Advances of high-performance LiNi1-x-yCoxMyO2 cathode materials and their precursor particles via co-precipitation process

Layered LiNi1-x-yCoxMyO2 (M = Mn or Al) is a promising cathode material for lithium-ion batteries due to its high specific capacity and acceptable manufacturing cost. However, the polycrystalline LiNi1-x-yCoxMyO2 cathode material suffers from disordered orientation of primary particles and poor geometric symmetry of secondary particles, which severely hampers the migration of Li thorn ions. Furthermore, the resulting anisotropy accelerates the disintegration of the secondary particle structure, significantly affecting the electrochemical performance of the polycrystalline cathode. In spite of less grain boundary, the single-crystal LiNi1-x-yCoxMyO2 cathodes still suffer from severe microcracks generated by repeated planar gliding during cycling, which poses a great challenge to the cycling stability of single-crystal materials. It's worth noting that the microstructure of the cathode material is mainly inherited from its precursor. Therefore, it is necessary to deeply understand the influence of the microstructure of Ni1-xyCoxMy(OH)2 on the electrochemical properties of LiNi1-x-yCoxMyO2 cathode materials, so as to optimize the production process of preparing high-performance cathode precursors. In this review, we summarize recent advances in the research and development of Ni-rich cathode precursor materials. Firstly, the challenges faced by the Ni-rich hydroxide precursor materials are presented, including the effect of primary particle morphology and arrangement on the electrochemical performance of cathode materials, the influence of secondary particle morphology on lithium insertion reactions in cathode, and the effect of particle size on the microcracking of single-crystal particles. Secondly, the presentation of the conventional co-precipitation reactor, the mechanism of precursor particle growth, and the influence of coprecipitation parameters are described in detail. Finally, the strategies are systematically discussed to solve the challenges of hydroxide precursors, such as the innovation and optimization on reactants, synthesis processes, and reaction equipment. To obtain satisfactory high-quality precursor materials, future work will require an in-depth understanding of the reaction mechanism, combined with simulation techniques such as flow field theory calculations to guide the synthesis of precursors. This review provides a comprehensive analysis of the current progresses on the producing technologies of highperformance cathode precursors and offers prospects for future industry developments. & COPY; 2023 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).