Dynamic Anion Enables Self‐Healing Single‐Ion Conductor Polymer Electrolyte for Lithium‐Metal Batteries

Abstract Lithium‐metal batteries (LMBs) are regarded as a promising option for high‐energy‐density storage systems. However, lithium dendrite growth in LMBs can damage electrolytes and cause short circuits, which severely limits the practical application of LMBs. It is highly desired to develop an advanced polymer electrolyte with self‐healing capability and the ability to inhibit the growth of lithium dendrites for enhancing safety and prolonging the cycle life of the LMBs. Herein, sp³ boron‐based single‐ion conductor polymer electrolytes (B‐SIPEs) with excellent self‐healing capability and interfacial stability are constructed. The rapid bond exchange reactions of dynamic borate anions enable B‐SIPE to fast self‐heal in mild conditions, with a high self‐healing efficiency of 87% within 30 min at an ambient temperature. In particular, B‐SIPE displays a high Li⁺ transference number (0.88) and excellent lithium dendrite inhibition ability. The Li|B‐SIPE|Li cells exhibit a stable overpotential over 2000 h without short‐circuit. Additionally, the LiFePO₄||Li cells with B‐SIPE exhibit superior long‐term cycling performance, with 93.5% capacity retention for 500 cycles. Significantly, B‐SIPE is capable of self‐healing the fracture in LiFePO₄||Li cells and recovering the battery performance. These results demonstrate that the advanced self‐healing single‐ion conductor polymer electrolytes effectively promote the reliability and safety of LMBs.