Self-discharge characteristics of a metal hydride electrode for Ni-MH rechargeable batteries

The factors that affect the self-discharge characteristics of a metal hydride (MH) anode are investigated, which include the state of charge (SOC), temperature, storage time and microencapsulation of the alloy with a thin copper (Cu) layer. It is found that the self-discharge rate of the MH electrode decreases with decreasing temperature and storage time. Microencapsulation of the alloy with a thin Cu layer is found to greatly decrease the self-discharge rate. Also, it is found that the self-discharge rate of the Ni-MH cells is not correlated with SOC. It is believed that the main mechanism for the self-discharge of the Ni-MH cells is related to the hydrogen release from the MH anode.