Investigations of AB_5-type negative electrode for nickel-metal hydride cell with regard to electrochemical and microstructural characteristics

摘要

In the present investigation, AB_5-type hydrogen storage alloys with compositions Mm_(0.8)La_(0.2)Ni_(3.7)Al_(0.38) Co_(0.3)Mn_(0.5)Mo_(0.02) and Mm_(0.75)Ti_(0.05)La_(0.2)Ni_(3.7)Al_(0.38)Co_(0.3)Mn_(0.5)Mo_(0.02) 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.