Int.J.Electrochem.Sci.,10(2015)4682-4687

InternationalJournalof

ELECTROCHEMICAL

SCIENCE

ShortCommunication

HollowSpherec-In2O3forApplicationinLithiumIonBattery

XinghuaLiang1,*,QingqingSong1,LinShi1,YusiLiu2,GongqinYan1,AnbangJiang1

1GuangxiKeyLaboratoryofAutomobileComponentsandVehicleTechnology,GuangxiUniversityof

ScienceandTechnology,Guangxi,Liuzhou545600,China;2ShanghaiJiaoTongUniversity,Shanghai

200240,China

*E-mail:lxh304@,

Received:23March2015/Accepted:18April2015/Published:28April2015

Thehollowspherec-InOweresynthesizedviahydrothermalreaction.Thecrystalstructureofthe

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samplewascollectedandanalyzedthroughX-raydiffractometry(XRD).Thesurfacemorphologyand

particlesizeofthesamplewereobservedbyscanningelectronmicroscope(SEM).The

electrochemicalpropertyofthehollowspherec-InOascathodeforLi-ionBatterieswerestudied.

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HollowSpherec-InOshowsadischargecapacitywas1162mAh·g-1atthecurrentdensityof30

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mA·g-1inavoltageof0.2-1.4V,andthereversiblecapacityisaround100mAh·g-1after40cycles.

Keywords:c-In2O3;hydrothermal;hollowsphere;metaloxide;lithiumionbattery

1.INTRODUCTION

Inrecentyears,growingdemandsinvariouselectronicdevices,digitalcommunication,hybrid

electricvehicles,otherrelateddevices,andhighpowersourcehavebeeninvestigated[1].Asnew

potentialanodeofmaterialsrechargeablelithiumbatteries,metaloxidesbeenapplicatedtotheareaof

theenergystorage[2,3].Duetouniquephysical,chemicalproperties[4],andhighertheoretical

reversiblecapacity(500~1000mAh·g-1),metaloxidesthanthatofthecurrentcommercialgraphite

(~370mAh·g-1)[5-8].

Hollowsphereofmetaloxideshavebeenattentedforseveralyears,becauseoftheirunique

propertiesofspecificstructural,nanometersizes,goodpermeation,lowdensity,andhighspecific

surfacearea[7].Manymethodshavebeendevelopedtofabricatehollowsphereofmetaloxides,for

instance,pyrohydrolytic[9],hydrothermalmethod[10-15],thermalevaporation[16],chemicalvapor

deposition[17],pulsedlaserdeposition[2,18]andelectrochemicaldeposition[18].

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Indiumoxide(In2O3)aspromisingcathodematerialhasbeenattractedattention,owningtoits

hightheoreticalcapacities,electricalconductivityandapplicationsextensively[19-20].In2O3isvery

importantn-typesemiconductorbinaryoxidewithdirectbandgapof3.55-3.75eVandindirectband

gaparound2.8eV,andhasbeenwidelyappliedinmicroelectronicareasincludinggassensors,

transparentconductors,solarcells,ultrasensitivetoxicgasdetectors,andliquidcrystaldisplaydevices

[9,10,21,22].In2O3hasthreedifferentcrystalstructures:cubicbixbyite-type(c-In2O3),hexagonal

corundunm-type(h-In2O3)andorthorhombicRh2O3(II)-type[23].c-In2O3isstableunderambient

conditionsandthelaststructureisstableonlyunderhighpressuresandtemperatures[3,4,11].

Inthiswork,wedemonstrateafacilehydrothermalprocessforcontrollablesynthesizationof

hollowspherec-In2O3.ThecrystalstructureandmorphologyofsamplesareobservedthroughX-ray

diffraction(XRD)andscanningelectronmicrographs(SEM).Moreover,theelectrochemical

propertiesofthehollowspherec-In2O3havebeeninvestigatedascathodematerialsforLi-ion

Batteries.Theresultsshowthattheas-preparedhollowspherec-In2O3exhibithighdischargecapacity

andcoulombicefficiency.

