Synthesis of Quasi-spherical LiNi0.86Mn0.1Co0.04O2 Cathode Particles via Hydroxide Coprecipitation: Influence of pH on Precursor Particle Size in Enhancing Capacity and Stability of Ni-Rich Cathode for Lithium-Ion Batteries

Abstract

Ni-rich Li[Ni_0.86Mn_0.1Co_0.04]O₂ cathode with low cobalt content is synthesized using the hydroxide coprecipitation method at distinct pH levels and primary particles of different sizes are obtained. The pH during synthesis significantly influences the nanostructure of the Ni_0.86Mn_0.1Co_0.04(OH)₂ precursors. Consequently, it affects the evolution of primary particle size and the cation ordering in the layered structure, characterized by the I₍₀₀₃₎/I₍₁₀₄₎ intensity ratio in the final lithiated Li[Ni_0.86Mn_0.1Co_0.04]O₂ cathode. The electrochemical performance reveals that the cathode with the largest primary particles synthesized at pH 11.25 (LNMC-25) exhibits superior electrochemical properties compared to those synthesized at pH 11.0 and 11.5. The LNMC-25 cathode exhibits a high reversible capacity of 205.8 mAh g⁻¹ at 67 mA g⁻¹, with an initial Coulombic efficiency of 96.3% and a capacity retention of 75.3% after 150 cycles, demonstrating superior performance compared to cathodes prepared at other pH levels, along with minimal voltage hysteresis. This study emphasizes the critical role of pH optimization in the synthesis of Ni-rich cathodes, demonstrating that pH control regulates hydroxide precursor growth and primary particle size via the (001) facet. This influences the particle morphology and cation ordering in the final cathode, enhancing electrochemical performance by mitigating surface-side reactions and minimizing voltage hysteresis.