Electric batteries--Electrodes

Full nickel-hydrogen (Ni-H2) boilerplate batteries were cycled and impedance measurements were made at different states-of-charge (SOC), electrolyte concentrations and charge/discharge rates. Experiments were conducted on cells containing new and cycled (11,000 cycles) electrodes. Additionally, an EIS study of Ni-H2 flightweight IPV satellite cells was performed. A number of experiments were conducted on silver oxide-metal hydride batteries. The interest was focused on both negative and positive electrodes and upon the system itself. This work was preliminary and aided in describing the general performance of the battery. For analysis, the data was fitted to an equivalent electrical circuit using the Nonlinear Least Squares Method (NLSM). The correlation between theoretical and empirical data was sufficiently good.

An automated procedure for integrated cycling and electrochemical impedance spectroscopy (EIS) testing of nickel sinter individualized pressure vessel electrodes for secondary nickel/hydrogen batteries was developed. Nickel electrodes from three major U.S. manufacturers were cycled under various conditions. The condition of the electrodes was monitored using both EIS and traditional electrochemical methods. In order to establish relationships between the status of the electrodes and the acquired impedance spectra, various cycling and electrode parameters were analyzed and compared with the EIS data. Nonlinear least squares (NLS) regression was used for analysis of the impedance data. An equivalent circuit was developed which produced good correlation with the impedance data at all states-of-charge and discharge rates. Problems with the experimental procedure which limit the validity of EIS testing were discussed.