2.EXPERIMENTALMETHODS

Thehollowspherec-In2O3samplewassynthetizedbyhydrothermalprocess:0.381g

In(NO)3·4.5H2Oand8gsucroseweredissolvedin30mLdistilledwater.1mLofdimethylformamide

wasaddedintotheformerliquorundervigorousstirringfor1h,atroomtemperature.Theresulting

mixturewastransferredintoaTeflon-linedstainlesssteelautoclaveof50mLcapacity.Theautoclave

wasthensealedandmaintainedat80oCfor20hinanovenfollowedbycoolingtheautoclavedownto

roomtemperaturenaturally.Afterbeingcooled,thepreparedwhiteprecipitatewascollectedby

centrifugationandwashedwithdistilledwaterandtheabsoluteethanol.Thewashingcyclewas

repeatedseveraltimes,followedbydryingat80oCovernight.TheproductwaswhiteIn(OH)3sample.

Finally,theyellowhollowspherec-In2O3samplewasobtainedfromthewhiteIn(OH)3samplevia

calcinationat550oCfor2hwitheatingrateof2oC·min-1,andcoolingrateof1oC·min-1,inamuffle

furnace.

ThecrystallinephaseofIn2O3wasidentifiedbyanX-raydiffractometer(BrukerD8Advance)

usingCuKαradiation(λ=0.154184nm)with40kVofvoltageand30mAofcurrent.XRDdatawas

recordedat2θwithastepsizeof0.03°intherangefrom10°to90°.Theparticlesizeandmorphology

ofhollowspherec-In2O3powderswereobservedwithascanningelectronmicroscope.

Theelectrochemicalperformanceofthehollowspherec-In2O3powdersascathodewas

evaluatedusingaCR2016coin-typecellwithalithiummetalanode.TheCR2016coin-typecellwas

fabricatedwiththehollowspherec-In2O3cathode,ametalliclithiumanode,andaCelgard

polypropyleneseparator.Theelectrolytesolutionwas1MLiPF6/DOL+DMC(1:1).Theelectrode

waspreparedbymixing80wt.%thehollowspherec-In2O3samplewith10wt.%acetyleneblackand

10wt.%polypropylenefluoride(PVDF)binderinN-methylpyrrolidone(NMP)toformaslurry.The

slurrywasstirred4h,thencoatedontoacopperfoil,anddriedat120oCfor12hinavacuumdrierto

preparethecathodefilm.Thecathodefilmwaspunchedintodiscs(diameter=14mm).Thecellwas

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fabricatedinanAr-filledglovebox.Theassembledcellwaschargedanddischargedbetween0.2Vand

1.4V(versusLi/Li+)ontheamulti-channelbatterytestsysteminstrumentatroomtemperature.

3.RESULTSANDDISCUSSION

Fig.1showsafullsetofdiffractionpeaksoftheIn2O3sample.Thesharppeaksinthepattern

showedgoodcrystallinityoftheIn2O3sample.Itisseenthatafewofstrongpeaksatthenear21.49°,

30.58°,35.47°,51.04°,83.20°canbeindexedtothecubicphaseofc-In2O3(JCPDSno.06-0416),

whichisinvisibleintheXRDpatterns[11].Thelatticeparametersrefinedwithinthisspacegroupfor

thenewphasearea=1.012nm(a=1.0118nmfromJCPDSno.06-0416),andunitcellvolumeV0=0.065

nm3.

