microporous carbons for electrochemical double layer capacitors

8/3/2019 Microporous Carbons for Electrochemical Double Layer Capacitors

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Microporous Carbons for Electrochemical DoubleLayer Capacitors

AABC Europe, ECCAP symposium, June7-8 2011

Patrice SimonUniv. Paul Sabatier de Toulouse, CIRIMAT, UMR 5085,118 route de Narbonne, 31062 Toulouse FRANCE

[email protected]


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1. Electrochemical Capacitors (ECs)

ECs (supercapacitors):- high power (10-20 kW/kg)

- medium energy (5 Wh/kg)- time constant:1 5 s


performance betweencapacitors and batteries

Complement to batteries

ECs:- Oxide-based (pseudocapacitors)

- Carbon-based (EDLCs)P. Simon and Y. Gogotsi, Nature Materials 7 (2008) 845-854


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1. Charge storage in EDLC: electrostatic

Electrochemical Double Layer Capacitor: no redox reaction

Electro

de

Electrolyte

Approaching


Cdl10-20 F/cm

Capacitance Electrolytedielectricconstant

Surface

High-surface area CarbonSSA 1500 m.g-1 100 150 F.g-1 of AC

Using non aqueous electrolyte Emax = 2.5 V

Electrostatic (NO REDOX)


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1.Hybrid (asymmetric) systemsCombination of a battery-like electrode with a SC electrode combines energy (faradic) and power (SC)

1.2 EDLC (Challenges)

Next Challenges for SupercapacitorsIncrease the energy density to >10 Wh/kg

(E=1/2 C.V)


3. EDLCs: Carbons with controlled Pore Size Distribution

Control the pore size to increase C

2. Pseudo-capacitive charge storage pseudo-intercalation reactions in mesoporous oxides (B. Dunn, S. Tolbert

groups)


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2. Carbide-Derived Carbons

Selective dissolution of a metal carbide (TiC, SiC, ZrC)

TiC(s) + 2 Cl2(g) TiCl4(g) + C(s) (Tsynthesis, H2 annealing)

1.1 nm

Why CDCs? fine tuning of the pore size and pore size distribution

Collaboration with Prof Y. Gogotsi, Drexel university in Philadelphia (USA)

1700 1.2

TiC: pores from 0.6 to 1.1 nm


6.8

7.0

7.4

7.6

8.1 600C

800C

1000C

1000

1100

1200

1300

1400

1500

0.6

0.7

0.8

0.9

1.0

1.1

500 600 700 800 900 1000

BETSSA

(m2/g)

Averageporesiz

e(nm)

Chlorination temperature (C)


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4 cm Lab Cells

2.1 CDCs in Organic Liquid Electrolyte

Electrolyte(C2H5)4N+,BF4- 1.5M in ACN

Et4N

+

BF4

-


95% CDC, 5% PTFE cast onto Al foils

4cm2 electrode area, 15 mg/cm


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2.1 CDCs: Anomalous capacitance increase in1M (C2H5)4N+,BF4- in AN electrolyte

Pores smaller thanthe solvated ion

size are accessibleto the ions


J. Chmiola, G. Yushin, Y. Gogotsi, C. Portet, P.L. Taberna and P. Simon, Science 313, 1760-1763 (2006)

Hypothesis: micropores accessible thanks to the distortion of the ion solvation shell

High capacitancein micropores;50% increase


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2.1 Cavity -electrode (CME) in TEABF4 electrolyte

How to evaluate from dynamic measurements (high-rate CV):- the effective ion size seen by the carbon?- the extent of solvation?


use Cavity -Electrode / CDCs combination to study

electrochemical behaviorV. Vivier, C. Cachet-Vivier, et al., Electrochem. Solid-State Lett. V. 2, 385 (1999)


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2. CDCs: High power capability in1M (C2H5)4N+,BF4- in AN electrolyte

120

130

140

150

CDC 500 CCDC 600 C

acitance(F/g)

B

0.64 nm

0.72 nm

0.76 nm

1.1 nm


Microporous CDCs: high capacitance and high power capability

80

90

100

110

0 20 40 60 80 100

CDC 800 CCDC1000 CNMACSMAC

Specificc

a

Current density (mA/cm2)

Activated

Carbons


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2.1 CDCs Structure

Quenched Molecular Dynamics modelling of CDCs

m

CDC 1200C (1.2 nm)CDC 600C (0.74 nm)

AABC Europe, ECCAP symposium, June7-8 2011J. C. Palmer, Y. Gogotsi et al, Carbon, 48. 1116-1123 (2010)

4

4 nm

Highly disordered structures(no graphitic plans, no slit pores)

interconnected, open porous structure

4 nm


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Limitation in ion adsorption

-

0

0.002

0.004

0.006

0.008

100 mV/s

Current/mA

CDC 0.68nm in NEt4,BF4 in AN

NEt4+ BF4-0

0.005

0.01100 mV/s

Current/mA

CDC 0.68nm in EMI,TFSI in AN

TFSI-EMI+

+ EMI+ ? + BF4- ?


Limited pore accessibility: steric effect or surface saturation?

-0.006

-0.004

- .

-1.5 -1 -0.5 0 0.5 1

E/V vs. Ag ref

Limited NEt4+

adsorption

-0.01

- .

