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

ABSTRACT 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% LiNO 3 ) 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.