Sodium polysulphide purification - by heating polysulphides at a low water vapour partial pressure

摘要

Na polysulphide (Na2Sx, x >1) are purified by heating the polysulphides to >=390 degrees C (400-550 degrees C) at a water vapour partial pressure 0.01 bar, effected by using a vacuum pump, or a dry inert gas stream. The treatment is carried out for 1-2 hr. The purified Na polysulphides are suitable as active material in high temp. batteries. Method is simple and does not require the use of chemical reagents.