Characterization of the Materials Comprising the Reactive Interfaces in the Li ( Si )  / FeS2 Primary Battery

Abstract

Photomicroscopic, electron‐microscopic, and surface analytical studies have been conducted on normalLifalse(normalSifalse)/normalLiCl·normalKCl/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.

Composition Gradients in Electrolyzed LiCl ‐ KCl Eutectic Melts

“…In situ measurements of composition are desirable. Although valuable information can be obtained from analysis of discharged cells (5,14), diffusional and other relaxations occurring after discharge alter the reactant and product distributions established during cell operation. A closer approach to in situ measurements is provided by analysis of systems in which the compositions during current fl0w have been frozen in by quenching the cell (1).…”

Phase transition behavior of a processed thermal battery.

“…The results confirm the presence of Li 2 S which is expected for a battery under discharge. [3,6,11,12] The formation of Li 2 S appears to occur during the transition from Li 13 Si 4 to Li 7 Si 3 . The anode shows a mixture of Li 13 Si 4 and Li 7 Si 3 which is expected for a thermal battery going through transition.…”

Low-hazard metallography of moisture-sensitive electrochemical cells

“…Extensive signs of anode–cathode self‐discharge are apparent in the separator, where a layer of Li 2 S is present at the anode interface and islands of Li 2 S occur throughout. Such behaviour has been observed previously in similar cells (Burrows et al ., 1981; Redy et al ., 1987).…”