Free-standing graphene/bismuth vanadate monolith composite as a binder-free electrode for symmetrical supercapacitors

Abstract

Preparation of new types of electrode material is of great importance to supercapacitors. Herein, a graphene/bismuth vanadate (GR/BiVO₄) free-standing monolith composite has been prepared <i>via</i> a hydrothermal process. Flexible GR sheets act as a skeleton in the GR/BiVO₄ monolith composites. When used as a binder-free electrode in a three-electrode system, the GR/BiVO₄ composite electrode can provide an impressive specific capacitance of 479 F g^-1 in a potential window of -1.1 to 0.7 V <i>vs.</i> SCE at a current density of 5 A g^-1. A symmetrical supercapacitor cell which can be reversibly charged-discharged at a cell voltage of 1.6 V has been assembled based on this GR/BiVO₄ monolith composite. The symmetrical capacitor can deliver an energy density of 45.69 W h kg^-1 at a power density of 800 W kg^-1. Moreover, it ensures rapid energy delivery of 10.75 W h kg^-1 with a power density of 40 kW kg^-1.