OATAO is an open access repository that collects the work of Toulouse
researchers and makes it freely available over the web where possible
Any correspondence concerning this service should be sent
to the repository administrator:
tech-oatao@listes-diff.inp-toulouse.fr
This is an author’s version published in:
http://oatao.univ-toulouse.fr/21769
To cite this version:
Lin, Zifeng
and Taberna, Pierre-Louis
and Simon, Patrice
Advanced
analytical techniques to characterize materials for electrochemical capacitors.
(2018) Current Opinion in Electrochemistry, 9. 18-25. ISSN 2451-9103
Advanced
analytical
techniques
to
characterize
materials
for
electrochemical
capacitors
Zifeng
Lin
1,2,
Pierre-Louis
Taberna
1,2and
Patrice
Simon
1,2,3,∗Thisreviewcoversrecentdevelopmentsinadvancedanalytical techniquestocharacterizematerialsforelectrochemical capacitors.Fordoublelayercapacitors,examplesoftheuseof insituX-rayphotoelectronspectroscopy(XPS),pulsed electrochemicalmassspectrometry(PEMS)technique, temperature-programmeddesorptioncoupledwithmass spectroscopy(TPD-MS)technique,insituNMRspectroscopy, andinsitudilatometrymeasurementarepresented,for studyingcarbon/electrolyteinterfacewithafocusonto electrolyteionsconfinementinnanoporesandchangesduring ageing.Forthepseudocapacitivesystem,insituX-ray (neutron)diffractionorscattering,insitudilatometrytechnique, cavitymicro-electrode,insituRamanspectroscopy,TPD-MS technique,andelectrochemicalquartzcrystalmicrobalance (EQCM)techniquehavebeenemployedforstudyingmaterials structure,electrochemicalkinetic,interfaceinteraction,and ionsadsorption/desorption.Theseadvancedanalytical techniquesprobeinsightintochargestoragemechanisms,and guidingthefastdevelopmentofsupercapacitors.
Addresses
1Université PaulSabatier,LaboratoireCIRIMATUMRCNRS,Toulouse 5085,France
2RéseausurleStockageElectrochimiquedel’Energie(RS2E),FR CNRSn°3459,France
3InstitutUniversitairedeFrance,1ruedesEcoles,Paris75003,France ∗Correspondingauthor: Simon,Patrice (simon@chimie.ups-tlse.fr)
https://doi.org/10.1016/j.coelec.2018.03.004
Introduction
Duringthepast15years,majorscientificadvanceshave
been made in the field of Electrochemical Capacitors
(ECs)which ledtoa2-foldincrease oftheenergy
den-sity of carbon-based (EDLCs) or to the development
ofhigh-ratepseudocapacitivematerials.Theseadvances
havebeenmainlyachievedthankstotheuseofanalytical techniques,usedincombinationwithinsitu
electrochem-icalconventionalmethodsand/orwithmodeling.Inthis
review,someadvancedtechniques,as wellastheirroles
instudyingchargestoragemechanismsareintroduced.
Electrochemical
double
layer
capacitors
InElectricalDoubleLayerCapacitors(EDLCs),
capaci-tivestorageisachievedthroughionadsorptionofan
elec-trolyteonto high surface areaporous carbon electrodes
[1].Then,mostoftheelectrochemicalprocessinEDLCs
occursatthecarbon/electrolyteinterface.Theanalytical
techniquesusedinEDLCsmainlyfocusonthisinterface.
OneoftheimportantparametersofECsistheoperating
voltagewindow,which drivestheenergydensityof the
system.In situX-rayPhotoelectronSpectroscopy(XPS)
techniquehasbeenusedtostudythestabilityofthe car-bon/electrolyteinterfaceduringelectrochemical polariza-tionofCDCcarbonsinionicliquidelectrolyte[2,3].By
tracking the changein theC1s and N1s energy levels,
Lustandco-workers identifiedthereactionmechanism
responsiblefortheelectrolytedegradationathigh poten-tial(>3.6V),which involves theoxidative dimerization
ofthe imidazoliumcation viaN–Nbond formation [2].
Anothertechniquerecentlydevelopedformonitoringgas
evolutionduringtheoperationof supercapacitors isthe
pulsedelectrochemicalmassspectrometry(PEMS)
tech-nique[4•],aspresentedinFigure1.PEMStechnique
al-lowsforfastquantitativemeasurementoflowgas produc-tionduringsupercapacitorcyclingorageing.Batisseand
Raymundo[4•
]evidencedandquantifiedtheformation
ofCO,CO2andH2atthepositiveandnegativeelectrode
duringsupercapacitorcellsageingatconstantvoltagesin
aqueouselectrolytes.Furthermore,they could correlate
gas production to the change of each electrode
poten-tialversusreferenceduringageing.Ageingmechanisms
inporouscarbonelectrodesstronglydependonthe
pres-enceofsurfacefunctionalgroupsonthecarbonsurface,as wellasthecarbonstructure(presenceofdefects)and tex-ture(surfaceareaandpore sizedistribution).Herealso,
manyadvances have been achieved withinthe past 10
years.
