Ab Initio Investigations of Lithium Diffusion in Carbon Nanotube Systems

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1、VOLUME88,NUMBER7PHYSICALREVIEWLETTERS18FEBRUARY2002AbInitioInvestigationsofLithiumDiffusioninCarbonNanotubeSystemsVincentMeunier,*JeremyKephart,ChristopherRoland,andJerryBernholcDepartmentofPhysics,NorthCarolinaStateUniversity,Raleigh,NorthCarolina27695(Re

2、ceived9July2001;revisedmanuscriptreceived24October2001;published1February2002)Li-nanotubesystemscansubstantiallyimprovethecapacityofLi-ionbatteriesbyutilizingbothnano-tubeexteriorsandinteriors.OurabinitiosimulationsshowthatwhileLimotionthroughthesidewallsi

3、sforbidden,Liionscanentertubesthroughtopologicaldefectscontainingatleastnine-sidedrings,orthroughtheendsofopen-endednanotubes.Onceinside,theirmotionisnotdiffusionlimited.Theseresultssuggestthatdamagingnanotuberopesbyeitherchemicalormechanicalmeanswillyield

4、su-periormaterialforelectrochemicalstorage.DOI:10.1103/PhysRevLett.88.075506PACSnumbers:61.48.+c,71.15.Mb,71.15.Pd,71.20.TxCarbonnanotubesnotonlyhaveoutstandingmechanicalinsidethenanotubesthemselves.Thesebarriersturnoutandelectroniccharacteristics,butalsoh

5、oldconsiderabletobequitelow,showingthatLimotioninsidenanotubepromiseasmolecularcontainerswithapplicationsashy-systemsisnotdiffusionlimitedfornanotubelengthsdrogenfuelcells[1]andrechargeableLibatteries[2].Thetypicalofcurrentexperiments.Theseresultshavebeenk

6、eyelementthatmakesnanotubessopotentiallyusefulasfurthertestedviadirectlarge-scaleabinitiosimulationselectrochemicalstoragedevicesistheirstructure.Forin-whichalsoelucidatetheeffectsofLi-Liioninteractionsstance,considerthecaseofLi-ionbatteries.Inmostbatter-i

7、nnanotubularsystems.ies,graphiticcarbonanodesareusedinsteadofmetallicLiExperimentally,Liintercalationintonanotubesystemselectrodesbecauseofbothsafetyandcycleefficiencycon-havebeenperformedonbothmultiwalled[9]andsinglecerns[3].However,theuseofgraphiteasahost

8、materialwalled[7,10,11]nanotubes.Initialresultsweresome-hassomedisadvantages,chiefofwhichisthesubstantialwhatdisappointing,showingonlyapoor25%increaseinreductionintheenergydensityascomparedtometallictherevers