(400e) Effect of Compositional and Structural Disorders on Electrochemical Properties in Substituted Nickel Hydroxide Spherical Powders
Nickel hydroxide for nickel-metal hydride and nickel-cadmium battery cathodes is known for its layered structure and is intrinsically insulative when in a single, perfect crystal form. Defects and stacking faults within the crystal structure facilitate the transport of electrons and protons required for the electrochemical reduction-oxidation reactions to occur. The (101) and (102) peak broadenings observed in the nickel hydroxide x-ray diffraction (XRD) patterns are key indicators of crystallite size that are theorized to be related to the degree of stacking faults within the crystal structure. The contributions of such subtle defects to the bulk crystal structure can be difficult to discern experimentally. We implement tools such as DIFFaX simulations of XRD patterns to elucidate the effect of stacking faults on nickel hydroxide electrochemical performance. Common co-precipitants, such as Co and Zn, also introduce compositional disorder into the material and have an effect on the degree of stacking faults and the electrochemical performance. The substituted nickel hydroxide spherical powders studied have high tapping densities and small crystalline sizes required for good battery performance, and reach up to 360 mAh g-1 of Ni(OH)2, an equivalent of 1.24 e- transferred per Ni. Insights into the disorder of nickel hydroxide materials and their effects on electrochemical performance provide another avenue for the optimization and design of layered active materials for battery applications.