Aging Characterization of Nickel: Metal Hydride Batteries Using Electrochemical Impedance Spectroscopy

During a battery's lifetime, its performance slowly deteriorates because of the degradation of its electrochemical constituents. This degradation produces undesirable effects that include the loss of rated capacity, faster temperature rise during operation, less charge acceptance, higher internal resistance, lower voltage, and more frequent self-discharge. The most drastic effect is the loss of capacity. This paper presents a method to quantify the electrochemical process behind the aging of a battery by using electrochemical impedance spectroscopy as a tool to measure the change in battery parameters. While classical methods would relate battery age to impedance measurements at one specific frequency, this method measures the battery impedance at different frequencies and evaluates the variation in the frequency response spectrum with respect to battery age. The variation of the impedance spectrum from one experiment to another allows to get a better characterization of the aging process.