Uniquely structured composite microspheres of metal sulfides and carbon with cubic nanorooms for highly efficient anode materials for sodium-ion batteries

Abstract

Metal sulfides are promising anode materials for high-performance sodium-ion batteries. However, their drastic volume variation and poor electrical conductivity during cycling result in poor performance, which is a major challenge. In this study, we report the facile and generalized aerosol-assisted synthesis of metal sulfide/C composite microspheres with cubic nanorooms (MeS_x/C-NR) by employing NaCl as a washable template. We investigated the optimization method for synthesizing this novel nanostructure by controlling the synthesis conditions. In the case of MoS₂/C-NR, which was selected as the main target material, few-layered MoS₂ nanosheets were successfully formed, and their restacking during cycling was prevented via incorporation with a dextrin-derived carbon matrix. Meso-/macropores generated by NaCl increased the affinity of MoS₂/C-NR to the electrolyte, increasing the active surface area for electrochemical reaction and reducing the diffusion length of Na⁺ without compromising the structural robustness. As a result, the MoS₂/C-NR delivered a stable reversible capacity of 385 mA h g⁻¹ for 350 cycles at a current density of 0.5 A g⁻¹ and a high rate performance of 287 mA h g⁻¹ at a current density of 7 A g⁻¹. This synthesis strategy can be utilized to prepare other porous metal sulfide/carbon composites, including FeS₂/C-NR and SnS/C-NR, without much difficulty, which may be valuable for many other applications, including energy storage.