CoS2 nanodots trapped within graphitic structured N-doped carbon spheres with efficient performances for lithium storage

Abstract

Cobalt sulfide (CoS₂)-based nanomaterials are promising electrode materials for various energy storage and conversion applications due to their large specific capacities and catalytic activities. However, CoS₂-based nanomaterials are still suffering from their volume expansion, agglomeration and poor cycling stability. Here, we demonstrated an intriguing and effective strategy to confine CoS₂ nanodots (<10 nm) within the graphitic carbon walls of porous N-doped carbon spheres (CoS₂-in-wall-NCSs), which both avoids the volume change and facilitates the promotion of reaction kinetics in lithium ion batteries (LIBs). Moreover, N-doped carbon spheres (NCSs) with nest-like architectures and graphitic carbon nanoribbons offer an ideal diffusion pathway for electrolyte ions and a highly rapid electron transfer pathway. As a result, the CoS₂-in-wall-NCSs still exhibit an excellent performance in LIBs with a high specific capacity of 1080.6 mA h g⁻¹ at a current density of 200 mA g⁻¹ even after 500 cycles, which is much better than those of CoS₂ nanoparticles (NPs) in the pores of N-doped carbon spheres (CoS₂-in-pore-NCSs), metallic Co NPs embedded in N-doped carbon spheres (Co/NCSs), and NCSs. Even at a current density as high as 1000 mA g⁻¹, a reversible capacity of 735.5 mA h g⁻¹ is obtained for CoS₂-in-wall-NCSs.