Carbon spheres with catalytic silver centres as selenium hosts for stable lithium–selenium batteries

Abstract

In the quest to develop next-generation lithium batteries to meet the expansive consumer energy demands, batteries based on conversion chemistry are explored. Selenium cathodes have recently gained attention due to their high conductivity and volumetric capacity compared to the existing sulfur-based cathodes. The practical implementation of lithium–selenium batteries is often hindered by the rapid capacity fading due to the poor electronic contact and the shuttle effect caused by polyselenides. By encapsulating selenium in conducting cavities and using a suitable catalyst, we can mitigate the effect of polyselenide shuttling. Herein, we demonstrate a facile strategy to synthesise carbon sphere reactors loaded with catalytically active silver nanoparticles at the centre that act as efficient selenium hosts for Li–Se batteries. Selenium-encapsulated carbon spheres are prepared by a simple microwave synthesis method followed by carbonization and selenisation. The role of these catalytic nanoreactor centres in improving the capacity, cycling stability, and rate capability of Li–Se batteries is thoroughly investigated. The improved discharge capacity and the excellent cycling stability (249 mA h g⁻¹ at 1C rate for 1000 cycles) are accounted for by the successful immobilization of selenides and polyselenides within the porous structure of the carbon spheres triggered by the silver catalyst.