碳納米材料課件

MnO/Ccore–shellnanorodsashighcapacityanodematerialsforlithium-ionbatteriesJournalofPowerSources碳納米材料Fourparts1.Introduction

2.Experiment3.Resultsanddiscussion4.Conclusions

碳納米材料Introductiontransitionmetaloxideshaveattractedgreatattentionasanodematerialsforlithiumionbatteries,dueto1theirhightheoreticalcapacity2safety3lowcost4naturalabundance碳納米材料Someobstacle1poorcyclingperformance(largevolumeexpansionduetothegenerationofLi2O)2poorelectronicconductivity(electrodematerialswithdesignednanostructurecanimproveit)碳納米材料MnOshowsrelativelylowelectromotiveforce電動勢

(emf)value(1.032

Vvs.Li+/Li)andhighdensity(5.43

g

cm?3).However,thiskindofmaterialhasseldombeenreportedasananodematerialnanocrystallineMnOthinfilm,andMnOpowderasanodehasshownlowoverpotential超電勢

andgoodcyclingperformance碳納米材料InthispaperThepreparedMnO/Ccore–shellnanorodsmuchhigherspecificcapacitythanthatofMnOmicroparticlesandMnO2nanowiresasanodematerialoflithiumionbattery.返回碳納米材料Experiment合成部分MnO/Ccore–shellnanorodsweresynthesizedbythereductionofcarbonprecursorcoatedMnO2nanowires.TheMnO2nanowiresweresynthesizedbyatypicalhydrothermalreaction碳納米材料Experiment表征X-raydiffractionFieldemissionscanningelectronmicroscopy(FESEM）

transmissionelectronmicroscopy(TEM)SAED碳納米材料Experiment電化學(xué)實(shí)驗(yàn)部分performingusing2032coin-typecellsassembledinanargon-filledgloveboxslurry:activematerials(70

wt%),acetyleneblack乙炔黑

(20

wt%),andpolyvinylidenefluoride聚偏二氟乙烯(PVDF10

wt%)inN-methyl-2-pyrrolidone氮甲基二吡咯烷酮(NMP).TheslurrywasspreadontotheCufoilwithadoctorblade刮墨刀片

anddriedat120

°Covernightundervacuum碳納米材料Experimentelectrodeareais1

cm2loadingofactivematerialis1.0–1.2

mg

cm?2

electrolyte:asolutionof1

MLiPF6inethylenecarbonate碳酸亞乙酯(EC)anddimethylcarbonate碳酸二甲酯(DMC)withaweightratioof1:1碳納米材料ExperimentPurelithiumfoilwasusedascounterandreferenceelectrodeCyclicvoltammetry循環(huán)伏安法

(CV)Charge–dischargetestingwasperformedintherangeof0.01–3.0

Vspecificcapacity返回碳納米材料Resultsanddiscussion1、MnO2nanowiresweresynthesizedbyhydrothermalreaction.Thecrystalstructureoftheas-preparedMnO2nanowireswasconfirmedbyXRD(Fig.1)Allthediffractionpeakscanbeindexedtothebody-centeredtetragonalα-MnO2phase碳納米材料Resultsanddiscussion2、MnO/Ccore–shellnanorodswereobtainedthroughsinteringthecarbonprecursorcoatedMnO2nanowiresinflowingArcontaining5

vol.%H2.AsshowninFig.1thecrystalstructureofMnO/Ccore–shellnanorodscanbeindexedtotheface-centeredcubicphaseofMnOlowintensitydiffractionpeakintherangeof20–30°islikelyassociatedwiththepresenceofamorphouscarbon無定形碳(originatedfromthedecompositionofthecopolymersurfactant).碳納米材料Resultsanddiscussion碳納米材料ResultsanddiscussionFESEM:nanowirestructurewithdiametersrangingfrom20–50nmandThereisnosignificantchangeindiameter

碳納米材料ResultsanddiscussionTEM碳納米材料Thenanorodsshowpolycrystallinefeatureandareagglomeratedintobundleswithalengthextendingtoafewhundrednanometers.ThefracturingofthenanowirestructureintonanorodsmaybecausedbythereductionfromMnO2toMnO.Anindividualnanorodconsistsofnanoparticleswithdiametersfrom20nmto30nm.Resultsanddiscussion碳納米材料ResultsanddiscussionAllthediffractionringscanbeindexedtotheface-centeredcubicFm-3mcrystalstructure.碳納米材料ResultsanddiscussionHRTEM碳納米材料ResultsanddiscussionIntheregionA:thesurfaceoftheMnOcrystal,andthelatticecanbeclearlyresolvedwithad-spacingof0.255

nmforthe(1

1

1)planes.intheregionB:carbonlayer,whichpresentsnumerousblackspots,indicatingthatthesurfaceofthenanorodiscoveredwithathinlayerofamorphouscarbon.Ontheedgeofthenanorod,athincarbonlayerwithathicknessof1–2

nmisclearlyvisible.碳納米材料Resultsanddiscussioncyclicvoltammetry(CV)碳納米材料Resultsanddiscussion碳納米材料Resultsanddiscussion碳納米材料ResultsanddiscussionCyclingperformance

碳納米材料ResultsanddiscussionThisnanorodelectrodeexhibitedhighercapacitythanthatofMnO2nanowireelectrodeafter40cycles.Thegoodelectrochemicalperformanceisaresultofthecombinedadvantagesofthenanorodstructureandtheporouscarboncoatinglayer.碳納米材料ResultsanddiscussionNanosizematerialswithlargesurfaceareacanprovidemoreactivesitesforLi+intercalation/de-intercalationandshortenthediffusionlengthforlithiumionsinthesolidphase.Thenanoporouscarboncoatinglayerwithmesoporescanformamixedconducting3DnetworkthatfacilitatesthemigrationofboththeLi+andthee?,sothattheyreacheachsurfaceoftheMnOnanorods.返回碳納米材料Conclusions1、UsingblockcopolymerF127asthecarbonsource,MnO/Ccore–shellnanorodsweresuccessfullypreparedfromMnO2nanowiresbycalcinationinagas?owof5vol.%H2inAr.2、TheXRDpatternshowsthattheproducthasaface-centeredcubicphasestructure.FESEMandTEMimagesshowthatathincarbonlayerwascoatedonthesurfacesoftheMnOnanorods.碳納米材料Conclusions3、TheMnO/Ccore–shellnanorodelectrodesdeliveredahigherspeci?cdischargecapacitythanMnO2nanowiresafter40cycles.H