Investigation of MmFe2 electrode for nickel–metal hydride battery applications

An electrochemical investigation is made on a Mischmetal–iron (MmFe2) alloy for its suitability as an electrode for nickel–metal hydride (Ni–MH) batteries. Change–discharge characteristics, kinetics and life-cycle are studied. The charging capacity is around 350 mAh g−1, which corresponds to a hydrogen concentration of 2.62 hydrogen atoms per formula unit and 25 activation cycles are required to attain the maximum capacity. Studies with the ac impedance method show that the kinetics are controlled by the charge-transfer mechanism. The MmFe2 electrode can withstand prolonged charge–discharge with no deterioration in performance and high-rate capacity.