Chemical Equilibrium Modeling of Nickel, Manganese, and Cobalt Carbonate Coprecipitation for Cathode Material Synthesis

Global trends in mobile electrification emphasize the critical importance of Li-ion battery recycling to alleviate environmental, social, and economic impacts linked to extensive mining. Recent advances in hydrometallurgical treatment of spent batteries demonstrate the streamlined recovery of transition metals, i.e., nickel, manganese, and cobalt, via cathode active material resynthesis from the acid leachate. Developing such processes requires careful consideration of the many cationic impurities present in the leachate, as they may deprive the reaction medium of complexing agents (ammonia) and precipitation reactants (either hydroxide or carbonate), potentially leading to lower recovery efficiencies. Moreover, the cationic impurities may incorporate into the crystal lattice of the resynthesized precursor, which can affect its crystallinity and morphology, both of which are crucial physical properties for subsequent processing steps. Hence, this paper presents a detailed solubility model for the coprecipitation synthesis of basic mixed metal carbonates. It demonstrates the competition among precipitating species for various precursor chemistries of LiNixMnyCozO2 (x + y + z = 1). The study involves predicting chemical equilibrium and optimizing experimental parameters to synthesize precursors with a high carbonate content while minimizing residual metal ions in the leachate. Thermogravimetric analyses coupled with mass spectrometry are used to determine the synthesized precursor carbonate and hydroxide content. Experimental results validate the predictions obtained from the chemical equilibrium model. This study provides valuable insights into the pH dependency of the coprecipitation of nickel, manganese, and cobalt basic carbonate precursors and discusses the foreseeable coprecipitation of impurities if present in the leachate.