Chicago Kiev Karlsruhe, Philadelphia Tokyo, Germany Japan ...computing.ornl.gov/workshops/peta08/presentations/y_gogotsi.pdf · Pore volume (cc/nm/g) Pore size (nm) Ti 3SiC 2-CDC

http://nano.materials.drexel.eduDANOTECHNOLOGY

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KievChicago

Karlsruhe,Tübingen,Germany

Tokyo,Japan

Oslo, Norway

Yury GogotsiDepartment of Materials Science and Engineering,

Department of Mechanical Engineering, A.J. Drexel Nanotechnology Institute

Drexel UniversityPhone: (215) 895 6446, [email protected]

Philadelphia

Scientific Impacts and Opportunities in Electrical Energy Storage


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1. Chemical Storage2. Capacitive Storage

Chairs:

John B. Goodenough, University of Texas, AustinHéctor D. Abruña, Cornell UniversityMichelle V. Buchanan, Oak Ridge National Laboratory


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Bruce Dunn,Yury Gogotsi*Michael ArmandMartin BazantRalph BroddAndrew BurkeRanjan DashJohn FerrarisWesley Henderson

Samson JenekheKatsumi KanekoPrashant Kumta

Keryn LianJeffrey Long

Joel SchindallBruno ScrosatiPatrice Simon

Henry White

John Chmiola, and other students/post-docs at Drexel UniversityDr. Jingsong Huang, ORNLProf. Katsumi Kaneko, Chiba UniversityProf. Miklos Kertesz, Georgetown University

AcknowledgementsCapacitive Storage Science panel members


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Supercapacitors Batteries

•Fundamentally different electrodes

•Batteries –electrochemically active

•Supercapacitors -electrochemically passive

•Leads to different properties

Supercapacitors and Batteries

J. Chmiola, Y. Gogotsi, Nanotechnology Law and Business, v. 4, 577 (2007)

anodecathodecell CCC111

+=


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• Virtually all portable electronics are powered by batteries. U.S. and Europe far behind (absent); Japan, Korea, and China in the commercialization of advanced batteries

• The market demand is for maximum energy and power with minimal volume and weight

• In order to entice consumers to replace cell phones and laptops, new features are continually added (more energy) and the demands increase

Batteries are Ubiquitous

• Supercapacitors have higher power density than existing technologies• Ability to compliment batteries in hybrid power systems and enable other

high power applications• Increasing energy density paramount - understanding and being able to

predict electrode and electrolyte properties the key factor

Supercapacitors are Coming


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NSTITUTE Electrical Energy StorageSupercapacitors are able to attain greater energy densities while still maintaining the high power density of conventional capacitors.

Supercapacitors are a potentially versatile solution to a variety of emerging energy applications based on their ability to achieve a wide range of energy and power density.

A battery-supercapacitor hybrid may be the battery of the future

Ragone plot of energy storage systems

R. Kotz, M. Carlen, Electrochimica Acta 45, 2483 (2001) R. F. Service, Science 313, 902 (2006).


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• Capacitor Systems and Devices- Increased energy density- Longer life cells (10 yr., 1M cycles)- Self-balancing- Cost

• Electrolytes for Capacitor StorageDesign electrolytes for EC operation: high ionic conductivity; wide electrochemical window, chemical and thermal stability; non toxic, biodegradable and/or renewable

• EDLC and Pseudocapacitive Charge Storage MaterialsNew strategies are needed to improve power and energy

density of charge storage materials

30 MJ CAPACITOR STORAGE SYSTEM30 MJ CAPACITOR STORAGE SYSTEM


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Materials for Supercapacitors

0

200

400

600

800

1000

1200

1400

AC

CNT

MPC CAGC60 NRC

PANI/AC

PEDT/AC

PIThi

PFDT

PPy/AC

MPFPT

DAAQ

PAn/CNT

P3MTPEDT

PAn

RuO2/PAPPA

RuO2(sol-gel)

