Study on the influence of ammonium sulfate on the grain growth behavior in manganese electrodeposition

To investigate the impact of ammonium sulfate concentration on the growth of manganese grains, this study was conducted under controlled conditions with a constant Mn²⁺ concentration of 20 g/L, Mg²⁺ concentration of 20 g/L, and current density of 450 A/m². By varying the electrodeposition duration, the effect of (NH₄)₂SO₄ concentration on the morphology and growth kinetics of electrodeposited manganese grains was examined. The results indicate that the growth of metallic manganese follows the screw dislocation mechanism, resulting in cauliflower-like grain structures. Regardless of the (NH₄)₂SO₄ concentration, all electrodeposited manganese exhibited an α-Mn crystal structure with a preferred orientation at the (411) plane. As the (NH₄)₂SO₄ concentration increased from 80 g/L to 120 g/L, the growth rate of manganese grains initially decreased and then increases. At lower concentrations of (NH₄)₂SO₄, grain growth was non-uniform, with some grains exhibiting preferential growth, while higher concentrations promoted uniform grain development. An optimal (NH₄)₂SO₄ concentration of 110 g/L yielded high current efficiency, along with lower cell voltage, and reduced energy consumption, making it the most favorable condition for economic performance.