High-energy-density flexible graphene-based supercapacitors enabled by atypical hydroquinone dimethyl ether

Supercapacitor is an electrochemical energy-storage technology that can meet the green and sustainable energy needs of the future. However, a low energy density was a bottleneck that limited its practical application. To overcome this, we developed a heterojunction system composed of two-dimensional (2D) graphene and hydroquinone dimethyl ether- an atypical redox-active aromatic ether. This heterojunction displayed a large specific capacitance (Cs) of 523 F g-1 at 1.0 A g-1, as well as good rate capability and cycling stability. When assembled in symmetric and asymmetric two-electrode configuration, respectively, supercapacitors can work in voltage windows of 0 ∼ 1.0 V and 0 ∼ 1.6 V, accordingly, and exhibited attractive capacitive characteristics. The best device can deliver an energy density of 32.4 Wh Kg-1 and a power density of 8000 W Kg-1, and suffered a small capacitance degradation. Additionally, the device showed low self-discharge and leakage current behaviors during long time. This strategy may inspire exploration of aromatic ether electrochemistry and pave a way to develop electrical double-layer capacitance (EDLC)/pseudocapacitance heterojunctions to boost the critical energy density.