Construction of WSSe2/C anode with enlarged layer spacing for efficient Na+ storage by anion synergistic strategy

High-capacity transition metal chalcogenides exhibit intrinsically low conductivity and ion transport efficiency when applied to sodium-ion energy storage devices. Here, carbon-encapsulated WS_x precursors are synthesized using high chloride hydrolysis properties combined with a hydrothermal process. Afterwards, WSSe₂/C anode with dual anion effect is prepared by replacing some S atoms in WS_x with Se atoms employing a microwave sintering process. The obtained WSSe₂/C electrode exhibits a significantly enlarged crystal spacing by constructing built-in electric fields, which ensures rapid and stable Na⁺ transport. The carbon-encapsulated strategy aims to improve electrical conductivity while providing a buffer medium for volume expansion during electrochemical phase transitions. Additionally, by exploring the effects of different carbon introductions on the electrochemical properties, it is determined that 1 g ribose encapsulated WSSe₂ (WSSe₂/C-1) provides the best intervening effect. Consequently, in the assembled Na half-cell, the WSSe₂/C-1 anode displays a high specific capacity of 715.3 mA h g⁻¹ after 200 cycles of activation at 1 A g⁻¹. Further, the assembled sodium-ion capacitor exhibits a high-capacity retention of 86.5 % after 13,000 cycles at a high-power density of 3800 W kg⁻¹. This strategy of combining carbon encapsulation and dual anion effect provides a reference for developing high-power density anodes.