Poly(ethylene oxide)-Based Composite Electrolyte with Lithium-Doped High-Entropy Oxide Ceramic Enabled Robust Solid-State Lithium-Metal Batteries

Solid polymer electrolytes using poly(ethylene oxide) (PEO) as matrix are mostly applied due to the superior Li⁺ transfer ability of oxyethyl chain. However, the high crystallinity, low oxidation potential window, and insufficient mechanical strength hinder PEO deployment in solid-state batteries. Here, a novel composite solid electrolyte combined PEO with a lithium-doped high-entropy oxide (Li_0.25 HEO) ceramic powder is presented, which exhibits excellent properties for solid-state lithium metal battery applications. On one hand, the rich oxygen vacancies of Li_0.25 HEO surface are favorable to capturing anionic groups (e. g. TFSI^- ), reinforcing the Li⁺ dissociation. On the other hand, Li_0.25 HEO with abundant Lewis acid sites markedly promotes the PEO oxidation potential window. Additionally, the incorporation of Li_0.25 HEO ceramic powder can effectively inhibit the PEO crystallization and enhance the mechanic strength of the composite electrolyte as well. The assembled solid-state lithium metal battery based on the composite solid electrolyte exhibits high rate capacity and durable cycle performance, showing potential development and application prospects.