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

Department of Chemical Engineering University of South Carolina Objectives To develop a new low cost alloy materials for a supercapacitor electrode based on MnO 2. 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.

Department of Chemical Engineering University of South Carolina Fabrication of Electrodes 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 Reduction of KMnO 4 with (CH 3 CO 2 ) 2 Mn and proper salt of Co, Sn, Pb, Ni (II)

Department of Chemical Engineering University of South Carolina Cyclic voltammograms of MnO 2 prepared by reducing KMnO 4 with (CH 3 CO 2 ) 2 Mn, scan rate : 5mV/s (a)1M Na 2 SO F/g (b) 2M KCl 160 F/g

Department of Chemical Engineering University of South Carolina Cyclic voltammograms of Mn/Co and Mn/Sn mixed oxide at scan rate : 5mV/s under 1M Na 2 SO 4 Mn/CoOx (8:2) 163 F/g Mn/SnOx (8:2) 170 F/g

Department of Chemical Engineering University of South Carolina Cyclic voltammograms of Mn/Pb and Mn/Ni mixed oxide at scan rate : 5mV/s under 1M Na 2 SO 4 Mn/PbOx (8:2) 185 F/g Mn/NiOx (8:2) 192 F/g

Department of Chemical Engineering University of South Carolina 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

Department of Chemical Engineering University of South Carolina 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

Department of Chemical Engineering University of South Carolina XRD patterns of Mn/Pb mixed oxide with annealing temperature 500 o C 400 o C 300 o C 200 o C 100 o C

Department of Chemical Engineering University of South Carolina Characterization of XRD peaks of Mn/Pb mixed oxide annealed at 500 o C

Department of Chemical Engineering University of South Carolina XRD patterns of Mn/Ni mixed oxide with annealing temperature

Department of Chemical Engineering University of South Carolina Characterization of XRD peaks of Mn/Ni mixed oxide annealed at 500 o C

Department of Chemical Engineering University of South Carolina TGA and DTA analysis of Mn/NiOx in He gas Heat flow : 10 o C/min + + Endothermic process

Department of Chemical Engineering University of South Carolina Element analysis of Mn/Pb and Mn/Ni Oxide using EDAX for different initial concentrations

Department of Chemical Engineering University of South Carolina Specific capacitance of Mn/NiOx and Mn/PbOx with the different ratio of Ni and Pb measured at 120mA/g of constant current discharge

Department of Chemical Engineering University of South Carolina Cyclic voltammograms of Mn/NiOx with respect to carbon ratio in the electrode at scan rate : 5mV/s Binder: 5wt% fixed for all the electrodes 5wt% Carbon7wt% Carbon10wt% Carbon

Department of Chemical Engineering University of South Carolina Cyclic voltammograms of Mn/NiOx with respect to carbon ratio in the electrode at scan rate : 5mV/s Binder: 5wt% fixed for all the electrodes 15wt% Carbon20wt% Carbon25wt% Carbon

Department of Chemical Engineering University of South Carolina Specific capacitance of Mn/NiOx and carbon composite electrode with the different carbon ratio

Department of Chemical Engineering University of South Carolina Characteristics of Mn/NiOx with different carbon ratio in the electrode Carbon ratio Capacitance (F/g) BET (m 2 /g) Pore volume (10 -3 mL/g) Resistance (  ) 5wt% wt% wt% wt% wt% wt% wt%

Department of Chemical Engineering University of South Carolina Energy density vs. power density plot of Mn/NiOx electrodes with the different carbon ratio

Department of Chemical Engineering University of South Carolina Constant power discharge of various Mn based oxide single electrode at 1kW/kg

Department of Chemical Engineering University of South Carolina Cycle life test of Mn/PbOx and Mn/NiOx using cyclic voltammogram (1M Na 2 SO 4, 5mV/s, -0.1 ~ 0.8V vs. SCE)

Department of Chemical Engineering University of South Carolina Comparison of low cost materials developed for supercapacitor applications NiO: –~250 F/g, 300 o C, 120 m 2 /g, Potential window : 0.5V, 1M KOH CoOx : –~291 F/g, 150 o C, Potential window : 0.4V, 1M KOH MnO 2 : –~166 F/g, 300 m 2 /g, Potential window : 0.9V, 1M KCl –Energy density of 6.9Wh/Kg at 1000W/Kg Pb 2 Ru 2 O 6.5 : –~100 F/g, 35m 2 /g, potential window : 1V, 0.5M H 2 SO 4 –Energy density of 11Wh/Kg at 750W/Kg Mn 8 Pb 2 O 16 : –~185 F/g, 100 o C, 320 m 2 /g, potential window : 0.9V, 1M Na 2 SO 4 –Energy density of 10.2 Wh/Kg at 700W/Kg Mn/NiOx –~210 F/g, 200 o C, potential window : 0.9V, 1M Na 2 SO 4 –Energy density of 14 Wh/Kg at 700W/Kg

Department of Chemical Engineering University of South Carolina Conclusions (1) Co, Sn, Pb, Ni mixed oxide based on Mn were fabricated by the reduction of KMnO 4 at 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 o C for Mn/NiOx and 100 o C 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 500 o C. The ratio of Pb in Mn alloy increased continuously over 30mol % while Ni was saturated at 16 mol%

Department of Chemical Engineering University of South Carolina 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.