Alleviating the anisotropic microstructural change and boosting the lithium ions diffusion by grain orientation regulation for Ni-rich cathode materials

Abstract

Generally, layered Ni-rich cathode materials exhibit the morphology of polycrystalline secondary sphere composed of numerous primary particles. While the arrangement of primary particles plays a very important role in the properties of Ni-rich cathodes. The disordered particle arrangement is harmful to the cyclic performance and structural stability, yet the fundamental understanding of disordered structure on the structural degradation behavior is unclarified. Herein, we have designed three kinds of LiNi_0.83Co_0.06Mn_0.11O₂ cathode materials with different primary particle orientations by regulating the precursor coprecipitation process. Combining finite element simulation and in-situ characterization, the Li⁺ transport and structure evolution behaviors of different materials are unraveled. Specifically, the smooth Li⁺ diffusion minimizes the reaction heterogeneity, homogenizes the phase transition within grains, and mitigates the anisotropic microstructural change, thereby modulating the crack evolution behavior. Meanwhile, the optimized structure evolution ensures radial tight junctions of the primary particles, enabling enhanced Li⁺ diffusion during dynamic processes. Closed-loop bidirectional enhancement mechanism becomes critical for grain orientation regulation to stabilize the cyclic performance. This precursor engineering with particle orientation regulation provides the useful guidance for the structural design and feature enhancement of Ni-rich layered cathodes.