03 AC IMPEDANCE OF THE Li(l-x)CoO2 ELECTRODE.pdf

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1、SolidStatelonics18&19(1986)794-798794NorIh-Holland,AmsterdamACIMPEDANCEOFTHELi(l_x)COO2ELECTRODEM.G.S.R.THOMASIBM(UK)LaboratoriesLTD.,HursleyPark,Winchester,U.K.P.G.BRUCEDept.ofChemistry,Heriot-WattUniversity,Edinburgh,U.K.J.B.GOODENOUGHInorganicChemistryLaborator

2、y,UniversityofOxford,SouthParksRoad,Oxford,U.K.Anequivalentcircuitforaporouspolycrystallineinsertionelectrodeispresented.ThismodelisfoundtobeinadequatetodescribetheacresponseoftheLi~I,Co02/LiBF4inpropylenecar-bonateinterfacebecauseoftheformationofaLi+-ionconducti~

3、g-X)layeronthesurfaceoftheelectrode.LithiumdiffusionintheelectrodeisdeterminedbythreemethodswhichallindicateavaluegraterthanthatreportedforTiS2.I.INTRODUCTIONIMLiBF4inpropylenecarbonate/Li(1_x)COO2LiCoO2isanexampleofalayeredoxide:its0.45<(l-x)<0.80.Thestudyprovide

4、sanex-structureisanalogoustoLiTiS2exceptthattheplanationfortheapparentstabilityofanionsintheformercaseadoptcubic-close-Li(l_x)COO2incontactwithsuchanelectrolytepackinginsteadofhexagonal-close-packing.andadeterminationofthelithiumdiffusionLithiumionscanbereversibly

5、extractedfrombe-coefficientwithintheelectrodebythreetweenthelayerswithacorrespondingoxidationseparatetechniques.ofCo3+toCo4+1.AcompositionrangeforLi(l_x)CoO2of0.I<(l-x)

6、linedinref-TheelectrochemicalpropertiesoftheerenceI.Li(l_x)COO2electrodehavebeenrecentlyinvest-AlloperationswerecarriedoutinaVac.2igatedbypulsetechniques.WebelievethatAtmospheresargonfilledglovebox(02<3ppm,actechniquesprovideanexcellentmeansofH20<7ppm).separatingp

7、hysicalprocessesoccurringattheACmeasurements,otherthanthoseassociatedliquidelectrolyte/intercalationelectrodein-withthemodifiedHebb-Wagnertechnique,wereterface,atwhichchargetransfer,adsorption,carriedoutonthethreeterminalcellshownin6surfacelayerformationanddiffusi

8、onmayallFig.ITheworkingelectrodeconsistedofaplayapart.Theresultsreportedhereinsup-13mmdiameterdisk-shapedstainlesssteelgridportourbelief.ontowhich%20mgo