nanostructured carbons for supercapacitors: beyond the

Nanostructured Carbons for Supercapacitors: beyond the double-layer concept

CIC Energigune, Vitoria, Spain, March 21 2012

double-layer concept

Patrice SIMON

Université Paul Sabatier CIRIMAT UMR CNRS 5085

Toulouse – FRANCEsimon@chimie.ups-tlse.fr

Outline

1. Supercapacitors- principles - charge storage mechanism

2. Electrical Double Layer Capacitors2.1 Activated carbons

3. High voltage EDLCs

2.1 Activated carbons2.2 Microporous carbons2.3 Modeling (MD)

1. Why supercapacitors?

� Intermediate performance betweenbatteries and capacitors

Electrochemical Capacitors:

- high power (10-20 kW/kg) - medium energy : 5 Wh/kg- time constant: ~ 5 s

(A. Burke’s talk)

batteries and capacitors

Various types of ECs:- Carbon-based: EDLCs (~90%)- oxydes (pseudo-capacitance)- asymetric and hybrid devices (A. Beliakov’s talk)

Applications: (J. R. Miller’s talk)- power electronics (<100F)- power delivery / energy harvesting: HEV (Citroën, Peugeot, Mazda) , trams…

EDLCs : Double layer capacitance

Electro

de

Electro

lyte

Electrostatic Storage

1.1 Charge storage in EDLCs

Electro

lyte

Cdl≈10-20 µF/cm²

Active material: high surface area carbon (1,500-2,500 m²/g): >100 F/g

2 nm

ff

2 nm10 nm

ActivatedCarbon

CarbonNanotubes

CarbonOnions

Graphene

1. Increase carbon capacitance

1.2 EDLCs : challenges

Next Challenges for Supercapacitors

Incease energy density (E=1/2 C.V²) from 5 to >10 Wh/kg� tdischarge > 10s

1. Increase carbon capacitancework on the carbon / electrolyte interface� understand the ion size /carbon pore size relationship

2. Increase the cell voltage� design carbon structure in conjunction with electrolyte

formulation

Outline

1. Supercapacitors- principles - charge storage mechanism

2. Electrical Double Layer Capacitors2.1 Activated carbons

3. High voltage EDLCs

2.1 Activated carbons2.2 Microporous carbons2.3 Modeling (MD)

2.1 Activated Carbons

Activated Carbon=

Porous carbon

2. Active Materials: high surface area carbon

� high SSA ~1500 m2/g

Activated Carbons(amorphous)

Large Pore SizeDistribution

2.2 Carbide-Derived Carbons

Selective etching of metal from carbide (TiC, SiC, ZrC…)

TiC(s) + 2 Cl2(g) →→→→ TiCl4(g) + C(s)

Why CDCs? � Controled, narrow pore size distribution

Pores from 0.6 to 1.2 nm

900°C

1 nm

1600

1700

1.1

1.2

800°C

0.8 nm

500°C

0.68 nm

1000

1100

1200

1300

1400

1500

1600

0.6

0.7

0.8

0.9

1.0

1.1

500 600 700 800 900 1000

BE

TS

SA

(

m2 /g

)

Average pore size (nm

)

Chlorination temperature (°C)

Selective etching of metal from carbide (TiC, SiC, ZrC…)

TiC(s) + 2 Cl2(g) →→→→ TiCl4(g) + C(s)

Why CDCs? � Very fine pore size control (unimodal)

Pores from 0.6 to 1 nm

900°C

1 nm

2. Carbide-Derived Carbons

800°C

0.8 nm

500°C

0.68 nm

Cellules Labo Electrolyte(C2H5)4N+,BF4

- 1,5M in ACNEt4N+

BF4-

2.1 CDCs in AN+1M (C2H5)4+,BF4-

95% CDC, 5% PTFE sur feuille Alélectrode 4cm2, 15 mg/cm²

Pores smaller thanthe solvated ion

size are accessibleto the ions

2.1 CDCs: Capacitance increase in 1M (C2H5)4N

+,BF4- in AN electrolyte

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 capacitance in micropores; 50% increase

100

110

120

130

140

150

Spe

cific

capa

cita

nce (F/g

)

