Increased Water Uptake of Li[Ni0.6Co0.2Mn0.2]O2 for Lithium-Ion Batteries in Humid Nitrogen above a Critical Gas Dew Point

Moisture management in the production of Li-ion batteries is a cost-driving and performance-affecting factor in mass production. The sorption processes that govern the interaction of cell components and the atmosphere need to be understood to optimize moisture management and mitigate degradation of electrode materials, therefore enhancing overall production efficiency. The sorption and its kinetics of the cathode active material (CAM) Li[Ni0.6Co0.2Mn0.2]O-2 (NMC-622) in a humid otherwise inert atmosphere is the focus of this experimental study via a sorption apparatus in perfusion mode. The CAM NMC-622 has a similar water uptake as a cathode with the same active material, showing the significance of the sorption of the CAM for the sorption behavior of the cathode. The kinetics of water sorption and the corresponding reversibility in NMC-622 at various distinct relative humidity (RH) have been observed. A significant increase in water uptake starts at a certain RH, showing that multiple sorption mechanisms occur. The reversibility of the sorption indicates that species other than hydroxides (e.g., Li-hydroxide) form.