Particle Surface Cracking Is Correlated with Gas Evolution in High-Ni Li-Ion Cathode Materials.

High-Ni layered oxide cathode materials (LiNiTMO, where > 0.8) are of great interest because they offer increased capacity compared to current commercial materials within a narrow voltage range. However, recent studies have shown that these materials in their current form suffer from capacity fading when an upper cutoff voltage above 4.

Altering Surface Contaminants and Defects Influences the First-Cycle Outgassing and Irreversible Transformations of LiNiMnCoO.

By altering the surface of LiNiMnCoO (NMC622) we show that surface defects and contaminants dominate the outgassing and irreversible surface transformations during the first electrochemical cycle. To alter the surface defects and contaminants without changing the bulk structure of the NMC622, we perform mild methanol and water rinses, a water soak, a water rinse and subsequent heat treatment, as well as purposeful increase of the surface LiCO. By combining isotopic labeling; gas analysis; and peroxide, hydroxide, and carbonate titrations we observe that these alterations change the surface LiCO, surface hydroxides, and the local defects, which in turn alter the nature and extent of the outgassing to O and CO.