Superiority of Single-Crystal to Polycrystalline LiNixCoyMn1–x–yO2 Cathode Materials in Storage Behaviors for Lithium-Ion Batteries

High nickel content LiNixCoyMn1–x–yO2 (NCM) cathode materials have been attracting increasing attention owing to their significant advantages, but in practical application, because of their poor storage performance their production and transportation cost a lot. The gap between polycrystalline particles can very easily become the site where impurities are first generated; thus, whether the single crystal structure will affect the storage properties of high nickel content NCM materials is worth studying. In this work, we take two typical high nickel content ternary materials, LiNi0.8Co0.1Mn0.1O2 (NCM811) and LiNi0.6Co0.2Mn0.2O2 (NCM622), as samples to study the differences in properties of single-crystal and polycrystalline materials after storage. Through comparative research, under the same storage conditions, the single-crystal structure materials have significantly less impurities formed on the surface, the structural stability of materials is obviously better, and they can also exhibit superior electrochemical performance after storage. Particularly for the NCM811 materials with a higher nickel amount, the specific capacity of polycrystalline NCM811 materials basically comes nearly to zero after storage, but the single-crystal structure NCM811 materials can still perform a relatively stable cycle with a certain capacity. It can be concluded from the work that for high nickel content NCM cathode materials, the single-crystal structure can greatly improve its storage performance.