A key technique for analyzing the carbon surface is
the temperature-programmed desorption coupled with
mass spectroscopy (TPD-MS) technique [4•–7].
TPD-MStechniqueallowsformeasuringthesurfacegroup
Figure1
Observationofgasevolutionatelectrode/electrolyteinterfacebyamodifiedpulsedelectrochemicalmassspectrometry(PEMS)method.Adapted withpermissionfromref.[4•].Copyright©2017AmericanChemicalSociety.
whichaccountsforthepresenceofcarbonactivesites: de-fectssuchasdislocations,stackingfaultsoratom vacan-ciesmainlylocatedintheedgeplanes[7].Usingcarbon
onionswithcontrolleddefectandsurfacegroupcontents
asmodelmaterials,adirectcorrelationwasreported
be-tweenthenumberofdefectsonthecarbonsurface
mea-suredbyTPD-MSandthecapacitanceinbothaqueous
andnon-aqueouselectrolytes.Surprisingly,the contribu-tionofthesurfacedefectstothecapacitancewasfoundto behigherthanthatofthefunctionalsurfacegroups,even
inaqueouselectrolytes.Theseresultsshowthatthe
sur-facedefectscontentalsoaffectsthecarboncapacitance.
Besidesthecarbonstructureand surfacegroupcontent,
theelectrochemicalperformancesof porous carbonsare
alsocontrolledbythecarbontexture:specificsurfacearea, porevolume,poresize,poresizedistribution.Backto15 yearsago,thecarbon-specificsurfaceareaSSAwasmainly
calculatedfromN2 gassorption isothermsat77Kusing
theBrunauer–Emmett–Teller(BET)equation.The
evi-denceofthecapacitanceincreaseincarbonporeslessthan 1nm[8–10]highlightedtheneedforrefiningthe
charac-terizationmethodstofinelymeasuretheporousvolume
and pore size in the ultra-microporous range (<1nm).
Following recommendations of the IUPAC, the BET
equationisnotsuitableforthemeasurementofspecific
surfaceareaofmicroporouscarbons[11].Instead,for
mi-croporosityassessment,CO2sorptionat273Kshouldbe
preferredto alleviatekineticsrestrictionsobserved
dur-ing measurements at low temperature with (77K with
N2) [11]. In the same way, calculation of the SSA
us-ingquenchedsoliddensityfunctionaltheory(QS-DFT)
avoids the fundamental limitations of the BET theory
[12].Finally,theporousvolumeaccessibletoionsshould
beconsidered,thatistheporousvolumeofporeslarger
thanthesizeofthedesolvatedion[13].Basedonthe
pre-viousrecommendations,Jäckeletal.[13]proposetouse
CO2gasformeasuringporousvolumebelow0.9nmand
N2gasforpores>0.9nm.Thechangeofthecapacitance
normalizedto QS-DFTSSAversusaccessiblepore size
showsacapacitanceincreaseinporeslessthan1nmsize forvariousporouscarbonsinnon-aqueouselectrolytes(in
acetonitrile- or propylene carbonate-based electrolyte).
Initiallyreportedin2006usingaseriesofporouscarbons with controlledpore size [10],the originof the
capaci-tanceincreaseincarbonnanoporeshasbeenextensively
studiedsincethattimemainlybyusingneworadvanced
Figure2
InsituNMRspectroscopyexperimentscarriedoutatdifferentchargestatesallowquantificationofthenumberofchargesstoringspecies.Adapted withpermissionfromref.[15].Copyright©2013AmericanChemicalSociety.
workwas directedtoward theunderstanding of theion
transport and adsorption in confined carbon nanopores
(<1nm),i.e.wherethereisnoroomforthebuildingofa
diffuselayer.InsituNMRspectroscopyexperiments
dur-ingelectrochemicalpolarizationofporouscarbonsinNaF
aqueous electrolyte have shown that ions could access
subnanometerporeswithpartialaniondehydrationunder
polarization[14].Usingdedicatedelectrochemicalcell,as
shownin Figure2,insituNMRexperimentsduring
po-larizationalsoevidenceddifferentchargestorage
mech-anisms depending on the electrode polarity [15–19••].
