Calorimetric Study of the Calcium/Sr(AICI₄)₂-SOCI₂ Battery

The behavior of Ca/Sr(AlCl4)2-SOCl2+ 7% (v/v) S02C-size cells during constant temperature discharge was studied. Fresh and stored (70°C for four weeks) cells were discharged inside a dedicated homemade calorimeter on two loads: 9.4 and 4Ω or at 30° and 55°C. The heat generation rate (WT) of the cells (thermal power) during discharge was measured as a function of discharge time. There was no significant difference between fresh and stored cells with respect to heat generation during discharge. There was no loss in capacity during four weeks of storage at 70°C. The following components of WT were calculated and plotted against discharge capacity: Ws, thermodynamic; Wp, polarization; Wc, chemical. In many cases Wp was found to be the largest component of WT. The maximum corrosion rate of the calcium anode during discharge and its minimum Faradaic efficiency (ε) were calculated from Wc on the assumption that anodic corrosion is the major component of Wc. At 30°C, E was about 0.9 while at 55°C it drops from 0.87 at 2 mA cm-2 to 0.84 at 4 mA cm-2. At 30°C the value of E is similar to that of ti of the SEI of the calcium, indicating a similar corrosion mechanism for the calcium anode (both under OCV conditions and under load). copyright.