Lithium Inorganic Electrolyte Cells Utilizing Solvent Reduction

A one-dimensional mathematical model for the lithium/thionyl chloride, primary cell has been developed to investigate methods of improving its performance and safety. The model includes many of the components of a typical lithium/ thionyl chloride cell such as the porous lithium chloride film which forms on the lithium anode surface. The governing equations are formulated from fundamental conservation laws using porous electrode theory and concentrated solution theory. The model is used to predict one-dimensional, time dependent profiles of concentration, porosity, current, and potential as well as cell temperature and voltage. When a certain discharge rate is required, the model can be used to determine the design criteria and operating variables which yield high cell capacities. Model predictions can be used to establish operational and design limits within which the thermal runaway problem, inherent in these cells, can be avoided.The lithium/thionyl chloride (Li/SOC12) cell is an attractive primary energy source because of its high energy density (1, 2). However, researchers have observed that the Li/SOCI~ cell is a serious safety hazard under certain conditions (2). High discharge rates and high temperatures promote thermal runaway which can result in the venting *Electrochemical Society Student Member. **Electrochemical Society Active Member.of toxic gases and explosion. A mathematical model of this battery has been developed to investigate the operational and design characteristics which can be adjusted to yield efficient, yet acceptably safe Li/SOC12 cells.

Section: Resultssupporting

confidence: 69%

“…[34]; and conservation of current using the Butler-Volmer equation, Eq. [38]. The six unknowns are the electrolyte concentration, c; the porosity, e; the volume average velocity, v=m; the faradaic current density, i2,=; the potential in the matrix phase, (P,; and the potential in the solution phase, q~2.…”

Section: C)e Solid Phases Sikvimentioning

confidence: 99%

A Mathematical Model of a Lithium/Thionyl Chloride Primary Cell

Evans

Nguyen

White

1989

“…Therefore, the maximum capacity of the cell can be calculated based on the volume available for LiCl precipitation. According to reaction 1, Faraday's law gives [18] Using the porosity and thickness values prior to assembly (i.e., d m o and ⑀ m o ) the maximum capacity would be 11.3 Ah, while capacities as high as 16.2 Ah were observed experimentally. The extra capacity can be attributed to the increased volume due to cathode swelling.…”

Section: Resultsmentioning

confidence: 99%

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

Jain

Nagasubramanian

Jungst

et al. 1999

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.

“…The conductivity data were analyzed using the following equation (7) A = A~ --S(~c) 1/2 + E(ac)ln(~c) + Jl(ac) 2 r Js(aC) 3/2 --AaCy*_S/(K%yn) [3] The Onsager and Fuoss-Onsager constants S and E were calculated using the present value for the dielectric constant of SOC12 and a value of 0.626 cp for the viscosity at 25~ (6). The remaining terms in Eq.…”

Section: Results and Data Analysesmentioning

confidence: 99%

Conductivities in Thionyl Chloride

Salomon

1981

Conductivity measurements in thionyl chloride are reported for dilute solutions of AICIs, LiAICI4, and the tetrapropylammonium (Pr4N) salts Pr4NCI, Pr4NCIO4, Pr4NAICI4. The data for electrolyte solutions having concentrations in the range of ,,,0.01 to 1 X 10 -5 mole dm -~ were fitted empirically to an equation of the Fuoss-Hsia type. In all cases except for AICIs ion pair formation was found to he extensive. AICIs solutions in thionyl chloride appear to be complex possibly owing to the formation of complex species such as A12C18 and AIsCIT-. The effect of ionic strength on the solubility of LiCl is discussed.In addition to the interesting general solvent properties of thionyl chloride (1), this solvent has received considerable attention as a cathode depolarizer in primary lithium batteries (2, 3). A number of important physico-chemical properties of electrolytic solutions have been reported (1, 4) including the conductivities of LiA1C14 solutions (4). In the present paper, the conductivities of dilute solutions (between 0.01 and 1 • 10 -5 mole dm -8) of various salts including L!A1C14 are reported and analyzed in accordance with an ion pairing model. The dielectric constants and densities of the pure solvent over a small temperature range are also reported. ExperimentalChemicals.--Purified LiA1C14 was supplied by W. K.Behl of this laboratory and was purified as described previously (3). Fluka purris A1C13 was sublimed in vacuum and transferred to a dry box while under vacuum. Tetrapropylammonium perchlorate (Pr4NC104) was recrystallized from distilled water, and Pr4NC1 was precipitated from an acetone/ether mixture: both salts were dried in a vacuum at 60~ and stored in the dry box. AR grade LiC1 was dried at 110~ and stored in the dry box. Tetrapropylammonium tetrachloroaluminate, Pr4NA1C14, was prepared in the dry box by mixing stoichiometric quantities of A1CI~ and Pr4NC1 followed by addition of the solvent. SOC12 (MC/B best grade) was refluxed with P205 at room temperature for 24-48 hr before distillation: the middle 2/3 of the colorless distillate was retained for use. A Vacuum Atmospheres Corporation dry box with an argon atmosphere was used in this work.Dielectric constant measurements.--The static dielectric constants at 15 ~ 25 ~ and 35~ were measured by the comparison method (5), The cell, which utilized Type 304 stainless steel, consisted of concentric steel electrodes threaded onto a Teflon base which also formed part of a water jacket. The cell capacitances were measured at 1 MHz by a substitution method with a General Radio 1606-B bridge and 722-D and 1422-ME precision capacitors. The cell constants were deter-* Electrochemical Society Active Member. mined from measurements with air, benzene, and tetrahydrofuran. The cell was filled with SOC12 in the dry box, sealed with a Teflon stopper, and removed to the laboratory for capacitance measurements at 15 ~ 25 ~ and 35 ~ -4-0.1~ Conductivity measurements.--These measurementswere carried out at 25 ~ __ 0.03~ (uncalibrated thermometer) at 1 kHz using a...