Interlayer‐Engineering and Surface‐Substituting Manganese‐Based Self‐Evolution for High‐Performance Potassium Cathode

Abstract Manganese‐based layered oxides cathodes have attracted enormous interest due to their advantages in cost and energy density. The significant challenges of Mn‐based layered oxides for potassium‐ion batteries (PIBs) are complex phase transition and Mn dissolution upon K⁺ intercalation/deintercalation. Here, a P3‐type K_0.45Rb_0.05Mn_0.85Mg_0.15O₂ (KRMMO) cathode material is proposed to address the above challenges. The results show that rubidium acts as a pillar to expand interlayer spacing and stabilize the structure, while magnesium partially replaces Mn to suppress the Jahn–Teller distortion of the Mn³⁺. The KRMMO cathode exhibits high capacity of 108.0 and 77.3 mAh g⁻¹ at 20 and 500 mA g⁻¹, respectively, and retains 98.2% of its initial capacity after 200 cycles. Compared with P3‐K_0.5MnO₂, the capacity fading of P3‐KRMMO is effectively suppressed, which is mainly due to the synergistic contribution of Rb and Mg ions in the alleviation of volume change and suppression of phase transition. This work may open a new avenue for the design and optimization of layered cathode materials for PIBs and beyond.