Initiator-Free Crosslinking Process Without Organic Solvent for Polymer Gel Electrolyte of Lithium Metal Batteries

For the next generation of lithium batteries, polymer-based electrolytes are promising candidates for resolving issues from liquid electrolytes such as leakage, flammability, and explosion. Various attempts have been carried out to develop polymer electrolytes based on poly(ethylene oxide) (PEO), polyacrylonitrile, polyvinylidene fluoride, etc., resulting in suppression for dendrite growth on Li metal and mechanical support against internal or external shock as well. Among these polymer electrolytes, PEO has been widely used due to their relatively high ionic conduction through the hopping of Li ions. Herein, poly(GAP-co-THF) diol (PGT) having a similar main chain to PEO while containing azide groups in a side chain is synthesized. To enhance the processability of polymer electrolytes, the thermal crosslinking process is performed via azide-alkene cycloaddition between PGT and poly(ethylene glycol) diacrylate with lithium bis(trifluoromethanesulfonyl)imide without any initiators and organic solvents. Thickness controllable thin film of polymer electrolyte is obtained after the crosslinking process, resulting in outstanding advantages with respect to stacking of batteries. To check the electrochemical stabilities and cell performances of these polymer electrolytes, cyclic voltammetry, linear symmetric voltammetry, LiFePO4 parallel to Li cell, and Li symmetric cell tests are accomplished. Poly(GAP-co-THF) diol (PGT), poly(ethylene glycol) diacrylate (PEGDA), and bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) are mixed to induce crosslinking. PGT and PEGDA are thermally crosslinked via azide-alkene cycloaddition, resulting in the fabrication of thin polymer gel electrolytes. Produced PGT/PEGDA/LiTFSI polymer electrolyte is utilized in lithium metal batteries. image