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27 28 US 9,905,856 B1 (preferably>80%,morepreferably>90%,andmostprefer- byweight.Herewehavefurthersurprisinglyobservedthat ably>95%)basedonthetotalweightsofthesulfurparticles thekeytoenablingahighspecificcapacityatthecathode or coating and the graphene material combined . under high rate conditions is to maintain a high S loading Inonepreferedembodiment,thesulfursourceisselected andstilkeeptheScoatingorparticlesizeassmallas from M,S,whereinxisanintegerfrom 1to3andyisan 5 posible,andthisisaccomplishedby usingthepresently integerfrom 1to10,andMisametalelementselectedfrom inventedpre-sulfurizationmethod. analkalimetal,analkalinemetalselectedfromMgorCa, Theelectronscomingfromorgoingoutthroughthe atransitionmetal,ametalfromgroups13to17ofthe externalloadorcircuitmustgothroughtheconductive periodictable,oracombinationthereof.Inadesired aditivesinaconventionalsulfurcathode)oraconductive embodiment,themetalelementM isselected from Li,Na, 10 framework (e.g.exfoliated graphitemeso-porousstructure K,Mg,Zn,Cu,Ti,Ni,Co,Fe,orAl.Inaparticularlydesired ornano-structureofconductivegrapheneshetsasherein embodiment,MS,isselectedfromLi2S6,Li2S7,Li2S3, disclosed)toreachthecathodeactivematerial.Sincethe Li2S9,Li2S10,Na2S6,Na2S7,Na2S3,Na2S,NaS10,K2S6, cathodeactivematerial(e.g.sulfurorlithiumpolysulfide)is apoorelectronicconductor,theactivematerialparticleor Inoneembodiment,theanodecomprisesananodeactive 15 coatingmustbeasthinaspossibletoreducetherequired materialselectedfromanalkalimetal,analkalinemetal,a electrontraveldistance. transitionmetal,ametalfrom groups13to17oftheperiodic Furthermore,thecathodeinaconventionalLi–Scel table,oracombinationthereof.Thisanodecanbethesame typicalyhaslesthan70%byweightofsulfurinacom anodeintendedforinclusioninaLi-Scel. positecathodecomposedofsulfurandtheconductiveaddi Thesolventandlithium orsodium saltusedinthe20tive/support.Evenwhenthesulfurcontentinthepriorart electrochemicaldepositionchambermaybeselectedfrom compositecathodereachesorexceds70%byweight,the anysolventorsaltinthelistgivenaboveforalithium-sulfur specificcapacityofthecompositecathodeistypically orsodium-sulfurbattery. significantlylowerthanwhatisexpectedbasedontheoreti Afteranextensiveandin-depthresearchefort,wehave calpredictions.Forinstance,thetheoreticalspecificcapacity come to realize thatsuch apre-sulfurization surprisingly 25 ofsulfuris1,675mAh/g.Acompositecathodecomposedof solvesseveralmostcriticalisuesasociatedwithcurent 70%sulfur(S)and30%carbonblack(CB),withoutany Li–SorNa-Scels.Forinstance,thismethodenablesthe binder,shouldbecapableofstoringupto1,675x70%=1,172 sulfurtobedepositedinathincoatingorultra-fineparticle mAh/g.Unfortunately,theobservedspecificcapacityis form,thus,providingultra-shortlithiumiondifusionpaths typicalylesthan75%or879mAh/g(oftenlesthan50% and,hence,ultra-fastreactiontimesforfastbatterycharges 30 or586mAh/ginthisexample)ofwhatcouldbeachieved. anddischarges.Thisisachievedwhilemaintainingarela- Inotherwords,theactivematerialutilizationrateistypically tivelyhighproportionofsulfur(theactivematerialrespon lesthan75% (oreven <50%).Thishasbeenamajorisue sible forstoringlithium)and,thus,high specific lithium intheartofLi– Scelsandtherehasbeennosolutiontothis storagecapacityoftheresultingcathodeactivelayerin problem.Mostsurprisingly,theimplementationofmassive termsofhighspecificcapacity(mAh/g,basedonthetotal35 