Counter ionadsorption wasfound atthenegative
elec-trode(X=1)andionexchangeatthepositive(X=0)[18],
confirmingresultsobtainedusingelectrochemicalquartz
crystalmicrobalancetechniqueunderagravimetricmode
[20].Inaddition,theeffectiveionicdiffusioncoefficients
inside thecarbon nanoporesweredecreasedbytwo
or-dersofmagnitudecomparedwithbulkelectrolyte[19••];
thiswasexplainedbytheincreaseoftheionpopulation
inpores.Asaresult,thechargingmechanism(counterion adsorptionversusionexchange)affectstheiontransport
kineticsinconfinednanopores.
Conventional techniques have been also developed to
studyiontransferinporouscarbons.Interestingly,insitu
dilatometry measurement duringelectrochemical
polar-izationshowsalsoanasymmetricbehaviorwithrespectto theelectrodepolarization,theelectrodethicknesschange
beingmoreimportant duringnegativepolarization[21].
Recently,Presseretal. improvedthetechniqueby
cou-pling insitudilatometry togetherwith X-ray absorption
spectroscopy(XAS)[22••][21].First,theyconfirmedthe
asymmetricswellingof porouscarbon electrodesduring
electrochemicalpolarizationinaqueouselectrolytes.Also, thankstotheuseofporouscarbonwithhierarchical
micro-porous/mesoporousstructure,mostofthevolumechange
couldbeassignedtothepresenceofporeslessthan1nm
size.Theoriginoftheasymmetrywasattributedto the
increaseoftheC–Cbondsduetoelectroninjectioninto
thecarbonduringnegativepolarization.Thisechoesthe
increaseintheionpopulationreportedbyForseand
co-workers by in situ NMR spectroscopy [15], leading to
thedecreaseofthe ionicdiffusioncoefficientin carbon nanopores.
Finally,thedevelopmentofinsituX-rayorneutron
scat-tering techniques has been particularly successful for
studyingion adsorption in carbon nanopores[23••
–25]. Prehaletal.[24]usedCsClaqueouselectrolytetostudy
theionadsorptioninnanoporouscarbonsunder
polariza-tion.BycouplingSAXSandMonteCarlomodeling,they
evidencedtheionpartial desolvationwhen confinedin
carbonnanopores.Theextentofdesolvationand
confine-mentwasfoundtoincreasewiththeappliedpotential,in
agreementwithpreviousstudies[26],whichgiveshints
toexplainthecapacitanceincreaseincarbonnanopores.
Also,Futamura et al. recently showed the existence of
co-ion pairs when theionic liquid electrolyte was
con-finedinto carbonpores of0.7nmsize,thatis whenthe
ionsizeiscloseto theporesize[25].Suchanimproved
co-ionpairingwastheconsequenceofthepartial
break-ingoftheelectrostaticCoulombicrepulsioninteractions
betweenco-ionsthankstothecreationofimagecharges
inthecarbon.Theycouldconfirmthecreationofa“super
ionic” statesuchaspredictedbyKornyshevandKondrat
Figure3
Schematicofthecavitymicro-electrode.Adaptedwithpermissionfromref.[40].
Asonecansee,themoreweadvanceinthe
understand-ingoftheionconfinementeffectinnanopores,themore
thingsgetcomplex.Thereisstillalottounderstand in thisfieldandalltheseanalyticaltoolswillbeofgreathelp tokeeponmovinginthisdirection.
Pseudocapacitive
and
high
charge–discharge
rate
materials
Pseudocapacitive materials store the charge through
fast,non-diffusion-limitedredoxreactions.Also,different
fromamorphousporouscarbonmaterialsusedinEDLCs,
most of the pseudocapacitivematerials show organized
crystallinestructure.So,mostof theconventional
tech-niques based on X-ray diffraction or scattering used to
characterize batteryelectrode materials have been
em-ployed with pseudocapacitive materials. We will then
just briefly mention some examples. In situ XRD has
beenextensivelyusedtostudytheswelling/contraction
ofpseudocapacitivematerialsduringion intercalation/de-intercalation,suchasinMnO2,NiOx,orMXene[28–30].
Withoutsurprise,theelectrodematerialvolumechanges
aredrivenbyelectrostatic repulsionbetweenthelayers
or the steric effects coming from ion
intercalation/de-intercalation to balance the charge [29]. In
monocrys-tallineNb2O5operatinginnon-aqueouselectrolytes,the
intercalation/de-intercalation process volume change is
drivenbystericeffect(swellingduringintercalation, con-traction during de de-intercalation) [31]. X-ray
absorp-tionwasusedtoevidencethechangeoftheTioxidation
state duringcharge/discharge of Ti3C2Tx MXene
elec-trode[32,33],aswellasinothermaterials[34,35].
