The Correlation between the Particle Morphology and the Electrochemical Stability for High-Ni Cathode and Understanding of the Mechanism of Parasitic Reaction.

Abstract

Understanding the correlation between physical and electrochemical/chemical properties are significantly crucial for the development of electrode materials for lithium ion batteries. Among the cathode materials, high-Ni cathode with high energy density has a degradation issue of electrochemical performance due to the parasitic reaction at the cathode electrolyte interface. The core-shell or full concentration gradient materials consisting of a high-Ni core and a relatively high-Mn outer layer might be a potential candidate providing the improved electrochemical stability as well as cycle life performance. In this respect, the porosity of the final sintered particle is the key to affect the electrochemical stability indicating the side reaction with organic liquid electrolyte. The strategy tuning the particle porosity and density is applied to synthesize different particle size of transition metal precursor during co-precipitation. The structural characteristics are compared for the materials with different physical properties by utilizing ex-situ or in-situ X-ray diffraction, electron microscopy, electrochemical performances, and particle size distribution. The interfacial kinetic reaction between the Ni-rich cathode and a nonaqueous electrolyte at different SOCs is investigated by our home-built high-precision leakage current measurement system. This study can give us a clear sight for understanding the mechanism of parasitic reaction as well as providing a solution for the safety issue of the high-Ni cathode in lithium ion battery.