Ramu Manikandan

Expeditious and eco-friendly hydrothermal polymerization of PEDOT nanoparticles for binder-free high performance supercapacitor electrodes

Poly(3,4-ethylenedioxythiophene) (PEDOT) is a promising conjugated polymer that has attracted attention because of its outstanding electronic properties, useful for a wide range of applications in energy storage devices. However, synthesis of high-quality PEDOT occurs via vapour phase polymerization and chemical vapour deposition techniques using extrinsic hard templates or complicated experimental setups. This study introduces a simple hydrothermal polymerization technique using ferric chloride (FeCl3) as an oxidizing agent to overcome the above drawback, which results in good conductive, crystalline PEDOT nanodendrites and nanospheres. The effects of varying the molar ratio of FeCl3 oxidant were investigated in terms of the structural, morphological and electrochemical properties of PEDOT. The supercapacitive performance of the as-polymerized PEDOT nanostructures was determined by fabricating an electrode without the aid of organic binders or conductive additives. PEDOT nanodendrites polymerized using 2.5 molar ratio of FeCl3 demonstrated enhanced electrochemical performance with a maximum specific capacitance of 284 F g−1 with high energy density of 39.44 W h kg−1 at 1 A g−1 current density in 1 M H2SO4 electrolyte. Moreover, the sample possessed higher conductivity, better specific surface area, improved electrochemical properties, comparable crystallinity, and excellent cycling stability after 5000 charge/discharge cycles than the other PEDOT nanostructures. Importantly, the results establish that these materials afford good redox behaviors with better conductivity suitable for the development of an organic electrode-based supercapacitor with high specific charge capacity and stability.

Rationally designed spider web-like trivanadium heptaoxide nanowires on carbon cloth as a new class of pseudocapacitive electrode for symmetric supercapacitors with high energy density and ultra-long cyclic stability

The design and construction of one-dimensional (1D) nanostructures on flexible electrodes without the use of polymer binders/conductive additives has shown great potential for engineering improved electrochemical properties in supercapacitors. Herein, a facile in situ hydrothermal technique was adopted for the growth of trivanadium heptaoxide nanowires on carbon fiber cloth (V3O7/CFC). The resultant V3O7 sample displayed the self-accumulated growth of nanowires on CFC after 48 h with a spider web-like morphology. The specially designed binder-free V3O7/CFC was used to fabricate a symmetric supercapacitor in aqueous 1 M Na2SO4 electrolyte, which showed excellent electrochemical performance. Specifically, in the half-cell configuration, the device exhibited a maximum specific capacitance (Csp) of 198 F g−1 at 1 A g−1 and in full-cell configuration, it showed a Csp of 151 F g−1 at the same current density with ultra-high cycling stability of ∼97% (after 100 000 cycles). In addition, the performance of the symmetric device in 1 M 1-ethyl-3-methylimidazolium trifluoromethanesulfonate electrolyte was studied and it showed a wide potential window of 2 V with a maximum Csp of 178 F g−1. Furthermore, the device exhibited high energy and power densities of 24.7 W h kg−1 (48.5 mW h cm−2) and 5.13 kW kg−1 (10.05 W cm−2), representing as a viable electrode in ionic liquid electrolyte.