For industrial applications, a number of single cells are stacked to assemble a high-voltage battery module. Each of the cells are equally charged and discharged. However, a difference in the state of charge (SOC) gradually increases with the increasing self-discharge in some cells, and these cells would be overdischarged. The positive electrode material, Ni(OH)2, is coated with CoOOH to increase the active material utilization [4]. The overdischarge causes not only disruption of the CoOOH conductive network, but also degradation of the cell and module performances. The self-discharge suppression and overdischarge-resistance improvement are important requirements to maintain the battery-module performance over the long term.