Effect of separators on the self-discharge reaction in nickel-metal hydride batteries

The effects of separators on the self-discharge behavior and the suppression of self-ischarge by a sulfonated polyolefn separator were investigated with test cells. The experimental results indicate that a sulfonated polyolefin separator effectively suppresses the self-discharge reaction in nickel-metal hydride batteries. It is also found that a suffonated polyolefin sheet does not necessarily need to be sandwiched by positive and negative electrodes to act as a separator; it can be placed anywhere within a cell to suppress the self-discharge reaction. The self-discharge reaction is considered to be suppressed by trapping redox shuttle substances, especially nitrogen-containing compounds, by the separator.