Hot alkaline treatment on hydrogen storage alloys in sealed Ni/MH batteries

Abstract

In the production of Ni/MH batteries the activation after sealing process was adopted and the free internal space is closed to the limit margin, which usually results in quality problems, including high internal pressure, electrolyte leakage and short cycle life during the activation and overcharging at high rates. In the present research we have directed our attention to the hot alkaline treatment conditions and the electrochemical properties of the treated Ni/MH batteries using AB5 or AB2 alloys as the negative electrodes. It is found that for Ni/MH batteries the hot alkaline treatment can decrease the internal pressure significantly, even when the battery is overcharged at high rates, for example 1 C, and the comprehensive characteristics are improved, especially the durability of Ni/MH batteries. The hot alkaline treatment can also shorten the activation to one single charge and discharge cycle at 0.2 C. The hot alkaline treatment also offers the possibility to provide more internal space for positive and negative electrodes to increase the battery capacity.