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

## TL;DR

This paper introduces a new gel electrolyte design inspired by mortise-tenon joints, using halogen bonds to improve lithium metal battery performance and stability.

## Contribution

A novel halogen bond-based solvation regulation strategy is introduced for gel polymer electrolytes, enabling high-voltage stability and performance.

## Key findings

- The electrolyte achieves high ionic conductivity (0.30 mS cm−1) and a Li+ transference number of 0.84.
- Li symmetric cells cycle stably for over 1000 hours.
- The Li/NCM811 cell maintains 161.0 mAh g−1 after 500 cycles at 1C.

## Abstract

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/LiNi0.8Co0.1Mn0.1O2 (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.

Inspired by “mortise‐tenon joints”, a halogen bond‐mediated solvation regulation strategy is proposed for gel polymer electrolytes. This approach utilizes π‐hole framework directed halogen bond interactions to weaken solvent‐Li+ coordination, thereby inducing an anion‐dominated weakly solvating structure that facilitates the formation of a highly ion‐conductive and stable interfacial phase.