Confining WS₂ hierarchical structures into carbon core-shells for enhanced sodium storage

The growing demand for clean energy has heightened interest in sodium-ion batteries (SIBs) as promising candidates for large-scale energy storage. However, the sluggish reaction kinetics and significant volumetric changes in anode materials present challenges to the electrochemical performance of SIBs. This work introduces a hierarchical structure where WS₂ is confined between an inner hard carbon core and an outer nitrogen-doped carbon shell, forming HC@WS₂@NCs core-shell structures as anodes for SIBs. The inner hard carbon core and outer nitrogen-doped carbon shell anchor WS₂, enhancing its structural integrity. The highly conductive carbon materials accelerate electron transport during charge/discharge, while the rationally constructed interfaces between carbon and WS₂ regulate the interfacial energy barrier and electric field distribution, improving ion transport. This synergistic interaction results in superior electrochemical performance: the HC@WS₂@NCs anode delivers a high capacity of 370 mAh g^-1 at 0.2 A/g after 200 cycles and retains261 mAh g^-1 at 2 A/g after 2000 cycles. In a full battery with a Na₃V₂(PO₄)₃ cathode, the Na₃V₂(PO₄)₃//HC@WS₂@NC full-cell achieves an impressive initial capacity of 220 mAh g^-1 at 1 A/g. This work provides a strategic approach for the systematic development of WS₂-based anode materials for SIBs.