Selective electrodeposition of Co-Ni alloys from synthetic quasi LiB NMC 532 cathode sulphate solutions using rotating plate potentiostatic electrowinning

Abstract

The interest in recycling spent lithium-ion batteries (Li-ionB) has surged due to the rising demand for valuable metals (e.g., Co, Ni, Li and Mn) and concerns about environmental repercussions emanating from conventional battery waste disposal. This research is centered on the recovery of the valuable Ni-Co alloys from synthetic Ni, Co, Mn and Li sulphate solutions mimicking the NMC 532 ratio of elements using a hydro-electrometallurgy process route that integrates hydrometallurgy and potentiostatic electrometallurgy techniques. This quasi-model is done to elucidate the effect of multiple influencing parameters, through isolation and varying, on the selective electrodeposition of Co-Ni from multi-ion (Li, Ni, Mn and Co) complex solutions before applying it using real cathode leachates. The selective electrowinning metal recovery process route is a cost-effective alternative to the energy, cost and material-intensive hydrometallurgy intermediate purification processes such as solvent extraction, selective precipitation, and ion-exchange. The study delves into the effects of various electrowinning parameters, including applied potential, temperature, pH, Co, Ni, Na2SO4, NaH2PO4 buffer concentration, and cathode rotational speed. These parameters were thoroughly investigated and effectively optimised to achieve the recovery of 98.2% pure Ni0.65Co0.35 at a rate of 0.060 g/cm2.h with an impressive 89.25 % current efficiency. The composition of the electrowon deposit was meticulously quantified using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and subjected to analysis through a Scanning Electron Microscope (SEM-EDS). Additionally, the phase composition was evaluated using X-Ray Diffraction analysis (XRD). The results successfully demonstrate the technical feasibility of recovering Ni-Co alloys, yielding high quantities of industrial-grade pure Ni-Co alloys. This comprehensive electro-hydrometallurgical process, designed for both closed and loop recycling purposes, promotes a more environmentally preservative approach to recycling spent lithium-ion battery cathode material. The approach contributes significantly to the development of sustainable resource management infrastructure.