Optimizing Lithium Battery Interface: Room Temperature Diels-Alder Cross-Linked In Situ Gel Electrolyte Inhibits Lithium Dendrite Growth

In situ gel polymer electrolytes (GPEs) are promising for lithium metal batteries due to their high ionic conductivity (≈ 10⁻³ S cm⁻¹) and outstanding compatibility with electrode interface. However, challenges such as initiator and monomer residue, high initiation temperatures, and low mechanical properties hinder their development. To address these challenges, a low-temperature, catalyst-free method utilizing the Diels-Alder reaction between fulvene and maleimide is proposed, offering a by-product-free solution. With this method, a GPE was prepared through the Diels-Alder reaction between PEG-fulvene and bismaleimide diphenylmethane (BMI), using lithium-sulfur electrolyte (1.0 M LiTFSI in DOL (1,3-dioxolane): DME (Dimethoxyethane) = 1:1 vol% with 1.0% LiNO₃) as the solvent. The in situ GPE demonstrates an ionic conductivity of up to 1.11 mS cm⁻¹ at 30°C and maintains stable cycling for 2000 h at a current density of 0.1 mA cm⁻². Furthermore, the formation of lithium dendrites is effectively suppressed. The discharge capacity of the LFP/GPE/Li battery was 118.9 mAh g⁻¹ after 200 cycles at 0.5C, with a capacity retention of 88.20%. These results demonstrate that the in situ GPE has excellent capacity retention and cycle life, making the catalyst-free crosslinking strategy at room temperature a new plan for preparing in situ GPE.