Study On The Fabrication And Performance Of Conducting Polymer-based Flexible Solid-state Supercapacitors

The ever-increasing consumption of personal electronics as well as advance inwearable electronics has promoted the development of high-performance energystorage. Supercapacitors are the state-of-the-art energy storage which fill the blankbetween the high specific energy batteries and the high specific power conventionalelectrostatic capacitors. Solid-state supercapacitors integrating electrodes, solidelectrolyte and separator to a solid whole, are superior to their liquid counterparts inlight-weight, high safety, high flexibility and environmental benign nature.Paper-based electronic devices have a wide-range of applications owing to their lowcost, high flexibility, great environment-friendly features and easy integration. Paperis composed of cellulose fibers with typical diameters of about20m, consisting ofmicrofibrils that have a diameter in the range of tens of nanometers, which renderspaper a rough and porous surface. This rough and porous paper structure is a naturaladvantage when electrochemical active materials were coated onto cellulose fibers,which could facilitate efficient electron transport and fast intercalation/deintercalationof ions and is beneficial for electrochemical energy storage. Conducting polymers,such as polypyrrole (PPy), polyaniline (PANI), are a class of polymers which havehigh conductivity, unique physical and chemical properties. They are ideal electrodesfor supercapacitors because of their facile synthetic methods, good electrochemicalperformance, high conductivity and low-cost characteristics, which make them a hotresearch area recently.In this essay, we focus on the synthesis of conducting polymer-based electrodematerials and device fabrication with these electrodes. PANI/graphite flexiblecompound electrode can be prepared using pencil-drawing and electrodepositionmethod. PPy/Paper flexible compound electrode can be prepared by “soak andpolymerization” method. These two methods are both feasible and can be applied to awide range of electrode synthesis based on other materials. The electrochemicalproperties are carefully studied via Cyclic Voltammetry(CV), GalvanostaticCharge-Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS) testmethods.Our accomplishments may be summarized as follows:1. A facile pencil-drawing method was taken on common A4printing paper to make it conductive, followed by polyaniline networks electrodeposition on it toenhance the conductivity and electrochemical activity of the electrode. The hybridelectrode showed a low sheet resistance of32.3/sq and a high areal capacitance of355.6mF/cm2at a current density of0.5mA/cm2. The solid-state supercapacitorsassembled by two G/PANI-Paper electrodes and PVA/H2SO4solid-state electrolytecan achieve a high energy density of0.32mWh/cm3at a power density of0.054W/cm3and retain83%of its initial capacitance after10000cycles.2. A facile “soak and polymerization” method to fabricate PPy-coated paper,which is highly conductive and can be used as electrode to assemble flexiblesolid-state supercapacitors is reported. The as-prepared PPy/Paper composite shows ahigh electrical conductivity of15S/cm and a low sheet resistance of4.5/sq. Theelectrode is highly flexible, which can be bent to180°, remaining the electrical andelectrochemical performances nearly unchanged. Electrochemical measurementsindicated that the fabricated flexible supercapacitors exhibited a highest energydensity of1mWh/cm3at a power density of0.27W/cm3, normalized to the volume ofthe whole cell (electrode, electrolyte, and separator). These encouraging results showtheir great potential in flexible and solid-state energy storage systems.