Polyethylene Oxide/Basalt Composite Electrolytes for Solid‐State Lithium Batteries

With the development of solid‐state lithium metal batteries, polyethylene oxide (PEO)‐based solid‐state electrolytes have been rapidly developed. However, their low ionic conductivity and low electrochemical window limit their further applications. Here, we added basalt, whose main components are SiO 2 and CaO, as fillers to the PEO electrolytes to obtain composite polymer electrolytes. The filler significantly reduces the crystallinity of PEO and effectively improves the ionic conductivity (0.8 mS cm −1 ) of the composite polymer electrolyte, and it also brings enhanced tensile strength as well as the stable electrochemical window (4.9 V) to the composite electrolyte. Combining the composite polymer electrolytes with lithium iron phosphate cathode and lithium anode, the corresponding solid‐state batteries deliver improved electrochemical performance.