Hansung Kim and Branko N. Popov

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/s under 1M Na2SO4
Mn/CoOx (82) 163 F/g
Mn/SnOx (82) 170 F/g
6
Cyclic voltammograms of Mn/Pb and Mn/Ni mixed
oxide at scan rate 5mV/s under 1M Na2SO4
Mn/PbOx (82) 185 F/g
Mn/NiOx (82) 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)
MnPb 82
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)
MnNi 82
9
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
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/s Binder 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/s Binder 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
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Characteristics of Mn/NiOx with different carbon
ratio in the electrode
Carbon ratio Capacitance (F/g) BET (m2/g) Pore volume (10-3mL/g) Resistance (?)
5wt 44.9 227 345 1.48
7wt 111.5 273 397 1.18
10wt 152.5 286 441 0.35
15wt 151.1 338 523 0.21
20wt 171.9 387 601 0.15
25wt 163.3 541 642 0.15
30wt 155.5 596 725 0.13
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 KMnO4 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
  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.