Electrode Processes in Sodium Polysulfide Melts

Abstract

Results are reported of three‐electrode measurements in sodium polysulfide melts. The composition range covered was Na2S3‐Na2S5 and the temperature range 300°–400°C. The electrode material used was vitreous carbon. Voltammetric, chronopotentiometric, and current interruption techniques were used to investigate cathodic and anodic processes. Evidence is produced that sulfide films are formed at the cathode and that these result in limiting currents. The lowest value of limiting current density was 28 mA · cm−2 obtained for Na2S3 at 350°C. At the anode the current appears to be limited by accumulation of liquid sulfur. The value of the limiting current density in Na2S5 was 100 mA · cm−2 at 350°C. A reaction scheme which best fits our results is suggested.

Highly Reversible Room-Temperature Sulfur/Long-Chain Sodium Polysulfide Batteries

“…Therefore, development of room-temperature Na-ion batteries with a similar working principle as Li-ion batteries for large-scale energy storage is an attractive alternative. , To date, many efforts have been made and a large number of compounds have been proposed as electrode materials for the development of the “rocking chair” Na-ion batteries. − However, it remains a great challenge for developing high-energy and high-power density materials with low volume change during cycling. One successful Na-ion energy storage technology is the high-temperature molten electrode Na–S battery, which has been used to support stationary energy storage systems for several decades. − However, the molten Na–S batteries require high operating temperatures of >300 °C, which limits their propagation into a wide range of applications.…”

The Effects of Current Density, Temperature, and Discharge Beyond Na2 S 3 on Sodium‐Sulfur Cell Performance and Life

“…During discharge, sodium is injected into the sulfur compartment and sodium polysulfides of various compositions form. The studies of Tischer and Ludwig (6) and South et al (10) indicate that electrochemically formed Na2S2 may be more effective than chemically formed Na2S2 in producing a blocking layer within the cell. Until the sulfur content in the polysulfides reaches -78 weight percent (w/o), an immiscible mixture ' Post-test examination of sodium-sulfur cells is part of an ongoing research effort.…”

Effects of Dynamic Electrodes on Sodium Sulfur Cell Performance

“…After the 25 Ah charge, charge voltage increased rapidly to 2.5 V. This sudden increase in charge voltage occurred at a charge acceptance as low as 41%, when the composition of the sulfur electrode approached the two-phase region. Charge operation of the test cell with a static sulfur electrode was limited to the single-phase region, because the sulfur generated in the electrode adjacent to the ~"-alumina tube formed a coherent film on the tube surface (9). An interesting feature of the charge curves for the test cell with dynamic electrodes as shown in Fig.…”