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by Hansung Kim and Branko N. Popov Department of Chemical Engineering

Development of Low Cost Composites for Supercapacitors. by Hansung Kim and Branko N. Popov Department of Chemical Engineering Center for Electrochemical Engineering University of South Carolina. Objectives.

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by Hansung Kim and Branko N. Popov Department of Chemical Engineering

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  1. Development of Low Cost Composites for Supercapacitors by Hansung Kim and Branko N. Popov Department of Chemical Engineering Center for Electrochemical Engineering University of South Carolina

  2. Objectives • To develop a new low cost alloy materials for a supercapacitor electrode based on MnO2. • It should be reversible over a large potential window and have a high specific capacitance and a good rate capability. • The Mn/X Ox(X= Co, Sn, Pb, Ni) mixed oxide will be synthesized at a low temperature to obtain amorphous structure. • The ratio of Mn/X (X= Co, Sn, Pb, Ni), composition of electrode and annealing temperature will be optimized.

  3. Fabrication of Electrodes Reduction of KMnO4 with (CH3CO2)2Mn and proper salt of Co, Sn, Pb, Ni (II) Stirring for 6hrs Filtration using a filtering membrane Annealing in air Mixing with 5wt% PTFE and 20wt% carbon Grounding to a pellet type electrode Cold pressing with two tantalum grids

  4. Cyclic voltammograms of MnO2 prepared by reducing KMnO4 with (CH3CO2)2Mn, scan rate : 5mV/s • 1M Na2SO4 • 166 F/g (b) 2M KCl 160 F/g

  5. Cyclic voltammograms of Mn/Co and Mn/Sn mixed oxide at scan rate : 5mV/sunder1M Na2SO4 Mn/CoOx (8:2) 163 F/g Mn/SnOx (8:2) 170 F/g

  6. Cyclic voltammograms of Mn/Pb and Mn/Ni mixed oxide at scan rate : 5mV/sunder1M Na2SO4 Mn/PbOx (8:2) 185 F/g Mn/NiOx (8:2) 192 F/g

  7. Specific capacitance of Mn/Ni mixed oxide with the annealing temperature measured at 120mA/g of constant current discharge (active / carbon / binder = 0.75 : 0.2 : 0.05) Mn:Pb = 8:2

  8. Specific capacitance of Mn/Ni mixed oxide with the annealing temperature measured at 120mA/g of constant current discharge (active / carbon / binder = 0.75 : 0.2 : 0.05) Mn:Ni = 8:2

  9. 500oC 400oC 300oC 200oC 100oC XRD patterns of Mn/Pb mixed oxide with annealing temperature

  10. Characterization of XRD peaks of Mn/Pb mixed oxide annealed at 500oC

  11. XRD patterns of Mn/Ni mixed oxide with annealing temperature

  12. Characterization of XRD peaks of Mn/Ni mixed oxide annealed at 500oC

  13. + Endothermic process + Endothermic process TGA and DTA analysis of Mn/NiOx in He gasHeat flow : 10oC/min

  14. Element analysis of Mn/Pb and Mn/Ni Oxide using EDAX for different initial concentrations

  15. Specific capacitance of Mn/NiOx and Mn/PbOx with the different ratio of Ni and Pb measured at 120mA/g of constant current discharge

  16. Cyclic voltammograms of Mn/NiOx with respect to carbon ratio in the electrode at scan rate : 5mV/sBinder: 5wt% fixed for all the electrodes 5wt% Carbon 7wt% Carbon 10wt% Carbon

  17. Cyclic voltammograms of Mn/NiOx with respect to carbon ratio in the electrode at scan rate : 5mV/sBinder: 5wt% fixed for all the electrodes 15wt% Carbon 20wt% Carbon 25wt% Carbon

  18. Specific capacitance of Mn/NiOx and carbon composite electrode with the different carbon ratio

  19. Characteristics of Mn/NiOx with different carbon ratio in the electrode

  20. Energy density vs. power density plot of Mn/NiOx electrodes with the different carbon ratio

  21. Constant power discharge of various Mn based oxide single electrode at 1kW/kg

  22. Cycle life test of Mn/PbOx and Mn/NiOx using cyclic voltammogram(1M Na2SO4, 5mV/s, -0.1 ~ 0.8V vs. SCE)

  23. Comparison of low cost materials developed for supercapacitor applications • NiO: • ~250 F/g, 300oC, 120 m2/g, Potential window : 0.5V, 1M KOH • CoOx : • ~291 F/g, 150oC, Potential window : 0.4V, 1M KOH • MnO2 : • ~166 F/g, 300 m2/g, Potential window : 0.9V, 1M KCl • Energy density of 6.9Wh/Kg at 1000W/Kg • Pb2Ru2O6.5 : • ~100 F/g, 35m2/g, potential window : 1V, 0.5M H2SO4 • Energy density of 11Wh/Kg at 750W/Kg • Mn8Pb2O16 : • ~185 F/g, 100oC, 320 m2/g, potential window : 0.9V, 1M Na2SO4 • Energy density of 10.2 Wh/Kg at 700W/Kg • Mn/NiOx • ~210 F/g, 200oC, potential window : 0.9V, 1M Na2SO4 • Energy density of 14 Wh/Kg at 700W/Kg

  24. Conclusions (1) • Co, Sn, Pb, Ni mixed oxide based on Mn were fabricated by the reduction of KMnO4at low temperature. • By introducing Pb, Ni into Mn, the capacitance increased to 185F/g and 210F/g from 166F/g. • The annealing temperature was optimized to be 200 oC for Mn/NiOx and 100 oC for Mn/PbOx. • With increasing annealing temperature, the structure changed into crystalline which caused the steep decrease of capacitance. In the case of Ni, phase separation occurred with heat decomposition over 500oC. • The ratio of Pb in Mn alloy increased continuously over 30mol % while Ni was saturated at 16 mol%

  25. Conclusions (2) • Carbon is used to increase conductivity of the electrode and the ratio was optimized to be 20wt%. In this ratio, Mn/NiOx showed high rate capability of 12Wh/kg at constant power discharge of 1kW/kg • It showed stable cycle life in the potential range of 0.9V. • From these facts, it can be concluded that Mn/PbOx and Mn/NiOx can be a promising material for a supercapacitor application.

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