In situ Janus polymerization of cyclic phosphate and ethers affording fluorine/phosphorus copolymer electrolyte for high-safety lithium metal batteries with long-cycle life

Abstract

Ether-based electrolytes exhibit promising features such as good lithium-ion solvation and lithium-metal compatibility, yet their limited oxidation stability and safety issues impede application in high-voltage lithium-metal batteries (LMBs). In this work, a new F/P-containing gel polyether-based electrolyte (FP-GPE) was prepared via in situ Janus polymerization of methyl ethylene phosphate (MeOEP), 3-(2,2,3,3-tetrafluoropropoxy)-1,2-propylene oxide (TFPO), and 1,3-dioxolane (DOL). The FP-GPE demonstrates high oxidative stability (4.8 V) and excellent compatibility with lithium metal. The capacity retention of the Li|FP-GPE|LiFeO₄ battery remains at 100% after 2000 cycles and remains at 72.9% after 500 cycles for the Li|FP-GPE|LiNi_0.8Co_0.1Mn_0.1O₂ battery. Furthermore, in situ Janus polymerization of monomers with different polymerization mechanisms in LMBs was achieved for the first time, integrating distinct functional groups in the same molecular chain, thus paving a hopeful way for the development of polymer electrolytes with multifunctionality.