Solid composite electrolyte based on oxygen vacancy effect of Lix(CoCrFeMnNi)O4-y high entropy oxides

Solid-state electrolytes are desired for reliable systems in the battery industry. In this study, high entropy oxide (HEO) composites of Lix(CoCrFeMnNi)3-xO4-y were introduced into a polyethylene oxide (PEO)-based solid composite polymer electrolyte (SCE). Li doping of the HEO compound induces more oxygen vacancies than traditional methods, and this facilitates Li ion transport through the three-dimensional (3D) channel of HEO composites and increases ionic conductivity. The ionic conductivity of the HEO/PEO SCE reached 1 × 10−4 S cm−1 (40°C), significantly higher than that of the PEO solid polymer electrolyte (SPE; 2.8 × 10−5 S cm−1). The tensile strength and elongation of the HEO/PEO SCE were greater by 140.1 % and 138 %, respectively than those of the PEO SPE, resulting in more effective suppression of Li dendrite formation. A solid-state LiFePO4/Li coin cell with the HEO/PEO SCE exhibited a maximum discharge capacity of 127 mAh g−1 at 0.1 C and a high rate capability of 97.2 % at room temperature. The HEO/PEO SCE exhibited superior ionic conductivity, structural integrity, and high thermal and electrochemical stability, making it suitable for safe and high-energy storage systems in Li-ion battery development.