Sulfur and nitrogen co-doped hollow carbon spheres for sodium-ion batteries with superior cyclic and rate performance

Sodium ion batteries (SIBs), based on earth-abundant and cost-effective elements, have attracted increasing attention. Carbon-based materials are still the most potential anode materials for SIBs. Because of insufficient interlayer spacing, graphite-based materials used currently in lithium ion batteries are not suitable for SIB anodes. Herein, combining macro-construction and micro-modification, we design and prepare novel SN-co-doped hollow carbon spheres (SN-HCSs) by a new method. The S and N play different roles during sodium ion storage. Due to the hierarchical porous structure and heteroatoms including S and N, the SN-HCS anode exhibits superior performance, especially with high rate capability (110 mA h g(-1) at a current density of 10 A g(-1)) and excellent cyclic stability (cycle as long as 2000 cycles with only 0.0195 mA h g(-1) specific capacity decay for each cycle).