Efficient phosphorus doping strategy to overcome lattice distortion in Mn-based cathodes for advanced potassium-ion batteries

Abstract

Manganese-based metal oxides have emerged as promising cathode materials for potassium-ion batteries (PIBs) due to favourable structural characteristics, such as large interlayer spacing and long diffusion paths for K⁺ ions. However, there are challenges due to the Jahn-Teller effect of the Mn³⁺ and the large volumetric strains of the charge/discharge process. In this study, the unfavorable lattice strains as well as the electrochemical properties were improved by phosphorus doped potassium manganate strategy. P-doped increases the K⁺ storage active sites by increasing the Mn³⁺ content to enhance the storage capacity. In addition, the PO₄ and MnO₆ octahedra share O to stabilize the lattice and suppress the Jahn-Teller effect as well as the bulk strain induced by K⁺ insertion/extraction. The reduced charge transfer resistance as well as the enlarged layer spacing help to reduce the K⁺ diffusion barrier, fast K⁺ diffusion kinetics, and improve the rate performance. K_0.6MnP_0.02O₂ (P-KMnO-2) has capacity of 50.97 mAh g⁻¹ at 1000 mA g⁻¹. And after 500 cycles at 500 mA g⁻¹, P-KMnO-2 still has capacity of 41 mAh g⁻¹. In addition, maximum energy density of full cell composed of P-KMnO-2 and soft carbon reached 176.4 Wh kg⁻¹.