Mathematical Modeling of a Primary Zinc/Air Battery

Abstract

The mathematical model developed by Sunu and Bennion has been extended to include the separator, precipitation of both solid ZnO and K2Zn(OH)4, and the air electrode, and has been used to investigate the behavior of a primary Zn-Alr battery with respect to battery design features. Predictions obtained from the model indicate that anode material utilization is predominantly limited by depletion of the concentration of hydroxide ions. The effect of electrode thickness on anode material utilization is insignificant, whereas material loading per unit volume has a great effect on anode material utilization; a higher loading lowers both the anode material utilization and delivered capacity. Use of a thick separator will increase the anode material utilization, but may reduce the cell voltage.Zinc is used widely as an anode in many alkaline batteries, such as Zn]Ni and Zn/Air. Optimum designs of these batteries depend on understanding the zinc chemistry and electrochemistry in alkaline solution and the mass-transport processes in the battery during charge and discharge. While the former has been extensively investigated experimentally, only a few mass-transport models have been presented. Choi, Bennion, and Newman (1) presented a mathematical model of a secondary Zn/AgO battery for analysis of the material redistribution in the battery during charge and discharge. Their model includes convective flow caused primarily by osmosis and electro-osmosis forces. It was found that the convective flow is primarily responsible for the nonuniform zinc distribution on the electrode plate. The validity of their conclusions was verified partially by their experiments that showed virtually no zinc redistribution when the convective flow was minimized (2). Sunu and Bennion (3) developed a comprehensive model of a porous zinc electrode to investigate the electrode phenomena in the direction perpendicular to the projected electrode surface. In their model, the masstransport equations were developed based on concentrated ternary electrolyte theory. Three electrode failure mechanisms (namely, depletion of hydroxide ions, pore plugging by zinc oxide, and surface passivation) were identified by analyzing the model simulations. The validity of their model was verified by good agreement between their model predictions and experimental data of porosity and zinc oxide distributions (4). Their model was used later by Isaacson et al. (5) and Miller et al. (6) to investigate zinc movement in both the vertical and parallel directions to the electrode surface. Good agreement was obtained by Isaacson et al. (5) between their model predictions and experimental chronopotentiometric data.It should be noted that all previous mathematical models were used to study secondary batteries and that the model verification was conducted using a half cell or a ZnNiOOH cell. Previous modeling efforts were focused on the zinc electrode; and, consequently, the concentration distributions in the separator were neglected. Although the findings from such resea...

First principles investigation of zinc-anode dissolution in zinc–air batteries

“…Clearly, the Zn(0001) surface is a bad model for bulk dissolution since the overpotential is poorly estimated to be 0.70 V, far from the experimentally measured one, i.e. 0.05-0.1 V. 41,42 The reason for this huge difference is that after dissolution of a single Zn atom the surface is left with a vacancy, hence the adsorption energy is higher. Similarly, black and blue lines in Fig.…”

Computational Fluid Dynamics Approach for Performance Prediction in a Zinc–Air Fuel Cell

“…The durability of the Zn-air battery has been one-dimensionally modeled, considering the effects of ZnO precipitates [14][15][16][17]. The improved models were used to analyze the experimental discharge behavior of Zn-air batteries, involving the effects of a microporous separator and a porous air cathode [14].…”

“…The improved models were used to analyze the experimental discharge behavior of Zn-air batteries, involving the effects of a microporous separator and a porous air cathode [14]. Another model that was combined with a dilute solution approach [15] has achieved good agreement with galvanostatic experiments where the charging-discharging behavior of an electrically rechargeable Zn-air battery was investigated.…”

A Review of Model-Based Design Tools for Metal-Air Batteries

“…Their simulations showed the inhomogeneous precipitation of ZnO and investigated the shape change of the Zn electrode during cycling. In 1992, Mao and White [135] developed an extended model that also resolved the separator and air electrode. They found that K 2 Zn(OH) 4 does not precipitate and compared simulated cell voltages with experimental measurements.…”