1.1nm0.80.76nm0.74nm

0.72nm

0.64 nm

0.72nm

0.74nm

0.76nm0.8nm1nm

2.1 CDCs in AN+1M (C2H5)4+,BF4-

High C at high rateLow capacitance loss (<10%)

80

90

100

0 20 40 60 80 100 120

Spe

cific

capa

cita

nce (F/g

)Current density (mA.cm-2 )

1 A.g-13 A.g-1

6 A.g-1

Microporous Carbons: high C AND high P

ESR: 0.6 Ohm.cm² @ 1kHzCDCs with 0.7-0.8 nm pore size

< 0.7 nm <

130

140

150

160

170

Cell Capacitance

Negative electrode

Specific

capacita

nce (F/g

)

Positive electrode

2.1 CDCs in AN+1M (C2H5)4+,BF4-

3-electrode cells

J. Chmiola. C. Largeot, P.L. Taberna, P. Simon and Y. Gogotsi, Angewandte Chemie Int. 120 (18), 2008, 3440

1. Adapt pore size to ion size

2. Ions partially desolvated to accessmicropores

3. Cmax for an optimum pore size

< 0.76 nm <

R. Lin, P.L. Taberna, J. Chmiola, D. Guay, Y. Gogotsi and P. Simon, JECS 158 (2009) A7-A12

100

110

120

130

0.6 0.7 0.8 0.9 1 1.1

Specific

capacita

nce (F/g

)

Pore size (nm)

TFSI- EMI+

Cell Capacitance (F/g)

Positive Electrode (F/g)

Negative Electrode (F/g)

100

120

140

160

180

C (F/g

)

2.2 CDCs in neat EMI,TFISI

60

80

0,6 0,7 0,8 0,9 1 1,1Pore Size (nm)

AC

C. Largeot, C. Portet, J. Chmiola, P.L. Taberna, Y. Gogotsi and P. Simon JACS, 130 (9), 2730 -2731 (2008)

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

2. Maximum C at ~ 0,72 nm � when ion size ~ pore size !!!

1. >50% capactiance increase commercial activated carbon (AC)

No solvent, cation size ≈ anion size:

Maximum Capacitance when ion size ~ pore size:

Ions aligned in pores >50% capacitance increase

Carbone

Carbon

e

2.2 Microporous CDCs: summary

Ions aligned in pores � >50% capacitance increase“Double-layer” sub-nanometer pores?

- potential well (K. Kaneko, Carbon 2009) ?

- screening (Kornyshev et al.?) 2009-2011

- exclusion of counter-ions (Shim et al.) ? 2011

~ 50 papiers since 2008

� C increase confirmed

� Modeling experiments needed for:

- understanding the capacitance increase in micropores

- designing new carbon structures with high capacitance

2.2 DFT modeling of EMI,TFSI in slit pores

D. Jiang et al. Nano Letter 11 (Dec. 2011) 5373

2. Very fine and precise control of the carbon pore size is neededto observe the capacitance increase

1. Confirmation of the capacitance increase in micropores

� Constructive superposition of the ionic density profiles

Ionic density profiles of ions near one charged wallCapacitance vs pore width (σ = ion size)

� Oscillation of capacitancevs carbon pore size!

Y. Feng et al, J. Phys. Chem. Lett 2 (Dec. 2011) 2859

2.2 MD modeling of EMI,TFSI in slits pores

� Oscillation of capacitancevs carbon pore size!

� Constructive superposition of the ionic density profiles from each wall

2. Precise control of the carbon pore size needed

1. Confirmation of the capacitance increase in micropores; trend OK

Models using ideal carbon structures (CNTS, graphite, graphene) confirms C increase but fail to reproduce the experimental C values

Starting point:

1) Use of “real” CDC structures( from RMC simulations)

IFPn: T. De Bruin, J. Jover-Azpurua,

PECSA (UMPC): M. Salanne, B. Rotenberg, C. Merlet

Collaboration with

2.3 MD modeling of BMI,PF6 in CDCs

1) Use of “real” CDC structures( from RMC simulations)

