Polymerized Ionic Networks Solid Electrolyte with High Ionic Conductivity for Lithium Batteries

Abstract

The performance of classical lithium-ion technologies based on liquid electrolytes has made great advances in the last two decades, but safety issues are inevitable for batteries assembled with liquid electrolytes, which have intrinsic instability. In response to this issue, solid polymer electrolytes are developed in the lithium batteries field extensively for improving safety issues, as well as miniaturizing and enhancing the energy densities. Considering the great advantages of polymerized ionic networks, such as facile synthesis, high charge density, and high stability, two polymerized ionic networks (PDM-TFSI-1 and PDM-TFSI-2) with different polysubstituted benzene groups have been developed. The new type of polymerized ionic network with cross-linked structure was synthesized by the simple radical copolymerization of 2-(dimethylamino)ethyl methacrylate and methyl methacrylate monomers, then the copolymer (Mn = 14.5 kg mol−1) reacted with polysubstituted bromobenzene to form a cross-linked structure, and finally this was ion exchanged with bis(trifluoromethane)sulfonimide lithium salt (LiTFSI). The ionic networks filled with ionic liquid/LiTFSI mixture exhibit high ionic conductivity (1.0 × 10–4 and 1.9 × 10–4 S cm–1) and high decomposition potential (4.7 V vs Li/Li+) at 30 °C. The batteries were assembled by sandwiching the obtained polymer electrolytes between a LiFePO4 cathode and a lithium anode, exhibiting good cycling stability and specific capacity, suggesting that these novel kinds of solid polymer electrolyte are promising for application in next-generation lithium-ion batteries.