Residual Li Compounds-Selective Washing Process for Ni-Rich Layered Oxide Cathode Materials for Li-Ion Batteries

The industrial manufacturing process for Ni-rich layered oxides for Li-ion batteries includes a washing step to remove residual Li compounds, such as LiOH and Li2CO3, from the oxide surface. However, Ni-rich layered oxides are deformed during a conventional water-based washing process, leading to the degradation of the oxide surface. In this regard, a significant challenge for Ni-rich layered oxides is to remove residual Li compounds without surface damage during a washing process. Herein, the residual Li compounds-selective washing process is introduced as a promising strategy for LiNi0.945Co0.04Al0.015O2 to suppress the degradation of the oxide surface during washing. The selectively hydrophobic LiNi0.945Co0.04Al0.015O2 powders are obtained through selective coating only on the LiNi0.945Co0.04Al0.015O2 surface with hydrophobic polydimethylsiloxane, leaving residual Li compounds uncoated. For this reason, the oxide surface is hydrophobic, whereas the residual Li compounds surface is hydrophilic. As a result, only residual Li compounds are selectively exposed to water and removed during washing, mitigating contact between the oxide surface and water. Eventually, this method suppresses the degradation of the LiNi0.945Co0.04Al0.015O2 surface during washing, resulting in the improved electrochemical performance compared to LiNi0.945Co0.04Al0.015O2 obtained through a conventional washing technique.