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

Abstract

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.