Sulfur in Polymers Make Better Cathodes in Batteries

Sulfur in Polymers Make Better Cathodes in Batteries

Researchers from the Favorsky Institute of Chemistry, Irkutsk, have synthesised sulfurated polyacethylene compounds with semiconducting properties. These polymers can be used for cathodes in lithium batteries.

Direct high-temperature sulfurization of polymers by elemental sulfur opens an unexpectedly simple way of synthesis of novel polymeric materials with important properties — paramagnetic, resistance to chemical agents and heating, electroconductivity, and electrochemical activity. One of the promising applications of the sulfurated materials is in the manufacture of cathodes for lithium batteries.

B.A. Trofimov and his colleagues from the Favorsky Institute of Chemistry, Siberian Division of Russian Academy of Sciences, have synthesised sulfurated polyacetylene in a high-temperature reaction with sulfur. The obtained polysulfide chains provide electric conductivity and have paramagnetic characteristics.

The process includes two stages. The first step is a synthesis of polyacetylene by the most simple method, and the second is sulfurization by heating with elemental sulfur at temperatures of 120–300 °C. The obtained materials look like black or yellow-grey powders with a sulfur content of 57–80%. In fact, such a high content of sulfur can be obtained only by multiple sulfurization, because only 16–36% of sulfur can be included in the polymer at once.

Due to the high sulfur content, the polymers are paramagnetic and semiconductive; as a result cathodes made of them have high capacities. The cathodes are ideal for multiple charging and discharging.

The highest value of electric conductivity (0.68 Ч 10–12 Siemen/cm) and concentration of spins was observed for a polymer sample with 80% sulfur. The conductivity depends on composition of the original polyacetylene and the conditions of sulfuration.

One of the advantages of direct sulfuration is that the polymers have almost perfect structures, without defects to lessen their properties.

For further information contact: B.A. Trofimov, Fax: +7 (395 2) 39 6046; E-mail: [email protected].