RuO2(ED)RuO2(sol-gel)RuO2/ACRuO2/ACRuO2(ESD)RuO2/CB

RuO2/CNTRuO2/ACRuO2/CXGRuO2/MPCRuO2/AC

NiO SnO2 / Fe3O4

MnOx

NiO/RuO2

MnO2

NiO

MnO2

Ir0.3Mn0.7O2

MnO2

Spec

ific

Cap

acita

nce

/ F g

-1

Carbons Polymers Metal Oxides RuO20

200

400

600

800

1000

1200

1400

0

200

400

600

800

1000

1200

1400

AC

CNT

MPC CAGC60 NRC

PANI/AC

PEDT/AC

PIThi

PFDT

PPy/AC

MPFPT

DAAQ

PAn/CNT

P3MTPEDT

PAn

RuO2/PAPPA

RuO2(sol-gel)

RuO2(ED)RuO2(sol-gel)RuO2/ACRuO2/ACRuO2(ESD)RuO2/CB

RuO2/CNTRuO2/ACRuO2/CXGRuO2/MPCRuO2/AC

NiO SnO2 / Fe3O4

MnOx

NiO/RuO2

MnO2

NiO

MnO2

Ir0.3Mn0.7O2

MnO2

Spec

ific

Cap

acita

nce

/ F g

-1

Carbons Polymers Metal Oxides RuO2

EDLC Charge Storage Materials: Majority of present day EDLC devices are based on activated carbon


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Charge Storage Materials by Design• Materials Synthesis

– Controlled structure and porosity

– Controlled surface functionality and charge

• Designed Architectures– Oriented High SSA – Conformal coatings

• Understanding of pore structure and ion size influences on charge storage

⇒ Will affect ESR, C, V, and thus…Power and Energy!

D. Choi, G. E. Blomgren, P. N. Kumta, Advanced Materials, 14 (2006)

VN


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1000

2000

3000

4000

0 50 100 150 200 250 300 350 400

20

40

60

80

Theo

retic

al S

peci

ficC

apac

itanc

e / F

cm

-3

Particle Size / nm

Mat

eria

l Util

izat

ion

/ %

1003950

30 nm

RuO2

HydratedLayer

Size Matters

Nanosize effect on ion and electron transfer


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Electrolytes

Aqueous and non-aqueous electrolytes with the following properties are required:

■ immobilized matrix■ produced from sustainable sources■ high ionic conductivity■ chemical and thermal stability■ large electrochemical stability window (>5V)■ non-toxic, biodegradable and/or recyclable■ exceptional performance with long device lifetime

Traditional Electrolytes:- aqueous (KOH, H2SO4) - corrosive, low voltage- organic (AN or PC and [Et4N][BF4] or [Et3MeN][BF4]) - low capacitance, toxicity and safety concernsIonic Liquid Electrolytes - safer, but viscosity too high, conductivity low; improvements in properties from mixing with organic solvents


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• Equivalent circuit models (transmission-line models)– Advantages: Simple formulae, fit to experimental impedance spectra– Disadvantages: No nonlinear dynamics, microstructure, chemistry…

• Continuum models (Poisson-Nernst-Planck equations).– Advantages: analytical insight, nonlinear, microstucture– Limitations: point-like ions, mean-field approximation, no chemistry

• Atomistic models (Monte Carlo, molecular dynamics).– Advantages: molecular details, correlations, atomic mechanisms.– Limitations: <10,000 atoms, < 10ns, limited chemical reactions.

• Quantum models (ab initio quantum chemistry and DFT) – Advantages: Mechanisms and chemical reactions from first

principles.– Limitations: <100 atoms, <ps, periodic boundary conditions

VERY FEW MODELS HAVE BEEN APPLIED TO SUPERCAPACITORS


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• Equivalent circuit modeling provides useful analytical formulas to understand impedance data - can understand things such as pure double layer currents, pseudocapacitive currents, Faradic currents and resistive/diffusive currents

• Complex circuits can offer insight into measured behaviors, but still have not been able to offer predictive capacity

