Controlling the flake size of bifunctional 2D WSe 2 nanosheets as flexible binders and supercapacitor materials.

A new approach using graphene as a conductive binder in electrical supercapacitors has recently been proposed. Graphene shows outstanding properties as a conductive binder, and can be used to replace conductive, additive, and polymer binders. However, graphene follows an EDLC behaviour, which may limit its electrochemical performance. In the process described in this work, we introduced WSe 2 nanoflakes as a new approach to using pseudocapacitive materials as binders. The WSe 2 nanoflakes were produced through liquid phase exfoliation of bulk WSe 2 , and the flake size was finely selected using a controlled centrifugation speed. The physical and electrochemical properties of the exfoliated WSe 2 flakes were analysed; it was found that the smallest flakes (an average flake size of 106 nm) showed outstanding electrochemical properties, expanding our understanding of transition metal dichalcogenide (TMD) materials, and we were able to demonstrate the applicability of using WSe 2 as a binder in supercapacitor electrodes. We also successfully replaced conductive additives and polymer binders with WSe 2 . The overall performance was improved: capacitance was enhanced by 35%, charge transfer resistance reduced by 73%, and self-discharge potential improved by 9%. This study provides an alternative application of using TMD materials as pseudo capacitive binders, which should lead to the continued development of energy storage technology.