A transmission electron microscopy study of crack formation and propagation in electrochemically cyc

文档简介Subsurfacedefectsandlocalcompositionalchangesthatoccurredingraphiteanodessubjectedtocyclicvoltammetrytests(vs.Li/Li+,usinganelectrolyteconsistingof1MLiClO4ina1:1volumetricmixtureofethylenecarbonateand1,2-dimethoxyethane)wereinvestigatedusinghigh-resolutiontransmissionelectronmicroscopy(HR-TEM).Cross-sectionsofanodespreparedbyfocusedionbeam(FIB)mil领indicatedthatgraphitelayersadjacenttosolidelectrolyte(SEI)/graphiteinterfaceexhibitedpartialdelaminationduetotheformationofinterlayercracks.TheSEIlayerformedonthegraphitesurfaceconsistedofLi2CO3thatwasidentifiedby{110}and{002}crystallographicplanes.Lithiumcompounds,LiC6,Li2CO3andLi2O,wereobservedonthesurfacesofseparatedgraphitelayers.Depositionofthesecointercalationcompoundsnearthecracktipcausedpartialclosureofpropagatinggraphitecracksduringelectrochemicalcyc领,andpossiblyreducedthecrackgrowthrate.Graphitefibresthatwereobservedtobridgecrackfaceslikelyprovidedanadditionalmechanismfortheretardationofcrackpropagation.