Highly efficient recovery of waste LiNixCoyMnzO2 cathode materials using a process involving pyrometallurgy and hydrometallurgy

Abstract

Substantial environmental and economic benefits can be achieved by recycling used lithium-ion batteries. Hydrometallurgy is often employed to recover waste LiNi_xCo_yMn_zO₂ cathode materials. As Ni, Co and Mn are transition metals, they exhibit similar properties; therefore, separating them is difficult. Thus, most researchers have focused on leaching processes, while minimal attention has been devoted to the separation of valuable metals from waste LiNi_xCo_yMn_zO₂ cathode materials. Herein, we propose an environment-friendly, gentle process involving the usage of pyrometallurgy and hydrometallurgy to gradually leach valuable metals and effectively separate them. Interestingly, Li is recovered through a reduction roasting and water leaching process using natural graphite powder, Ni and Co are recovered through ammonia leaching and extraction processes and Mn is recovered through acid leaching and evaporation-crystallization processes. Results show that ∼87% Li, 97.01% Co, 97.08% Ni and 99% Mn can be leached using water, ammonia and acid leaching processes. The result obtained using the response surface methodology shows that the concentration of (NH₄)₂SO₃ is a notable factor affecting the leaching of transition metals. Under optimal conditions, ∼97.01% Co, 97.08% Ni and 0.64% Mn can be leached out. The decomposition of LiNi_xCo_yMn_zO₂ is a two-step process. This study provides valuable insights to develop an environment-friendly, gentle leaching process for efficiently recycling valuable metals, which is vital for the lithium-ion battery recycling industry.