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1、专业英文文献选读1ASnO2/graphenecompositeasahighstabilityelectrodeforlithiumionbatteriesCarbonVolume49,Issue1,January2011:133–1392IntroductionLithiumionbatteriesusingthelithiumtransitionmetaloxidecathodeandgraphiteanodehavebeenthepowersourcesforvariousmobilecommunicationdevices,portableel
2、ectronicdevices,andelectric/hybridvehicles.However,graphitehasaninherentlimitationwithatheoreticalgravimetriccapacityestimatedat370mAh/g.Forthepurposeofimprovingtheenergydensityofbatteries,scientistshavemadegreateffortstoexplorealternativeanodematerialswithhighercapacity.3Asalarg
3、ebandgapsemiconductor,SnO2hasattractedalotofattentionduetoitsrelativelyhightheoreticalreversiblecapacity(790mAh/g),whichismorethantwicethatofthecurrentlyusedgraphite.TherearetwoelectrochemicalprocessesintheSnO2-basedlithiumionbatteries:Asthereaction(2)demonstrates,avolumechangeof
4、200–300%occursduringlithiation/delithiationprocessbetweenSnandLi4.4Sn.Thisreactioncangeneratealargeinternalstress,leadingtocrackingofelectrode,lossofelectricalcontact,largeinitialirreversiblecapacity,andeventuallyquickfadingofcapacity.4Toovercometheinternalstressproblem,greatatte
5、ntionhasbeenpaidtonano-structuredSnO2andSnO2/carboncompositeelectrodes.Graphene,amonolayerofgraphite,exhibitsanumberofintriguinguniquepropertiessuchashighsurfaceareaofover2600m2/g,largesurface-to-volumeratio,highroomtemperature(RT)carriermobility,conductancequantizationTherefore,
6、graphenehasbeenregardedasanidealcarbonnanostructurewhichcanbeusedtodesignhighperformanceSnO2/carboncompositeelectrodes.5Uptodate,therehavebeenafewreportsaboutthepreparationofSnO2/graphenecomposite.Paeketal.[2]synthesizedaSnO2/graphenecompositewiththree-dimensionallydelaminatedfle
7、xiblestructurebymechanicalmixingSnO2nanoparticleswithgraphenenanosheets.Theas-preparedSnO2/grapheneelectrodematerialexhibitedanenhancedcyclicperformanceandlithiumstoragecapacity.Asclaimed,thechargecapacitycouldremain570mAh/gafter30cyclesatacurrentdensityof50mA/g.Yaoetal.[22]synth
8、esizedSnO2/graphenecompositebydirectoxid