New insights in the leaching kinetics of cathodic materials in acidic chloride media for lithium-ion battery recycling

Leaching reactions in hydrochloric acid of several cathodic materials used in lithium-ion batteries were investigated between 25 degrees C and 82 degrees C. The dissolution rate increased as follows: NMC811 (LiNi0.8Mn0.1Co0.1O2) > NMC622 (LiNi0.6Mn0.2Co0.2O2) > > NMC532 (LiNi0.5Mn0.3Co0.2O2) > NMC111 (LiNi1/3Mn1/3Co1/3O2). The dissolution of lithium is faster than that for nickel, cobalt and manganese. Data analysis demonstrated that NMC dissolution is always a two-step process. In the first step, NMC was transformed very quickly into a new lithiumdefficient phase. This phase was subsequently dissolved during a second-rate limiting step. No significant impact of the solid/liquid ratio on the leaching kinetics was observed as far as the solid-liquid ratio remained below the stochiometric composition. Finally, a shrinking core model and a first-order rate law were used to investigate the leaching kinetics of the second rate-limiting step, which is the main step involved during NMC digestion in hydrochloric acid.