Mortise-Tenon Joint Inspired Weakly Solvated Gel Electrolyte Based on Halogen Bonds for High-Voltage Lithium Metal Batteries

In situ gel polymer electrolytes (GPEs) offer a promising approach to improve safety and cycling stability in lithium metal batteries (LMBs), yet often suffer from poor electrode compatibility, especially at high temperatures. This work reports a “mortise-tenon joint” inspired non-covalent interaction — “π-hole” based halogen bond, that enables solvation structure regulation beyond traditional van der Waals force or hydrogen bond. The electrophilic π-hole on the polymer skeleton engages in halogen bonding with solvents, thereby weakening their coordination with Li⁺ to form a weakly solvated structure. Moreover, the fluorine-rich skeleton participates in the formation of the electrode-electrolyte interphases, achieving good anode compatibility and high-voltage stability simultaneously. The resulting electrolyte exhibits high ionic conductivity (0.30 mS cm⁻¹) and a Li⁺ transference number of 0.84. Li symmetric cells stably cycle over 1000 h. The Li/LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cell delivers discharge specific capacities of 161.0 mAh g⁻¹ after 500 cycles at 1C. Especially, the cell can work stably for 100 cycles at 80 °C (1C, 156.0 mAh g⁻¹). Furthermore, the pouch cell achieves an energy density of 462.2 Wh kg⁻¹. This study demonstrates that the concept of a weakly solvated gel electrolyte based on halogen bonds provides a new approach to achieving high-energy-density LMBs.