Processing of aqueous polymer electrolytes for supercapacitors via different industrial application methods

Abstract

Abstract To date, various types of gel polymer electrolytes have been studied as a potential substitute for liquid electrolytes in energy storage systems, using almost exclusively lab-scale application methods. With a view to scalability and processing time, these methods fail to meet the industrial requirements for fabricating completely printable or coatable supercapacitors. To address the industrial needs, this study investigates the fabrication of a potassium-based gel polymer electrolyte (GPE) layer for an activated carbon supercapacitor via industrial printing and coating methods. The study examined how a PVA-KOH-based GPE solution can be processed by screen printing and slot-die coating. It proved that the industrial application methods were suitable for coating a GPE layer directly on a supercapacitor electrode as well as for producing free-standing GPE layers. The influence of additives on flow properties was determined via rheological measurements. To evaluate the electrochemical performance, test cells for galvanostatic charge-discharge experiments and impedance spectroscopy measurements were built. It was found that cells containing a GPE layer produced with screen printing and slot-die coating show good cyclability. At a current density of 2 mA cm−2, the cells with the slot-die-coated GPE layer reached a specific capacitance of 87.3 Fg−1 and at 50 mA cm−2 a specific capacitance of up to 28.5 Fg−1. Different layer thicknesses have been realized by varying the parameters of the application methods. The influence of layer thickness on conductivity and specific capacitance was analysed using casted layers. It was found that an optimum exists between the layer thickness of the electrolyte layer and its molar concentration.