Hollow cobalt disulfide/nitrogen-doped carbon nanoboxes for high stability sodium-ion battery anodes

Metal sulfides have attracted significant attention in sodium-ion battery research owing to their high theoretical capacity. However, their practical application is hindered by volume fluctuations and low conductivity caused by conversion reactions. In this study, hollow cobalt disulfide/nitrogen-doped carbon (CoS₂/NC) nanoboxes were synthesized from cobalt-based Prussian blue analogues (PBA) through a sulfidation process. The resulting nanoboxes, approximately 500 nm in size, possess hollow interiors constructed from interconnected primary nanoparticles (~ 50 nm). The unique hierarchical structure provides abundant void space to accommodate volume changes and shortens transport pathways. Furthermore, the integration of nitrogen-doped carbon matrix significantly enhances the electronic conductivity. When employed as an anode material for sodium-ion batteries, hollow CoS₂/NC nanoboxes delivered an outstanding desodiation capacity of 619.4 mAh·g⁻¹ at 5 A·g⁻¹ over 400 cycles with an average capacity loss of only 0.04% per cycle. This study highlights the potential of PBAs as precursors for synthesizing nanoscale metal sulfides with nitrogen-doped carbon matrices, offering a promising approach to enhance electrochemical performance in energy storage systems.