Cathode Performance Improvement in Calcium‐Thionyl Chloride Cells

Abstract

Carbon cathode performance in ealcium-thionyl chloride cells was markedly improved with a cathode comprised of a mixture of high and low surface area carbon blacks. Addition of sulfur dioxide gas to the electrolyte further enhanced cathode performance and electrolyte conductivity. Load potentials and cathode life were nearly equal to that of the analogous lithium based system. The advantage of the calcium based system is its potential for greater safety.The calcium-thionyl chloride battery system has been attracting considerable attention (1-6) for its high opencircuit potentials (->3.2V), high theoretical energy density (1100 Wh/kg), broad operating temperature range~ and projected high degree of system safety. This increased safety is due to the high melting point of calcium metal (839 ~ vs. 180~ for lithium) which precludes the likelihood of difficulties traceable to a molten anode.

Current Understanding of Nonaqueous Electrolytes for Calcium‐Based Batteries

“…Additional studies examined effects of SO2 gas additive, which further increased ionic conductivity. [39][40][41][42] For example, adding 10% (v/v) SO2 to 1.3 M Ca(AlCl4)2/SOCl2 led to an increase from ~6 to ~11 mS/cm at 25°C. [39] SO2 was also found to increase capacity, though this was proposed to be a physical rather than chemical effect resulting largely from physical release of SO2 at the cathode during discharge, increasing porosity and postponing cathode passivation.…”

“…[39] SO2 was also found to increase capacity, though this was proposed to be a physical rather than chemical effect resulting largely from physical release of SO2 at the cathode during discharge, increasing porosity and postponing cathode passivation. [40,43] The reasons underlying improvements in ionic conductivity were not well understood until fundamental studies were conducted into Ca 2+ solvation in the analogous Ca-sulfuryl chloride (SO2Cl2) system. In 1982, Binder et al reported the Ca-SO2Cl2 primary battery as a potential improvement to Li-SO2Cl2.…”

Calorimetric Study of the Calcium / Sr ( AlCl4 ) 2 ‐ SOCl2 Battery

“…Thus Eq. [6] holds for this calorimeter up to a temperature difference of about 3.6~ where the experimental K value is 0.6 W/~ At higher temperature differences air convection starts to be appreciable, and this leads to nonlinearity.…”

“…1. This type of calorimeter is based on Newton's law dq/dt = W = K(T~ -T2) [6] where K is the thermal leakage factor of the calorimeter (i.e., of the thermal conductor around the internal cham- Equation [6] is valid only for temperature differences smaller than 2~176 (22). We found that choosing the heat conductor is not a simple task.…”

“…The calcium-thionyl chloride battery has recently attracted attention as a safer alternative to high-power lithium batteries (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). The major drawback of this system (the corrosion of the calcium anode) has been recently solved (10,14) by replacing the Ca(A1C14)2 electrolyte by either Ba(A1C14)2 or Sr(A1CI4)2.…”