Rational Design of the CoS/Co₉S₈@NC Composite Enabling High-Rate Sodium-Ion Storage

Metal sulfides have been considered promising anode materials for sodium-ion batteries (SIBs) due to their high specific capacities. However, the poor electrical conductivity and sluggish electrochemical kinetics of metal sulfides are the critical factors that are limiting their applications. In this work, cobalt sulfides with heterostructures embedded in an N-doped carbon composite (CoS/Co₉S₈@NC) have been synthesized to further investigate Na⁺ diffusion in the SIBs. With contributions from the heterostructure, the N-doped carbon, and the unique morphology, the composite can deliver enhanced rate capability and cycling stability compared to Co₉S₈. This work depicts the change of Na⁺ diffusion under the influence of heterostructures, providing an effective strategy of material design for enhancing the electrochemical performance of sodium-ion storage.