锂硫电池技术文档聚多巴胺亲水改性-锂硫电池

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2015.4.182025/3/162012-10-122025/3/162012-10-12

Disadvantage

hydrophobicsurface,whichseriouslyhindertheadequateuptakeanddiffusionoforganicelectrolyteswithintheseparators.Moreover,itisdifficulttocompletelyensuretheelectricalisolationbetweenthecathodeandanodeduetotheirpoorthermalshrinkage,leadingtolowcapacity,poorpowercapabilityand

securityrisksuponcycling.

Polydopamine

Polydopamine,withamolecularstructurethatincorporatesmanyfunctionalgroupssuchascatechol,amineandimine,canbeeasilydepositedonalltypes

of

inorganicandorganicsubstrates,evensuper-hydrophobicsurfaces.2025/3/162012-10-12ExperimentalS:AB=6:4300r/h球磨2hputitintoaPTFEcontainerfilledwithargoncontainerwasheatedat155°Cfor12hcooleddowntoroomtemperatureS/Ccomposite:acetyleneblack:PTFE=7:2:1withethanolasadispersantcompressedintoathinpieccutintoadiskfilmof8mmindiameterand1.5~1.8mginweightdriedintheovenat55°Cfor12hS/ABcompositesulfurcathode2025/3/162012-10-12Thesurfacemodificationofseparatorsseparatorsweresoakedinto50mlmethanolsolution(30minutes)putintothedopaminesolution(24h)rinsedwithdistilledwaterforseveraltimesdriedat30°Cfor12h.2025/3/162012-10-12Results

Itcanbe

observedfromFig.1thattheweightlossofthecompositebegin

fromabout150°C,andfinishedover400°C,duetoevaporation

ofsulfurfromthemeso/microporesofthehostcarbon.

Itis

shownthatthecarbonblackappearsasalooseparticle

aggregatedofsomeuniformandsmallcarbonspheres.Forthe

S/Ccompositewith60wt%sulfurloading,theaggregatesbecomedenserandtheparticalsizebecomebiggerascomparedtothecarbonblack.2025/3/162012-10-12Resultswettingtestafterdroppinganorganicelectrolyte[1wt%LiNO3and1.0M30LiN(CF3SO2)2dissolvedinDOL/TEGDME,v/v=1:1)]ontothesurfaceoftheseparator,thedropletcanhardlywetthebareseparator(left),whereasthePDAmodifiedseparato(right)isfullywettedimmediately.2025/3/162012-10-12Results

ItcanbeseenthatonlythepeakofC1scanbeobserved,whileforthePDAmodifiedseperator,twoadditionalpeaksattributedtoN1sandO1sappearat400.4and532.7eV,respectively,indicatingthatPDAcoatinglayerisgeneratedonthesurfaceofseperatortoproduceahydrophilicseperator2025/3/162012-10-12Results

However,forthecellusingbareseparator,

twocathodicpeakappearatabout2.25and1.80V(vsLi/Li+)

(Fig.6b),whichareslightlylowerthantheaforementioned

results.Inaddition,twooverlappedanodicpeakpotentialsinthe

voltagerangeof2.6-2.7Vcanbeobserved,suggestingatwoplateauoxidationprocessoccurredintheanodicscan,whichis

differentwiththeonlyonebroadanodicpeakpotentialat2.60V

forthecellusingPDAmodifiedseparator.2025/3/162012-10-12Results

Twotypicaldischargepotentialplateauatabout2.30Vand2.0V(vsLi/Li+)canbeeasilyobservedintheinitialcycleforthetwocomparativecells,assignedtothereductionfromsulfurtolithiumpolysulfidesandfurtherreductiontoLi2S2/Li2SandinconsistentwiththeCVs.

ForthecellusingPDAmodifiedseparator,obviousdecreasingofdischargecapacitycanbeobservedinthesecondcycle,whichmayrelatetothedissolutionofpolysulfideandwillbefurtherdisscussedinthebelow

S的利用率提高2025/3/162012-10-12Resultshigh-ratecharge/dischargecapabilitycyclingstabilityahighercoulombicefficiency2025/3/162012-10-12

ItisobviousthatthecellusingthePDAmodifiedseperatorcanobviousdecreasethecharge-transferresistanceofthesulfurcathodesascomparedtobareseparator,especiallyintheseconddischargestate.

polysulfidewilldissolvedintotheelectrolyteandmoreandmoreLi2S2/Li2Swillbedepositedonthecathodes,leadingtothelossofactivematerialsandfastdroppingofcapacity.Results2025/3/162012-10-12ConclusionPDAmodifiedhydrophilicseparatorsarepreparedbyasimpledippingmethodDuetothePDAmodification,thesurfacecharacterofthepolyolefin-basedseparatorschangesfromhydrophobicitytohydrophily,thusresultingintheimprovementofuptakeamountsofliquidelectrolytesandionicconductivity,Accompanyingwithremarkablyenhancementofcharge/dischargecapacities,cyclingperformance,andhigh-ratecapabilityAt0.2Crate,theinitialdischargecapacityofthecellusing

hydrophilicseparatoris1217mAh/g,anditcanbestably

retainedat1020.3mAh/g,showingobviousadvantagesoverthe

conventi