Electrocatalytic characteristics of the metal hydride electrode for advanced Ni/MH batteries

The electrocatalytic characteristics of a metal hydride (MH) electrode for advanced Ni/MH batteries include the hydrogen adsorption/ desorption capabi lity at the electrode/electrolyte interface. The hydrogen reactions at the MH electrode/electrolyte interface an also related to factors such as the s urface area of the MH alloy powder and the nature of additives and binder m aterials. The high-rats discharge capability of the negative electrode in a Ni/MH battery is mainly determined by the mass transfer process in the bul k MH alloy powder and the charge transfer process at the interface between the MH alloy powder and the electrolyte. In this: study, an AB(5)-type hydr ogen-absorbing alloy, Mm (Ni, Co, Al, Mn)(5.02) (where Mm denotes Mischmeta l, comprising 43.1 wt.% La, 3.5 wt.% Ce, 13.3 wt.% Pr and 38.9 wt.% Nd), wa s used as the negative MH electrode material. The MH electrode was charged and discharged for up to 200 cycles. The specific discharge capacity of the alloy electrode decreases from a maximum value of 290-250 mAh g(-1) after 200 charge/discharge cycles. A cyclic voltammetry technique is used to anal yze the charge transfer reactions at the electrode/electrolyte interface an d the hydrogen surface coverage capacity. (C) 2001 Elsevier Science B.V. Al l rights reserved.