A112–A115.

[14]L.Negre,B.Daffos,P.L.Taberna,P.Simon,Solvent-FreeElectrolytesfor ElectricalDoubleLayerCapacitors,J.Electrochem.Soc.162(2015)A5037– A5040.

[15]M.Armand,F.Endres,D.R.MacFarlane,H.Ohno,B.Scrosati,Ionic-liquid materialsfortheelectrochemicalchallengesofthefuture,Nat.Mater.8(2009) 621–629.

[16]R.Lin,P.-L.Taberna,S.Fantini,V.Presser,C.R.Pérez,F.Malbosc,etal., CapacitiveEnergyStoragefrom!50to100"_{CUsinganIonicLiquidElectrolyte,} J.Phys.Chem.Lett.2(2011)2396–2401.

[17]W.-Y.Tsai,R.Lin,S.Murali,L.Zhang,J.K.McDonough,R.S.Ruoff,etal., Outstandingperformanceofactivatedgraphenebasedsupercapacitorsin ionicliquidelectrolytefrom!50to80"_{C,NanoEnergy2(2013)403–411.}

[18]P.L.Taberna,P.Simon,J.F.Fauvarque,ElectrochemicalCharacteristicsand ImpedanceSpectroscopyStudiesofCarbon-CarbonSupercapacitors,J. Electrochem.Soc.150(2003)A292.

[19]J.Gamby,P.L.Taberna,P.Simon,J.F.Fauvarque,M.Chesneau,Studiesand characterisationsofvariousactivatedcarbonsusedforcarbon/carbon supercapacitors,J.PowerSources101(2001)109–116.

[20]W.C.Oliver,G.M.Pharr,Animprovedtechniquefordetermininghardnessand elasticmodulususingloadanddisplacementsensingindentation experiments,J.Mater.Res.7(1992)1564–1583.

[21]M.Ue,Conductivitiesandionassociationofquaternaryammonium tetrafluoroboratesinpropylenecarbonate,ElectrochimicaActa39(1994) 2083–2087.

[22]S.M.Zebarjad,S.A.Sajjadi,T.E.Sdrabadi,S.A.Sajjadi,A.Yaghmaei,B.Naderi,A StudyonMechanicalPropertiesofPMMA/HydroxyapatiteNanocomposite, Engineering03(2011)795–801.

[23]B.Mohammadi,A.A.Yousefi,S.M.Bellah,Effectoftensilestrainrateand elongationoncrystallinestructureandpiezoelectricpropertiesofPVDFthin films,Polym.Test.26(2007)42–50.