Monitoring of FeS2 Reactions Using High Temperature XRD Coupled with Gas Chromatography (GC)

Kerry-Ann M. Stirrup, Mark A. Rodriguez, James J. M. Griego, Eric N Coker, Travis M. Anderson

Sandia National Laboratories

Thermal batteries are an important technology for applications requiring long shelf-life
and high electrical power output. Sulfide compounds such as FeS2 can be employed
within these fabricated cells to generate the cathode portion of the cell. Behavior of the
cathode material in the presence of an electrolyte (often K/Li salts) as well as differing
atmospheric conditions (e.g air vs. inert) can play a role in the possible decomposition of
the sulfide cathode. We have configured our high temperature XRD system with a
portable Gas Chromatography (GC) instrument to enable in-situ characterization of iron
sulfide phases during heat treatment schedules along with simultaneous detection of off-
gassing species during such reactions. We shall report the impact of electrolyte content
as well as pO2 on the changes in iron sulfide phases and possible side reactions during
heat treatment. Results will be presented in the context of phase stability of the FeS2
compound and the impact of decomposition on the ultimate functionality of a fabricated
thermal cell.