The Electrochemistry with Lithium versus Sodium of Selenium Confined To Slit Micropores in Carbon

Substitution of selenium for sulfur in the cathode of a rechargeable battery containing S-s molecules in microporous slits in carbon allows a better characterization of the electrochemical reactions that occur. Paired with a metallic lithium anode, the Se-x chains are converted to Li2Se in a single-step reaction. With a sodium anode, a sequential chemical reaction is characterized by a continuous chain shortening of Se-x upon initial discharge before completing the reduction to Na2Se; on charge, the reconstituted Se-x molecules retain a smaller x value than the original Se-x chain molecule. In both cases, the Se molecules remain almost completely confined to the micropore slits to give a long cycle life.