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. LiFePO₄|SHPE|Li and LiCoO₂ (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.