Differently, micro-electrodes or cavity micro-electrodes
tools (Figure 3) are well-suited for the electrochemical characterizationof high-ratepseudocapacitivematerials.
Thankstothesmall amountof materialstested,alarge
rangeof potentialscan rates(v) canbeexplored—from
fewmVs−1uptofewVs−1—whichwasextremelyuseful
forstudyingtheelectrochemicalkineticsof pseudocapac-itivereactions[36–38].Thedeconvolutionofthecurrent intonon-diffusionlimitedsurfaceprocess(changingwith v) anddiffusion-limited(changingwithv1/2)hasmadeit
possibleto extract thepseudocapacitivecontributionto
thetotalcurrentateachpotential,whichhelpsin optimiz-ingthestructurestodesignhigh-ratematerials[36–39].
Another original initiative comes from Hu et al., who
usedRamanspectroscopytocharacterizethecharge
stor-age during polarization of Ti3C2Tx MXene electrodes
inSO42− ionscontaining aqueouselectrolyte of various
cations[41••].MXenesare2-Dimensionalmaterials
pio-neeredbyBarsoumandco-workers[42],whichcontains
O- andF-surfaceterminations.Thosegroupscomefrom
thesynthesis process, thatis etching of MAX phasein
thefluorine-containingacidicsolutions[33].Itwasfound
that hydronium ions in sulfuric acid could bond with
theoxygen-containingterminationsoftheTi3C2Tx
MX-enenegativeelectrodeuponreduction(oxidation)while
imidazolium-basedionicliquid electrolyte [47].MXene
electrodeswellingwas measured duringnegative
polar-ization,suggesting the preferential insertion of cations. Underpositivepolarization,theelectrodecontractseven
further compared to the un-polarized sample,
suggest-inganionexchangemechanism.Similarresultswere
ob-tainedfrominsituXRDmeasurements[28]anda
molec-ulardynamicssimulation study [48],which confirm the
differenceinthechargestoragemechanismwiththe elec-trodepolarity.Also,themodestcapacitancesuggestsa ma-jorcontributionfromthedoublelayer.
Newanalyticaltoolsbasedontheelectrochemicalquartz
crystalmicrobalance(EQCM)techniquehavealsobeen
developedtostudyenergystoragematerialsthatoffer
in-terestingopportunitiesintheECarea.Differentlyfrom
thegravimetricEQCM,theEQCMwithdissipation
mon-itoring(EQCM-D)operatedwithmultipleovertones of
theresonance frequency,thus probing awide range of
penetrationdepthδn[49,50].Thestructuralparametersof
theelectrodescanbeobtainedbymeasuringthechange
in the resonance frequency 1F and thechange in the
full-widthathalf-heightoftheresonancepeak1Wover
a wide range of overtone numbers n, and fitting the
processisaccompaniedbyachangeintheoxidationstate ofTifromTi(+III)downtoTi(+II).Theredoxreaction onTiexplainstheextremelyhigh capacitanceTi3C2Tx
MXene canreach in acidicelectrolytes [33,43]. In
con-trast,inneutralelectrolytes,onlydoublelayeradsorption occurswithoutchargetransferonTiatoms[41••].
Broad-eningtheuseofinsituRamanspectroscopytechniqueto
othermaterialscouldbringnewinsightsinthe
pseudoca-pacitivechargestoragemechanism.
The discoveryof 2DMXenematerials hasboostedthe
research in pseudocapacitivematerials. One of the key
features of MXenes is the presence of surface oxygen
and fluorineterminationsontheirsurface.The
TPD-MS technique has been successfully used to measure
the change of the amount and the nature of these
groupsduringhydrazineintercalationintoTi3C2Tx
MX-ene material [44]. The capacitance of MXene in the
non-aqueouselectrolyteiswellbehindthatinthe
aque-ousacidicelectrolytes[45]andthechargestorage
mech-anism of MXenes in non-aqueous electrolytes is still
unclear [28,46]. In situ dilatometry technique,which is
well-suitedfor 2Dmaterials,hasbeenusedto measure
theswelling/expansionof Ti3C2Tx MXene electrodein
Figure4
Gravimetricandnon-gravimetricapplicationsofEQCM-Dforthecharacterizationofenergy-storageelectrodes.(Bottompanel)Acousticwavesfor fundamentalfrequencyandits3rdovertone.Adaptedwithpermissionfromref.[49].Copyright©2018AmericanChemicalSociety.
hydrodynamic equations.Structural parameters include electrodefilmdensityorthickness,permeabilitylength, particlesradiusandcoveragedensity(Figure4)[49].This
technique is an efficient tool for tracking in one shot
thegeometricalchangeintheelectrodes(contractionor
swelling,morphologicalchanges)aswellasthechangein reactionmechanisms(formationofpassivelayersor elec-trolytedecomposition)[51••].
