Effect of morphology on the performance of metal-hydride electrodes

Electrochemical studies on AB(2) type Zr0.5Ti0.5V0.6Cr0.2Ni1.2 metal hydride electrodes with varying particle size suggests that the electrodes with alloy particles of about 60 mu m yield the optimum performance. The values for diffusion coefficient of hydrogen in the alloy particles > 25 mu m are found to be nearly invariant. Both a.c. impedance and linear polarization data on electrodes with varying particle size suggest that the charge-transfer resistance depends on state-of-charge of the electrodes. A comparison of scanning electron micrographs of fresh electrodes and subsequent to their prolonged charge-discharge cycling suggests that the metal hydride particles develop stress-induced cracks owing to their inherent expansion and contraction during the hydriding/dehydriding processes.