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

Na 0.67 Ni 0.33 Mn 0.67 O 2 (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 0.67 Ni 0.18 Cu 0.10 Zn 0.05 Mn 0.67 O 2 (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 Ni 2+ with a small amount of Zn 2+ prevents the P2-O2 phase transformation, while replacing Ni 2+ with an appropriate amount of electrochemically active Cu 2+ eliminates Na-vacancy ordering and additionally contributes to capacity. Thus, the dual substitution of Cu 2+ and Zn 2+ for Ni 2+ 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.