Zn²⁺-doped Mn-based layered oxide cathode with suppressed P3-O3 phase transition for high-efficiency potassium-ion...

Mn-based layered oxides are promising cathode materials for potassium-ion batteries (PIBs) owing to their high energy density, cost-effectiveness, and scalability. Nevertheless, their practical application remains hindered by the Jahn-Teller effect associated with Mn³⁺ and detrimental phase transitions upon cycling. Herein, we report a Zn²⁺ doping strategy to synthesize P3-type K_0.55Mn_0.75Ni_0.15Zn_0.1O₂ (KMNZO-0.1). Multiscale characterization combined with density functional theory calculations reveals that the introduction of lower-valence Zn²⁺ triggers charge compensation, elevating the average Mn valence toward +4 and thereby fundamentally suppressing the Jahn-Teller distortion. Furthermore, the electrochemically inert Zn²⁺, with its larger ionic radius, serves as an intralayer lattice pin to stabilize the transition metal layer and prevent the detrimental P3-O3 phase transition. In addition, Zn²⁺ doping enhances the covalency of chemical bonds via electronic structure modulation, alleviating MnO₆ octahedral distortion and lowering the K⁺ migration barrier by optimizing the local coordination environment. As a result, KMNZO-0.1 delivers a high initial reversible capacity of 118.4 mAh g^-1 at 0.1 C (1 C = 100 mA g^-1) and retains 73.5% of its capacity after 800 cycles at 1 C, significantly outperforming the undoped counterpart. To validate practical viability, KMNZO-0.1||graphite full cells are assembled, demonstrating 81.5% capacity retention over 400 cycles at 1 C. This work establishes that electrochemically inert Zn²⁺ doping in Mn-based layered oxides is an effective strategy for developing high-performance cathodes for PIBs.