A Multiphase Mathematical Model of a Nickel/Hydrogen Cell

Abstract

A mathematical model for a nickel/hydrogen cell is developed to investigate the dynamic performance of the cell's charge and discharge processes. Concentrated solution theory and the volume averaging technique are used to characterize the transport phenomena of the electrolyte and other species in the porous electrode and separaton Other physical fundamentals, such as Ohm's law, are employed to describe the electrical and other physical processes in the cell. The model is designed to predict the distribution of electrolyte, hydrogen, and oxygen concentrations within the cell, hydrogen and oxygen pressure, potential, current density, electrochemical reaction rates, and state of charge. The model can be used to evaluate the influences of all the physical, design, and operation parameters on the behavior of a nickel-hydrogen cell. The model simulations show excellent agreement with experimental data for charge and discharge operations. The model simulations show the formation of a secondary discharge plateau by the end of discharge. This plateau is caused by oxygen reduction at the nickel electrode. It is the first model that predicts this feature, which is a characteristic of the nickel electrode. The model simulations also show the existence of an optimum charge rate that maximizes the charge efficiency, which can be used for the implementation of optimal operating conditions. InfroductionIn this article we present a mathematical model for a nickel/hydrogen cell (NiOOH/H,) for charge and discharge operations. The nickel/hydrogen battery has several attractive features that make it the prime candidate for energy storage in many aerospace applications. Salient features of this battery are a long cycle lifetime that exceeds any other maintenance-free secondary battery system, high specific energy (energy/weight), high power density, and tolerance to overcharge.1

Optimization of the Cathode Long-Term Stability in Molten Carbonate Fuel Cells: Experimental Study and Mathematical Modeling

“…The cathode polarization results shown in Figure 26 agree with the previous theoretical and experimental investigations of Lee et al [20] and hence confirm the validity of the model. Electrode conductivity, σ 13 S/cm [20] Electrode conductivity, κ 1.5e -2 S/cm [21] Correction for diffusion coefficient, b 1.5 [25] Correction for conductivity, d 1.5 [25] Specific surface area at the liquid/solid interface, a (sl) 8000 cm 2 /cm 3 [27] Specific surface area at the liquid/gas interface, a …”

“…Several theoretical models have been derived for the molten carbonate fuel cathode [20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Earlier approaches to modeling the MCFC cathode have relied on empirical equations, which are restricted to the specific cathode material and design parameters for which the equations have been derived.…”

Optimization of the Cathode Long-Term Stability in Molten Carbonate Fuel Cells: Experimental Study and Mathematical Modeling

“…Prins-Jansen et al [34] and De Vidts [38,39]. As compared to the agglomerate model where macropores and micropores remain as separate entities, in this approach the pores in the electrode exist in a single continuum.…”

Modeling of a Nickel-Hydrogen Cell: Phase Reactions in the Nickel Active Material

“…Their model predicted that proton diffusion could be a limiting factor at high discharge rates. De Vidts et al 3 constructed a comprehensive nickel-hydrogen cell model, which included five reactions and processes in both gas and liquid phases. The predictions of their model showed good agreement with the data obtained from an experimental cell module.…”

“…A thermal model with the theoretical heat generation rate was developed later by Kim et al 5 Their model was used to investigate the influence of the location of heat generation on the temperature profile inside the nickel-hydrogen battery, which was found to be insignificant. The model by De Vidts et al 3 was further improved with a general energy balance, temperature dependent parameters, and simplified equations of mass balances. 6 This model predicted that adiabatic operations of a nickel-hydrogen cell were unsafe for both charge and discharge processes.…”