Zn doped delta-MnO2 nano flakes: An efficient electrode material for aqueous and solid state asymmetric supercapacitors

Asymmetric supercapacitors based on aqueous and solid-state electrolytes are useful for a variety of applications. The birnessite delta-MnO2 is one of the efficient materials from the MnOx family characterized by large interlayer distance (similar to 7.3 angstrom) and high theoretical specific capacitance (similar to 1370 F g(-1)). However the main concern which hinders its usage for practical applications is its low electronic conductivity (similar to 10(-6) S cm(-1)). There are different means to enhance the conductivity and in the present studies, two simultaneous methods viz; a method of synthesis of nano-flakes along with Zn-doping in delta-MnO2 is implemented. A specific capacitance of similar to 466 F g(-1) at a current density of 0.5 A g(-1) is obtained for an optimum Zn doping concentration of 1 mol% which is almost two times more than the corresponding pristine one. Both aqueous and solid-state asymmetric supercapacitor devices are fabricated using Zn doped delta-MnO2 as electrode material which can be easily scalable to industrial level. A lab-scale demonstration prototype is constructed which essentially validated the charging of solid-state supercapacitor using battery and allowing the supercapacitor to discharge through a red-LED by means of a two-way switch. (C) 2018 Published by Elsevier B. V.