Development of Porous carbon for high performing Supercapacitors

Super capacitors have been recognized as promising energy storage devices due to their fast charge-discharge time, very high power density and long life cycle period. It is commercially available but widespread usage is restricted by their high cost and low energy density. These drawbacks can be mitigated by developing a new class of high performance carbon electrodes which consist of a combination of materials produced from abundant, cheap and environmentally friendly resources with low processing costs. ARCI focuses mainly on the development of large scale process to convert various bio-wastes into a high surface area porous carbon material with graphitic structure suitable for super capacitor application. ARCI successfully synthesized high performance porous carbon materials using bio-waste like jute stick, cotton fabric by a simple chemical activation process. The resulting carbon material delivers excellent super capacitor performance in terms of capacitance, rate capability and cyclic stability in comparison to commercial activated carbon material. Also, ARCI in collaboration with HPCL has developed graphene-like activated porous carbon from petroleum coke (Petcoke) by a low-cost chemical activation process and demonstrated its superior electrochemical properties in comparison to commercial supercapacitor grade carbon. Petcoke, a by-product in oil refining process, is a rich carbon source material (> 90%) and also contains significant amount of sulfur impurity. There is an environmental concern of using petcoke as low cost fuel in cement and steel industries due to the emission of hazardous CO2 and SOx gases. Alternatively, use of petcoke for energy storage application abates the emission problem while finding a high value addition to it. A semi-pilot plant involving various equipments such as the coating machine, Semi-auto winding machine, Grooving machine, Sealing machine, flattening machine, Electrolyte filling machine etc are installed at ARCI and are functional for fabricationg cylindrical supercapacitor cells. Large scale synthesis of materials in Kg level is optimized to make carbon slurry and the jelly rolls obtained from coated electrodes are laser welded to achieve large area electrical contact to terminals and demonstrated the first indigenous 1200 F supercapacitor that performs on par with a benchmark commercial supercapacitor. For comparison, the performance of commercial supercapacitor device obtained from market was also validated under similar experimental conditions and the indigeneous device exhibits performance onpar with the commercial device. Cyclic Voltammetry studies were performed at 1 mV/s for both indigenous cell and commercial cell. The capacitance was calculated to be 1198 F at 1 Amp. for indigenous ARCI cell with a voltage window of 2.7 V. The total energy stored is about 1.2 Wh for indigenous ARCI cell with a energy density of 5.01 Wh/Kg, whereas the energy stored for commercial device is about 1.18 Wh with a energy density of 4.5 Wh/Kg.