Abstract

Secondary spent Ni-Cd, Ni-MH and Li-ion batteries are motley and composite materials thus before any metallurgical recovery process, it is necessary to separate the different materials by means of mechanical pre-treatment, in this way scrap metals and plastics can be recovered and sold on the market, minimizing waste deriving from the breaking separation process. By considering the hydrometallurgical processes, they require several steps for dissolving and separating various metals. The main drawback, in recycling secondary batteries, is to separate the different types of battery because they contain not only different metals, but also different Ni and Co concentrations. This work shows as the latter problem could be overcome, by demonstrating that, whatever the resulting Ni/Co ratio in the purified solution, a codeposition of good quality Ni-Co alloy, having determined composition, can be obtained. Ni-Co alloys have been electrowon, from a pH 4 acidic sulphate catholyte containing 40 g/L Ni and Co in the range 0.1-16 g/L, at 60 °C temperature and 250 A/m² current density. A cell having cathodic and anodic compartment separated by a polypropylene membrane has been used. The electrowinning tests results have been compared with those obtained, in the same operative conditions, by using an anionic membrane. The effect of cobalt ion concentration in the electrolyte on current efficiency, specific energy consumption and on composition, morphology and structure of the produced binary alloys has been investigated.

Keywords: Anomalous co-deposition, electrowinning, hydrometallurgy, metal recovery, Ni-Co alloys, secondary battery recycling.

Graphical Abstract