Another technique derived from EQCM is called
AC-electrogravimetry or AC-EQCM [52]. The AC-EQCM
techniqueconsistsofachievinggravimetricEQCM
mea-surements at a steady state (constant potential for
in-stance) and over-impose a sinusoidal perturbation to
the bias signal such as achieved in electrochemical
impedance spectroscopy. Differently from gravimetric
EQCM,AC-EQCMallowsthedeconvolutionofaglobal
gravimetricECQMresponseintoindividualcations,
an-ions,andsolventmoleculescontributionsbyplottingthe dQ/dE(Q:charge,E:potential)ordm/dE(m:mass,E: po-tential)transferfunctions;thisisonekeyadvantageofthis techniquewhichcantracktheelectrochemicalactivityof onetypeofanion(cation)inamixtureofanions(cations)
[53].Somepapers havejust been publisheddescribing
theuseof AC-EQCM to studypseudocapacitive
mate-rials[54•].Thepossibilityfordifferentiatingtheion
con-tributions presentgreatinterestfor studyingthecharge storagereactionmechanismsinvariouselectrolytes.
References
and
recommended
reading
Papersofparticularinterest,publishedwithintheperiodofreview,have beenhighlightedas:
•Paperofspecialinterest. ••Paperofoutstandinginterest.
1. SimonP,GogotsiY:Materialsforelectrochemicalcapacitors. NatMater2008,7(11):845–854.
2. KruusmaJ,TõnisooA,PärnaR,NõmmisteE,KuusikI,VahtrusM, TalloI,RomannT,LustE:Theelectrochemicalbehaviorof 1-ethyl-3-methylimidazoliumtetracyanoboratevisualizedbyin situX-rayphotoelectronspectroscopyatthenegativelyand positivelypolarizedmicro-mesoporouscarbonelectrode.J ElectrochemSoc2017,164(13):A3393–A3402.
3. KruusmaJ,TõnisooA,PärnaR,NõmmisteE,TalloI,RomannT, LustE:Influenceofthenegativepotentialofmolybdenum carbidederivedcarbonelectrodeontheinsitusynchrotron radiationactivatedX-rayphotoelectronspectraof 1-ethyl-3-methylimidazoliumtetrafluoroborate.Electrochim Acta2016,206:419–426.
4. •
BatisseN,Raymundo-PiñeroE:Pulsedelectrochemicalmass spectrometryforoperandotrackingofinterfacialprocessesin small-time-constantelectrochemicaldevicessuchas supercapacitors.ACSApplMaterInterfaces2017, 9(47):41224–41232.
Inthispaper,thegasemissionsduringpolarizationofacarbon-–carbon supercapacitorcellwereanalyzedasafunctionofthecellvoltage.The datawerecorrelatedtothetexturalchangesoftheofthecarbon electrodes,givingacompletepictureoftheprocessestakingplaceat theelectrode/electrolyteinterface.
5. FigueiredoJL,PereiraMFR,FreitasMMA,ÓrfãoJJM: Modificationofthesurfacechemistryofactivatedcarbons. Carbon1999,37(9):1379–1389.
6. GhimbeuCM,GadiouR,DentzerJ,VidalL,Vix-GuterlC:A TPD-MSstudyoftheadsorptionofethanol/cyclohexane mixtureonactivatedcarbons.Adsorption2011,17(1):227– 233.
7. MoussaG,MateiGhimbeuC,TabernaP-L,SimonP,Vix-GuterlC: Relationshipbetweenthecarbonnano-onions(CNOs)surface chemistry/defectsandtheircapacitanceinaqueousand organicelectrolytes.Carbon2016,105:628–637.
8. EliadL,SalitraG,SofferA,AurbachD:Ionsievingeffectsinthe electricaldoublelayerofporouscarbonelectrodes: estimatingeffectiveionsizeinelectrolyticsolutions.JPhys ChemB2001,105(29):6880–6887.
9. EliadL,SalitraG,SofferA,AurbachD:Onthemechanismof selectiveelectroadsorptionofprotonsintheporesofcarbon molecularsieves.Langmuir2005,21(7):3198–3202.
10. ChmiolaJ,YushinG,GogotsiY,PortetC,SimonP,TabernaPL: Anomalousincreaseincarboncapacitanceatporesizesless than1nanometer.Science2006,313(5794):1760–1763.
