Facile synthesis of Ni(OH)₂/graphene/bacterial cellulose paper for large areal mass, mechanically tough and flexible supercapacitor electrodes

A general approach toward flexible supercapacitor electrode based on metal hydroxide is developed, which offers ultrahigh areal capacitance without compromising their gravimetric capacitance and mechanical properties. As a prototype, bendable freestanding film is fabricated by coating graphene (RGO)-wrapped flowery Ni(OH)₂ on bacterial cellulose (BC) with a rational combination of hydrothermal method and filtration technology. This as-assembled hierarchically structured flexible electrode is characterized by remarkable areal capacitance of 10.44 F cm⁻² (877.1 F g⁻¹) at a large mass loading of 11.9 mg cm⁻², excellent cycling stability with 93.6% capacitance retention after 15,000 cycles, high flexibility including bending to arbitrary angles (even 180°) and prominent tensile strength (48.8 MPa at wet state). Furthermore, it is hoped that the typical method can be applied for realizing other metal oxide/hydroxide flexible electrodes. The simple, high scalable, low-cost, and general strategy could open up new opportunities for flexible energy storage devices.