2) MD simulation including electrolyte tank

3) Constant potential at carbon electrode; local charge on carbon

depends on adsorbed ions

CDC 900°C CDC 1200°CBMI, PF6

electrolyte = EMI-PF6 (100°C)

CDC CDC

Potentiel appliqué

2.3 MD modeling of BMI,PF6 in CDCs

1. Electrolyte accède aux pores même à Ψ=0V2. Echanges d’ions avec l’électrolyte !!!3. Nombre de coordination diminue pour les ions (“desolvation”)

C. Merlet, B. Rotenberg, P.A. Madden, P.-L. Taberna, Y. Gogotsi, P. Simon and M. Salanne, Nature Materials (April 2012)

électrolyte = EMI-PF6 (100°C)

CDC CDC

Potential

2.3 MD modeling of BMI,PF6 in CDCs

1. Electrolyte is inside pores even at Ψ=0V2. Ion exchange with the electrolyte bulk !3. Coordination number of ions decreases inside the pores (“desolvation”)

C. Merlet, B. Rotenberg, P.A. Madden, P.L. Taberna, Y. Gogotsi, P. Simon, M. Salanne, Nature Materials (in press)

E=0.5V E=0,5V E=-0.5V

2.3 MD modeling of BMI,PF6 in CDCs

1) Small number of co-ions with counter ions vs graphite

2) One ion per pore observed!

2.3 MD modeling of BMI,PF6 in CDCs

Ions get closer to the carbonsurface for CDCs than for graphite

Charge (per V) per carbon atom largerfor CDCs than for graphite

Capacitance increase comes from partial « desolvation », closerapproach of ions and the absence of the overscreening effect because

of ions confinement

� In progress….

C. Merlet, B. Rotenberg, P.A. Madden, P.L. Taberna, Y. Gogotsi, P. Simon, M. Salanne, Nature Materials (April 2012)

1. Increase carbon capacitance

1.2 EDLCs : challenges

Next Challenges for Supercapacitors

Incease energy density (E=1/2 C.V²) > 10 Wh/kg� tdischarge > 10s

1. Increase carbon capacitancework on the carbon / electrolyte interface� understand the ion size /carbon pore size relationship

2. Increase the cell voltage� approach: adapt carbon structure to electrolytes

3. Ionic Liquid mixtures

1) Ionic Liquid mixtures: PIP-PYR/FSI

(A)

Flow (End

oUp)

NC

C

C

CC

CC

CC +

C

CC

C

C

C

C

C

C

N

+

(I) PIP13FSI

(II) PYR14FSI-18

6

-30-72

(B)

Con

duc

tivity

(S c

m-1)

60.1 12.6 -23.2 -50.9 -73.2

T (°C)

10-610-510-410-310-210-1

50% PIP13FSI / 50% PYR14FSImixture: no melting down to -80°CConductivity:

Heat

Flow (

CC

S

O

S

OO

O

N

FF

_

(III) PIP13-PYR14-FSI

-30

-45

Temperature (°C)

-72

-100 -50 0 50 100

Con

duc

tivity

PIP13FSIPYR14FSIPIP13-PYR14

-FSI

103/T (103K-1)

10-910-810-710-6

2.5 3 3.5 4 4.5 5

Poster Rongying Lin

2) Carbons

High surface area, fully accessible:1. Onion-Like Carbons (OLCs)2. NTC grown onto Al foil (PECVD)

Onion-Like Carbon

3. Exohedral Carbons with IL mixture

OLCs

3. OLC et CNT with IL mixture

CNTs

R. Lin, P.-L. Taberna, et al.J Chem. Phys. Let.19 (2011) 2396-2401

Ionic Liquids and exohedral carbons: - 3.7V Voltage window at room T- from -50°C up to 100°C (2.9V) ; - BUT small capacitance (100 mF/cm², 5 mg)

3. OLC et CNT avec mélange de IL

IL mixture and exohedral carbons: cell voltage improvement and wider T operation range

� Key is the carbon / electrolyte interface

R. Lin, P.-L. Taberna, et al.J Chem. Phys. Let.19 (2011) 2396-2401

Graphene for SCs:

Zhu, et al., Science 12 May 2011

3.2 Activated graphene

SSA = 3000 m²/g, pore size: 1.5 nm

High C (150 F/g) and accessible surface

But:- low electrode loading: 1 mg/cm² (1 µm-thick films)- low graphene density � low C vol.

