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LiFePO4150种合成方法汇编大力李2009-12-61LiFePO4andC-LiFePO4werepreparedusingstoichiometricLi2CO3(99.95%),FeC2O4·H2O(99%),NH4H2PO4(98%),andglucose(99%).Thestartingmaterialswerefirstprecalcinedat400◦Cfor6hinflowingultra-pureArinordertodecomposethecarbonate,oxalate,andammonium.Aftercoolingdown,thedecomposedmixtureswerepressedintopellets(20mm,L10mm,10kN)andtransferredtoquartztubes,whichwerethensealedinvacuum.Thevacuum-sealedsampleswerethencalcinedinamufflefurnace.Thequartztubeswiththesampleswereremovedfromthefurnaceandimmediatelyputintowater.TheproductLiFePO4wasobtainedbyremovalfromabrokenquartztube.Inthispaper,thenotationsNCandWQrepresentsamplespreparedbynaturalcoolingandbywaterquenchingtreatment,respectively.参考略2ALiFePO4/carboncompositewassynthesizedfromstoichiometricquantitiesofFePO4·4H2O,LiOH·H2Oandaproperamountofcitricacid.Themixtureunderwentthefollowingthreeprocesses:(i)high-energyballmillingtakenbytwosteps,byprimaryballmilling(coarsegrinding)for3handsecondaryballmilling(finegrinding)for6hwithzirconiaballs;(ii)spray-drying,and(iii)thermaltreatmentunderflowingnitrogenat450◦Cfor1handthenat675◦Cfor8h.3TheFePO4precursorwaspreparedasfollows.ThestoichiometricamountsofH3PO4andFeNO3·9H2Oweredissolvedindistilledwater.ToobtaintheFePO4colloid,thedissolvedaqueoussolutionwasrecipitatedbyaddinganNH3solutionof5molL−1,underanargonatmosphere,withcontinuousstirringat50◦CandapHof1.0–2.0.Theco-precipitationmixturewasthenpressure-filtratedat20MPa,driedundervacuumat80◦Cfor6h,washed,driedagainundervacuumat80◦Cfor6h,andground,yieldingthefinalproduct.4LiFePO4waspreparedbythesolid-statereactionofLi2CO3(99.9%,Fluka),Fe(II)C2O4.H2O(99%,Aldrich)and(NH4)2HPO4(99%,Fluka).Topreventoxidationoftheiron,thesynthesiswasperformedunderaflowofnitrogengas.Thestartingmaterialswereweighedinstoichiometricamountsandhomogenizedusingamixer.Todecomposetheoxalateandthephosphate,themixturewasplacedinatubularfurnaceandheatedat300°Cfor20h.Thepowderwascooledatroomtemperatureandmixedwithhigh-surfaceareacarbonblack(KetlenJackBlak,AkzoNobel,surfacearea1250m2g−1).Aftergrindingandhomogenization,themixturewastransferredtothefurnaceandannealedat800°Cfor16hundernitrogenflow.Afterthistime,thepowderwasallowedtocoolatroomtemperature.5LiFePO4sampleswerepreparedbymixingstoichiometricamountsof(NH4)2HPO4,FeC2O4·2H2O,andLiFasstartingmaterials;theprecursorsweredispersedintoacetoneandthenballmilledfor7hinaplanetarymill.Therotatingspeedwas250rpmandtheballtochargeweightratiowas20:1.Afterevaporatingacetone,themixturewasfirstdecomposedat350◦CinaN2atmospherefor10htoallowH2OandNH3toevolve.Thereagentswerethenre-groundpriortoheatinginasealedtubefurnace.Thesampleswereheatedatarateof2◦Cmin−1tothetemperaturesrangingfrom650◦Cto800◦C,respectively,underastreamofamixtureof95%Ar+5%H2.Thematerialswereheldfor10hattheuppertemperatureandslowlycooleddowntoroomtemperaturepriortoremovalfromthefurnace.Thegraypowders(bareLiFePO4)wereobtained.Forthecarbon-coatedLiFePO4,carbongel(withthetotalamountof10wt%forthefinalproductLiFePO4)wasaddedtothemixtureofthestartingmaterials.Afterthesamemechanochemicaltreatment,thecarbon-coatedLiFePO4powdersweresynthesizedwiththesameheat-treatmentconditionsaswasadoptedforbareLiFePO4.6MaterialsChemistryandPhysics115(2009)245–2501.Solid-statereactionSolid-statesynthesisisaconventionalmethodforpreparingceramicsandincludesseveralsuccessivestepsofintimategrindingandannealingofthestoichiometricmixtureofstartingmaterials.Ingeneral,inthecaseofLiFePO4,thestartingmixtureconsistsofastoichiometricamountofironsalt(Fe(II)-acetate,Fe(II)-oxalate),alithiumcompound(lithiumcarbonateorlithiumhydroxide),andmostcommonlyammoniumphosphateasaphosphoroussource[5,18–24].Thestartingmixturefirstlydecomposesatthetemperatureof300–400◦Ctoexpelthegases,and,afterbeingreground,calcinesatatemperaturesrangingfrom400to800◦Cfor10–24h.Beforethesecondgrindingstep,somecarbon-containingcompound,forexamplecarboxylicacid[25],canbeaddedtotheprecursorandcanbeemployedasacarbonsourceintheLiFePO4/Ccompositeformation.2.Hydrothermalsynthesisisquick,easytoperform,low-cost,energy-savingandeasilyscalablemethodtopreparefineparticles.Yangetal.[53]originallyshowedthatlithiumironphosphatecouldbesynthesizedhydrothermally,startingfromFeSO4,H3PO4andLiOHmixedinmolarratio1:1:3.FeSO4andH3PO4solutionweremixedfirsttoavoidtheformationofFe(OH)2becauseiteasilyoxidizestoFeO(OH),thenLiOHsolutionwasaddedtothemixture,whichwasthenhydrothermallyprocessedat120◦Cforupto5h.However,thecapacityoftheresultinglithiumironphosphatephasewasnothigh,whichwasduetosomelithium/irondisorderwitharound7%irononthelithiumsites,aslatershownbythesamegroupofauthors[54].Asthestructurehasone-dimensionaltunnels,anyironinlithiumtunnelswouldseverelylimitlithiuminsertionandremoval.Itisthereforeessentialtoensurecompleteorderingoflithiumandironatoms.Thefiringofthehydrothermalmaterialat700◦Cwithcarbonaceousmaterialsresolvedthedisorder3.Forthepurposesofsol–gelsynthesisofLiFePO4varioussolventswereused:N,N-dimethylformamide[16,66,67],waterwithascorbicacid[67],orcitricacid[22,68–71]aschela