Interfacial Self‐Healing Polymer Electrolytes With Gradient Covalent–Noncovalent Dynamic Bonds for 4.6 V‐Class Lithium Metal Batteries

ABSTRACT Solid‐state lithium batteries (SSLBs) have attracted significant attention due to their high energy density and safety. However, the volumetric expansion/contraction of electrodes, along with persistent interfacial side reactions, leads to mechanical stress damage and failure of interfacial ion transport. Herein, we report an interfacial self‐healing polymer electrolyte (SHPE) based on gradient covalent–noncovalent dynamic bonds, enabling multi‐interfacial dynamic self‐healing throughout the lifecycle of SSLBs. Via molecular engineering, high‐strength boronic ester bonds are combined with ultrafast dynamic responsive hydrogen bonds to enable efficient room‐temperature self‐repair of interfacial defects in SSLBs. The rapid dynamic exchange between polymer chains further promoted fast lithium‐ion conduction, achieving an ionic conductivity of 1.6 × 10 −3 S cm −1 (25°C). The Li|SHPE|Li cells demonstrated stable cycling for >3000 h. The incorporation of oxidation‐resistant boron‐ and fluorine‐containing functional groups extended the electrochemical window to 5.2 V. LiFePO 4 |SHPE|Li and LiCoO 2 (LCO)|SHPE|Li cells delivered >1000 and 700 cycles, respectively, while being compatible with LCO under high voltage (4.6 V) and loading (14 mg cm −2 ). Furthermore, the LCO|SHPE|Li (1.2 Ah) and LCO|SHPE|Si‐C (2.5 Ah) pouch cells exhibited 200 and 400 cycles, respectively, and passed nail penetration safety tests. This study provides an interfacial self‐healing strategy for developing high‐energy‐density and high‐safety SSLBs.