A binder-free wet chemical synthesis approach to decorate nanoflowers of bismuth oxide on Ni-foam for fabricating laboratory scale potential pencil-type asymmetric supercapacitor device.

The present study involves the synthesis of a bismuth oxide (Bi2 O3 ) electrode consisting of an arranged nano-platelets for evolving a flower-type surface appearance on nickel-foam (Bi2 O3 -Ni-F) by a simple, inexpensive, binder-free and one-step chemical bath deposition (CBD) method, popularly known as a wet chemical method. The as-prepared Bi2 O3 on Ni-foam, as an electrode material, demonstrates 557 F g-1 specific capacitance (SC, at 1 mA cm-2 ), of which 85% is retained even after 2000 cycles. With specific power density of 500 kW kg-1 , the Bi2 O3 -Ni-F electrode documents a specific energy density of 80 Wh kg-1 . Furthermore, a portable asymmetric supercapacitor device, i.e. a pencil-type cell consisting of Bi2 O3 -Ni-F as an anode and graphite as a cathode in 6 M KOH aqueous electrolyte solution, confirms 11 Wh kg-1 and 720 kW kg-1 specific energy and specific power densities, respectively. An easy and a simple synthesis approach for manufacturing a portable laboratory scale pencil-type supercapacitor device is a major outcome of this study, which can also be applied for ternary and quaternary metal oxides for recording an enhanced performance. In addition, we presented a demonstration of lighting a light emitting diode (LED) using a home-made pencil-type supercapacitor device which, finally, has confirmed the scaling and technical potentiality of Bi2 O3 -Ni-F in energy storage devices.