Modulating Salt Dissociation and Solvent Immobilization Through Dipole Interactions in Polymer Electrolytes for Lithium Metal Batteries

Abstract Poly(vinylidene fluoride) (VDF)‐based solid polymer electrolytes (SPEs) show great potential for application in solid‐state lithium batteries. However, their poor ion transport capabilities and uncontrolled electrode/electrolyte interfacial reactions induced by residual solvents limit their overall electrochemical performance. To address these challenges, a LiTFSI‐replaced dual‐functional cationic covalent organic framework (COF) is strategically designed, denoted COF‐LiTFSI, as organic fillers into poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVHF)‐based solid polymer electrolyte (SPE) to regulate Li + transport and electrode/electrolyte interface stability. The introduction of dipole interactions between cationic moieties embedded in the COF‐LiTFSI framework and Li salt significantly enhances dissociation, thereby improving Li⁺ transport and lowering the activation energy ( E a ), while the strong dipole interaction between residual N‐methylpyrrolidone (NMP) and the COF‐LiTFSI framework immobilizes the NMP molecule, markedly enhancing the electrochemical stability of the PVHF‐COF‐CPE with a Li metal anode. Consequently, the optimized PVHF‐COF‐CPE achieves a high room temperature ionic conductivity of 0.63 mS cm −1 . Furthermore, the Li/Li, Li/LFP (LiFePO 4 ), and Li/NCM811(LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) cells equipped with PVHF‐COF‐CPE achieve remarkably stable cycling. This work presents a novel strategy to regulate ion transport and interface stability in VDF‐based SPEs by leveraging dipole interactions, enabling high‐performance solid‐state lithium batteries.