Solid Composite Polymer Electrolyte Lithium-Ion Battery With an Improved Electrochemical Stability Window and Cycle Characteristics

Abstract

Polymer electrolytes for lithium-ion batteries (LIBs) face challenges such as low ionic conductivity, insufficient mechanical flexibility, and limited thermal stability, which restrict their use in high-energy density applications. To address these issues, a solid composite polymer electrolyte (SCPE) is developed by blending poly(ethylene oxide) (PEO) with poly(ethylene glycol) dimethyl ether (PEGDME) as a synthetic electrolyte and adding an F-doped lithium aluminum titanium phosphate inorganic filler. As a result, the prepared CPE exhibits a high ionic conductivity of 1.24 × 10⁻⁴ S/cm and excellent thermal stability, along with an extended electrochemical stability window (ESW) up to 6.8 V. When applied to LiFePO₄ half-cells, the CPE enables charge and discharge capacities of 152.3 and 152.0 mA h/g, respectively, while maintaining a low voltage hysteresis of approximately 0.16 V throughout the cycles. Although the initial cycle shows a relatively high irreversible capacity of 3.7 mA h/g, the cell demonstrates outstanding cycling stability, retaining 98.9% of its initial capacity after 100 cycles. The developed composite electrolyte shows potential for use in safe and high-performance all-solid-state LIBs, providing a viable pathway toward safer and high-performance solid-state LIBs suitable for advanced energy storage applications.