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

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

bandsbetween400and1050cmÀ1canbeindexedtovarious(group)vibrationsofV–Otype.26Thecharacteristicbandsitu-atedat1023cmÀ1isrelatedtotheV]Ostretching,thebandslocatedat598and824cmÀ1canbeattributedtothesymmetricandasymmetricvibrationalmodesoftheV–O–VstretchinginV2O5,respectively.15,27,28InFig.2b,thetypicalbandsofpoly-anilinecanbeobservedclearly.Thepeaksintherangeof3200–3500cmÀ1(e.g.3231cmÀ1)areduetotheN–Hstretchingvibrationsoftheleucoemeraldinecomponent.Thecharacteristicpeaksat1575cmÀ1and1487cmÀ1areassignedtotheC]Cstretchingmodeofquinoidandbenzenoidrings,respectively.Thepeaksat1323cmÀ1and1248cmÀ1correspondtothestretchingvibrationsofC–NandC]N,respectively.Thepeakat1138cmÀ1isassignedtothein-planebendingofC–H.20,29Theappearanceofallthesepeaksindicatesthatprotonatedpoly-anilineisformedafterthereactionofinitialV2O5precursorwithanilineunderhydrothermalconditions.ThecharacteristicbandofV]Ostretchingat995cmÀ1(Fig.2c)and1023cmÀ1(Fig.2a)areoftheoxidationandreductionstatesofthevanadiumV4+andV5+oxides,respectively.30TheshiftoftheV]Ostretchingvibrationmodefrom1023cmÀ1intheV2O5precursorto1002cmÀ1inthenanocompositesuggeststhatV5+isreducedtoV4+partially.

Fig.3showstheRamanspectraoftheV2O5precursor,sample1,andsample2.AllsamplesshowthetypicalRamanscatteringbandsoforthorhombicV2O5,whichisingoodagreementwiththosedescribedintheref.31and32.Thelow-wavenumberpeaksat143and189cmÀ1correspondtotheexternal[VO5]–[VO5]modes,indicatingtheretentionoflongrangeorderinthesestructures.31Thepeaksat686and521cmÀ1canbeattributedtoantiphasebridgingV–OandchainingV–Ostretchingmodes,characteristicsoforthorhombicV2O5.31,32Thestrongpeakat988cmÀ1isattributedtothestretchingmodeofthevanadylV]Omoiety.33Morphology

Fig.4showstheSEMimagesoftheV2O5precursor,sample1andsample2.TheV2O5precursorhasthemorphologyofirregularnano akes.Ontheotherhand,sample1,polyaniline-

Fig.4SEMimagesof(a),(b)V2O5precursor,(c),(d)sample1,and(e),(f)sample2.

intercalatedlayeredvanadiumoxidenanocomposite,hasthemorphologyofwhitefungusself-assembledfromthenanosheets.Asshowninthemagni edSEMimages(Fig.4d),thethicknessofthenanosheetsisbetween10and20nm,andthetypicallateraldimensionofthenanosheetsisintherangeofhundredsofnanometrestoseveralmicrometres.Inaddition,theSEMresultsalsosuggestthatthereisnobulkdepositionofpolyanilineonthesurfaceofmicrocrystallites.The2Dwhitefungus-likenano-structurecanalsobeseenclearlyinthecorrespondingTEMimage(Fig.5a).ThethicknessandlateraldimensionofthenanosheetsareconsistentwiththeSEMresult.Theelectrondiffractionpattern(insetofFig.5a)indicatesthatthepolyani-line-intercalatedlayeredvanadiumoxidenanocompositeisquasi-crystalline,whichisquitesimilartotheresultreportedbyZhangetal.22Moresigni cantly,theHRTEMimageinFig.5bshowsthehierarchicalarchitecturesoftheobtainedlayerednanocomposite,suggestingthattheinsituredoxintercalativepolymerizationbyhydrothermaltreatmentistopotacticandthelayeredhoststructurestillremainsunchanged.ItcanalsobeseenfromtheHRTEMimagethattheobtainednanocompositeconsistsofseveralconductingpolymernanosheetsandthelowscatteringpowercausedbrightcontrastforwhitelines,eachwithawidthof$1.5nmbetweentwodarkfringesofhostlayers,whichisingoodagreementwiththeinterlayerspacingd001¼1.4nmevaluatedfromXRD.Thus,fromtheHRTEMimageandXRD,itcanbeconcludedthathighlycrystallinevanadiumoxidelayersareseparatedalternativelybypolyanilinenanosheetsinthehybridnanocomposite.

Formationmechanisms

Fig.3Ramanspectraof(a)V2O5precursor,(b)sample1,and(c)sample

2.

TheinsituintercalationandpolymerizationreactionofanilinewithlayeredV2O5wascarriedoutunder

hydrothermal