Gel Electrolyte Self-Healing via Dynamic Reversible Bonds for Stable Lithium Plating/Stripping in Lithium Metal Batteries

Solid polymer electrolytes in lithium metal batteries (LMBs) are susceptible to mechanical damage from lithium dendrite puncture and deformation. Although integrating self-healing functionality helps to alleviate this issue, it typically compromises either mechanical strength or ionic conductivity. To overcome this trade-off, self-healing electrolytes (AU_<i>x</i>-BMIM_<i>y</i> IGEs) were developed through the synergistic combination of ureido pyrimidinone (UPy)-based polymers and an imidazolium ionic liquid. The designed supramolecular networks feature quadruple hydrogen bonds from UPy units and ion-dipole interactions between imidazolium cations and polymer carbonyl groups. The mechanical strength of the electrolyte is enhanced by these dynamic reversible bonds, while the exceptional self-healing efficiency is enabled by their capacity for rapid reorganization. The ionic liquid further enhances the ionic conductivity. The optimized IGEs, named as AU₇-BMIM₁₅ IGEs, balance the tensile stress of 1.26 MPa, the ionic conductivity of 3.40 × 10^-4 S cm^-1, and ultrahigh self-healing efficiencies. After being cut and healed at 45 °C for merely 1 h, the Healed-AU₇-BMIM₁₅ IGEs achieved healing efficiencies of 97.6% in tensile strength and 99.1% in ionic conductivity. This efficient healing capability contributes to the remarkable stability of lithium plating/stripping. The Li||Li symmetric cell assembled with Healed-AU₇-BMIM₁₅ IGEs stably cycled for over 4500 h at 0.1 mA cm^-2. Furthermore, a Li||LiFePO₄ cell using Healed-AU₇-BMIM₁₅ IGEs delivered cycling for 2000 h at 0.2 C with an average Coulombic efficiency exceeding 99%, performing comparably to fresh AU₇-BMIM₁₅ IGEs. The practical viability was further underscored by multipoint puncture tests. The AU₇-BMIM₁₅ IGE with 16 puncture sites retained a critical current density of 0.30 mA cm^-2 after being healed at 45 °C for 1 h. This work demonstrates a promising strategy for creating self-healing electrolytes for next-generation LMBs.