A wide-temperature superior ionic conductive polymer electrolyte for lithium metal battery

Abstract

Polymer electrolytes are one of promising candidates that can meet the demands of high safety and stability of high-energy lithium metal batteries. However, the practical applications of polymer electrolytes are usually limited by the low ionic conductivity, narrow electrochemical window and highly interfacial resistance. Here we designed a poly(vinyl ethylene carbonate) polymer electrolyte for polymer lithium metal battery by in-situ polymerization method. The new polymer electrolyte provides superior ionic conductivity with 2.1 × 10⁻³ S cm⁻¹ at 25 °C, wide electrochemical window up to 4.5 V (vs. Li⁺/Li) and excellent interfacial compatibility to electrodes. The ions transports are mainly achieved from the coupling/decoupling between Li ions and oxygen atoms in CO groups, partially from the coupling/decoupling between Li⁺ and oxygen atoms in C–O groups, and probably moving/exchange of Li⁺ between CO and C–O groups in the process of segmental motions in high and low molecular polymers of polymer electrolyte. The lithium metal batteries with LiFePO₄ cathode can deliver a high discharge capacity of ~165 mA h g⁻¹ at 25 °C, and even ~104 mA h g⁻¹ at −15 °C with current density of 0.1C. Therefore, the novel polymer electrolyte designed in this study is a promising candidate for high performances polymer lithium metal batteries.