Diaper-derived selenium–carbon composites as high-capacity anodes for sodium-ion batteries

Abstract

Exploring ideal electrode materials and overcoming key issues such as large changes in electrode volume resulting from the big radius of Na ions and slow redox kinetics are urgent issues in the large-scale applications of sodium-ion batteries. Here, through freeze-drying and annealing strategies, a molecular complex of Se encapsulated in superabsorbent polymers carbon (Se@SAPC) has been constructed. The superabsorbent polymers carbon base serves as a storage space for the reaction of Se and Na+ and shows good physical constraints and can ensure the overall structural stability of a Se@SAPC composite anode. In addition, the hierarchical pore structure effectively can adjust the volume effect of Se, so that electrons and ions are transferred smoothly in the circulation. Electrochemical measurements showed that the Se@SAPC electrode show excellent performance, including a long cycle life (198 mA h g−1 after 1000 cycles at 2 A g−1), and high-rate performance (200 mAh g−1 at 5 A g−1). At the same time, in-situ Raman, ex-situ transmission electron microscopy and electrochemical analysis reveals the working principle of intercalation/deintercalation of Na ions in Se@SAPC composites. In addition, the full Se@SAPC // Na3V2(PO4)3/C battery shows a large reversible capacity of 198.4 mAh g−1 even after 200 cycles at 0.2 A g−1 current density. This work provides guidance for the further development and utilisation of Se anodes.