Resumen
Three different methods were used to produce a-Ni(OH)2 with higher discharge capacities than the conventional ß-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 a-Ni(OH)2 or a/ß mixed-Ni(OH)2 with capacities higher than that of conventional ß-Ni(OH)2 and a stable cycle performance. The second method produces a special core?shell ß-Ni(OH)2/a-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 a-Ni(OH)2 nano-crystals embedded in a ß-Ni(OH)2 matrix, which helps to reduce the stress originating from the lattice expansion in the ß-a transformation. A review on the research regarding a-Ni(OH)2 is also included in the paper.