Effects of Pressure Fluctuations on Nickel Electrodes.
AEROSPACE CORP EL SEGUNDO CA CHEMISTRY AND PHYSICS LAB
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The rapidly fluctuating pressure environment that exists in todays nickel-hydrogen battery cells during high rate charge discharge operation can potentially act as an important source of stress to the active materials in the nickel electrodes. This study examines the coupling between the rapidly fluctuating pressure environment of hte nickel hydrogen cell and degradation of the nickel electrodes arising from expansion and contraction of the active materials. A model is developed to describe this coupling, and the sensitivity of the coupling to the parameters in the model is analyzed. The model is used to determine modes of nickel hydrogen cell operation for which the pressure environment is particularly critical in terms of potential degradation. The results indicate that cell operation involving rapid cycling or quite large dynamic operating pressure ranges may cause significant stress to the nickel electrodes, and may be an important component in degradation and failure rates. Finally, cell tests are suggested that should allow the effect of the nickel-hydrogen cell pressure environment on performance to be determined. Keywords Nickel electrode, Nickel hydrogen, Degradation, Pressure, Hydrogen.
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