Continuous Li⁺ Coordination Polymer Electrolyte for Fast Li⁺ Migration, Stable Electrolyte Interphases, and Safe Quasi-Solid Lithium Metal Batteries

The advancement of quasi-solid lithium metal batteries strongly hinges on attaining fast Li + transport, stable electrode/electrolyte interphases, and high safety. The present study reports a high-continuous Li + coordination polymer electrolyte composed of a poly(1,3,5-trioxane) (PTXE) skeleton and mixed solvent of triethyl phosphate (TEP) and fluoroethylene carbonate (FEC). The continuous ether chains (−[C–O] n −) in PTXE coordinated with binary solvents and anions of dual lithium salt (TFSI – and DFOB – ) optimize the solvent structure and establish rapid Li + migration, achieving high Li + conductivity (1.87 mS cm –1 at 25 °C) and Li + transference number (0.64) prior to the liquid electrolyte. Simultaneously, via the synergistic induction and regulation exerted by polymer chain segments on the coordination of solvents and anions around Li +, phosphorus- and fluorine-rich cathodic and anodic electrolyte interphases are formed. Furthermore, flame-retardant TEP significantly improves the thermal stability at high temperature (60 °C) as well as under harsh mechanical testing. The assembly of a lithium metal battery with high loading mass of LiNi 0.6 Co 0.2 Mn 0.2 O 2 (10 mg cm –2 ) and ultrathin Li (50 μm) exhibits a high capacity retention rate of 87.1% with 120 cycles. Furthermore, a large-capacity pouch cell (7 Ah) with Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 (40 mg cm –2 ) achieves high reversible capacity (6.58 Ah) with a high energy density of 505 Wh kg –1 .