Sodium/metal sulfide batteries

In the sodium—sulfur storage battery above 300°C, the overall chemical reaction occurs between molten sodium metal and sulfur to form sodium polysulfide. The cell voltage is related to the activity of the sodium ( Aia) sulfide relative to its activity in the metal. 

Antimony is used in alloys, with lead for storage battery plates, with lead and tin in type metals and body solders, with tin and copper in bearing or antifriction metals. Antimony occurs chiefly as the sulfide (stibnite, Sb2S3) which is produced mainly in China, only small amounts in Mexico and Bolivia. Stibnite is (1) melted and reduced to antimony by iron metal and separated from fused ferrous sulfide (See also Stibnite) (2) roasted in air, and sublimed antimonous oxide collected and reduced by heating to fusion with carbon and sodium carbonate. 

Metallic sodium, or sodium hydroxide and sulfur, may also be extracted from flue gas by electrolysis of molten sodium sulfide (produced in the gas desulfurization process) by application of the charging reaction of the sodium-sulfur battery. This could conceivably be converted to a power-producing system if oxygen can be reduced at the cathode without severe polarization. Again, a beta-alumina diaphragm must be used to separate the sodium sulfide from the sodium hydroxide. 

For the treatment of battery pastes, which are a mixture of PbS04, Pb02, PbO and metallic lead, a sulfidisation process has been proposed, converting all lead components into PbS, which can then be subjected to ferric fluoborate leaching as above. Sodium sulfide can be used for this step but involves a complex procedure for its recovery. Alternatively, a biological sulfate reduction process developed by PAQUES Biosystems of the Netherlands has been applied (Olper et al, 2000). 

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