AEROSPACE CORP EL SEGUNDO CA CHEMISTRY AND PHYSICS LAB
The density of nickel electrode active materials has been measured in situ as a function of the state of charge and operating conditions of the nickel electrode. Sintered electrodes made by both chemical and electrochemical impregnation methods were studied, and the effects of cobalt additives on the density and compressibility of the active material were determined. The results clearly indicate a phase transition that occurs when the active material is charged above an oxidation state of about 2.7. The transition involves large changes in the density, volume, and compressibility of the active material. Changes in density during open circuit stand, cycling, and trickle charging have been measured and the results correlated with the operating characteristics of nickel electrodes in battery cells. Keywords Energy storage systems, Nickel sinter, Material compressibility.