Regulating Li Solid-State Coordination to Enhance Hopping Kinetics within Polymer Electrolyte of Li Metal Batteries

Abstract

The pursuit of high-energy solid-state lithium metal batteries (ssLMBs) is challenging, due to the sluggish ion transport in solid electrolytes and unstable electrode–electrolyte interfaces. Herein, we showcase regulating Li⁺ solid-state coordination as a feasible strategy. By constructing Li⁺ coordination with poly-1,3-dioxolane chains and anions, an in situ polymerized solid electrolyte (PDTE) is obtained with an ionic conductivity of 1.45 mS cm^–1, Li⁺ transference number of 0.67, and high interfacial compatibility. As the bifunctional promoter, it alleviates Li⁺ hopping barriers via the ligand-field effects and establishes the conformal solid/cathode-electrolyte interfaces. Its derived Li|PDTE|LiFePO₄ ssLMBs maintains cycling for over 1000 cycles at 2 C with 92.5% retention in capacity, and at the fast-charging rate up to 20 C. When coupled with a LiNi_0.8Co_0.1Mn_0.1O₂ cathode, PDTE further showcases promises in stable operation under a wide voltage window from 2.8 to 4.5 V and a low-temperature range down to −20 °C. Toward practical promises, 5.7 Ah solid-state pouch cells are further assembled with an energy density of 513 Wh kg^–1 and the elevated safety for thermal runaway.