11. ThommesM,KanekoK,NeimarkAlexanderV,OlivierJamesP, Rodriguez-ReinosoF,RouquerolJ,SingKennethSW: Physisorptionofgases,withspecialreferencetothe evaluationofsurfaceareaandporesizedistribution(IUPAC TechnicalReport).PureApplChem2015,87(9-10):1051– 1069.
12. GorGY,ThommesM,CychoszKA,NeimarkAV:Quenchedsolid densityfunctionaltheorymethodforcharacterizationof mesoporouscarbonsbynitrogenadsorption.Carbon2012, 50(4):1583–1590.
13. JäckelN,SimonP,GogotsiY,PresserV:Increaseincapacitance bysubnanometerporesincarbon.ACSEnergyLett2016, 1(6):1262–1265.
14. LuoZ-X,XingY-Z,LiuS,LingY-C,KleinhammesA,WuY: Dehydrationofionsinvoltage-gatedcarbonnanopores observedbyinsituNMR.JPhysChemLett2015, 6(24):5022–5026.
15. WangH,ForseAC,GriffinJM,TreaseNM,TrognkoL,TabernaP-L, SimonP,GreyCP:InsituNMRspectroscopyof
supercapacitors:insightintothechargestoragemechanism.J AmChemSoc2013,135(50):18968–18980.
16. DeschampsM,GilbertE,AzaisP,Raymundo-PiñeroE,
AmmarMR,SimonP,MassiotD,BéguinF:Exploringelectrolyte organizationinsupercapacitorelectrodeswithsolid-state NMR.NatMater2013,12:351.
17. GriffinJM,ForseAC,TsaiW-Y,TabernaP-L,SimonP,GreyCP:In situNMRandelectrochemicalquartzcrystalmicrobalance techniquesrevealthestructureoftheelectricaldoublelayerin supercapacitors.NatMater2015,14(8):812–819.
18. ForseAC,Merlet,GriffinC,GreyJM,NewCP:Perspectiveson thechargingmechanismsofsupercapacitors.JAmChemSoc 2016,138(18):5731–5744.
19. ••
ForseAlexanderAC,GriffinJohnJM,MerletC,
Carretero-GonzalezJ,RajiA-RahmanRO,TreaseNicoleNM, GreyClareCP:Directobservationofiondynamicsin supercapacitorelectrodesusinginsitudiffusionNMR spectroscopy.NatEnergy2017,2(3):16216Articlenumber:.
Inthispaper,in-situpulsedfieldgradientNMRspectroscopywasused tomeasureionicdiffusioninporouscarbonelectrodes.In-poreionic diffusioncoefficientswerefoundtobe2ordersofmagnitudebelow comparedtobulkelectrolyte.Ionicdiffusioncoefficientcanbeaffected bothbycarbonporesizedistributionsandtheelectrolyteconcentration inpores.
20. TsaiWY,TabernaPL,SimonP:Electrochemicalquartzcrystal microbalance(EQCM)studyofiondynamicsinnanoporous carbons.JAmChemSoc2014,136(24):8722–8728.
21. HantelMM,PresserV,KötzR,GogotsiY:Insituelectrochemical dilatometryofcarbide-derivedcarbons.ElectrochemCommun 2011,13(11):1221–1224.
22. ••
KoczwaraC,RumswinkelS,PrehalC,JäckelN,ElsässerMS, AmenitschH,PresserV,HüsingN,ParisO:Insitumeasurement ofelectrosorption-induceddeformationrevealsthe
importanceofmicroporesinhierarchicalcarbons.ACSAppl MaterInterfaces2017,9(28):23319–23324.
Inthispaper,nanometerscaleandmacroscopicscaledimensional changesincarbon-basedsupercapacitorelectrodeswereinvestigated usingacombinationofelectrochemicaldilatometryandinsitu small-angleX-rayscattering.
23. ••
BoukhalfaS,GordonD,HeL,MelnichenkoYB,NittaN, MagasinskiA,YushinG:Insitusmallangleneutronscattering revealingionsorptioninmicroporouscarbonelectricaldouble layercapacitors.ACSNano2014,8(3):2495–2503.
Forthefirsttimethatin-situsmallangleneutronscattering(SANS)was utilizedtorevealtheelectroadsorptionoforganicelectrolyteionsin carbonporesofdifferentsizes.Enhancedionsorptioninsubnanometer poresundertheappliedpotentialwasobserved.
24. PrehalC,KoczwaraC,JackelN,SchreiberA,BurianM,
AmenitschH,HartmannMA,PresserV,ParisO:Quantificationof ionconfinementanddesolvationinnanoporouscarbon supercapacitorswithmodellingandin-situX-rayscattering. NatEnergy2017,2(3):16215Articlenumber.
