N-doped silk wadding-derived carbon/SnOx@reduced graphene oxide film as an ultra-stable anode for sodium-ion half/full battery

Achieving high-stability, long span-life, and fast sodiation reaction kinetics in sodium ion battery (SIB) can significantly promote its practical application. Here, we use freeze-drying and carbonization to prepare a flexible N-doped silk wadding-derived carbon/SnOx@reduced graphene oxide (N-SWC/SnOx@rGO) film as an ultra-stable anode for a half/full SIB. A superior capacity of 572.2 mA h g−1 at 0.1 A g−1 and long span-life over 1000 cycles are obtained in the N-SWC/SnOx@rGO film anodes. Moreover, a super-stable capacity of 245.7 mA h g−1 can be secured in the assembled SIB full cell, outperforming the current studies. After the detailed structural and performance characterization, we attribute these superior capacities to the following unique structural characteristics: 1) SnOx nanoparticles (<100 nm) are attached to the surface of SWC to provide more active sites for Na+; 2) rGO and SWC form a double-layer conductive system, which can tremendously promote the transmission efficiency of electrons in N-SWC/SnOx@rGO film, thereby greatly accelerating the reaction kinetics of SIB; 3) the N-SWC/SnOx@rGO film contains a conductive network with voids, which can increase the contact area between electrolyte solution and SnOx and in turn effectively shorten the transmission path of Na+. This work provides a new perspective for the preparation of ultra-stable flexible SIB anodes.