R. de Levie, Electrochimica Acta v. 8, 751 (1963).

Theoretical Work: Transmission-line Models

0

4

8

12

16

20

24

0 2 4 6 8 10 12

CDC 500°CCDC 600°CCDC 700°CCDC 800°CCDC 1000°C

-Z''

/ (Ω

.cm

2 )Z' / (Ω.cm2)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0

1

2

3

4

5

6

0.01 0.1 1 10 100 1,000

CDC 500ºCCDC 600ºCCDC 700ºCCDC 800ºCCDC 1000ºC

Z' /

(Ω.c

m2 )

-Z'' / (Ω.cm

2)

Frequency (Hz)


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• Some recent efforts have been made to better model microstructure• Use fractal models to describe microstructure and transmission line equations

describing blocking electrodes• Large number of variables that need to be fit• First principles calculations of parameters going into the model would provide a

better solutionM. Eikerling, A. A. Kornyshev, E. Lust, J. Electrochemical Society 152, E23 (2005).

Theoretical Work: Transmission-line Models


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A periodic carbon nanotube forest in a common organic electrolyte (1 M TEA + BF4- in propylene carbonate). Time series of the carbon nanotube potential in response to a sudden change in surface charge, showingpicosecond response. L. Yang, B. Fishbine, and L. R. Pratt, unpublished, 2007

Initial molecular configuration.

Molecular-Dynamics Simulations of EDLC

L. R. Pratt and A. Pohorille, Modeling of aqueous solution interfaces in biophysics, Chemical Reviews (2002).


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Grind

Activated carbon powderActivated carbon powder

Activation

Electrodefabrication

CoatingRolling/Kneading/Pasting

Extraction

K. Naoi

Coconut shell


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Process FeaturesPrecise control over structure and pore size distribution in CDCNetwork of open poresVarious forms: coatings, free standing monoliths and powderNumerous carbides can be usedLinear kinetics (can be grown to a large thickness)

VSiC = VCDC

Etching Agent:Cl2, F2 ,Br2, I2, HCl, HBr, HI

200-1200oCTemperature:

Carbide

2 nm

CarbidePorosity = 0%

Carbide Derived Carbon

2 nm

Nanoporous CarbonPorosity >50%

Y. Gogotsi, S. Welz, D. Ersoy, M.J. McNallan, Nature, v. 411, p. 283 (2001); J. Chmiola, G. Yushin, Y. Gogotsi, C. Portet, P.L. Taberna, P. Simon, Science, v. 313, p. 1760 (2006)


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Z.G. Cambaz, G. Yushin, Y. Gogotsi, et al. J. American Ceramic Soc. V. 89, 509, 2006.

5 nm

CDC

SiC[111]

0.25 nm

By chlorination for 5 min at 800oC.

TEM of the CDC/SiC interface on SiC whisker obtained by chlorinated for 5 min at 800oC. Graphene

fringes0.5nm

[111]

Interface Between SiC and CarbonAt the boundary, one graphene sheet forms from two SiC (111) planes


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Positions and spatial distribution of carbon atoms in the carbide affect the structure and pore size/shape of CDC

G. Yushin, A. Nikitin, Y. Gogotsi, Carbide Derived Carbon, in Nanomaterials Handbook, Y. Gogotsi, Editor. 2006, CRC Press

Carbide Lattice – Template for CDC


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G. Yushin, A. Nikitin, Y. Gogotsi, in Nanomaterials Handbook, ed. by Y. Gogotsi (CRC Press, 2006)

Carbide Lattice – Template for CDC

0 1 2 3 4 5 6 70.0

0.1

0.2

0.3

0.4

Por

e vo

lum

e (c

c/nm

/g)

Pore size (nm)

Ti3SiC2-CDC (1200°C) SiC-CDC (1200°C)

0 1 2 3 4 5 6 7

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Por

e vo

lum

e (c

c/nm

/g)

Pore size (nm)

Pore-size distributions calculated using NL DFT model

Ar sorption at 77 KAutosorb-1


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Gogotsi, Y., et al., Nature Materials, v. 2, 591 (2003)

0.1 1 10 100

Dm=0.51 nm

Dm=0.58 nm

300 400 500 600 700 8000.5

0.6

0.7

0.8

P

ore

size

(nm

)

Temperature of synthesis (°C)

Por

e vo

lum

e (a

.u.)

