Functional-selected LiF-intercalated-graphene enabling ultra-stable lithium sulfur battery

摘要

Using a functionally selective solid electrolyte interphase(SEI)as an anodic protection layer can effectively avoid the subsequent settlement of uneven lithium electrodeposits for lithium sulfur(Li-S)batteries.To address the issues of single functional,mechanical crushing and peeling of the conventional rigid LiF SEI,a unique functional-selected rigid-flexible-coupled LiF-intercalated-graphene(LiF-GN)SEI as anodic protection is constructed,which is verified by in-operando X-ray photoelectron spectroscopy(XPS)spectra.Owing to the synergistic effect of the LiF and graphene layer,this intercalated functionalselected SEI architecture exhibits a dramatic elastic modulus(rigid-flexible coupling with a shallow Young’s modulus(~430 MPa)and a tremendous Young’s modulus of~20 GPa),high mechanical strength,and can be repulsive to polysulfides,accompanied unprecedented trafficability of Li ions.Consequently,the forceful exclusion of polysulfides from the LiF-GN SEI,as confirmed by means of in-situ UV/vis analysis,Li2 S nucleation tests,and visual permeation experiments,is of profound significance for the effective protection of Li anodes and enables Li-S batteries to achieve remarkable electrochemical performance(ultralow capacity decay rate of 0.022%during 300 cycles at 1 C and high discharge capacity of 1092 mAh/g at 0.5 C).