Process Development for the Recovery of Manganese Dioxide, Cobalt(II) Sulfate, and Nickel(II) Sulfate Powders from the Reduction Smelted Alloys of Spent Lithium-Ion Batteries

The smelting reduction of spent lithium-ion batteries at high temperature results in metallic alloys containing cobalt, copper, nickel, and manganese, in addition to aluminum and lithium oxides. A process has been proposed to selectively recover high-purity powders of manganese dioxide, cobalt(II) sulfate, and nickel(II) sulfate from these metallic alloys. Initially, the metallic alloys were completely dissolved using a mixture of 2.0 M sulfuric acid and 15% (v/v) hydrogen peroxide with a pulp density of 25 g/L over a duration of 120 minutes. Subsequently, copper(II) ions were removed through cementation with manganese powder, and aluminum hydroxide was precipitated by adjusting the solution pH to 4.5 at room temperature. Pure manganese dioxide was then obtained from the resulting filtrate through oxidative precipitation, utilizing sodium hypochlorite as an oxidizing agent. The separation of cobalt(II) and nickel(II) was achieved via a two-stage counter-current extraction using a 20% saponified 0.5 M Cyanex 272 solution. The loaded cobalt(II) was stripped using a 0.3 M sulfuric acid solution, leading to the crystallization of cobalt(II) sulfate powders. The pH of the raffinate was adjusted to 9.0, resulting in the precipitation of nickel(II) hydroxide, which was subsequently dissolved to recover nickel(II) sulfate powders from the solution. Most of the experiments were conducted at ambient temperature, except for the evaporation stage of crystallization. Continuous experiments verified that the purity of the recovered cobalt, manganese, and nickel powders was 99.9%.