Fabrication of Polyaniline/Organic • Inorganic Composites for Supercapacitor Electrodes

Abstract

A supercapacitor has widely been utilized in diverse vehicles needing rapid energy delivery because of its high power density: within automobile, trams, light-rails, and cranes. As smaller forms, they have also been utilized as memory backup for static random-access memory. Materials used for supercapacitor electrode possess their pros and cons. For example, carbon materials show a good cycling stability, but specific capacitance is relatively low. In the case of conducting polymers (CPs), in contrast to carbon materials, they possess high specific capacitance, but the cycling stability is relatively poor due to their poor mechanical strength. Thus, large efforts have been made to fabricate supercapacitor with high capacitance and good cycling stability. In this dissertation, three different polyaniline (PANI)/organic • inorganic composites were prepared using self-stabilized dispersion polymerization (SSDP) method to achieve supercapacitors with high capacitance and good electrochemical stability. First, PANI/silicon dioxide (SiO2) nanocomposite was fabricated by SSDP method. Produced PANI/SiO2 nanocomposite exhibited improved electrochemical performances (specific capacitance: ca. 305 F g-1, cycling stability: maintaining 72 % of initial gravimetric capacitance after 500 cycles) compared with PANI/SiO2 nanocomposite synthesized by conventional polymerization method and other previously reported PANI nanomaterials owing to high electrical conductivity (ca. 25.6 S cm–1), large specific surface area (ca. 170 m2 g–1), and improved crystallinity. Second, PANI/ molybdenum disulfide (MoS2) nanocomposite, synthesized by SSDP method, showed enhanced specific capacitance (ca. 400 F g-1) in comparison with both PANI (ca. 232 F g-1) and MoS2 nanosheet (ca. 3 F g-1) due to high electrical conductivity (ca. 28.6 S cm-1) and pseudo capacitive characteristics of PANI and MoS2. Additionally, PANI/MoS2 nanosheet exhibited good cycling stability (84 % after 500 cycles) due to honeycomb-like structured PANI on MoS2 nanosheet and incorporation of MoS2 nanosheet possessing good mechanical properties. Lastly, PANI/reduced graphene oxide (RGO) film was fabricated through solution processing for highly scalable and flexible supercapacitor electrodes. Produced PANI/RGO film exhibited extremely high electrical conductivity of ca. 906 S cm-1 due to improved crystallinity. In the electrochemical tests, PANI/RGO film exhibited enhanced capacitance (ca. 431 F g-1) and cycling stability (74 % after after 500 cycles) in comparison with pure PANI film (specific capacitance: ca. 256 F g-1, cycling stability: 60 % after 500 cycles). The PANI/RGO film also demonstrated excellent performance ability as a scalable and flexible electrode material. The stratigies and specific synthetic methods described here can be useful tool for fabricating supercapacitor electrodes with high capacitance and good elctrochemical stability.