Spontaneous current and DC bias induced current in nickel–metal hydride secondary battery

The responses to biasing a nickel–metal hydride secondary battery with a dc pulse train, as well as to spontaneous discharging, are studied. A comparison is made between the current during biasing, i _e, and the current during off-biasing, i _g. It is suggested that both currents arise from the motion of the same charge carriers in the electrolyte, possibly the OH⁻ ions. The only difference is that the motive force for i _e is a bias voltage, while the motive force for i _g is an open-circuit voltage of the battery. It is suggested that battery action proceeds by a single electrochemical reaction. In the course of discharging, the current drops abruptly by the formation of a resistive layer, possibly by depletion of the OH⁻ ions in the vicinity of the positive electrode.