The aim of this study is to develop a mathematical model for the cylindrical nickel metal-hydride cell that can be used to describe discharge/charge behavior of the cell. The model was used to predict the cell performance at various discharge/charge rates, where proton diffusion and polarization effects are important.
The model includes the trend of the discharging behavior of the nickel metal-hydride cells. Also the effects of the solid-state proton diffusion and electrode's solid particle shrinking core are described. The cathode is shown to be the limited electrode and the proton diffusion resistance is the dominant factor that affects the performance of the cell at high discharge rates. Under variant constant current discharge rates conditions, a lower discharge rate results in delivering higher energy capacity.
Various discharge schemes and different parameters were analyzed for a complete bobbin cell. Different discharge methods result in disparate cell capacities. The discharge schemes take place often under constant power or load conditions. The discharge rate for a constant power or load case, however, changes with time. During a small time increment, the system of equations are solved for a constant cell current discharge. For variant discharge schemes, this model predicts that the constant load discharge possess the lowest average discharge rate, thus the largest capacity is obtained when compared to the constant power discharge which was found to deliver the lowest capacity.
Pulsed discharge is another discharge variation, and the mode can be of pulsing current, power or load. However, only pulsed current discharges are examined in this work. The effects of the controlling parameters, which govern pulse discharge, are presented. During pulsed current discharge the cell capacity is increased, by reducing overpotentials, due to the creation of more uniform concentrations.
Constant current charging is also investigated. The cycle life and performance of this battery are presented.
|Advisor:||Cheh, Huk Y.|
|School Location:||United States -- New York|
|Source:||DAI-B 70/08, Dissertation Abstracts International|
|Keywords:||Constant current charging, Metal hydrides, Nickel metal hydride battery, Pulsed discharge|
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