Enabling aqueous processing for LiNi0.80Co0.15Al0.05O2 (NCA)-based lithium-ion battery cathodes using polyacrylic acid

Replacing N-methyl-2-pyrrolidone (NMP) with water in the production of lithium-ion battery cathodes is critical to realizing process cost savings and improved worker safety. LiNi0.80Co0.15Al0.05O2 (NCA) is a poor fit for aqueous processing due to destructive Al current collector corrosion resulting from highly basic slurries and detrimental surface reconstruction reactions that occur in water. In this study, poly acrylic acid (PAA, MW = 450,0 0 0 g.mol(-1)) is examined as a corrosion-mitigating and surface-stabilizing agent. Adding PAA to an aqueous NCA slurry can provide a stable pH (4.0-8.5) for at least 4 h, since the carboxyl groups from PAA dissociate and increase the proton concentration in the slurry. These groups can also adsorb to the surface of NCA particles and provide electrostatic stability from active material particle agglomeration, as revealed by zeta potential measurements. Minor cracking does occur at the electrode surface; this cracking likely caused poorer adhesion to the Al current collector in the aqueous processed film when compared to the NMP-processed baseline. Electrochemically, the leached Li does cause a lower initial capacity for the aqueous-processed cathode, though the capacity retention of the aqueous-processed cathode is better than the baseline. The cracks in the coating led to a rise in charge transfer resistance that hindered rate capability above 1C. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the use of poly acrylic acid (PAA) as a corrosion-mitigating and surface-stabilizing agent in aqueous processing of LiNi0.80Co0.15Al0.05O2 (NCA) for lithium-ion battery cathodes. Adding PAA to the aqueous NCA slurry helped maintain stable pH and enhance electrochemical stability, but led to minor cracking and hindered rate capability. Despite lower initial capacity, the aqueous-processed cathode showed better capacity retention compared to the baseline.