Iron-substituted AB5-type MH electrode

The present investigation is aimed to study MmNi5-type (Mm = Mischmetal) hydrogen storage alloys with composition, Mm0·8La0·2Ni3·7Al0·38Co0·3Mn0·6−xMo0·02Fex (x = 0, 0·1, 0·2 and 0·3). The alloys are synthesized by radio-frequency induction melting. To study their electrochemical properties via measurements of discharge capacity, activation process, rate capability and cyclic stability, electrodes are fabricated using as-synthesized and annealed version of the alloys. The maximum discharge capacity is recorded as 288 mAhg−1 for the iron concentration, x = 0·1, as compared to 270 mAhg−1 for the alloy electrode without iron. Similarly, 99% cyclic stability is observed in annealed alloy electrode (x = 0·1) as compared to 78% in the alloy electrode without iron. Hence, small amount of iron-substitution (x = 0·1) in the alloy is found to improve the electrochemical properties. This improvement is thought to be due to less pulverization of the alloy in electrochemically-cycled alloy, as confirmed through structural and microstructural characterizations carried out by X-ray diffraction phase analysis and scanning electron microscopy of as-fabricated and electrochemically-cycled electrodes.