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

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 functional-selected 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, Li2S 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).