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

Department of Chemical EngineeringUniversity of South Carolina

by Hansung Kim and Branko N. Popov

Department of Chemical EngineeringCenter for Electrochemical Engineering

University of South Carolina

Development of Low Cost Composites for Supercapacitors


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.


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 KMnO4 with (CH3CO2)2Mn and proper salt of Co, Sn, Pb, Ni (II)


Cyclic voltammograms of MnO2 prepared by reducing KMnO4 with (CH3CO2)2Mn, scan rate : 5mV/s

(a) 1M Na2SO4

166 F/g(b) 2M KCl 160 F/g


Cyclic voltammograms of Mn/Co and Mn/Sn mixed oxide at scan rate : 5mV/s under 1M Na2SO4

Mn/CoOx (8:2)163 F/g

Mn/SnOx (8:2)170 F/g


Cyclic voltammograms of Mn/Pb and Mn/Ni mixed oxide at scan rate : 5mV/s under 1M Na2SO4

Mn/PbOx (8:2)185 F/g

Mn/NiOx (8:2)192 F/g


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


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


XRD patterns of Mn/Pb mixed oxide with annealing temperature

500oC

400oC

300oC

200oC

100oC


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


XRD patterns of Mn/Ni mixed oxide with annealing temperature


2-Theta (deg)

20 30 40 50 60 70

Inte

nsi

ty (

Co

un

ts)

0

500

1000

1500

2000

Mn2O3

MnNiO3

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


TGA and DTA analysis of Mn/NiOx in He gasHeat flow : 10oC/min

+

+ Endothermic process

Endothermic process


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


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

current discharge


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


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


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


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

Carbon ratioCapacitance

(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


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


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


Cycle life test of Mn/PbOx and Mn/NiOx using cyclic voltammogram

(1M Na2SO4, 5mV/s, -0.1 ~ 0.8V vs. SCE)


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


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%


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.

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

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