Mathematical model of a NiOOH/metal hydride cell. Final report, September 15, 1993--November 14, 1996 Page: 4 of 9
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One of the objectives of our work on the nickel/metal hydride cell has been
to develop a mathematical model of the performance of the cell. We have
had three sources of funds for our work on the nickel/metal hydride system:
ORD 93-F148100-100, LBL Contract DE-ACO3-78SF00098, Subcontract No
4614610 and BES DE-FGO5-93ER14382. This is a summary of our work to
date based on these funding sources and is meant to be a Final Report for our
Mathematical model of the nickel/metal hydride cell depends on the kinetics,
thermodynamics, and transport properties of the metal hydride electrode. Con-
sequently, investigations were carried out to determine: (i) the exchange current
density and the equilibrium potential as a function of hydrogen content in the
electrode; (ii) the hydrogen diffusion coefficient in the bulk of the alloy; (iii) the
hydrogen reaction rate order; (iv) the symmetry factor for hydrogen evolution
reaction and (v) to determine the reaction mechanisms of the hydrogen charge
and discharge processes including overcharge and overdischarge mechanism.
Investigations carried out at the Center of Electrochemical Engineering at
USC have resulted in development of a mathematical model for the discharge
performance of NiOOH-MH cell. The model can be used to study the effect
of various parameters on predicted discharge curves. The solutions obtained
using the model showed the expected decrease of charge utilization as the rate
of discharge is increased. Increasing the particle size of the alloy and decreasing
the diffusion coefficient of the hydrogen atoms in the hydride showed a similar
effect on the discharge curves. The model simulations also show the critical role
that the kinetic transport parameters play in the determining the overall shape of
the predicted discharge curves for a metal-hydride electrode.1
Porous electrode theory was applied to estimate the exchange current den-
sity, the polarization resistance, and symmetry factor for LaNi4.27Sn0.24 hydride
electrode in alkaline solution.2 It was found that conventional Tafel polarization
method cannot be applied for the porous metal hydride system due to the presence
of internal mass transfer effects and internal ohmic voltage drop of the electrode.
Potentiostatic and galvanostatic techniques were developed to deter-
mine the diffusion coefficient of hydrogen through MH electrodes in al-
kaline aqueous solutions.3 Using this technique the transport properties of
Lao.65Ceo.35Ni3.55Co0.75Mn.4Al0.3 alloy were determined in alkaline solution.4
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White, R.E. & Popov, B.N. Mathematical model of a NiOOH/metal hydride cell. Final report, September 15, 1993--November 14, 1996, report, December 31, 1996; United States. (digital.library.unt.edu/ark:/67531/metadc677422/m1/4/: accessed November 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.