Concentration-Gradient LiNi_0.85Co_0.12Al_0.03O₂ Cathode Assembled with Primary Particles for Rechargeable Lithium-Ion Batteries

Concentration-gradient structure design is a promising strategy to stabilize layered nickel-rich LiNi_1–x–yCo_xAl_yO₂ (NCA, 1 – x – y ≥ 0.8) cathode materials. However, the influence of the particle size on the properties of concentration-gradient NCA material has not been explored in detail. Here, we report the synthesis of concentration-gradient LiNi_0.85Co_0.12Al_0.03O₂ (CG-NCA) cathode microspheres assembled with different sizes of primary particles by adjusting the calcination temperature. The prepared CG-NCA assembled with 300–500 nm primary particles exhibits remarkable cyclic stability (capacity retention of 99.9% after 100 cycles at 1 C), high rate capability (145.6 mAh g^–1 at 10 C), and thermal stability. The superior electrochemical performance is mainly attributed to the combination of the ordered layered structure and concentration-gradient distribution of Ni and Al in NCA. Small primary particles lead to a rapid impedance increase and severe side reactions, while large primary particles unfavor Li-ion diffusion. The results indicate the importance of primary particle size control in enhancing the performance of concentration-gradient Ni-rich cathode materials.