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1 SYNTHESISOFGAMMA MONOCLINIC SULFUR AND SULFUR BATTERIES CONTAINING MONOCLINIC SULFUR CROSS REFERENCE TO RELATED APPLICATIONS 2 demonstratedtheuseofLi–Sbaterieswithcarbonate basedelectrolyteswithstableandreversiblecapacity18-20. Thesepapersproposeafewdiferentconcepts/hypotheses thatpotentialyenablesucesfulbateryoperationincar 5 bonateelectrolytes.Acommonfeatureintheseworksisthe nano-confinementofsulfur. US 10,991,944B2 Forexample,Xinetal.synthesizedsulfurcathodesby ThisaplicationisabypascontinuationofInternational confiningsulfurmoleculesinto0.5nmporesofmicroporous aplicationno.PCT/US20/13490,filedonJan.14,2020, carbonhostmaterials19.Theyproposedthattheconfinement which,inturn,claimsthebenefitofU.S.ProvisionalAppli10 withinthesub-nanoporespreventedtheformationoflarger cationNo.62/792,068,filedonJan.14,2019,theentire disclosuresofwhichareherebyincorporatedbyreferenceas ifsetforthfulyherein. STATEMENT OF GOVERNMENT INTEREST Thisinventionwasmadewithgovernmentsuportunder ContractNumberNSF-1804374awardedbytheNational ScienceFoundation.TheGovernmenthascertainrightsin theinvention. BACKGROUND OF THE INVENTION Stateoftheartlithium-sulfur(Li—S)bateriesareatrac- tivecandidatesforuseinhybridelectricvehicles(HEVs)25forcedthede-solvationoflithiumionsandresultedin andadvancedportableelectronicdevicesduetotheirorder solid-statelithiationandde-lithiationofconfinedS,mol ofmagnitudehighertheoreticalenergydensitycomparedto ecules.Overal,theseworksproposestringentporesize conventionallithium-ionbateries(LIB).-4.Inadition,sul- requirements(<0.5nm)forthehostcarbonrequiringcom furisbothenvironmentalyfriendlyandnaturalyabundant plexsynthesisprocedureslimitingbroaddeployment,while intheearth’scrust.However,thecurentLi–Ssystemis30alsotheoreticalylimitingtheposiblesulfurloading(dueto plaguedbynumerouschalenges5,6.Theinsulatingnatureof limitedavailablevolumeofprecisely-sizedmicropores). bothsulfurandthefinaldischargeproduct,Li,Sresultsin Moreover,noneofthesereportsatempttocharacterizethe lowmaterialutilizationduringtheredoxproceses.Abiger initialsulfuralotropes(reactants)northedischargeor chalengeisthedisolutionoftheintermediatereaction chargeproductsformedandthereforethesourceofenergy products,lithium-polysulfides(LiPs),intotheelectrolyte35storage/capacityisunclear. causingthewel-known“shutle-efect”.Polysulfideshutle Comercialyavailableion-basedbaterieshavereached resultsinuncontrolabledepositionofsulfidespeciesonthe theirpeakoftheoreticalenergydensity.Thus,newspecific lithiummetalanode,reducescoulombiceficiency,and capacitymaterialsaresoughtforimprovingtheenergy increasescapacityfade?.Thesechalengeshavebenexten- densityofion-basedbateries.Lithium-sulfurbaterieshave sivelystudiedinthepastdecadewithmoststudiesfocused40gainedsignificantatentionowingtotheirpromisinghigh onetherelectrolyte-basedLi—Sbateries6,8,9. energydensity(~260Wh/kg)overthetraditionalmetal-ion Amuchlesdiscused,butextremelysignificantchal- bateries(~340Wh/kg).Also,sulfurisapromisingcathode lengeforcomercialviabilityistheuseoftheether materialowingtoitsnaturalabundance,lowadverseimpact electrolyte.Ether-basedsolventsarehighlyvolatileand ontheenvironmentandlow-cost. havelowflashpointsposingasignificantriskofoperating45 Reductionofsulfurinvolvesamulti-electrontransfer suchbateriesaboveroomtemperature10-12.Forexample, redoxreactionduringdischargeandconvertstolithium dimethoxyethane(DME),animportantingredientusedin sulfideandvice-versaduringcharge,contributingtothe presentdayLi–Sbateries,hasaboilingpointofonly42° highercapacityandtherebyhigherenergydensity.However, C.Therefore,thepracticalityofsuchLi–Sbaterychem- state-of-the-artLi—Sbateriesemployether-basedelectro istriesisdoubtfulduetoseveresafetyconcernsandtransport50lytesthatfaceanarayofchalenges.Firstly,theinterme isues13 diatedischargeproducts(polysulfides)formedinLi–S Lithium-ionbaterieshavebeendominantinthecommer- bateriesthatemploytheether-basedelectrolytesarehighly cialmarketforthepast30years,usingcarbonate-based solubleinether-basedsolventsandcaneasilytransportand electrolytes,welknownfortheirreasonablysafebehavior shutlebetweenthecathodeandanode.Thisphenomenon, beyondromtemperature(typicalboilingpointsof>20°5the“shutleefect,”resultsinlosofactivesulfurand C.)andwideoperationalwindow14,15.Inadition,flame pasivationofLimetalleadingtocapacity(runtime)fade retardantaditiveshavebenextensivelyresearched, withcycling.Secondly,ether-basedsolventsarehighly designedandapliedincarbonate-basedelectrolytesto volatilewithlowflashpoints,therebylimitingbateryapli beterenhancetheirreliability16,17.Hence,theknowledge cationandposingasignificantriskforbateriesoperatingat gainedoncarbonateelectrolytesintheLi-ionbateryfield60elevatedtemperatures.Finaly,theuseofthemostcommon overthepastthredecadescanpotentialybeapliedforthe aditive,LiNOz(nededforether-basedLi–Sbateries)is futuredevelopmentofLi–Sbateries.However,itisknown bannedunderU.S.transportationlawduetoisuesrelatedto thatwhenacarbonateelectrolyteisusedinLiSbateries, theformationofexplosivegases.Therefore,despitethe anireversiblereactionbetwencarbonateandpolysulfides recentdevelopmentofhostmaterialstobindpolysulfidesin takesplacetoformthiocarbonateandethyleneglycol,65ether-basedLi–Sbateries,thepracticaluseofthiselec therebyterminatingfurtherredoxreactionsandshuting trolytesystemfacessignificantoperationalandsafetycon downthebatery17.A handfulofreportshaverecently sulfuralotropes(S5-8)andposiblyresultedinsmalsulfur alotropes(S2-4)only,whichinturnconvertedtoLins withouttheintermediatepolysulfides(Li,Sg,Li,S.,etc.). 15 Theydemonstratedstablecapacity(withasingledischarge plateau)incarbonateelectrolyteforupto20cycles. However,itisnotclearhowthesmaleralotropesexhibited acapacityclosetothetheoreticalcapacityofSg>Li2S conversion. 20 Inanotherwork,Fuetalsynthesizedcarbon/sulfurcath odeswithsulfurconfinedinsub-nanometercarbonpores (0.4nm-1nm)20.Thismaterialexhibitedasingleplateau dischargeandastablereversiblecapacityfor10cyclesin carbonateelectrolyte.Theyproposedthatthesmalporesize cerns.PDF Image | SYNTHESIS OF GAMMA MONOCLINIC SULFUR
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