Regulating the Li/Ni Mixing Ratio to Enhance Transition Metal‐Lattice Oxygen Interaction for Achieving Long Life Lithium‐Rich Layered Oxides

Lithium-rich layered oxides (LLOs) emerge as promising cathode materials for next-generation high-performance Li-ion batteries (LIBs) due to their superior specific capacity characteristics. The similar ionic radii of Li⁺ (0.72 Å) and Ni²⁺ (0.69 Å) inevitably cause Li/Ni mixing. However, the relationship between Li/Ni mixing and the electrochemical performance of LLOs remains poorly understood. This study investigates LLOs with varying Li/Ni mixing ratios. The results indicate that an optimal increase in Li/Ni mixing can strengthen TM─O bond, reduce lattice strain, and thus enhance the cycling stability of LLOs. When the Li/Ni mixing further increases, Ni atoms tend to aggregate in the Li layer, which reduces the structural stability of LLOs and causes severe electrolyte decomposition. In comparison to the sample with lower Li/Ni mixing (1.90%), the LLOs with optimized Li/Ni mixing (4.07%) exhibit an enhancement in initial Coulombic efficiency from 83.0% to 87.4%, along with an improvement in capacity retention from 71.7% to 85.2% after 500 cycles at 1C. Moreover, the corresponding pouch cell maintains 82.5% capacity retention after 200 cycles at 0.3C. This study elucidates the impact of Li/Ni mixing ratio on the electrochemical performance of LLOs, providing valuable insights for synthesizing high-performance LLOs.