Influence of surface pretreatment and charge–discharge mode on cycle performance of metal hydride electrodes

The influence of surface pretreatment and charge–discharge mode on the cycle performance of metal hydride (MH) electrodes is studied by using stable, AB5-type, hydrogen-storage, alloy particles. The initial electrochemical performance of MH electrodes, which use copper-coated and electroless nickel-plated hydrogen-storage alloy particles, respectively, is improved, but the cycle lives are the same as that of a bare MH electrode. It is considered that the cycle lives of MH electrodes depend primarily on the bulk properties of hydrogen-storage alloy particles. The pulverization of these particles is the main cause of the degradation in electrode life. In addition, it is found that overcharging accelerates the decline in the capacity of the MH electrode. The decreasing charge efficiency of the MH electrode during the course of charge–discharge cycling is due partly to the declining charge–discharge coulombic efficiency of the MH electrode, and its accumulated effect is an important cause of performance degradation of sealed MH/Ni batteries.