Spatially Confined Synthesis of SnSe Spheres Encapsulated in N, Se Dual-Doped Carbon Networks toward Fast and Durable Sodium Storage.

On account of the high theoretical capacity and preferable electrochemical reversibility, tin selenides have emerged as potential anode materials in the field of sodium ion batteries (SIBs). Unfortunately, the large volume changes, low electrical conductivity, and shuttling effect of polyselenides have impeded their real application. In this work, we present a spatially confined reaction approach for controllable fabrication of SnSe spheres, which are embedded in polydopamine (PDA)-derived N, Se dual-doped carbon networks (SnSe@NSC) through a one-step carbonization and selenization method. The NSC shell can not only buffer the volume changes during the cycling but also ensure strong coupling interaction between the SnSe core and carbon shell through Sn-C bonds, leading to excellent conductivity and structural integrity of the composite. Meanwhile, DFT theory calculations confirm that N, Se codoping in the carbon shell can endow the composite with enhanced adsorption energy and accelerated transfer ability of Na. Consequently, the SnSe@NSC anode exhibits a high discharge capacity of 302.6 mA h g over 500 cycles at 1 A g and a competitive rate capability of 285.3 mA h g at 10 A g. Additionally, a sodium ion full battery is assembled by coupling the SnSe@NSC anode with the cathode of NaV(PO) and verified with good cycling durability (190 mA h g at 1 A g over 500 cycles) and high energy density (204.3 W h kg). Our scalable and facile design of heterostructured SnSe@NSC provides a new avenue to develop novel advanced anode materials for SIBs.