Investigations of AB5-type negative electrode for nickel-metal hydride cell with regard to electrochemical and microstructural characteristics

In the present investigation, AB5-type hydrogen storage alloys with compositions Mm0.8La0.2Ni3.7Al0.38Co0.3Mn0.5Mo0.02 and Mm0.75Ti0.05La0.2Ni3.7Al0.38Co0.3Mn0.5Mo0.02 are synthesized by radio-frequency induction melting. The electrochemical properties are studied through the measurements of discharge capacity, activation process, rate capability, self-discharge rate and cyclic stability of both the electrodes. Pressure-composition isotherms are plotted by converting the electrode potential into the hydrogen pressure following the Nernst equation. The structural and microstructural characterizations are performed by means of X-ray diffraction phase analysis and scanning electron microscopy of as-fabricated and electrochemically tested electrodes. An attempt is made to correlate the observed electrochemical properties with the structural–microstructural characteristics.