Fabrications of High-Capacity Alpha-Ni(OH)2

Three different methods were used to produce α-Ni(OH)2 with higher discharge capacities than the conventional β-Ni(OH)2, specifically a batch process of co-precipitation, a continuous process of co-precipitation with a phase transformation step (initial cycling), and an overcharge at low temperature. All three methods can produce α-Ni(OH)2 or α/β mixed-Ni(OH)2 with capacities higher than that of conventional β-Ni(OH)2 and a stable cycle performance. The second method produces a special core–shell β-Ni(OH)2/α-Ni(OH)2 structure with an excellent cycle stability in the flooded half-cell configuration, is innovative and also already mass-production ready. The core–shell structure has been investigated by both scanning and transmission electron microscopies. The shell portion of the particle is composed of α-Ni(OH)2 nano-crystals embedded in a β-Ni(OH)2 matrix, which helps to reduce the stress originating from the lattice expansion in the β-α transformation. A review on the research regarding α-Ni(OH)2 is also included in the paper.