Mathematical Modeling of the Lithium, Thionyl Chloride Static Cell: I . Neutral Electrolyte

A one-dimensional mathematical model of a spirally wound lithium/thionyl chloride primary battery is developed and used for parameter estimation and design studies. The model formulation is based on the fundamental conservation laws using porous electrode theory and concentrated solution theory. The model is used to estimate the transference number, the diffusion coefficient, and the kinetic parameters for the reactions at the anode and the cathode as a function of temperature. These parameters are obtained by fitting the simulated capacity and average cell voltage to experimental data over a wide range of temperatures (Ϫ55 to 49ЊC) and discharge loads (10-250 ⍀). The experiments were performed on D-sized, cathode-limited, spirally wound lithium/thionyl chloride cells. The model is also used to study the effect of cathode thickness on the cell capacity as a function of temperature, and it was found that the optimum thickness for the cathode-limited design is temperature and load dependent.

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confidence: 95%

Section: Cathode Dimension (Effect Of Swelling)-thementioning

confidence: 99%

Analysis of a Lithium/Thionyl Chloride Battery under Moderate‐Rate Discharge

Jain

Nagasubramanian

Jungst

et al. 1999

“…One assumption usually implicit when formulating the material balance for a one-dimensional model of a porous electrode is that the volume is conserved during reaction (see, for example, Ref. [1][2][3]. However, if the volume of the reactants is not equal to that of the products, then a volume change results due to the reaction.…”

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confidence: 99%

Material Balance Modification in One‐Dimensional Modeling of Porous Electrodes

Jain

Weidner

1999

The material balance used previously in one-dimensional mathematical models of porous electrodes is invalid when there is a nonzero volume change associated with the reaction. It is shown here how the material balance should be modified either to account for a loss in volume, or to account for an inflow of electrolyte from the header into the active pores. A one-dimensional mathematical model is used to illustrate the effect of this correction on the prediction of the delivered capacity and the electrolyte concentration in a lithium/thionyl chloride primary battery.

“…Other modeling efforts employed concentrated solution theory and porous electrode theory in the various regions of the cell (e.g., separator, porous cathode) to develop one-dimensional models of the battery. [3][4][5][6] These models examined utilization issues at low to moderate currents, but they differ in how the excess electrolyte was treated.In the lithium/thionyl chloride cell, the solvent is also the reactant, and the volume it occupies is more than that of the reaction products. Therefore, more electrolyte is placed in the cell than can occupy the initial void volume of the separator and porous cathode.…”

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confidence: 99%

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confidence: 99%

Computational Fluid Dynamics Modeling of a Lithium/Thionyl Chloride Battery with Electrolyte Flow

Wang

Weidner

et al. 2000

This paper is a continuation of the recent series of work to explore computational fluid dynamics (CFD) techniques in conjunction with experimentation for fundamental battery research. The application of interest in this work is a lithium/thionyl chloride primary battery. As a power source, this battery has many desirable characteristics such as high energy and power densities, high operating cell voltage, excellent voltage stability over 95% of the discharge, and a large operating temperature range. As such, there has been a number of one-dimensional modeling studies [1][2][3][4][5][6] in the literature. Modeling efforts by Szpak et al. 1 and Cho 2 focused on the battery's high-rate discharge and the ensuing thermal behavior. Other modeling efforts employed concentrated solution theory and porous electrode theory in the various regions of the cell (e.g., separator, porous cathode) to develop one-dimensional models of the battery. [3][4][5][6] These models examined utilization issues at low to moderate currents, but they differ in how the excess electrolyte was treated.In the lithium/thionyl chloride cell, the solvent is also the reactant, and the volume it occupies is more than that of the reaction products. Therefore, more electrolyte is placed in the cell than can occupy the initial void volume of the separator and porous cathode. The excess electrolyte resides in the head space volume above the active regions. Due to the one-dimensional nature of their models, Tsaur and Pollard 3 and Evans et al. 4 introduced a fictitious reservoir region between the separator and the porous cathode. In these models, the electrolyte fills uniformly from this reservoir region, through the separator, and into the cathode. In contrast, Jain et al. 5,6 modified the one-dimensional equations so that the electrolyte flows from the head space directly into the porous cathode, thus replicating flow in a second, perpendicular direction. An advantage of this latter approach is that the model can predict the drying of the cell due to insufficient electrolyte loading. While these one-dimensional models are simple and efficient at predicting the discharge of a Li/SOCl 2 battery, a multidimensional model fully accounting for the electrolyte flow without making ad hoc approximations is deemed valuable to gain a more fundamental understanding of the processes that occurr in this battery system. The present paper describes such a model and a finite-volume method of CFD to simulate a Li/SOCl 2 battery in the operating regime of low to intermediate discharge rates. The model uses the physical parameters estimated from experimental data 6 to predict discharge curves accurately at various temperatures. Numerical ModelDescription of a Li/SOCl 2 system.-A schematic of a lithium/ thionyl chloride (Li/SOCl 2 ) cell is shown in Fig. 1. The system is identical to the one studied most recently by Jain et al. 5,6 Basically, the cell consists of a lithium foil anode and LiCl film, a separator (glass matting), and a porous carbon cathode support with the ...