First report on binder-free boehmite (AlOOH) based prototype, flexible, high-energy and high-power density solid-state symmetric supercapacitor

Supercapacitor has potential to accomplish the world-wide growing demand for clean and sustainable energy. It has virtue of both the battery and the conventional capacitor. The proper selection of electrode material is one of the deterministic factors for the excellent performance of supercapacitor. This work presents the first report on the boehmite phase of a polymorph of earth abundant and inexpensive aluminum based oxy hydroxide for energy storage application. The binder-free synthesis of AlOOH electrode has been carried out by the simple, userfriendly, and low-cost successive ionic layer adsorption and reaction (SILAR) technique at 300 K. The X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy characterizations are performed for the knowledge of crystal structure, chemical bonds, oxidation states, morphology and elements present in the sample, respectively. The electrochemical activities of electrode as well as fabricated solid-state symmetric device are disclosed by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The maximum specific capacitance of 726.5 F g-1 @ 5 mV s-1 has been achieved for AlOOH electrode with -67 % cyclic stability for 6500 cycles. The assembled device exhibits an excellent specific capacitance of 314 F g-1 @ 5 mV s-1, energy density of 242 Wh Kg-1 and power density of 4701 W Kg-1 with -80 % stability up to 6500 cycles. The device has ability to glow red, green, blue and white coloured light emitting diodes (LEDs) for 50, 52, 27 and 21 min respectively. Also, the fabricated device is successful for glowing a panel 'MNNIT' made up by 56 red coloured LEDs. These results indicate that this work can be beneficial for fulfilling the energy demand of future generation.