Electrolyte compositions for batteries using sulphur or sulphur compounds

A lithium-sulphur battery comprising:

• a negative electrode (anode) comprising an anode active material for providing ions;
• a positive electrode (cathode) comprising a cathode active material comprising sulphur, organic or inorganic sulphur compounds;
• and
• an intermediate separator element containing a liquid or a gel electrolyte solution through which ions from the negative electrode move to the positive electrode during charge and discharge cycles of the lithium-sulphur battery, wherein the liquid or gel electrolyte solution comprises:
• a nonaqueous aprotic solvent and an alkali metal salt,
• wherein said electrolyte composition is chosen in a way that a concentration of the alkali metal salt is at least 90% of a saturation concentration of the alkali metal salt in the solvent at operating temperature and pressure, and
• wherein the combination of salt and solvent is selected to promote non-ionic molecular sulfur transfer into the electrolyte composition at the expense of ionic sulfur transfer and the formation an electrolyte system that allows the formation of an electrolyte system and the dissolution of lithium polysulfides in the electrolyte system.