Fabrication of polymer electrolyte via lithium salt-induced surface-initiated radical polymerization for lithium metal batteries

The fabrication of flexible polymer electrolytes (PEs) which possess simultaneously high thermal stability, robust mechanical strength , and high ionic conductivity is very challenging for lithium (Li) batteries. Herein, cellulose-based PE is fabricated via a Li salt-induced surface-initiated radical polymerization of polyethylene glycol methyl ether acrylate (PEGA). The polymerization of PEGA is catalyzed by various Li salts, such as Li perchlorate (LiClO 4 ), bis(trifluoromethane)sulfonimide Li (LiTFSI), Li difluoro(oxalato)borate (LiDFOB), and LiClO 4 /LiDFOB, which also serve as charge transfer carriers in PEs. The Li salt can be used as the catalyst to promote the cleavage of C–Br bond on the surface of Br-modified cellulose, and then initiate the polymerization of PEGA. The PE obtained from the dual salt (LiClO 4 /LiDFOB)-induced radical polymerization system exhibits high ionic conductivity of 3.5 × 10 −5  S cm −1 at 30 °C, good thermal stability (up to 240 °C), and wide electrochemical stability window (5.0 V vs. Li/Li + ). Moreover, Li/PE/Li symmetric cells show good interfacial stability between PE and Li foil and the assembled Li/PE/LiFePO 4 cells possess 150 mA h g −1 at 0.1C. Li salt-induced surface-initiated polymerization provides a simple and efficient method for fabricating PE for high-performance Li metal batteries (LMBs).