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1、ElectrochimicaActa49(2004)42134222EmulsiondryingsynthesisofolivineLiFePO4/CcompositeanditselectrochemicalpropertiesaslithiumintercalationmaterialSeung-TaekMyung1,ShinichiKomaba∗,2,NorimitsuHirosaki,HitoshiYashiro,NaoakiKumagai2DepartmentofFrontierMaterialsandFunctionalEngineering,GraduateSch
2、oolofEngineering,IwateUniversity,4-3-5Ueda,Morioka,Iwate020-8551,JapanReceived14January2004;accepted5April2004Availableonline28May2004AbstractTheelectroactiveLiFePO4/Cnano-compositehasbeensynthesizedbyanemulsiondryingmethod.Duringburning-outtheoilyemulsionprecipitatesinanair-limitedatmospher
3、eat300◦C,amorphousorlowcrystallinecarbonwasgeneratedalongwithreleasingcarbonoxidegases,andtrivalentironasacheapstartingmaterialwasimmediatelyreducedtothedivalentoneatthisstageasconfirmedbyX-rayphotoelectronspectroscopy,leadingtoalowcrystallineLiFePO4/Ccomposite.Heat-treatmentofthelowcrystalli
4、neLiFePO4/CinanAratmosphereresultedinawell-orderedolivinestructure,asrefinedbyRietveldrefinementoftheX-raydiffractionpattern.Fromsecondaryelectronmicroscopicandscanningtransmissionelectronmicroscopicobservationswiththecorrespondingelementalmappingimagesofironandphosphorous,itwasfoundthattheLiF
5、ePO4powdersaremodifiedbyfinecarbon.Theinsituformationofthenano-sizedcarbonduringcrystallizationofLiFePO4broughtabouttwoadvantages:(i)anoptimizedparticlesizeofLiFePO4,and(ii)auniformdistributionoffinecarbonintheproduct.TheseeffectsofthefinecarbononLiFePO/Ccompositeledtohighcapacityretentionuponcy
6、clingat25and50◦Candhighratecapability,4resultingfromagreatenhancementofelectricconductivityashighas10−4Scm−1.Thatis,theobtainedcapacitywashigherthan90mAh(g-phosphate)−1byapplyingahighercurrentdensityofabout1000mAg−1(11C)at50◦C.©2004ElsevierLtd.Allrightsreserved.Keywords:Emulsiondryingmethod;
7、OlivineLiFePO4;Composite;Lithiumbattery;Lithiumintercalation1.Introductionwaytoovercomethelimitedratecapability,becausethewell-dispersedcarbonsprovideapathwayforelectrontrans-OlivinetypeLiFePO4showsarelativelyhighcapacityport,resultinginimprovement
