Abstract
Nickel hydroxide is the positive electrode material of Ni-Cd, Ni-Fe, and Ni-MH secondary batteries. The hydroxides of Ni(II) are known to crystallize in two polymorphic modifications known as α and β. α-Nickel hydroxide have attracted considerable attention over the past decade because of its higher theoretical capacity and better cycling stability than β-nickel hydroxide. In this dissertation, we focus on the synthesis, characterization and application of α-nickel hydroxide in Ni-Fe battery. In chapter 3, the novel semi-solid reaction method and the coordinate precipitation method are developed to synthesize α-nickel hydroxide nanoparticles, and the particles are characterized using several techniques to determine their particle size, morphology, phase stability, tap density, surface area, and electrochemical capacity. The tap density of the particles is around 1.0–1.1 g/cm3, and the capacity is about 290–300 mAh/g under 0.5C condition. The size and morphology of particles synthesized by the semi-solid reaction is 40–50 nm long, needle-like structure. The product from the coordinate precipitation is 25–40 nm in diameter and sphere in shape.In chapter 4, α-nickel hydroxide particles are aggregated by two different methods, i.e. isoelectric point method and freeze/thaw method. The results show that the primary nano-particles of α-Ni(OH)2 forms micro-sized particles, the tap density of α-nickel hydroxide increases to 1.3–1.4 g/cm3 and the capacity increases to 330 mAh/g through both methods. The primary particles of α-nickel hydroxide form hard agglomerates through the freeze/thaw method and remain aggregated even after sonication.In chapter 5, β-cobalt hydroxide is synthesized by the semi-solid reaction, and the product has 40–50 nm long, needle-like structure. The conducting agent, β-cobalt hydroxide, is added to α-nickel hydroxide paste to prepare the nickel electrode, and the capacity of α-nickel hydroxide is 230 mAh/g under 5C, which is better than commercially purchased cobalt oxide powder. In chapter 6, the spherical nanoparticles obtained by the coordinate precipitation method are used to prepare slurries for dynamical particle sizing test to investigate its coagulation behavior. The effects of both solid content and solution pH are studied. Generally, particles aggregate more rapidly when the solid content is high and when the solution pH is near its isoelectric point. The stability ratio, defined as the ratio of the fast coagulation rate to the present coagulation rate, is a fuction of these two parameters. We then develop an empirical equation to correlate this ratio to the solid content of the suspension and zeta potential of particles. We also develop another empirical equation to correlate the tap density of coagulated particles to both the solid content of the suspension and zeta potential of particles.