Improved Thermal Durability and Mechanical Robustness of LCTO-Embedded Composite Electrolytes Derived from PEO for Lithium Metal Battery Applications

Cost-effective and versatile poly (ethylene oxide) (PEO)-based electrolytes have been a viable option within solid-state battery application systems due to their exceptional salt solvation capability and compatibility with electrode interfaces. However, the restricted lithium-ion mobility under standard temperature conditions and the formation of lithium dendrites pose substantial impediments to their application in high-capacity lithium metal batteries. To tackle this challenge, a thermally and mechanically robust solid-state electrolyte composite incorporating lithium-doped cobalt titanium oxide (LCTO) and PEO has been used. This electrolyte exhibits an extended electrochemical window of 5 V versus Li+/Li and a notable lithium-ion transference number. The presence of surface hydroxyl groups on the LCTO particles eliminates the interplay between lithium ions and anions in the lithium salt while simultaneously reducing the crystallinity of the PEO electrolyte and forming a three-dimensional lithium-ion pathway, ultimately leading to an enhanced lithium-ion conductivity of 0.85 mS cm–1 at 60 °C. The lithium symmetrical cell with LCTO-incorporated electrolyte demonstrates outstanding cycling (over 750 h under 0.1 mA cm–2). Additionally, LCTO-composite electrolyte-based LiFePO4 batteries exhibit excellent Coulombic efficiencies (>99.8%), low overpotentials (91.5 mV on average), and good cycling stability (120 cycles) at 60 °C.