0

50

100

150

200

C (

F.g

-1)

Cellule Swagelok, 2 mg/cm²;5%PTFE-95%grahene, T=25°C

@ 20 mV/s

3.2 Activated graphene in IL mixture

-200

-150

-100

-50

0 0.5 1 1.5 2 2.5 3 3.5

C (

F.g

E (V)

a) 3,7V @ 25°Cb) C=170 F/g

High voltage and high C!!!

@ 20 mV/s

Cellule Swagelok, 2 mg/cm²;5%PTFE-95%grahene, T=25°C – 60°C

@ 100 mV/s

3.2 Activated graphene in IL mixture

a) 3V for 25°C<T< 80°Cb) C=170 F/g

@ 100 mV/s

ESR of 5-10 ohm.cm²

High C and low ESR @ 80°C

3.2 Activated graphene in IL mixture

a) Cycled @ -40°C and -50°Cb) C=100 – 120 F/g

High ESR but still SC working

Validation of the approach: high C (150 F/g) and ∆∆∆∆E > 3V (3,7V@RT)

3.2 Graphene: hype or reality?

Graphene interesting for thin-film, small size devices; not really for Grid storage or HVE/EV applications!!!!

P. Simon and Y. Gogotsi, Science 334 (Nov. 2011) 917-918

4. Conclusions

1. Capacitance increase in micropores due to - desolvation,- absence of over-screening - closer approach of ions to carbon surface

Microporous Carbons (CDCs) for EDLCs

2. Influence of the solvent ?� coupling in-situ NMR and modelling

1. Eutectic mixture of ILs: ∆T of 150°C

2. Activated graphene : high C and ∆E (3.7V @ RT)

� Multiple combinations possible for optimizing C and ∆E

Mastering carbon / electrolyte interface

Thanks

P.L. Taberna, B. DaffosJ. Ségalini, R. Lin, E. Iwama, C. Lecoeur (CIRIMAT)

Y. Gogotsi (Drexel university, Philadelphia)

MAICANANO project programme Blanc (2010-2012)

EADS Foundation Chair of Excellence “NanoMultifonctionnels Embarqués”(2012-2016)

ERC 2011 Advanced Grant “IONACES”2012-2016, project n°291543

1.2 Applications transports : tramways

Source : Alstom

Module SCs :1) récupération de l’énergie de freinage

2) autonomie de traction sur 100s m

Collaboration Alstom / Batscap

Autres tramways à Madrid, Cologne, Mainz (…)

=

Carbone activé : matériau désordonné

+Graphite

Feuillet de graphène

2.1 Carbone activé

Carbones activés

Distribution de taille de pore

Photo MET d’un CA

A. Terzyk et al., Phys. Chem. Chem. Phys., 2007, 9, 5919

Collecteursde courant

Carbone activéElectrolyte

Anion del’électrolyte

Carbone activé

1.1 Stockage des charges

+

2.5 V-2.7 V

Séparateur

- Charbon actif (1500 m2/g) : 100 F/g- Electrolyte organique : ΔV=2.5V- Tfonctionnement : -40°C;+80°- Milions de cycles de charge/décharge

Credit: Argone Nal Lab

1.2 Applications

Alterno/démarreur ET récupération freinagemicro-hybride e-Hdi pour Citroen C3, C4, C5 diesel (2012)

• -15 % gasoil• CO2 < 130g par km

http://www.citroen.fr/citroen-ds4/technologies/#/citroen-ds4/technologies/

http://www.leblogauto.com/2011/11/mazda-i-eloop-place-au-supercondensateur.html

Mazda: i-ELOOP concept

http://www.turbo.fr/peugeot/peugeot-308/essai-auto/410344-essai-peugeot-308/

Peugeot: e-HDI sur 308 1.6 HDi 110 ch

2. Active Materials: high surface area carbon

Onion Like Carbon Carbon Nanotubes Graphene

Activated Carbon Carbon-DerivedCarbides

Templated Carbons