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 (similar to 430 MPa) and a tremendous Young's modulus of similar to 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, Li-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). (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

By utilizing a functionally selective solid electrolyte interphase as an anodic protection layer, the settlement of uneven lithium electrodeposits in lithium sulfur batteries can be effectively avoided. The novel LiF-intercalated-graphene SEI exhibits a high elastic modulus, mechanical strength, and repulsive capability towards polysulfides, leading to the effective protection of lithium anodes and remarkable electrochemical performance in Li-S batteries.