Polyaniline-intercalated layered vanadium oxide nanocomposit(2)

Polyaniline-intercalated layered vanadium oxide nanocomposites—One-pot hydrothermal synthesis and application in lithium battery

theadditionof3molLÀ1hydrochloricacid.Theslurrysolutionwasstirredforabout30minandtransferredtoa50mLTe on-linedautoclave.Theautoclavewasheatedto120 Candheldfor24h,thenallowedtocooldowntoroomtemperature.Thedarkgreenprecipitatewascollectedandwashedseveraltimeswithdistilledwaterandanhydrousalcohol,thendriedat60 Cforseveralhoursandkeptforfurthercharacterization.Thesamplessynthesizedat120 Cand180 Carenotedassample1andsample2,respectively.Characterization

Downloaded on 02 December 2010Published on 08 September 2010 on | doi:10.1039/C0NR00246A

AllsampleswerecharacterizedbypowderX-raydiffraction(XRD)onaPhilipsX’PertX-raydiffractometerwithmono- incidentradiation.ThesizechromatizedCuKa(l¼1.5418A)

distributionandmorphologyofallsampleswereanalyzedbyTEMobservationonaJEOLJEM-200CXtransmissionelectronmicroscope.SEMimagesandenergy-dispersiveX-rayspectra(EDS)wereobtainedonaJEOLJEM-6300Felectronmicro-scopeequippedwithEDSdetector.HRTEMimagesweretakenonaJEOL2010microscopeatanacceleratingvoltageof200kV.Fouriertransforminfrared(FT-IR)spectrawereacquiredwithaNicolet6700FT-IRspectrometerusingKBrpellets.RamanspectrawererecordedonaRenishawinViaRamanmicroscope(excitedwithanAr+lineat514nm).Electrochemicaltest

Totesttheobtainedsamplesascathodeinlithiumcells,theas-preparedsamplesweremixedwithcarbonblackandTe onpowder(Dupont)inaweightratioof80:15:5.Lithiumfoil(Aldrich)wasusedasthenegativeelectrode,1MLiPF6inEC:DMC¼1:1wasusedastheelectrolyte,andCelgard2320wasusedastheseparator.Thecellswereassembledinanargon- lledgloveboxwithlessthan5ppmofwaterandoxygen.Cyclingandcharge-dischargeperformancesofthetestingcellswerecarriedoutonabatterytestsystemLANDCT2001Aingalvanostaticmode,operatingataconstantcurrentdensityof29.5mAgÀ1withcontrolledcutoffpotentialsof1.8–3.5V(vsLi/Li+).

Fig.1XRDpatternof(a)V2O5precursor,(b)sample1,and(c)sample

2.

interlayerspacing.Uponintercalation,theinterlayerspacingofV2O5isincreasedfrom0.43to1.4nm,whichisingoodagreementwiththeresultreportedbyHugueninetal.19Ontheotherhand,allthediffractionpeaksofsample2asshowninFig.1ccanbeindexedtothemonocliniccrystallinephaseofVO2(JCPDS81-2392,withthelatticeconstantsofa¼1.129nm,b¼0.3702nm,c¼0.6433nm)andnocharacteristicpeakswereobservedforotherimpurities.

Theenergy-dispersiveX-rayspectra(EDS)weremeasuredtodeterminethechemicalcompositionoftheas-preparedsamples.AsshowninFig.S1(supportinginformation), sample1containsV,O,CandN;however,theatomicratioofVandOcannotbedeterminedbecauseonepeakfortheelementVoverlapswiththepeakfortheelementO.

Fig.2presentsFT-IRspectraofV2O5precursor,sample1,andsample2.InFig.2a,twoabsorptionbandsat3460and1643cmÀ1canbeattributedtothestretchingandbendingmodesofO–Hvibrations,respectively.ItmeansthatsomewatermoleculesareintercalatedintoV2O5layers.26The

absorption

Resultsanddiscussion

Structuralstudy

Thecompositionandphasepurityoftheproductswerechar-acterizedbyXRD.Fig.1showstheXRDpatternsofV2O5precursor,sample1andsample2.ThediffractionpeaksinFig.1acanbereadilyindexedtothepureorthorhombiccrys-tallinephaseofV2O5(JCPDS41-1426,withthelatticeconstantsofa¼1.151nm,b¼0.3565nm,c¼0.4372nm,spacegroupPmmn)andnocharacteristicpeakswereobservedforotherimpurities.Asetofpeakscharacteristicof(00l)re ectionsforthelayeredphaseareobservedinsample1(seeFig.1b),indicatingthatpolyanilineisintercalatedintothelayeredV2O5underhydrothermalconditions.15,16Itisconcludedthatpolyaniline-intercalatedlayeredvanadiumoxidenanocompositescanbeobtainedunderthepresentsyntheticconditions.Thestrongestpeakobservedatthelowest2qanglecorrespondstothe(001)planeofthelayeredV2O5structureandisdirectlyrelatedtothe

Fig.2FT-IRspectraof(a)V2O5precursor,(b)sample1,and(c)sample2.