Dual‐Substitution Strategy Utilizing Cation Chelation and Assembly Process to Realize Solid Solution Reaction in Layered Oxide Cathode for Na‐Ion Batteries

Na_0.67Ni_0.33Mn_0.67O₂ (NNM) is regarded as a promising cathode material for Na-ion batteries (NIBs), but suffers from irreversible phase transformations characterized by multiple voltage plateaus, resulting in poor cycle stability and inferior rate capability. To address these issues, the Na_0.67Ni_0.18Cu_0.10Zn_0.05Mn_0.67O₂ (NNCZM) cathode material is synthesized by a cation chelation and reassembly process, which can promote a more uniform element distribution than that prepared by the solid-state method (S-NNCZM), resulting in better Na⁺ diffusion kinetics and rate capability. Replacing Ni²⁺ with a small amount of Zn²⁺ prevents the P2-O2 phase transformation, while replacing Ni²⁺ with an appropriate amount of electrochemically active Cu²⁺ eliminates Na-vacancy ordering and additionally contributes to capacity. Thus, the dual substitution of Cu²⁺ and Zn²⁺ for Ni²⁺ makes the NNCZM electrode synergistically achieve a complete solid solution reaction and better cycling stability. Accordingly, it exhibits a large discharge capacity (110.2 mA h g^-1 at 10 mA g^-1) with a high initial coulombic efficiency (97.3%), remarkable cycle stability with 84.1% capacity retention over 200 cycles at 200 mA g^-1, and excellent rate capability with a discharge capacity of 61.0 mA h g^-1 at 2000 mA g^-1, significantly outperforming the NNM and S-NNCZM electrodes.