A poly(1,3-dioxolane) based deep-eutectic polymer electrolyte for high performance ambient polymer lithium battery

Solid-state polymer electrolytes have recently drawn intense attention as alternatives to traditional liquid electrolytes in lithium batteries due to their high energy-density and reliable safety. Unfortunately, current all-solid-state polymer electrolytes suffer from the low ionic conductivity, limiting the power density of energy storage batteries. Here, we propose a deep-eutectic electrolyte, formed directly by the interaction between poly (1,3-dioxolane) and lithium salt without other auxiliary solvents. The ionic conductivity of the designed deep-eutectic polymer electrolyte can approach to 1.5 × 10⁻⁵ S/cm at ambient temperature, which is twenty times higher than that of polyethylene oxide-based electrolytes. Specifically, solid-state NMR verifies the interaction between oxygen in poly (1,3-dioxolane) and lithium ion. The LiFePO₄/Li battery assembled with deep-eutectic polymer electrolyte delivers a discharge capacity of 139.6 mAh/g at 0.1 C and a capacity retention of 90% after 200 cycles at 0.2 C. Pouch LiFePO₄/Li batteries also present excellent safety performances. This finding provides a new approach for materials engineering of polymer electrolytes for advanced lithium batteries.