A Redox-Mediator-Doped Gel Polymer Electrolyte Applied in Quasi-Solid-State Supercapacitors

Methylene blue (MB) redox mediator was introduced into polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) blend host to prepare a gel polymer electrolyte (PVA-PVP-H2SO4-MB) for a quasi-solid-state supercapacitor. The electrochemical properties of the supercapacitor with the prepared gel polymer electrolyte were evaluated by cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy, and self-discharge measurements. With the addition of MB mediator, the ionic conductivity of gel polymer electrolyte increased by 56% up to 36.3 mS.cm(-1), and the series resistance reduced, because of the more efficient ionic conduction and higher charge transfer rate, respectively. The electrode specific capacitance of the supercapacitor with PVA-PVP-H2SO4-MB electrolyte is 328 F.g(-1), increasing by 164% compared to that of MB-undoped system at the same current density of 1 A.g(-1). Meanwhile, the energy density of the supercapacitor increases from 3.2 to 10.3 Wh.kg(-1). The quasi-solid-state supercapacitor showed excellent cyclability over 2000 charge/discharge cycles. (C) 2013 Wiley Periodicals, Inc.