Lattice Stabilization in P2-Type Layered Oxide Cathodes by Zn Doping for High-Voltage Sodium Storage

P2-Na_0.67Ni_0.33Mn_0.67O₂ represents an attractive cathode candidate for sodium-ion batteries. This material benefits from environmental sustainability, relative ease of synthesis, a high specific capacity, and operation at elevated voltages. However, its practical implementation is hindered by accelerated performance degradation and detrimental structural changes when charged beyond 4.2 V. Herein, we propose a strategic zinc-doping approach to address these limitations. Combined in situ XRD and DEMS, the Zn-doped P2-Na_0.67Ni_0.32Mn_0.67Zn_0.01O₂ demonstrates remarkable suppression of lattice distortion (volume change <4%) and oxygen evolution even during high-voltage operation. Ex situ XPS confirms that Zn doping effectively mitigates Mn³⁺ induced Jahn-Teller distortion during cycling. The optimized cathode exhibits exceptional rate capability, delivering 99.1 mAh g^-1 and 84.9 mAh g^-1 at 5 and 10 C, respectively, within 1.5-4.3 V (vs Na/Na⁺). Furthermore, it demonstrates exceptional cycling stability at 10 C, retaining 92.9% of its capacity after 300 cycles. Complementing these findings, theoretical calculations reveal that NMNZ exhibits reduced volume changes, lowers the energy band center of O 2p orbitals, and enhances the stability of lattice oxygen.