Synergistically Coupling Chalcogen Vacancy-Modified WS_2–xSe_x Microspheres with a Conductive Carbon Network for Sodium-Ion Storage

Tungsten disulfide (WS 2 ) is a typical transition metal sulfide anode for sodium-ion batteries (SIBs) with multiple valence transitions and a high specific capacity. However, bulk WS 2 suffers from inferior electron conductivity and a sluggish sodium-ion migration rate, severely limiting electrochemical activity. In this work, a strategy to significantly enhance the sodium-ion storage efficiency of tungsten disulfide by synergistically coupling chalcogen vacancy (sulfur and selenium) engineering with a conductive carbon network (V c -WS 2– x Se x @NC) is proposed. The design approach addresses the critical limitations of bulk WS 2 by introducing abundant chalcogen vacancies that act as both negative charge centers and electron carriers, thereby improving the electrochemical kinetics. Simultaneously, these chalcogen vacancies also serve as active sites to significantly contribute high levels of Na + pseudocapacitive storage. Furthermore, the unique hybrid architecture, featuring nitrogen-doped carbon nanolayers intimately coupled with chalcogen vacancy-enriched WS 2– x Se x microspheres, creates a seamless and highly efficient ion/electron transport network. Thus, this design enables the V c -WS 2– x Se x @NC composite to achieve an exceptional specific capacity of 328 mA h g –1 at 0.5 A g –1 in SIBs, with an impressive 94% capacity retention after 100 cycles. Moreover, the practical applicability of this material is demonstrated through the assembly of a full cell (V c -WS 2– x Se x @NC||Na 3 V 2 (PO 4 ) 3 ), which exhibits a remarkable reversible capacity retention of 87% after 100 cycles at 0.5 A g –1 .