Facile fabrication of cross-linked polymer electrolyte via imidazole-based deep eutectic solvent-induced in situ polymerizations

Fabricating the cross-linked network is an efficient strategy for improving the mechanical and electrochemical performances of polymer electrolytes (PEs). However, present methods used for the preparation of the cross-linked PEs is difficult to remove the residual catalyst and avoid the side reactions, and the ion conduction in solid PEs is often confined. Herein, we report that the deep eutectic solvent (DES) via the Li–N interaction of 1,2-dimethylimidazole (DMIm) and bis(trifluoromethane)sulfonimide lithium (LiTFSI) displays synergistic effects in inducing the ring-opening polymerization (ROP) of trimethylene carbonate (TMC) and thiol-Michael addition reaction, permitting in situ preparation of PEs with a cross-linked structure. Moreover, DMIm-based DES not only endows PEs with the flame-retardant property but also promotes the conduction of Li ions (Li+) in PEs, leading to a good ionic conductivity at 60 °C (1.8 × 10−4 S cm−1) and Li+ transference number (0.41). Notably, no obvious short-circuit at 0.1 mA cm−2 appears during the deposition process of lithium symmetric batteries assembled with PEs after 1200 h.