Moisture sorption and microstructural and electrochemical properties of Nickel-rich NCM based cathodes processed in normal atmosphere

Summary:

Recently, investigations are focusing on Nickel-rich layered cathode active materials like LiNi0.8Co0.1Mn0.1O2 (NCM811) to improve the energy density of Lithium-ion batteries (LIBs), providing reversible capacities of approximately 200 mAh g-1. Unfortunately, the increase in nickel-content comes along with a higher sensitivity of the active material to moisture and carbon dioxide, which is why it is generally recommended to conduct production and processing at low dew points [1]. This leads to several challenges, as already existing production lines often do not provide the possibility of executing every process step at low dew point atmosphere. In addition, conducting the whole production route at low dew points would lead to a massive increase in costs. Manufacturers aim at meeting these challenges by either doping or coating the bulk phase, among other things, but do not provide further details about the bulk treatment or special requirements during electrode and cell production.
This is why different Ni-rich active materials (polycrystalline and monocrystalline, Nickel-content ≥ 80 mol-%) that were either doped or coated were used to produce and process LIB cathodes at normal ambient atmosphere in this study. At every process step of the electrodes, the moisture content as well as microstructural properties were analyzed. The electrochemical performance was finally tested in half coin cells.
Overall, it was shown that Ni-rich active materials produced and processed at normal atmosphere can provide good cell properties and performance, when treated with a suitable post-drying procedure before cell assembly. The best properties were achieved by a polycrystalline active material, which reached a discharge capacity of 200 mAh g-1 (after formation). Future research is necessary to show whether the current results also apply to electrochemical long-term stability. Comparative investigations in dry room atmosphere will also be carried out.

[1] C. Heck, M. von Horstig, F. Huttner, J. Mayer, W. Haselrieder, A. Kwade, Review – Knowledge-Based Process Design for High Quality Production of NCM811 Cathodes,
J. Electrochem. Soc. (2020)