Wide-temperature solid polymer electrolytes: Li⁺ coordination structure, ionic transport and interphases

Solid-state batteries have gradually become a hotspot for the development of lithium-ion batteries due to their intrinsic safety and potential high energy density, among which, solid polymer electrolytes (SPEs) have attracted much attention due to the advantages of low cost, good flexibility and scalability for commercial application. However, the low ionic conductivity at room temperature, low mechanical strength and unstable interfaces of SPEs hinder further practical applications. In this paper, the modulation of the Li coordination structure and different ion transport channels in the wide-temperature range are reviewed. In addition, the effects of the Li coordination structure on the electrolyte/electrode interfaces/interphases and electrochemical performance are also presented. Furthermore, future research directions including coordination structure, ion transport, manufacturing techniques and full cell performance are summarized and an outlook is given, which will provide general principles to design safe and high-performance solid-state lithium batteries.