Cobalt Sulfide-Graphene (CoSG) Composite based Electrochemical Double Layer Capacitors
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Cobalt Sulfide-Graphene (CoSG) Composite based Electrochemical Double Layer Capacitors
Ramachandran R1 , Nirmala Grace A1 , Subramaniam Chittur K2,3 1 Center
for Nanotechnology, VIT University , Vellore, Tamilnadu, India. Physics Division, VIT University, Vellore, Tamilnadu, India. 3 Endeavour Executive Fellow, College of Engineering and Science, Victoria University, Footscray, 3011,Victoria, Australia. 2 Materials
Electrochemical Double Layer Capacitors, EDLC, using Cobalt sulfide- Graphene (CoSG) composite electrodes, were fabricated and the storage process was studied. CoSG composite was prepared by a simple chemical route. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Field Emission Scanning Electron microscopy (FESEM) were used to characterized the as prepared composites which indicated formation of Co S phase. Solutions of perfluorosulfonic acid and Polyvinylidene Fluoride (PVDF) were used as electrode binding material. The storage capacitance of the composites were studied in 1M KCl and 6M KOH electrolytes using standard electrochemical techniques like cyclic voltammetry, CV, electrochemical impedance spectroscopy, EIS, and discharge profiles. The capacitance was estimated for various binder concentrations for both the electrolytes. The concentration of perflurosulfonic acid binder of 0.8 wt% and PVDF of 0.04 wt% showed optimized specific capacitances of 657.8 F/gm and 1418.8 F/g, respectively. Some of the problems in storage density in activated carbon, like varying micro or meso pores, poor ion mobility due to varying pore distribution, low electrical conductivity, can be overcome by using Graphene and composites of Graphene. Graphene in various structural nomenclatures have been used by different groups for charge storage. Optimization of the electrode structure in terms of blend percentage, binder content and interface character in the frequency and time domain provides insights to the double layer interface structure.
Electrochemical double layer capacitors, EDLCs, are very promising devices for energy storage for various electronic applications, due to their long cyclic life and fast charge and discharge characteristics.[1] As such, the EDLCs can replace batteries in many applications[2]. They can be classified into Double Layer Capacitor or Pseudocapacitors depending on whether the storage involves a non Faradiac or a Faradiac process.[3]. In the double layer capacitor, it is difficult to achieve higher specific energy with high operating voltage which is required for some new applications[4]. Carbon based composite materials may be able to achieve high power density with
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long cyclic stability. Graphene and metal oxides/polymer electrode materials have attracted a lot of interest due to the synergy available in the storage process from both materials. [5, 6, 7] Generally, RuO2 possess higher specific capacitance than other metal oxides like NiO, Co3 O4 and MnO2 . However, it has not been considered as electrode material due to its high cos
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