Mitigating Oxygen Electrostatic Repulsion in P'2 Mn-Based Layered Oxide Cathodes via K⁺/Zn²⁺ Dual Pillaring for...

Despite the high specific capacity of P'2-Na_xMnO₂ (NMO), its practical application is severely hindered by rapid capacity decay caused by drastic structural evolution. Herein, a P'2-[Na_0.57K_xZn_0.10-x]Mn_0.90Ti_0.10O₂ (NK_xZMTO) cathode featuring K⁺ and Zn²⁺ as pillar cations is developed to mitigate O^2--O^2- electrostatic repulsion and suppress detrimental phase transition. Physicochemical characterization and theoretical calculations reveal that K⁺ and Zn²⁺ co-occupy the Na_e site, acting as inert pillars in the Na layers. While NMO undergoes an abrupt and irreversible OP4-P'2-P″2 triphase transition, NK_0.02ZMTO maintains a high fraction of P layers within the OP4 phase and exhibits a mild and reversible P'2-OP4 biphase transition. This stabilized interlayer evolution arises from the combined effects of K⁺ and Zn²⁺: K⁺ enlarges the Na layer spacing owing to its large ionic radius, while Zn²⁺ reduces the electron density on O^2- through its high positive charge, thereby simultaneously mitigating O^2--O^2- electrostatic repulsion in accordance with Coulomb's law. Benefiting from this structural stabilization, NK_0.02ZMTO delivers superior cyclability (99.2% capacity retention after 150 cycles at 100 mA g^-1) and a high specific capacity of 180 mAh g^-1 at 10 mA g^-1. This work provides an innovative strategy for designing highly stable cathode materials.