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 inductionmelting. To study their electrochemical properties viameasurements 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.
Volume 43, 2020
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