Deciphering the Impacts of Al, Fe, Li Sulfate Impurities on the Synthesis and Performances of LiNi_0.6Mn_0.2Co_0.2O₂ Cathode Materials

The recycling of LiNi 0.6 Mn 0.2 Co 0.2 O 2 cathode active material (CAM) from Li-ion batteries cannot avoid the presence of impurities in the recycled Ni-, Co-, or Mn sulfates. The precise understanding of the impurities influence on the resynthesis is of uttermost importance. To tackle this goal, this study simulated the resynthesis process by adding on purpose and separately Al-, Fe-, and Li-sulfate in the regular CAM synthesis. Their effects on the morphology, elemental composition, crystal structure, and electrochemical performances of Ni 0.6 Mn 0.2 Co 0.2 M x (OH) 2 and LiNi 0.6 Mn 0.2 Co 0.2 M x O 2 were systematically investigated for x = 0.0005, 0.005, and 0.05. The in-house reference material synthesized via a coprecipitation reaction allowed to produce a well-characterized basis. Above x Al = 0.0005, the hydroxide secondary particles lost their spherical form and above x Fe = 0.005, the crystal structure was affected. Both effects led to cell capacity decay, contrary to the discrete influence of Li. The absence of any positive effects reported by similar studies, the complexity of the various influences of these foreign ions and the limitations of the coin cells tests were pointed out. These results are a solid groundwork for future academic and industrial studies in the field of circular economy, by determining a tolerance threshold for each impurity.