The effect of 'crystallinity' and structural disorder on the electrochemical performance of substituted nickel hydroxide electrodes

beta(bc)-Nickel hydroxide exhibit non-uniform broadening reflections in their PXRD pattern due to the presence of structural disorder. beta(bc)-Nickel hydroxide electrodes with smaller crystallite size and structural disorder reversibly exchanges 0.9e/Ni. Co/Zn/Ca/Cd-substituted beta(bc)-nickel hydroxide samples also display non-uniform broadening of reflections in their powder X-ray diffraction patterns with smaller crystallite size and exchanges 0.7-0.8e/Ni. Hydrothermal treatment of beta(bc)-nickel hydroxide slurry at 170 A degrees C results in an ordering of reflections in their powder X-ray diffraction pattern with an increased crystallite size. Crystalline beta-nickel hydroxide electrode reversibly exchanges 0.3-0.4e/Ni. Hydrothermal-treated Co/Zn/Ca/Cd-substituted beta(bc)-nickel hydroxide slurries at 170 A degrees C display sharp reflections with similar crystallite size and electrochemical activities as that of crystalline beta-nickel hydroxide. This clearly demonstrates that partial substitution of Co/Zn/Ca/Cd in the nickel hydroxide matrix does not show any dramatic improvement in their electrochemical activity at 25-30 A degrees C. Structural disordered material with smaller crystallite size delivers electrochemical activity close to theoretical capacity.