Regulating cation–solvent interactions in PVDF-based solid-state electrolytes for advanced Li metal batteries†

Abstract

Poly(vinylidene fluoride) (PVDF)-based solid-state electrolytes (SSEs) have been considered promising candidates for advanced Li metal batteries due to their adequate mechanical strength and acceptable thermal stability. However, the poor compatibility between residual solvent and Li metal inevitably leads to fast capacity decay. Herein, we propose a multifunctional cation-anchor strategy to regulate solvation chemistry in PVDF-based SSEs to boost the electrochemical performance of Li metal batteries. The strong interaction between N,N-dimethylformamide (DMF) and Zn²⁺ decreases the participation of DMF in the inner solvation sheath of Li⁺, inducing an anion-reinforced solvation structure. The unique solvation structure facilitates the formation of a robust LiF-rich solid electrolyte interphase layer to eliminate interfacial side reactions. In addition, a continuous ion-conducting network is constructed by introducing extra TFSI⁻ anions, enabling accelerated Li⁺ transport. As a result, the corresponding Li‖Li symmetrical cells achieve stable lithium plating/stripping over 780 h, and the rate performance and cycling stability of Li‖LiFePO₄ cells are significantly improved. This work highlights the key role of regulation of solvation chemistry in PVDF-based SSEs for Li metal batteries.