Fabrication of S,N-Doped Carbon-Coated SnS2/SnS Heterostructures Supported by Hollow Carbon Microspheres for Sodium-Ion Storage

Developing novel anode materials containing electroactive heterostructures which boost ion and charge transfer kinetics in a carbon matrix is still a great challenge. Here we report on a new smartly designed material: SnS2/SnS p-n heterostructures embedded in S,N-doped carbon layer supported by hollow carbon spheres (C@SnSx@C) by a facile method and applied as negative electrode material in sodium ion batteries. The C@SnSx@C2 (at optimized carbon ratio) negative electrode can deliver an initial reversible capacity of 636.5 mAh center dot g(-1) at 0.1 A center dot g(-1), superior rate capability (265.1 mAh center dot g(-1) at rate of 10.0 A center dot g(-1)) and long cycle life (capacity retention of 96.3 % at 1.0 A center dot g(-1) after 150 cycles). The SnS2/SnS p-n heterojunctions provide a lower sodium ion diffusion energy barrier (0.38 eV), higher Na+ adsorption energy (-4.66 eV) and higher electronic conductivity due to an internal electric field according to density functional theory calculations compared to plain SnS. Moreover, S,N-doped carbon facilitates electronic conductivity and buffers the volume changes during the conversion reaction-based SnSx upon sodium insertion and extraction process. Porous hollow carbon spheres contribute to prevent the agglomeration of SnS2/SnS nanosheets and keep the structural integrity. Our findings on this unique material might be extended to other ion battery technologies.

Automated summary

A novel negative electrode material containing SnS2/SnS p-n heterostructures embedded in S,N-doped carbon layer supported by hollow carbon spheres has been developed for sodium ion batteries. This material shows promising initial reversible capacity, superior rate capability, and long cycle life, making it a potential candidate for future battery technologies.