Sodium-sulfur battery is a molten-salt battery made up of sodium (Na) and sulfur (S) that operates at high temperature ranges and is primarily suitable for >4-h duration applications.
A sodium–sulfur (NaS) battery is a type of molten-salt battery that uses liquid sodium and liquid sulfur electrodes. This type of battery has a similar energy density to lithium-ion batteries, and is fabricated from inexpensive and low-toxicity materials.
Why are sodium-sulfur batteries used in stationary energy storage systems?
Introduction Sodium-sulfur (Na-S) batteries with sodium metal anode and elemental sulfur cathode separated by a solid-state electrolyte (e.g., beta-alumina electrolyte) membrane have been utilized practically in stationary energy storage systems because of the natural abundance and low-cost of sodium and sulfur, and long-cycling stability , .
Whereas nonaqueous lithium-sulfur 4, 5, 6 and high-temperature sodium-sulfur batteries 7 use sulfur as the cathode, an all-aqueous system must use sulfur as the anode material to preserve aqueous stability while reaching a meaningful cell voltage.
Sodium also has high natural abundance and a respectable electrochemical reduction potential (−2.71 V vs. standard hydrogen electrode). Combining these two abundant elements as raw materials in an energy storage context leads to the sodium–sulfur battery (NaS).
Like many high-temperature batteries, sodium–sulfur cells become more economical with increasing size. This is because of the square–cube law: large cells have less relative heat loss, so maintaining their high operating temperatures is easier. Commercially available cells are typically large with high capacities (up to 500 Ah).
Driven by the abundance and low costs of sulfur and bromine salts, this study investigates the viability of an aqueous flow battery system, in which sodium bromide (NaBr) is used as a catholyte, and a novel electrolyte called elemental added sulfur sodium polysulfide (EASSP) is utilized as an anolyte.