The electrochemistry of the FeS2 , CoS2 , and NiS2 electrode phases in molten normalLiCl‐normalKCl electrolyte at 400°C was studied using cyclic voltammetry at sweep rates of 0.02–1 mV/sec. Emf's, polarization characteristics, and nucleation overpotentials were obtained for each major electrode reaction; the anodic nucleation overpotentials increased with emf for all three electrodes. The disulfide electrodes lost sulfur during the extended cyclic‐voltammetry tests. These losses appear to be associated with a nonequilibrium species that is involved in the electrochemical formation of the disulfides from their precursors.

The phases present in FeS2 electrodes operated in normalLiCl‐normalKCl eutectic electrolyte were determined by x‐ray diffraction and by metallographic examination. The phases were FeS2 , KFeS2 , Li3Fe2S4 , Li2.33Fe0.67S2 , Fe1−xS , Li2FeS2 , LiK6Fe24S26normalCl , Li2S , and Fe. The metallographic and crystallographic characteristics of these phases are presented. The sequence of Li‐Fe‐S phases in the FeS2 electrode was in accord with the sequence predicted from the equilibrium Li‐Fe‐S phase diagram. Two of the Li‐Fe‐S phases found at room temperature ( Li2.33Fe0.67S2 and Li2FeS2 ) result from decomposition on cooling of a solid solution phase: Li2+xFe1−xS2 false(0≤x≤0.33false) .

The reactions of FeS electrodes in LiC1-KC1 electrolytes of various compositions were determined by a combination of phase studies, cyclic voltammetry, and emf measurements. The effect of temperature, charge-cutoff voltage, and electrolyte composition on the phases present in the sulfide electrode were determined. Six electrochemical and four chemical reactions can occur. The emf's of three of the six electrochemical reactions were measured over a temperature range of 380~176 and were computed for the other three electrochemical reactions. The free energy changes for the chemical reactions were also calculated.* Electrochemical Society Active Member. Key words; fused salts, free energy, voltammetry, emf. potential of this electrode in LiCIoKC1 electrolyte at 400~ is approximately 300 mV less anodic than that of liquid lithium, and the electrode reaction is simplySome properties of the FeS electrode, which has a voltage of about 1.34V vs. Li-A1, have also been reported (9-17). Five phases have been identified: FeS, LiKsFe~4SesC1 (~J-phase), Li2FeSe (~X-phase), Li2S, and Fe. The FeS phase corresponds to a fully charged electrode, the J-and X-phases are present at intermediate states of discharge or charge, and the Fe and Lies phases correspond to the fully discharged electrode. Additional phases are formed when cells are overcharged (12). These higher voltage phases were usually avoided in the present study. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.15.241.167 Downloaded on 2015-03-08 to IP VoL 128, No. 4 FeS ELECTRODES 761 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.15.241.167 Downloaded on 2015-03-08 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.15.241.167 Downloaded on 2015-03-08 to IP VoL 12,8, No. 4 FeS ELECTRODES 767 E z u3 n... t.D ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.15.241.167 Downloaded on 2015-03-08 to IP

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Die Phasen in FeSz Elektroden, die in eutektische LICFKCI‐Schmelzen bei 400‐450°C betrieben wurden, sind metallographisch und durch Röntgenbeixgung untersucht worden.