Trifunctional surface engineering of Lithium-rich manganese-based oxides via Al³⁺/PO₄³⁻ co-doping and oxygen vacancy regulation for High-performance lithium-ion batteries

Lithium-rich manganese-based oxides (LMR) are promising cathode materials for next-generation lithium-ion batteries because of their high capacities, wide voltage ranges, and low production costs. However, irreversible capacity loss, voltage decay, and limited cycling stability impede their practical application. A trifunctional surface modification strategy utilizing a wet treatment technique to co-dope an LMR surface with Al³⁺ and PO₄³⁻, thereby creating oxygen vacancies and promoting a spinel-like phase, was introduced. These modifications enhance the Li⁺ diffusivity and structural stability and inhibit side reactions. The optimized LMR sample (AP-1.5) demonstrated a reversible capacity of 176.4 mAh/g after 200 cycles at 1C, with a capacity retention of 74.8 %, and delivered 146.5 mAh/g at 10C. Al³⁺ doping increases the interlayer spacing and Li⁺ transport, oxygen vacancies improve electrolyte infiltration and activation, and PO₄³⁻ doping stabilizes the oxygen framework and inhibits gas evolution. This scalable surface-engineering approach controls phase transitions, minimizes electrode degradation, and positions the LMR as a promising candidate for high-energy lithium-ion batteries (LIBs).