Figure1.XRDpatternofhollowspherec-In2O3

InFig.2,itvividlyrevealsthattheIn2O3sampleconsistsofhollowspheremicrospheresand

sphere-sectionwithadiameterofabout1-3μm.Moreinterestingly,boththeinnerandoutersurfaceof

thehollowc-In2O3samplearerough(Fig.2a.b).Thethicknessofthehollowballisabout0.6μm.It

worthnotingthatsomeofthehollowballisincomplete.Spherewallwasstructurebynanocrystals

(Fig.2c).Itiswell-knownthatratecapabilityplaysanimportantroleinlithiumionbattery.The

electrochemicalperformanceofhollowspherec-In2O3wereevaluatedbygalvanostaticmeasurements.

Fig.3showsthatthefirstdischargecurveofthecoincellbetween0.2Vand1.4V,ataconstantcurrent

densityof30mA·g-1.

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(a)

(b)

(c)

Figure2.(a)(b)SEMimageofhollowspherec-In2O3;(c)magnifiedSEMimageofhollowspherec-

InOnanoparticlesofthepositionmarkedin(b).

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Intheinitialdischargingprocess,thereisalongsmoothvoltageplateausaround0.9V,andThe

firstdischargecapacityis1162whichishigherthanthatreportbyZhouetal[2].However,withthe

increaseofthecyclingtimes,thedischargecapacityofthecoincellpresentsadownwardtrend.

Especially,theseconddischargecapacitydownsquicklyfrom1162mAh·g-1to201mAh·g-1.Afterthe

fivecycle,thedischargecapacitycurveofthecoincellkeepsastablecondition.

Figure3.ThefirstdischargecurveoftheLi/In2O3coincell

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a

b

c

Figure4.Electrochemicalpropertiesofhollowspherec-InO:(a)specificcapacityofLi/InOcoin

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cell;(b)coulombicefficiencyofLi/InO23coincell;(c)rateperformanceofLi/In2O3coincell

Itsuggeststhathollowspherec-In2O3haslargeirreversiblecapacity.Inthe40thcycle,the

dischargecapacityofthecoincellonlyremainsabout100mAh·g-1(Fig.4a).Themassivecapacity

reductionmaybeattributedtolithiationreactioninitiallyanddelithiationoftheelectrodeinthelithium

ionbattery[5].Coulombicefficiencyisakeyindexforevaluatingthestabilityofthecoincell.Itcan

beseenthatthecoulombicefficiencyinthefirstcycleislowandunstable,andbecamesgradually

increasingfrom70%to94%(Fig.4b),whichmaybeduetothediffusionrateofLi+ionsinhollow

spherec-In2O3becomingstable.AsshowninFig.3c,itcanbeseenthatthedischargecapacityofthe

coincelldecreasedquicklyatthecurrentdensityof30mA·g-1duringthefirstfivecycles.Whenthe

currentdensitygraduallyincreasedfrom60mA·g-1to240mA·g-1,theIn2O3electrodedelivereda

capacityof90mAh?g-1,82mAh?g-1,74mAh·g-1,respectively.Whilethecurrentdensitybackto30

mA·g-1afterbeingcontinuouslycycledfor10times,acapacityof101mAh?g-1canbe

obtained,indicatinggoodrobustnessandstabilityofhollowspherec-In2O3material.

4.CONCLUSION

Inconclusion,thehollowspherec-In2O3samplewaspreparedbyhydrothermalmethod.

AccordingtotheXRDandSEM,samplewascubicbixbyite-typestructure(Ia-3)In2O3,good

crystallinityandhollowsphere.Thesamplepresentedthelargedischargecapacityof1162mAh·g-1at

thecurrentdensityof30mA·g-1between0.2Vand1.4V.Thedischargecapacityfadedquiklyinthe

charge-dischargeprocess.After40cycles,thereversiblecapacitywasaround100mAh·g-1,and

coulombicefficiencyrisesto94%.

ACKNOWLEDGEMENTS

ThisworkwasfinanciallysupportedbytheBuildingFund(No.13-051-38)andOpeningProjectof

GuangxiKeyLaboratoryofAutomobileComponentsandVehicleTechnology(No.2012KFMS04,

2013KFMS01).

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