A long life sodium–selenium cathode by encapsulating selenium into N-doped interconnected carbon aerogels

Abstract

Selenium cathodes have attracted a great deal of attention due to their much higher electronic conductivity compared to sulfur cathodes and similar volumetric capacity to them. However, selenium cathodes still suffer from rapid capacity fading because of low utilization of active materials, high volume changes and the shuttle effect of polyselenides. Herein, we prepared selenium–carbon aerogel composites as cathodes for sodium–selenium batteries by infiltrating selenium into the microporous structure of N-doped interconnected carbon aerogels (Se@NCAs). The carbon matrix could effectively accommodate the volume change of Se during cycling and alleviate the shuttle effect of polyselenides. The Se@NCA cathode exhibits an excellent discharge capacity (600 mA h g⁻¹ after 50 cycles at 0.1 A g⁻¹) and a superior rate capability (430 mA h g⁻¹ at 2 A g⁻¹) for Na–Se batteries. In addition, it also shows a superior long cycling life of 407 mA h g⁻¹ at a current density of 0.5 A g⁻¹ after 800 cycles with only 0.04% capacity decline per cycle.