Highly Conductive Nanostructured Polyaniline Films for Supercapacitor Applications

摘要

Conducting polymer compositions based on polyanilines and poly(3,4-alkylenedioxythiophenes now have electrical conductivities reaching into the thousands of S/cm (Refs. 1 and 2). It is understood that the proper combination of chemical composition, processing to ordered and oriented structures, and packaging can produce materials with exceptionally high conductivity and stability that are on the edge of truly metallic behavior. In addition to being conductive, conjugated polymers also are redox electroactive allowing for electrochemically switching between charge states. This electrochemical redox property, results in a significant amount of electrical charge stored within the polymer structure enabling high energy density electrochemical capacitor applications. Depending on the method of preparation (electrochemical deposition or solution processing methods), highly porous structures are attained that can be switched quite rapidly. These electrochemical capacitors, often termed supercapacitors due to there combined high charge capacity with rapid discharge characteristics, have potential utility in back-up electrical and electronic systems where typical capacitors provide too little net charge and batteries are too slow to respond. Since electron hopping governs the conductivity of ICPs, spacing between the chains plays an important role in determining the electrical conductivity of the polymer. This paper will describe recent results on enhancing electrical conductivity of ICPs with the ultimate goal of providing high energy and power density supercapacitors. Our efforts involve the optimization of material composition, polymerization method, doping procedure and processing techniques of polyaniline (PANI) and this has resulted in the formation of doped PANI that is not only solution processable but also exhibits stable electrical conductivity as high as 400 S/cm. PANI systems under development are found to exhibit stable electrochemistry and high faradaic capacitance and can be employed as flexible free standing film electrodes or substrate coated electrodes.