Bimetallic Substitution Engineering Enabled Fast‐Charging Layered Oxide Cathodes for Potassium‐Ion Batteries

Abstract Potassium‐based layered transition metal oxides, one of the most promising cathodes for potassium‐ion batteries (PIBs), suffer from detrimental intrinsic phase transitions and sluggish K + ‐diffusion kinetics, resulting in inferior fast‐charging capability. Herein, a facile bimetallic substitution strategy is proposed to synthesize Ni/Cu substituted manganese‐based layered oxide (KMNCO) cathode with exceptional fast‐charging capability. Benefiting from the precise substitution of Ni/Cu for Mn, KMNCO features suppressed high‐spin Mn 3+ concentration and enhanced potassium content. As expected, KMNCO demonstrates a high reversible specific capacity, extraordinary fast‐charging specific capacity, and cycling stability. In situ X‐ray diffraction combined with in situ kinetics analysis and microstructural characterization elucidates a highly reversible, solid‐solution mechanism governing K + intercalation/deintercalation in KMNCO. In‐depth electrochemical analysis and theoretical calculations confirm that Ni/Cu substitution eliminates the K + ‐vacancy ordered structure, thereby enhancing potassium storage kinetics of KMNCO. In addition, full‐cells based on the KMNCO cathode deliver a reversible specific capacity of 93 mAh g −1 and satisfactory cycling stability. This work provides an alternative route for precisely engineering fast‐charging cathode materials for PIBs.