3D hierarchical architectures of CoSe ₂ nanoparticles embedded in rice‐derived hard carbon for advanced sodium storage

Abstract A low‐cost and feasible method to fabricate three‐dimensional (3D) hierarchical composites composed of CoSe 2 nanoparticles embedded in rice‐derived hard carbon (HC) interconnected with carbon nanotubes (CNTs) is devised in this study. The deployment of CoSe 2 in the elecrode has provided a very high rate capacity, which is crucial for sodium‐ion commercialization. The deployment of HC with CNTs further provides a 3D hierarchical structure effective in shortening the diffusion paths of both electrons and Na + ions, offering abundance of active sodium storage sites. Consequently, the CoSe 2 acted as an active material with the carbonaceous template, a commonly utilized sodium‐ion battery anode material, which exhibited a superior reversible capacity of 550 mAh g −1 at 0.5 A g −1 , outstanding rate performance (451 mAh g −1 at 20 A g −1 ) and excellent cycling performance (~100% capacity retention over 2500 cycles at 20 A g −1 after electrochemical stabilization).