A Biodegradable Polyester-Based Polymer Electrolyte for Solid-State Lithium Batteries

The low ionic conductivity, narrow electrochemical window, poor interfacial stability with lithium metal, and non-degradability of raw materials are the main problems of solid polymer electrolytes, restricting the development of lithium solid-state batteries. In this paper, a biodegradable poly (2,3-butanediol/1,3-propanediol/succinic acid/sebacic acid/itaconic acid) ester was designed and used as a substrate to prepare biodegradable polyester solid polymer electrolytes for solid-state lithium batteries using a simple solution-casting method. A large number of ester-based polar groups in the amorphous polymer become a high-speed channel for carrying lithium ions as a weak coordination site. The biodegradable polyester solid polymer electrolyte exhibits a wide electrochemical window of 5.08 V (vs. Li/Li⁺), high ionic conductivity of 1.03 mS cm⁻¹ (25 °C), and a large Li⁺ transference number of 0.56. The electrolyte exhibits good interfacial stability with lithium, with stable Li plating/stripping behavior at room temperature over 2100 h. This design strategy for biodegradable polyester solid polymer electrolytes offers new possibilities for the development of matrix materials for environmentally friendly lithium metal solid-state batteries.