-1 -0.5 0 0.5 1

E/V vs. Ag ref

Limited TFSI-

adsorption

Addition of EMIBF4


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Addition of EMIBF4NEt4BF4 1.5M in ACN +

addition of EMIBF4

0

0.5

1

current

Limited pore accessibility or surface saturation?

EMI,TFSI 2M in ACN +addition of EMIBF4

0.5

1

1.5

100 mV/s

urrent

[EMIBF4] in EMITFSI 2M+ACN:

0.68 nm CDC


-1.5

-1

-0.5

-1.5 -1 -0.5 0 0.5 1

0M

0.2M

0.5M

1M

2M

Normaliz

ed

E/V vs. Ag ref

[EMIBF4]:

.

Current increase with EMI,BF4 additions no C surface saturation

1. Pore size/ion size relationship drives the capacitance2. Selective ion adsorption

-1.5

-1

-0.5

0

-1 -0.5 0 0.5 1

0.00 M0.2 M0.5 M

1 M2 M

Normalize

d

E/V vs. Ag ref


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Limited pore accessibility or surface saturation?

-0.5

0

0.5

1 20 mV/s

alizedcurrent

0

0.5

1

1.5 100 mV/s

NEt4BF

41.5M+ACN

EMIBF4

2M+ACNalizedcurrent

EMI,TFSI


EMI,BF4 no limitation, ideal capacitive behavior

No surface charge saturation, only steric (size) effect

-1.5

-1

-1.5 -1 -0.5 0 0.5 1

NEt4BF

41.5M + ACN

EMIBF4

2M + ACN

N

or

E/V vs. Ag ref

-1.5

-1

-0.5

-1 -0.5 0 0.5 1

No

r

E/V vs. Ag ref


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2.2 3-electrode cell in neat Ionic Liquid

ElectrolyteEthyl-MethylImmidazolium-TriFluoro-methane-SulfonylImide (EMI-TFSI)4 cm Cell


EMI+: 0.76 nm(longest dimension)

TFSI-

: 0.79 nm(longest dimension) Same size

Temp. 60C; Active materials: CDCs

EMI+ TFSI-Galva.


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2.2 3-electrode cell in EMI-TFSI

Cell Capacitance (F/g)

Positive Electrode (F/g)

Negative Electrode (F/g)

100

120

140

160

180

C(

F/g)

TFSI- EMI+


P. Simon, Y. Gogotsi Nature Materials, 7 (2008) 845-854

R. Lin, P. Huang, J. Segalini, C. Largeot, PL Taberna, Y. Gogotsi and P. Simon., Electrochimica Acta 54 (2009)

1. +50% increase capacitance vs YP17 AC2. Maximum at 0.72 nm when ion size ~ pore size!!!

Ions aligned into the pores!

60

80

0.6 0.7 0.8 0.9 1 1.1Pore Size (nm)

YP17 AC


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ElectrolyteEthyl-MethylImmidazolium-TriFluoro-methane-SulfonylImide (EMI-TFSI)

3-electrode cell in neat Ionic Liquids

Maximum Capacitance when pore size ~ ion size

Ions aligned in pores capacitance increase


- potential well (K. Kaneko, Carbon 2010)?

- screening effect (Kornyshev et al., 2011)?

- exclusion of counter ions (Shim et al., 2010)?

Combining Modelling with in-situ experiment are needed tounderstand ion adsorption in nanopores


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2.2 3-electrode cell in PYR14-TFSI

70 F.g-1 130 F.g-1 80 F.g-1

High temperature EDLC in PYR14,TFSI

2.5V supercapacitor cell operating at 100C


0.64 nm

Small pore size: CV distortion

0.8 nm

Medium pore size: Ideal CV, high C

1.1 nm

Larger pore size: Ideal CV, low C

5mV.s-1 5mV.s-1 5mV.s-1

Adapt the carbon pore size to the ion size is the key to reach high C

in-situ NMR (Prof C. Grey) and modelling (K. Kaneko) on-going


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TiC bulk (ceramic)

3. From powder to bulk films

Bulk CDC films


1. Chlorination @ 500C TiC derivedcarbon film

Monolithic TiC 2. Cell

TiC plate CDC film

Electrolyte + separator

Teflon plates No binder, dense electrode


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3.2 Electrochemistry (CVs)

Aqueous electrolyte(H2SO4)

Organic electrolyte(NEt4BF4 + ACN)


Similar capacitive behavior as for powder CDCs

vol. capacitance ?


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3.3 Volummetric capacitance

BA

ACN + 1M NEt4BF4 H2SO4 1M


Vol. Capacitance of 180 F/cm3 for e = 1 m (CA = 50 F/cm3) Thin films with high energy density (+300% !!!)

CA CA

J. Chmiola, C. Largeot, P.L. Taberna, P. Simon and Y. Gogotsi, Science 328, 480-483 (2010)


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Chlorination(500C


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4. Conclusions

1. Capacitance increase thanks to partial desolvation twice volummetric capacitance; no power limitation

Microporous Carbons (CDCs) for EDLCs


3. Thin-films high energy (x3) with bulk microporous carbons

2. High capacitance when pore size ion size; mechanism? need for modelling coupled with in-situ experiments (NMR, XRD

microporous carbons for electrochemical double layer capacitors

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