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 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

Die Reaktionen der FeS‐Elektroden in LiCl‐KCI‐Elektrolyten verschiedener Zusammensetzung werden durch kombinierte phasenanalytische,cyclisch voltammetrische und EMK‐Messungen bestimmt.

No abstract

A Ca-Al-Si/FeS 2 cell has been developed and has exhibited reasonably stable capacity through 3200 h of operation. This system is expected to be capable of meeting the ultimate performance goals (i.e., 160 W-h/kg) of this development program. Further tests of this cell system in the coming year will better define its ultimate performance capabilities. SUMMARY Separator Chemistry. A reaction between the Ca-Si negative electrode and the boron-nitride (BN) separator material has limited the cycle life and performance of calcium cells. Chemical tests showed that the reaction could be eliminated by preventing the formation of high-calcium-activity compounds such as Ca 2 Si. Lower activity compounds, such as CaSi and CaAl 2 , did not react with BN. Negative-Electrode Development. A high-performance negative electrode with a composition of CaAl 1. 2 Si 0 .4 was developed in cyclic voltammetry experiments. According to the separator chemistry tests, this alloy will not react with BN separators. Positive-Electrode Development. Tests of the FeS electrode indicated acceptable utilization (652) at a current density of 40 mA/cm 2. Cyclic voltammetry tests were used to evaluate two types of carbon current collectors for FeS 2 electrodes. A finely divided carbon (E-Coke Flour) appeared to be superior to carbon foam. Electrolyte Development. The effects of electrolyte composition on the performance of FeS2 electrodes were evaluated by cyclic voltametry. Variations in the concentration of sodium, potassium, and barium ions had no effect; higher calcium-ion concentrations were beneficial. A ternary LiCl-KCl-CaF 2 electrolyte for use with CaF 2 powder separators was subjected to a preliminary cell test and gave encouraging results. Cell Development. Eight cell tests were conducted to evaluate various possible solutions to the problem of BN-separator degradation. The CaAl1.2Si0.4/FeS2 cell test was highly successful. The cell, which employed BN-felt separators, operated for over 3200 h with only a slight decline in cell capacity.