PEO‐Based Solid‐State Polymer Electrolytes for Wide‐Temperature Solid‐State Lithium Metal Batteries

Developing solid-state lithium metal batteries with wide operating temperature range is important in future. Polyethylene oxide (PEO)-based solid-state electrolytes are extensively studied for merits including superior flexibility and low glass transition temperature. However, ideal usage temperatures for conventional PEO-based solid-state electrolytes are between 60 and 65 °C, and unequable temperature degrades their electrochemical performances at low and high temperatures (≤25 °C and ≥80 °C). Herein, modification methods of PEO electrolytes for low, high especially wide-temperature applications are reviewed based on detailed analyses of mechanisms involved in its modification at different temperatures. First, shortcomings of PEO solid electrolytes due to influence of temperature are pointed out. Second, existing modification strategies are summarized in detail from three aspects of high, low especially wide temperatures, including application of PEO derivatives or chain segment modification treatment of PEO, addition of fillers, and other modification methods such as reasonable regulation of lithium salts, introduction of functional layers and addition of metal-organic frameworks (MOFs) or covalent organic frameworks (COFs). Finally, a summary and description of PEO-based solid electrolyte research and development trends for wide-temperature applications are provided. The review aims to offer some guidance for the creation of PEO solid batteries with wider working temperature ranges.