Experimental evaluation and modeling of leaching kinetics and fine particle challenges in sodium chloride and sulfuric acid solutions for lithium-ion battery recycling plant design

Abstract

Electromobility’s growth for CO2 reduction has driven the demand for lithium-ion batteries (LIBs), which led to an increasing demand for Li, Co, and Ni with an imminent risk for production shortages. Recycling these spent batteries can mitigate production shortages, as well as disposal issues in landfilling. However, the rheology and composition of LIBs for recycling provided difficulties in the processing. The particle size distribution of LIBs provided high shear stress in the solid-liquid reactors, causing an increased water consumption from the high volume of feed material, including a significant amount of graphite, which also created difficulty in extracting metals. Thus, the study aims to evaluate leaching kinetics for spent battery recycling in different operating parameters for scale-up methodology.

Due to the rheology of fine particles in leaching, a material with similar particle size was used in leaching, which was the smelter flue dust. Different leaching parameters were varied, such as temperature, pulp density, and agitation speed, to determine the optimal parameters for reactor scaling up. High leaching recoveries were achieved with 90℃, 10% solids, and 0.68 m/s tip speed. However, upon scaling up, maintaining the impeller Re minimized the recovery due to an inefficient mixing and suspension of fine particles.

Different kinetic models were assessed based on the σ of experimental and model values and their error distribution from the bench-scale tests of NaCl-H2SO4 leaching. The first-order diffusion-controlled model, using R∞, k, and α, provided a better fit to describe the kinetic data with a mean σ of 0.83±0.1645. The high recoveries of Li, Co, and Ni from the diffusion reaction in the bench-scale tests achieved 970 mV potential of the solution in which a model was created using a neural network with the parameters – temperature, TDS, and theoretical conductivity of the reagents from the NaCl and H2SO4 solutions. This exhibited that NaCl could increase the oxidizing potential of sulfidic leaching by generating a Cl2 byproduct for battery recycling achieving high maximum metal recoveries. Utilizing the provided battery recycling simulation from Aspen Plus, it was determined as technically and economically feasible in specific conditions; however, further modifications are required to exhibit actual kinetic data, especially when handling finer sizes.