Flooded utilization and electrochemical voltage spectroscopy studies on nickel electrodes

A group of standard nickel electrodes were evaluated at different test temperatures and in different electrolyte concentrations. These production quality electrodes came from different backgrounds in terms of number of charge/discharge cycles, cycling temperature, electrolyte concentration, and cobalt level in the active material. The results of the matrix of tests using the flooded utilization (FU) technique demonstrated that capacity gains are available when cycling at lower temperatures and when higher concentrations of KOH are used as the electrolyte. Electrochemical voltage spectroscopy (EVS) scans were also taken for the complete matrix of tests. Since the cycling conditions used in the FU technique are much closer to those in actual cell cycling tests, they will be emphasized in this study in regard to the capacity trends. Comparative EVS scans were helpful in displaying the shifting potentials of the charging peaks of the active material relative to the oxygen evolution characteristics of these electrodes. The voltage span between the potential at which the active material is charged and the potential at which the co-evolution of oxygen becomes a significant parallel reaction determines the charging efficiency for the recharge step and is the root cause of the differences in useable electrode capacity.