Supercapacitors based on carbon nanofibers from polyacrylonitrile precursors

Eui-young Shin, Deutsches Textilforschungszentrum Nord-West/ Universität Duisburg-Essen, Krefeld/ Essen, Germany
Muhammad Saif Maqsood, Deutsches Textilforschungszentrum Nord-West, Krefeld,
Wael Ali, Deutsches Textilforschungszentrum Nord-West, Krefeld,
Jochen S. Gutmann, Deutsches Textilforschungszentrum Nord-West/ Universität Duisburg-Essen, Krefeld/ Essen,
Andreas Wego, Deutsches Textilforschungszentrum Nord-West, Krefeld,

Electrochemical capacitors also known as supercapacitors or electric double layer capacitors (EDLCs) have an electrolyte between positive and negative electrodes instead of dielectric material. When compared with conventional capacitors, EDLCs store tens of times more energy per unit volume. Like conventional capacitors, supercapacitor’s capacitance is directly proportional to the surface area of its electrodes. Limited physical and morphological features of conventional materials restrict their use as electrodes in supercapacitors. Therefore, to get high capacitance, electrodes with high surface area are required. Due to high surface area of carbon nanofibers (CNFs), they are used in a wide array of application e.g., electrode material for biosensors, lithium-ion batteries, fuel cells and supercapacitors. In this work PAN nanofibers were made through electrospinning technique. After electrospinning, PAN nanofibers were oxidized under air and subsequently converted into carbon nanofibers by carbonization at higher temperatures under a continuous flow of nitrogen gas. The produced CNFs have a low surface area. In order to enhance the surface area of the fibers a sacrificial polymer polymethylmethacrylate (PMMA) was blended with PAN before electrospinning. That way, PAN:PMMA blended fibers were produced. PMMA was decomposed out of fibers during high temperature carbonization, leaving behind pore structure in the fibers. Such carbon nanofiber mats can be used directly as self-supporting electrodes in supercapacitors.

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