Binder-free WS2 nanosheets with enhanced crystallinity as a stable negative electrode for flexible asymmetric supercapacitors

Abstract

Tungsten disulfide (WS₂) has been emerging as an attractive electrode material for supercapacitors because of its intrinsically layered structure and high capacitance. Unfortunately, most of the currently developed WS₂-based electrodes suffer from poor conductivity and fast capacitance fading. In this work, we demonstrated that the durability of WS₂ nanosheets can be remarkably boosted via improving their crystallinity and the first example of using these WS₂ nanosheets as a high-energy and stable negative electrode for flexible asymmetric supercapacitors (ASCs). Electrochemical results reveal the WS₂ nanosheets with enhanced crystallinity were able to deliver an excellent durability with more than 82% capacitance retention after 10 000 cycles and an areal capacitance of 0.93 F cm⁻² at 4 mA cm⁻². Importantly, when using the as-prepared WS₂ nanosheets as a negative electrode, a flexible and stable ASC device with an extraordinary volumetric energy density of 0.97 mW h cm⁻³ is obtained. This work affords new opportunities to use WS₂ nanostructures and other 2D TMDs in constructing high-performance energy-storage devices.