Pore size (nm)

Dm=0.64 nm (T=700oC) dD/dT ~ 0.0005 nm/o C,

or: +/- 10o C temperature control - better than 0.1 Å pore control.

Tunable Pore Size in CDC

Choice of starting material and synthesis conditions gives an almost unlimited range of porosity distributions

High surface area Uniform pores

Ti3SiC2 -CDC


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Pore volumeis tunable

Can the carbon pore structure be predicted?

Yushin, G.; Nikitin, A.; Gogotsi, Y., Carbide Derived Carbon. In Nanomaterials Handbook, Gogotsi, Y., Ed. CRC Press: Boca Raton, 2006; pp 237.


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Carbide-Derived Carbon Structure

• Increasing synthesis temperature increases graphitization but carbon remains amorphous until at least 1000ºC

RDF from neutron scattering + reverse Monte-Carlo simulation?

600600ººCC 800800ººCC 12001200ººCC

600600ººCC 800800ººCC 12001200ººCC

TiC

ZrC

J. Chmiola, G. Yushin, R. Dash, Y. Gogotsi, Journal of Power Sources 158, 765 (2005).R. Dash et al., Carbon 44, 2489 (2006).


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- With the recent development in the production of porous carbons with controllable pore size the basic question arises: what are the stable pore sizes and shapes in porous carbons on the nanoscale?

- The size and shape of pores have a profound effect on the energetics of adsorptive storage, a problem of great potential technological importance.

• Due to the nano-size of the pores, the chemical details of the environments matter, therefore quantum mechanical treatment is important and necessary at the atomic level.

• The difficulty is due to the multiple scales, the statistical distributions of the pores and their contents and the fact that multiple components (electrode, ions and solvents) are all essential for the functioning electrode.

Y. Gogotsi, et al, J. Am. Chem. Soc. 127, 16006 (2005)I. Laszlo, M. Kertesz, Y. Gogotsi In Multiscale Modeling of Materials, Mater. Res. Soc. Symp. Proc. 978E, GG13-15 (2007)

Modeling of Porous Carbons


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1C

arbo

n

Surface

Carbon3

Pore

2

Carbon

Too large pore sizeIdeal pore sizeToo small pore size

Conventional wisdom says increasing surface area is only good insomuch as the pores are large enough to accommodate the ion and its solvation shell

M. Endo et al., Carbon 40, 2613 (2002). M. Hahn et al., Electrochemical and Solid-State Letters 7, A33 (2004).


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H. L. F. von Helmholtz, Annalen der Physik 89, 211 (1853).

H. L. F. von Helmholtz, Annalen der Physik 337, 7 (1879).G. Gouy, Compt. Rend. 149, 654 (1910).D. L. Chapman, Philosophical Magazine 25, 475 (1913).O. Stern, Z. Elektrochem 30, 508 (1924).D. C. Grame, Chemistry Review 41, 441 (1947).J. O. M. Bokris, M. A. Devanathan, K. Muller, Proceedings of the Royal Society A274, 55 (1963).

The Double-Layer


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+ ++

+

++

++

+

+

++

--

-

-

-

--

-

-

-

-

-

+

+

Electric Double Cylinder Capacitor

-

Endohedral type Exohedral type

Nanoporous carbons Nanotubes (hollow) Nanowires (solid)

+ ++

+

++

++

+

+

++

----

---

- - ---

+ ++

+

++

++

+

+

++

----

---

- - ---

With double layer formed in the pores, it should be a double cylinder capacitor, not a parallel plate capacitor.

Huang, J.; Sumpter, B. G.; Meunier, V. Angew. Chem. Int. Ed. 2008, 47, 520.


