Built-in Single-Ion-Conducting Polymer Bridges for Superior Ion Transport Enabling Long-Life and High-Voltage Lithium-Metal Batteries

Composite polymer electrolyte (CPE)-based Li metal batteries have emerged as the most promising candidates for next-generation batteries. However, intrinsic incompatibility between composite phases severely compromises electrolyte performance. Herein, we propose a built-in single-ion-conductor bridge that seamlessly links the garnet-type oxide phase with PVDF-based polymer matrixes, enabling excellent composite compatibility and superior Li⁺ fluxes throughout the bulk electrolyte. The 2‐acrylamido‐2‐methylpropanesulfonic acid molecule is chosen to in-situ convert the inert surface layer of garnet fast‐ion conductors into a molecular single‐ion-conducting layer with rapid ionic transport, effectively bridging ion transport among multiple components. The resulting CPE exhibits remarkable long-cycling stability under extreme conditions (e.g., high voltage of 4.5 V, high loading of 10.2 mg cm−2, and low temperature of –30 °C). Specifically, the assembled Li||LiNi0.9Co0.05Mn0.05O2 pouch cells delivered a stable cycling for 1200 cycles at 0.5 C. Moreover, the strategy is readily applicable to sodium metal batteries, achieving decay-free performance over 2200 cycles. Thus, it offers a promising approach for fabricating high-performance solid-state batteries.