Requirement of high lithium content in Ni-rich layered oxide material for Li ion batteries

The formation of lithium residuals in Ni-rich nickel cobalt manganese oxide is inevitable, due to of the cation mixing by Ni2+ and excess Li required for high energy density. The purpose of this study is to examine the role of Li content in such materials after the washing process, which could reduce Li residuals and enhance the electrochemical performance of lithium ion batteries containing Li1.0Ni0.91Co0.06Mn0.03O2 (NCM) as the cathode. The washing process reduced the Li residuals on the surface as well as the Li in the NCM structure. When a low Li content is used in the NCM, the Li content remaining in its structure after washing is lower than 1 mol. This removal of Li residues from the surface after washing leads to a capacity drop in spite of the improved cycle retention. Therefore, a high Li content is required in order to obtain enhanced electrochemical performance of high-Ni NCM. This trend regarding the Li content is also shown for NCM with small particle size.