Customized polymer electrolytes for high-energy-density lithium batteries

Solid-state batteries with lithium-rich manganese layered oxide (LRMO) cathodes, anode-free architectures, and polymer electrolytes offer high energy density and enhanced safety. However, unstable cathode morphology and irreversible redox reactions at the electrolyte-cathode interface lead to severe interfacial degradation and poor cycling stability. Recently, a fluoropolyether-based polymer electrolyte has been developed, which is a copolymer synthesized via in situ polymerization of poly(ethylene glycol) methyl ether acrylate and fluorohydrocarbon monomers. Its anion-rich solvation environment drives the in situ formation of fluorine-rich interphases at both electrodes and significantly improves the redox reversibility of LRMO. This quasi-solid polymer electrolyte, containing 30 wt% trimethyl phosphate, enables the LRMO cathode to achieve energy densities of 604 Wh kg^-1 and 1,027 Wh L^-1 in pouch batteries. Despite this progress, practical deployment still requires the development of low-fluorine electrolytes, uniform in situ polymerization in large-format batteries, improved mechanical robustness, and long-term stability with lithium metal and high-voltage LRMO cathodes.