High-Performance Poly(ethylene Oxide)-Based Composite Solid Electrolyte with Enhanced Room-Temperature Ionic Conductivity for Lithium-Metal Batteries

Poly(ethylene oxide) (PEO)-based solid-state polymer electrolytes have emerged as one of the most promising candidates for high-energy-density lithium-metal batteries in energy storage applications. However, their notably low ionic conductivity has significantly hindered PEO-based polymer electrolytes’ practical application and development, particularly at room temperature (RT). To address the critical challenge of low RT ionic conductivity in PEO-based solid-state electrolytes, this study develops a composite solid electrolyte (CSE) synergistically reinforced by high-concentration lithium salts and Al 2 O 3 filler. The “polymer-in-salt” strategy disrupts PEO crystallinity via concentrated Li salt to form continuous ion channels, while Al 2 O 3 further suppresses crystallization and bridges ionic cluster transport. This dual optimization achieves an ultrahigh ionic conductivity of 9.62 × 10 −4 S cm −1 and a 4.8 V electrochemical stability window at RT. The Li symmetric cell exhibits stable cycling for 1000 h at 1 mA cm −2 /1 mAh cm −2 , and the all-solid-state Li//LiFePO 4 coin cell retains 70.7% capacity after 300 cycles at 0.1C. Moreover, Li//LiFePO 4 pouch cell maintains 96.4% capacity over 100 cycles at RT. This work establishes a new paradigm for material design and performance enhancement in practical solid-state lithium batteries. Graphical This study develops a novel PEO-based composite solid electrolyte (CSE) by combining PEO, high-concentration lithium salt, and Al 2 O 3 . The CSE achieves a high ionic conductivity of 9.62×10 -4 S·cm -1 at room temperature. The designed structure disrupts PEO crystallization and facilitates Li+ transport. The resulting solid-state battery exhibits stable cycling over 300 cycles with 70.7% capacity retention and demonstrates 96.4% retention in pouch cells, showing great potential for commercial application.