Effects of Pyrite (FeS2) Particle Sizes on Electrochemical Characteristics of Thermal Batteries

In this study, effects of pyrite () particle sizes on the electrochemical characteristics of thermal batteries are investigated using unit cells made of pulverized pyrite by ball-milling. At unit cell discharge test, the electrochemical capacity of pyrite-cell largely increases compared to pyrite-cell, and their internal resistances also decrease. These results are attributed to the increase in the active reaction area of pyrite by ball milling. However, at unit cell discharge test, a pyrite cell shows lower internal resistance than that of pyrite cell only at Z-phase region (). After that, a pyrite cell shows a decrease in the cell voltage and an rapid increase of the internal resistance in J-phase region () is observed compared to those of pyrite cell. It can be concluded that at the higher temperature, the thermally unstable pulverized pyrite is decomposed thermally as well as self discharged, simultaneously, which causes the higher resistance and lower capacity at in J-phase than that of pyrite cell.