Surface phosphating of layered oxide cathode materials for potassium-ion battery

Potassium-ion batteries (PIBs) are eco-friendly alternatives to lithium-ion batteries for large-scale energy storage, in which P3-type manganese-based layered oxides offer the benefits of non-toxicity, low cost, and high energy density. However, they encounter increasing electrostatic repulsion during K⁺ migration, causing slippage between manganese-oxygen layers, which leads to irreversible phase transitions and structural degradation. Herein, a synergistic strategy of P-doping induced lattice regulation and K₃PO₄ surface coating is proposed to achieve high structural stability of P3-K_0.5Mn_0.72Ni_0.15Co_0.13O₂ (KMNCO@KPO-3). The P doping leads to the expansion the interlayer spacing and facilitates the K⁺ storage, resulting in the alleviated diffusion-induced stress and enhanced structural stability during K⁺ (de)intercalation. Besides, the stronger P-O bonds enhance O^2- stability, leading to reduce lattice oxygen loss and inhibiting P3-O3 phase transitions. Meanwhile, the K₃PO₄ surface coating further mitigates the erosion from the electrolyte. Thus, KMNCO@KPO-3 achieves improved structural stability and minimized mechanical damage. The full cell with KMNCO@KPO-3 cathode exhibits a capacity retention of 88.1 % over 100 cycles as well as exceptional rate performance. These findings highlight the significant potential of KMNCO@KPO-3 for industrial applications.