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Supercapacitors are nominally electrochemical double-layer, capacitor devices, fabricated from high specific surface area carbon materials (EDLC’s), or from pseudocapacitive metal oxide systems, or combinations of these. Generally, they can be classified as: electrochemical double-layer capacitors (EDLCs), with carbon as the primary electrode material; as pseudocapacitors, with metal-oxide/polymer composites as the electrode material; or as hybrid capacitors, a combination of both the EDLCs and pseudocapacitive systems [2]. Their charge storage mechanisms are based upon physical charge separation at the electrode surfaces, such that no chemical reactions occur, and no charges are transferred between electrode and electrolyte (EDLC’s), or upon chemical processes such as redox reactions, for pseudocapacitive storage [2]. Although these electrode systems have attained relatively high charge storage capabilities, this performance level is strongly influenced by material composition, structure and properties, in a manner still not fully understood, in particular, for composite polymer/conducting oxide based pseudocapacitive electrode systems. The objective of this research, therefore, was focused on developing an insight into the mechanisms for enhanced charge storage capabilities in these advanced composite electrodes systems. Non-conductive polymer systems such as PEO, SBS, and PVDF were employed as the matrix phase in these studies, with high surface area graphite ~ (115m2/gm), and co-precipitated, heat-synthesized, and pseudocapacitive NiO as the conducting phases in the fabricated composite electrode systems. In this work, the electrode systems were developed as thin/thick film coatings on cleaned SS metal-foil substrates, using spin-coating MOD methodology, and heat treatments in the range of 180 to 300 degree Celsius, guided by the TGA characteristics of the Polymer matrix phase. Addition of graphite to the non-conducting polymers resulted in the development of well-recognized redox characteristics, most notably in PEO, SBS and PPA/AA systems, resulting in significantly enhanced pseudocapacitive charge storage capability, The further incorporation of pseudocapacitive NiO into the polymer/ graphite solutions, resulted in a large additive charge storage effect, and high supercapacitor performance. This work has demonstrated that composite metal oxide/graphite/non-conducting polymer based binder systems, through the percolative principle, can produce high quality, and high storage capacity film electrodes for supercapacitive devices and advancement. |