graphenesurfacesassociatedwithaporousgraphenestruc weightofthecathodelayer,includingthemassesofthe tureasaconductivesupportingmaterialforsulfurorlithium activematerial,S,supportinggrapheneshets,binderresin, polysulfidehasmadeitposibletoachieveanactivemate and conductive filer). rialutilization rateoftypically >>80%,more often greater Itisofsignificancetonotethatonemightbeabletouse than90%,and,inmanycases,closeto95%-99%. apriorartproceduretodepositsmalSparticles,butnota40 Alternatively,thecathodeactivematerial(e.g.Sora highSproportion,ortoachieveahighproportionbutonly sulfurcompound)maybedepositedonorbondedbya inlargeparticlesorthickfilmform.But,thepriorart functionalmaterialornano-structuredmaterial.Thesulfur procedureshavenotbeenabletoachievebothatthesame compoundmaybeselectedfromorgano-sulfur,polymer time.Thisiswhyitissuchanunexpectedandhighly sulfur,carbon-sulfur,metalsulfide,S-Sb,S-Bi,S-Se, advantageousthingtoobtainahighsulfurloadingandyet,45 S-Temixture,oracombinationthereof.Thesespeciesmay concurrently,maintaininganultra-thin/smallthicknes/di- besuportedbyaconductivecarierparticle,suchas ameterofsulfur.Thishasnotbeenposiblewithanyprior activatedcarbonorsmallgraphenepiece.Thefunctional art sulfur loading techniques.For instance,we have been materialornano-structured materialmay be selected from abletodepositnano-scaledsulfurparticlesorcoatingthat thegroupconsistingof(a)anano-structuredorporous occupy a >90 % weight fraction of the cathode layer and yet 50 disordered carbon material selected from a soft carbon,hard maintainingacoatingthicknesorparticlediameter<3nm. carbon,polymericcarbonorcarbonizedresin,meso-phase Thisisquiteafeatintheartoflithium-sulfurbateries.As carbon,coke,carbonizedpitch,carbonblack,activated anotherexample,wehaveachieveda>95%Sloadingatan carbon,nano-celularcarbonfoamorpartialygraphitized average S coating thickness of 4.8-7nm . carbon;(b)anano grapheneplateletselectedfrom asingle ElectrochemistsormaterialsscientistsintheartofLi–S5layergrapheneshetormulti-layergrapheneplatelet;(c)a batterieswould expectthatagreateramountofhighly carbonnanotubeselectedfromasingle-walledcarbonnano conductinggrapheneshetsorgraphiteflakes(hence,a tubeormulti-walledcarbonnanotube;(d)acarbonnano smalleramountofS)inthecathodeactivelayershouldlead fiber,nano-wire,metaloxidenano-wireorfiber,conductive toabeterutilizationofS,particularlyunderhighcharged polymernano-fiber,oracombinationthereof;(e)acarbo dischargerateconditions.Contrarytotheseexpectations,we 60nyl-containingorganicorpolymericmolecule;(f)afunc haveobservedthatthekeytoachievingahighSutilization tionalmaterialcontainingacarbonyl,carboxylic,oramine eficiencyisminimizingtheScoatingorparticlesizeandis group;andcombinationsthereof.Inapreferedembodi independentoftheamountofSloadedintothecathode ment,thefunctionalmaterialornano-structuredmaterialhas providedtheScoatingorparticlethickness/diameteris aspecificsurfaceareaofatleast500mo/g,preferablyatleast smalenough(e.g.<10nm,orevenbeterif<5nm).The65 1,000m2/g. problem hereisthatithasnotbeenposibletomaintaina Typicaly,thecathodeactivematerials(sulfurormetal thinScoatingorsmalparticlesizeifSishigherthan50% sulfide)arenotelectricalyconducting.Hence,inone K2S7,K2S8,K2S,orK2S10.PDF Image | FLEXIBLE AND SHAPE-CONFORMAL ROPE-SHAPE ALKALI METAL-SULFUR BATTERIES
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