Characterization of the materials comprising the reactive interfaces in the li(si)/fes₂ primary battery

Photomicroscopic, electron-microscopic, and surface analytical studies have been conducted on Li(Si)/LiCl • KCl/FeS₂ electrochemical cells before and after discharge, and on individual anode and cathode components. Physical and chemical compositional changes were observed at both the anode and cathode interface that have significance in the discharge mechanism. Oxygen-rich species were found at the surface of the FeS₂ cathode particles and migration of sulfur away from the cathode during discharge was also observed. Thermal shock of FeS₂ single crystals confirmed the tendency for sulfur to move away from the bulk with the application of heat to the surface. Exposure of the Li(Si) alloy to atmosphere and/or thermal shock resulted in the formation of a lithium-rich surface in the carbonate or oxide form. These findings have significance to battery systems that must be stored for long time periods, as well as the possible source of resistive interfaces in charge and discharge cycles.