Wet-CO₂ Pretreatment Process for Reducing Residual Lithium in High-Nickel Layered Oxides for Lithium-Ion Batteries

As the push for inexpensive vehicle electrification grows, high-energy-density cathodes for lithium-ion batteries, such as high-nickel layered oxides, have received a great deal of attention in both industry and academia. These materials, however, suffer from severe residual lithium formation, which causes slurry gelation during electrode fabrication and gas evolution during cycling. Herein, a novel cobalt hydroxide coating method on wet-CO₂ gas-treated LiNi_0.91Mn_0.03Co_0.06O₂ (Co-CO₂-NMC91) is presented. Notably, the wet-CO₂ treatment prior to a dry cobalt hydroxide coating plays a critical role in improving the coating uniformity and ultimately decreases the effective residual lithium content. Furthermore, full cells of Co-CO₂-NMC91 exhibit excellent capacity retention of 91% after 200 cycles. This study highlights how a wet-CO₂ treatment can be used to improve a typical dry coating and provides new insights toward the development of cathodes for high-energy-density LIBs without severe slurry gelation or gas evolution.