Vacuum Calcination Induced Conversion of Selenium/Carbon Wires to Tubes for High‐Performance Sodium–Selenium Batteries

Abstract

AbstractA vacuum calcination approach is developed to fabricate selenium/carbon composites, which does not require intensive mixing and durable heating such as in commonly used melt‐infusion methods of loading selenium into carbon hosts. Starting from carbon‐coated selenium wires prepared via a wet‐chemical reaction, selenium/carbon tubes are fabricated by a straightforward calcination process. The calcination is conducted in a confined space to reduce the insulating carbon shell under vacuum, and selenium melts but remains a constituting part of the composite. Paired with sodium metal anode, the resultant selenium/carbon tubes deliver a high reversible capacity of 601 and 509 mA h g−1 at 0.2 and 2 C normalized by the mass of selenium, which corresponds to energy and power densities of 860 and 667 Wh kg−1 at 193 and 1770 W kg−1, respectively. Such capacity and rate performance surpasses most typical cathode materials for lithium or sodium (ion) batteries, according to the comparative literature analysis. Moreover, the robust tubular‐like hollow structure of the selenium/carbon composites ensures for impressive capacity retention of more than 90% after 1000 cycles at 20 C.