Carbon-coated tungsten diselenide nanosheets uniformly assembled on porous carbon cloth as flexible binder-free anodes for sodium-ion batteries with improved electrochemical performance

As large-scale energy storage systems, rechargeable sodium-ion batteries (SIBs) are promising to replace the lithium-ion batteries. Among transition-metal dichalcogenides, which exhibit high theoretical capacities and specific two-dimensional layered structures, tungsten diselenide (WSe₂) is an efficient anode material for SIBs owing to the good energetics and large lattice parameter. In this study, well-crystallized WSe₂ nanosheets uniformly assembled on a porous carbon cloth (WSe₂@PCC) were fabricated by an underwater electrical explosion of a tungsten wire, dip coating, and complete selenization from WO₃ to WSe₂. To further improve the cycling performance of the WSe₂@PCC electrode, a carbon coating was carried out by simply adding sucrose into a WO₃ ink before dip coating. The carbon-coated WSe₂@PCC (C@WSe₂@PCC) electrode exhibited outstanding electrochemical performances as a flexible and binder-free anode for SIBs due to enhanced electrical conductivity and mitigation of volume expansion of WSe₂ during repeated sodiation/desodiation. Benefiting from unique structural merits and efficient carbon coating, C@WSe₂@PCC can deliver large reversible areal capacity of 1.37 and 1.05 mA h cm⁻² at the 1st and 150th cycles, respectively, with excellent capacity retention and Coulombic efficiency even at a high current density of 0.75 mA cm⁻².