锂硫电池

锂电池与锂离子电池孙睿敏2012/11/20Companyname锂离子电池工作原理第一部分锂电池的介绍基础介绍分类优点缺点锂电池的介绍锂电池是用金属锂作负极活性物质的电池的总称。Li-I2、Li-Ag2CrO4、Li-（FCX)n、Li-MnO2、Li-SO2和Li-SOCl2六种锂电池现已商品化。锂电池广泛应用于医疗、电子、通讯、航空和军事等领域。各种型号的锂电池锂电池的分类（1）按照电池的可充性：分为一次电池和二次电池；（2）按工作温度：分为室温、中温和高温电池，但无严格温度界限；（3）按照电解质分为：液体电解质，固体电解质和熔融电解质锂电池等；（4）按电极活性物质种类：分为锂电池和锂离子电池。通常按电解质性质分类。123比能量高，是普通锌锰电池的2~5倍；锂电池的优点电池电压高达3.9V并且放电电压平稳；比功率大，并且可以大电流放电；锂电池缺点（1）锂枝晶生长明显，金属锂电极表面不均匀，充电时造成锂沉积不均匀，枝晶脱落或折断时，产生“死锂”，造成锂的不可逆，降低活性材料的利用率；尖锐枝晶会穿透隔膜，使正负极短路发生自放电，同时产生大量热，使电池着火，甚至爆炸。（2）锂的活性高，很容易与电解质溶液发生反应，产生高压，造成危险。（3）高温下容易发生爆炸。（4）高氯酸锂等电解质和隔膜分解也是电池爆炸的因素。第二部分锂电池的工作原理锂电池工作原理负极反应：LiLi++e-锂电池正极反应有两种情况：一种是放电时，作为正极活性物质的卤化物、硫化物、氧化物、含氧酸盐及单质元素等还原成低价金属离子或元素，形成新的物相。如：正极反应：AgCl+e-Ag+Cl-CuS正极分步还原反应：CuS+e-1/2Cu2S+1/2S2-1/2Cu2S+e-Cu+1/2S2-另一种正极反应是还原后不出现新相。这类活性物质具有层状或隧道式晶体结构。来自负极的电子进入晶格内，使晶体中的某一金属离子还原，但晶体结构不发生变化。如：正极反应：MnO2+Li++e-LiMnO2TiS2+Li++e-LiTiS2C-SCompositeCathodeMaterialsMixturebeforeheatingMixtureafterheatingAfterheating,themeltisimbibedintothechannelsbycapillaryforces,whereuponitsolidifiesandshrinkstoformsulphurnanofibresthatareinintimatecontactwiththeconductivecarbonwalls.0.1C0.1CTheScontentof69.3wt%.C-SCompositeCathodeMaterialsa,b,SEMimagesofCMK-3/S-155before(a)andafter(b)the15thcharge.c,d,SEMimagesofPEG-modifiedCMK-3/Sbefore(c)andafter(d)the15thcharge.Imagesshowtheeffectsof“polymerprotection”ininhibitingsurfacedeposition.0.1CThePEG-CMK-3/Scompositeexhibitverylittlechangeinsurfacemorphology2.PEG-CMK-3/STheeffectofthePEG-functionalizedsurfaceistwofold.First,itservestotrapthepolysulphidespeciesbyprovidingahighlyhydrophilicsurfacechemicalgradientthatpreferentiallysolubilizestheminrelationtotheelectrolyte.Second,bylimitingtheconcentrationofthepolysulphideanionsintheelectrolyte,theredoxshuttlemechanismiscurtailedtoalargedegree.C-SCompositeCathodeMaterialsPEG-CMK3/SCMK3/SAB/S▲CMK3/SPEG-CMK3/SThereleaseofthePEGtetheredtotheCMK-3occursat50oChigherthaninPEGitselfowingtotheesterbondsC-SCompositeCathodeMaterials3.MicroporescarbonspheresB.ZhangX.QinG.R.LiaandX.P.Gao;Energy&EnvironmentalScience10.1039/c002639eTEMimagesofcarbonspheres(aandb)andthesulfur–carbonspherecompositewith42wt%sulfur(c),andHAADF-STEMimage(d)BETMicroporesC843.5m2g-1C-S（42%）6.5m2g-1C-SCompositeCathodeMaterialsBecausethetheoreticalloadingis49.5wt%sulfurbasedonthetotalporevolumeofcarbonspheres(0.474cm3g-1)andthedensityofelementalsulfur(2.07gcm-3forthealphaphase,atroomtemperature)40mAg-1C-SCompositeCathodeMaterials0.1mVs-142wt%S400mAg-1400mAg-1Thelowpotentialplateauwiththesulfurembeddedthenarrowporesofcarbonsphereslieswithinthefactthattheelectrochemicalreactionduringthedischargeprocessneedstoovercometheabsorbingenergy,leadingtosuchadischargepotentialhysteresis.Thesmallcathodicpeakpotentialat2.4V(vs.Li+/Li)disappearscompletelyafterthefirstcyclebecauseofthedissolutionofatraceofsulfuronthecarbonspheresurfaceinelectrolyte,furtherconfirmingthatsulfurisalmostloadedinsidethemicroporesofcarbonspheresConclusion1.ForLi-Sbatteries,cathodeshouldbeconductiveandcantraptheSinside.2.Enoughroomforvolumetricexpansion.3.Themesoporous/microporouscarboncansatisfyboth.Graphene-WrappedSulfurParticlesHailiangWang,†,§YuanYang,‡,§,Graphene-WrappedSulfurParticlesasaRechargeableLithium
SulfurBatteryCathodeMaterialwithHighCapacityandCyclingStability.NanoLett.2011,11,2644–2647Figure3.Energydispersivespectroscopic(EDS)characteriz-ationofgraphenesulfurcomposite.Azoom-inSEMimage(Figure2b)showedgraphenesheetscoatedaroundasulfurparticle.Figure2.SEMcharacterizationofgraphenesulfurcompositeatlow(a)andhigh(b)magnifications.ChemicalmappingconfirmedthatthebrightparticlesintheSEMimage(Figure3a)weresulfur(Figure3c,sulfurmapping),withoverlayingCsignalsduetomGOcoatingonthesulfurparticles(Figure3d,carbonmapping).Graphene-WrappedSulfurParticlesElectrochemicalcharacterization(a)10thcyclechargeanddischargevoltageprofilesofthegraphenesulfurcompositewithPEGcoatingatvariousrates.(b)Cyclingperformanceofthesamecompositeasin(a)atratesof∼C/5and∼C/2.(c)CyclingperformanceofPEGcoatedsulfurwithoutgraphenecoatingattherateof∼C/5.(d)CyclingperformanceofgraphenecoatedsulfurwithoutanysurfactantPEGcoatingattherateof∼C/5.highperformanceofthesulfurgraphenecompositecathodematerial.thegrapheneandPEGcoatinglayersonsulfurparticlestwoimportantfactorstotheobservedcyclingstabilityofsulfurparticles.RGO–TG–SnanocompositeBoththefunctionalgroupandsp2-hybridizedcarbonoftheRGOandTGhavestrongchemicalinteractionswithsulfur.largespecificsurfacearea,Highporevolume,ExcellentconductivityBroadporedistributiontheTG(thermallyexfoliatedgraphenenanosheet)andRGOcoatingeffectivelyconfinedthesulfurandpolysulfidesinthecarbonframework.TheRGOcoatinglayereffectivelyrestrainstheshuttlingloss.Fig.3(a)Typicalvoltagecapacityprofilesand(b)cyclelifeoftheTG–SandRGO–TG–Snanocompositesatarateof0.2Ag-1.Fig.4(a)TypicalvoltagecapacityprofilesoftheRGO–TG–Snanocompositeatvariousrates.(b)5)RatecapabilityoftheRGO–TG–Snanocomposite.(c)CyclelifeandcoulombicefficiencyoftheRGO–TG–Snanocompositeatahighcurrentdens