A functional silicon composite polymer electrolyte with hydrofluoric acid scavenging for quasi-solid-state lithium metal batteries

Abstract

Lithium metal is considered as one of the most promising anode material candidates for high-energy-density batteries. However, the solid electrolyte interface (SEI) of the lithium metal surface is susceptible to corrosion by hydrofluoric acid (HF) and H₂O, which hinders the practical application of lithium metal. In this work, a functional composite polymer electrolyte (FCPE) containing Si nanoparticles can scavenge HF and H₂O to protect the SEI from corrosion. The Si nanoparticles in the FCPE react with HF to form SiF₄, which reacts with H₂O to produce LiF and Li_xSiO_y without generating other harmful by-products. The LiF and Li_xSiO_y are ionic conductors, which are deposited on the surface of lithium metal constructing an SEI layer with high ionic conductivity. The high ionic conductivity of the SEI can contribute to the induction of uniform Li-ion plating/stripping behavior, thereby preventing the growth of lithium dendrites. As a result, a Li‖Li symmetric cell with the FCPE under extreme conditions with a water content of 8078 ppm (V_H2O:V_{base electrolyte} = 1.0%) can cycle stably for 800 h. These results highlight that the FCPE can remove water impurities to maintain the excellent performance of lithium metal batteries and provide a direction for the development of polymer electrolytes.