Regulating the Solvation Structure in Polymer Electrolytes for High‐Voltage Lithium Metal Batteries

Abstract

Solid polymer electrolytes are promising electrolytes for safe and high‐energy‐density lithium metal batteries. However, traditional ether‐based polymer electrolytes are limited by their low lithium‐ion conductivity and narrow electrochemical window because of the well‐defined and intimated Li + ‐oxygen binding topologies in the solvation structure. Herein, we proposed a new strategy to reduce the Li + ‐polymer interaction and strengthen the anion‐polymer interaction by combining strong Li + ‐O (ether) interactions, weak Li + ‐O (ester) interactions with steric hindrance in polymer electrolytes. In this way, a polymer electrolyte with a high lithium ion transference number (0.80) and anion‐rich solvation structure is obtained. This polymer electrolyte possesses a wide electrochemical window (5.5 V versus Li/Li + ) and compatibility with both Li metal anode and high‐voltage NCM cathode. Li||LiNi 0.5 Co 0.2 Mn 0.3 O 2 full cells with middle‐high active material areal loading (~7.5 mg cm −2 ) can stably cycle at 4.5 V. This work provides new insight into the design of polymer electrolytes for high‐energy‐density lithium metal batteries through the regulation of ion‐dipole interactions.