Self-assemblyAssistedNanostructureFabricationsforLithiumMetalBatteries

Abstract

Thegrowthoflithium(Li)dendritesreducesthelifespanofLi-metalbatteriesandcausessafetyissues.Herein,hierarchicallyporousaramidnanofiberseparatorsarereportcapableofeffectivelysuppressingtheLidendritegrowthwhilemaintaininghighlystablecycleperformancesathighcharge/dischargerates.Atwo-stepsolventexchangeprocesscombinedwithreprotonation-mediatedself-assemblyisutilizedtocontrolthebimodalporousstructureoftheseparators.Inparticular,whenethanolandwaterareusedsequentially,aramidnanofibersformhierarchicalporousstructurescontainingnanoporesinmacroporouspolymerframeworkstoyieldamechanicallyrobustmembranewithhighporosityof97%ormore.Theoptimizedsamplesexhibithighionicconductivitiesof1.87–4.04mScm-1andhighLi-iontransferencenumbersof0.77–0.84becauseoftheultrahighporosityandselectiveaffinitytoanions.Li-metalsymmetriccellsdonotshowanynoticeablepresenceofdendritesafter100cycles,andtheyoperatestablyformorethan1500cyclesevenunderextremeconditionswithahighcurrentdensityof>20mAcm-2.Inaddition,theLiFePO4/Lifullcellretains86.3%ofitscapacityafter1000cyclesatachargerateof30C.

SurfacemodificationofCucurrentcollectorsisnecessaryforthecommercializationofanode-freebatteries.BecauseLinucleationoccursduetothelithiophobicCufoil,leadingtodendritegrowth.Therefore,itreportsthatlithiophilicAgwascoatedonCufoillayer-by-layer(LbL)tosuppressthenucleationoverpotentialofLi.Agnanowireandnanoparticles(AgNWP)weresynthesizedbysol-gelmethodand,itwasattachedbyvoltex-assistedLbLprocess.AgthinfilmfabricatedbyLbLsystemwithshortchainmaterialhasmeltfusionsbetweenNPswithincreaseofconductivitythroughligandexchange.ThisprocesswasstackedbycoordinationbondingtoAgmetalswithoutdisturbingionicconductivity.ThethicknessoftheoptimizedAgthinfilmstacked10bilayer,wasultrathinto<1μm,whichimprovestheenergydensity.ItwasconfirmedthattheoptimizedAgthinfilmhasamechanismthathelpssuppressLidendriteformationbyforminginorganic-richSEIlayerssuchasLiFthathavestablemechanicalproperties.TheCu/LihalfcellshowedarapiddropinCoulombicefficiencyafter38cycles,buttheoptimizedAgthinfilm/LihalfcellshowedaslowdropinCoulombicefficiencyafter115cycles.