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

Abstract

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.

A Ni/MH Pouch Cell with High-Capacity Ni(OH)2

“…In WM12, zinc-the γ-phase inhibitor in AP50-is replaced by aluminum, the γ-phase promoter, which results in a nominal cation composition of Ni 84 Co 12 Al 4 . After activation, WM12 has a structure consisted of a β-rich core and a α-rich shell that was confirmed by both scanning and transmission electron microscopes [7]. Although being similar in shape (both spherical), WM12 has a highly-decorated surface while AP50's surface is relatively smooth Half-cell capacity measurement results for WM12 and AP50 (using a counter electrode made with the standard AB 5 MH alloy) are shown in Figure 3.…”

“…Other than the usual transformation from β-Ni(OH) 2 to β-NiOOH during charge (and vice versa during discharge), the evolution in half-cell voltage profile of WM12 shows that once the activation (Figure 4a-c, where only a single voltage plateau is observed during charge or discharge) is complete, a transformation of α-Ni(OH) 2 to γ-NiOOH during charge (and vice versa during discharge) appears (Figure 4d,e, where two voltage plateaus are observed during charge or discharge). Although WM12 delivers a higher gravimetric energy density, its lower tap density (0.9 g·cc −1 ) [7] when compared to that of AP50 (2.3 g·cc −1 ) decreases the volumetric energy density of the battery. Details about the microstructures of WM12 at different states and after cycling were reported previously [7].…”

“…Although WM12 delivers a higher gravimetric energy density, its lower tap density (0.9 g·cc −1 ) [7] when compared to that of AP50 (2.3 g·cc −1 ) decreases the volumetric energy density of the battery. Details about the microstructures of WM12 at different states and after cycling were reported previously [7]. In this study, pouch cells made with AP50 and WM12 are identified as Cell AP50 (control) and Cell WM12 (experimental).…”

“…Ni/MH pouch cells in the ARPA-E RANGE program achieved three major accomplishments: the discovery of high-capacity Si-anode with ionic liquid electrolyte [5], use of ionic liquid as electrolyte [6], and a high-capacity β-α core-shell Ni(OH)2 positive electrode [7]. This paper elaborates on the continuing efforts to validate the third item-high-capacity positive electrode material in the pouch design tested with various regimens.…”

“…[8]; it was supplied by Eutectix (Troy, MI, USA). Positive electrode active materials (AP50 and WM12) were fabricated by a continuous stirred-tank reactor process [7,9,10] in BASF-Ovonic (Rochester Hills, MI, USA). Electrochemical charge/discharge tests were performed on an Arbin BT-2143 battery test station (Arbin, College Station, TX, USA).…”