25. FutamuraR,IiyamaT,TakasakiY,GogotsiY,BiggsMJ,
SalanneM,SégaliniJ,SimonP,KanekoK:Partialbreakingofthe Coulombicorderingofionicliquidsconfinedincarbon nanopores.NatMater2017,16(12):1225–1232.
26. MerletC,PeanC,RotenbergB,MaddenPA,DaffosB,TabernaPL, SimonP,SalanneM:Highlyconfinedionsstorechargemore efficientlyinsupercapacitors.NatCommun2013,4:2701Article number:.
27. KondratS,KornyshevA:Superionicstateindouble-layer capacitorswithnanoporouselectrodes.JPhys,vol232011 022201Articlenumber:.
28. LinZ,RozierP,DuployerB,TabernaP-L,AnasoriB,GogotsiY, SimonP:Electrochemicalandin-situX-raydiffractionstudies ofTi3C2TxMXeneinionicliquidelectrolyte.Electrochem
Commun2016,72:50–53.
29. GhodbaneO,AtaherianF,WuN-L,FavierF:Insitu
crystallographicinvestigationsofchargestoragemechanisms inMnO2-basedelectrochemicalcapacitors.JPowerSources
2012,206:454–462.
30. ChengJ,CaoG-P,YangY-S:Characterizationof
sol–gel-derivedNiOxxerogelsassupercapacitors.JPower
Sources2006,159(1):734–741.
31. ComeJ,AugustynV,KimJW,RozierP,TabernaP-L,GogotsiP, LongJW,DunnB,SimonP:Electrochemicalkineticsof nanostructuredNb2O5electrodes.JElectrochemSoc2014,
161(5):A718–A725.
32. LukatskayaMR,BakS-M,YuX,YangX-Q,BarsoumMW, GogotsiY:Probingthemechanismofhighcapacitancein2D titaniumcarbideusinginsituX-rayabsorptionspectroscopy. AdvEnergyMater,vol520151500589Ariclenumber:.
33. AnasoriB,LukatskayaMR,GogotsiY:2Dmetalcarbidesand nitrides(MXenes)forenergystorage.NatRevMater2017, 2(2):16098Articlenumber:.
34. PandeP,DebA,SleightholmeAES,DjireA,RasmussenPG, Penner-HahnJ,ThompsonLT:Pseudocapacitivechargestorage viahydrogeninsertionformolybdenumnitrides.JPower Sources2015,289:154–159.
35. YeagerMP,SuD,Marinkovi´cNS,TengX:PseudocapacitiveNiO finenanoparticlesforsupercapacitorreactions.JElectrochem Soc2012,159(10):A1598–A1603.
36. AugustynV,ComeJ,LoweMA,KimJW,TabernaP-L,TolbertSH, AbruñaHD,SimonP,DunnB:High-rateelectrochemicalenergy storagethroughLi+intercalationpseudocapacitance.Nat
Mater2013,12(6):518–522.
37. KimH-S,CookJB,LinH,KoJS,TolbertSH,OzolinsV,DunnB: Oxygenvacanciesenhancepseudocapacitivechargestorage propertiesofMoO3-x.NatMater2017,16(4):454–460.
38. HanJ,LinY-C,ChenL,TsaiY-C,ItoY,GuoX,HirataA,FujitaT, EsashiM,GessnerT,ChenM:On-chipmicro-pseudocapacitors forultrahighenergyandpowerdelivery.AdvSci,vol22015 1500067Articlenumber:.
39. KimJW,AugustynV,DunnB:Theeffectofcrystallinityonthe rapidpseudocapacitiveresponseofNb2O5.AdvEnergyMater
2012,2(1):141–148.
40. BozlarM,MiomandreF,BaiJ:Electrochemicalsynthesisand characterizationofcarbonnanotube/modifiedpolypyrrole hybridsusingacavitymicroelectrode.Carbon2009, 47(1):80–84.
41. ••
HuM,LiZ,HuT,ZhuS,ZhangC,WangX:High-capacitance mechanismforTi3C2TxMXenebyinsituelectrochemical
Ramanspectroscopyinvestigation.ACSNano2016, 10(12):11344–11350.
Inthispaper,authorsinvestigatedthechargestoragemechanismof Ti3C2TxMXenebyin-situRamantechnique.It’sItisshownthat hydroniuminH2SO4electrolytereversiblebonding/debondingwith OterminalsaccountforthehighcapacitanceMXeneinacidic electrolytes.
