Effects of cobalt replacement by nickel, manganese, aluminium and iron on the crystallographic and electrochemical properties of AB5-type alloys

Cobalt has been partially or totally replaced by other elements such as Ni, Mn, Al or Fe in MmNi(4.07)Mn(0.63)Al(0.2)Co(0.4) composition in order to evaluate the effects on microstructure and electrochemical properties (capacity, cycle life, corrosion...). The cycle life of the electrodes for which cobalt has been replaced by nickel or manganese is strongly diminished. However, interestingly, Fe-containing electrodes behave as well as Co-containing electrodes in terms of cycle life, despite a slight capacity reduction. Moreover, the SEM picture revealed that in a similar way to Co, Fe reduces the alloy pulverisation during cycling. This result is in agreement with a low discrete lattice expansion for these Fe-containing alloys. (C) 2003 Elsevier B.V. All rights reserved.