Eutectic Solution Enables Powerful Click Reaction for In-Situ Construction of Advanced Gel Electrolytes

Thiol-ene click reaction is an intriguing strategy for preparing polymer electrolytes due to its high activity, atom economy and less side reaction. However, the explosive reaction rate and the use of non-electrolytic amine catalyst hamper its application in in-situ batteries. Herein, a nitrogen-containing eutectic solution is designed as both the catalyst of the thiol-ene reaction and the plasticizer to in-situ synthesize the gel polymer electrolytes, realizing a mild in-situ gelation process and the preparation of high-performance gel electrolytes. The obtained gel polymer electrolytes exhibit a high ionic conductivity of 4 × 10⁻⁴ S cm⁻¹ and lithium-ion transference number (t_Li⁺) of 0.51 at 60 °C. The as-assembled Li/LiFePO₄ (LFP) cell delivers a high initial discharge capacity of 155.9 mAh g⁻¹, and a favorable cycling stability with the capacity retention of 82% after 800 cycles at 1 C is also obtained. In addition, this eutectic solution significantly improves the rate performance of the LFP cell with high specific capacity of 141.5 and 126.8 mAh g⁻¹ at 5 C and 10 C, respectively, and the cell can steadily work at various charge–discharge rate for 200 cycles. This powerful and efficient strategy may provide a novel way for in-situ preparing gel polymer electrolytes with desirable comprehensive performances.