42. NaguibM,KurtogluM,PresserV,LuJ,NiuJ,HeonM,HultmanL, GogotsiY,BarsoumMW:Two-dimensionalnanocrystals producedbyexfoliationofTi3AlC2.AdvMater2011,
23(37):4248–4253.
43. LukatskayaMR,KotaS,LinZ,ZhaoM-Q,ShpigelN,LeviMD, HalimJ,TabernaP-L,BarsoumMW,SimonP,GogotsiY: Ultra-high-ratepseudocapacitiveenergystoragein two-dimensionaltransitionmetalcarbides.NatEnergy2017, 2(8):17105Articlenumber:.
44. MashtalirO,LukatskayaMR,KolesnikovAI,Raymundo-PineroE, NaguibM,BarsoumMW,GogotsiY:Theeffectofhydrazine intercalationonthestructureandcapacitanceof2Dtitanium carbide(MXene).Nanoscale2016,8(17):9128–9133.
45. LinZ,BarbaraD,TabernaP-L,VanAkenKL,AnasoriB,GogotsiY, SimonP:CapacitanceofTi3C2TxMXeneinionicliquid
electrolyte.JPowerSources2016,326:575–579.
46. Dall’AgneseY,RozierP,TabernaP-L,GogotsiY,SimonP: Capacitanceoftwo-dimensionaltitaniumcarbide(MXene)and MXene/carbonnanotubecompositesinorganicelectrolytes.J PowerSources2016,306:510–515.
47. JäckelN,KrünerB,VanAkenKL,AlhabebM,AnasoriB,KaasikF, GogotsiY,PresserV:Electrochemicalinsitutrackingof volumetricchangesintwo-dimensionalmetalcarbides (MXenes)inionicliquids.ACSApplMaterInterfaces2016, 8(47):32089–32093.
48. XuK,LinZ,MerletC,TabernaPL,MiaoL,JiangJ,SimonP: Trackingionicrearrangementsandinterpretingdynamic volumetricchangesintwo-dimensionalmetalcarbide supercapacitors:amoleculardynamicssimulationstudy. ChemSusChem2017.https://doi.org/10.1002/cssc.201702068.
49. ShpigelN,LeviMD,SigalovS,DaikhinL,AurbachD:Insitu real-timemechanicalandmorphologicalcharacterizationof electrodesforelectrochemicalenergystorageandconversion byelectrochemicalquartzcrystalmicrobalancewith
dissipationmonitoring.AccChemRes2018,51(1):69– 79.
50. LeviMD,DaikhinL,AurbachD,PresserV:Quartzcrystal microbalancewithdissipationmonitoring(EQCM-D)forin-situ studiesofelectrodesforsupercapacitorsandbatteries:a mini-review.ElectrochemCommun2016,67:16–21.
51. ••
DargelV,ShpigelN,SigalovS,NayakP,LeviMD,DaikhinL, AurbachD:Insitureal-timegravimetricandviscoelastic probingofsurfacefilmsformationonlithiumbatteries electrodes.NatCommun2017,8(1):1389Articlenumber:.
Inthispaper,Electrochemicalelectrochemicalquartz-crystal microbalancewithdissipation(EQCM-D)monitoringmeasurements wereperformedtoprobetheformationofsurfacefilmsoncomposite Li4Ti5O12electrodecoupledwithlithiumionsintercalationintothis electrode.
52. GabrielliC,KeddamM,PerrotH,PhamMC,TorresiR:Separation ofionicandsolventtransportduringchargecompensation processesinelectroactivepolymersbya.c.electrogravimetry. ElectrochimActa1999,44(24):4217–4225.
53. Escobar-TeranF,ArnauA,GarciaJV,JiménezY,PerrotH,SelO: GravimetricanddynamicdeconvolutionofglobalEQCM responseofcarbonnanotubebasedelectrodesby Ac-electrogravimetry.ElectrochemCommun.2016,70(Suppl. C):73–77.
54. •
AriasCR,Debiemme-ChouvyC,GabrielliC,Laberty-RobertC, PailleretA,PerrotH,SelO:Newinsightsintopseudocapacitive charge-storagemechanismsinLi-birnessitetypeMnO2
monitoredbyfastquartzcrystalmicrobalancemethods. J PhysChemC2014,118(46):26551–26559.
AC-electrogravimetry(ac-EQCM)wasusedforthefirsttimefor studyingpseudocapacitivechargestoragemechanism.Resultsclearly evidencethede-hydrationofdifferentcationswhentransfertothe electrode/electrolyteinterfaces.Thereactionkineticsandresistanceof chargedandnonchargedspeciestransferredatthe
electrode/electrolyteinterfacesandthenumberofwatermoleculesin thehydrationshelloftheionswereestimatedaswellasthefluxoffree warer.