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BFBF44--/8PC/8PC

Et4NEt4N++/4PC/4PC

Diameter: 1.40 nmDiameter: 1.40 nm


<<

BFBF44--/9ACN/9ACN

Et4NEt4N++/7ACN/7ACN



SOSO4422--(H(H22O)O)1212

Diameter: 0.53 nm

<<

C.-M. Yang, Y.-J. Kim, M. Endo, H. Kanoh, M. Yudasaka, S. Iijima, and K. Kaneko, J. Am. Chem. Soc., 129, 20-21 (2007)


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Unexpected capacitance increase as pores decrease below 1nmChmiola, J.; Yushin, G.; Gogotsi, Y.; Portet, C.; Simon, P.; Taberna, P.-L., Science, 2006, v. 313, 1760

Anomalous increase in carbon capacitance at pore size below 1 nm

80

90

100

110

120

130

140

150

0 20 40 60 80 100

CDC 500�CCDC 600�CCDC 700�CCDC 800�CCDC1000�CNMACSMAC

Spe

cific

cap

acita

nce

(F/g

)

Current density (mA/cm 2)

BCation: (CH3CH2)4N+

Anion: BF4-


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• Studied capacitance arising from the anion and cation separately• In all cases, greater than 85% of pores were less than the diameter of the

electrolyte ion + shell of associated solvent molecules• The average pore size was still greater than or equal to the size of the bare

electrolyte ion• Results show that the smaller anion has larger capacitance• But… why does the capacitance increase with decreasing pore size?• Could the energy required to remove solvent molecules from an ion (supplied by

the external circuit) be recovered during discharge?

J. Chmiola, C. Largeot, P.-L. Taberna, P. Simon, Y. Gogotsi, Ang. Chem. Int. Ed. 2008, In Press.

Ions in Subnanometer Pores


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• Including the effect of pore curvature allows experimental data to be fit

• Still no ability to predict behaviors -further modeling work needed

εr : electrolyte dielectric constantε0 : vacuum permittivityd : effective thickness of the double layerA : electrode specific surface areaL : pore lengthb : outer cylinder radiusa : inner cylinder radius

Small Pore Model

Huang, J.; Sumpter, B. G.; Meunier, V. Angew. Chem. Int. Ed. 2008, 47, 520.


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SiC

T=1700°C, 10-6 vacuum

graphite

nanotubes

Graphite and Nanotubes – Model Systems

Z. G. Cambaz, G. Yushin, S. Osswald, V. Mochalin, Y. Gogotsi, Noncatalytic Synthesis of Carbon Nanotubes on SiC, Carbon (2008) in press

Factors affectingcarbon structure:

•Temperature, •Oxygen P•Surface state (roughness)•Surface chemistry•Heating rate


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Carbon pore wall

Ionic Structure of

“NANOSOLUTION”

Hydration structure of ions in bulk ionic solutionY. Marcus, Chem. Rev. 88, 1475 (1988)

H. Ohtaki, T. Radnai, Chem. Rev. 93, 1157 (1993)

+ H2O

Electrical double layer at nanoscale ?

Restricted Solvation Structure

K. Kaneko, Chiba U, Japan


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• 1.6 mol/dm3

Ca2+ Cl-H2O

K. Kaneko, Chiba U, Japan


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A. Tanimura, A. Kovalenko, F. Hirata, Chemical Physics Letters 378, 638 (2003).L. Yang, S. Garde, Journal of Chemical Physics 126, 084706 (2007).

• Uncharged tubes do not permit entry of ions • Increasing charge increases the number of cations that enter

the tubes• Ion entry requires partial desolvation• Double-layer capacitance in very narrow pores influenced

more by shift in ion chemical potential than Helmholtz layer

Small Pore Model

Single-Walled Carbon Nanotube (SWCNT)–A convenient model system


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If potassium channels can strip a K+ ion of its hydration shell entirely (with no potential) why under large potential (>2V!!!) wouldn’t the same happen in a supercapacitor pore?

Valiyaveetil, F. I.; Leonetti, M.; Muir, T. w.; MacKinnont, R., Science 2006, 314.

Ionic Channels


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• Need to increase energy (>100W-h kg-1) to directly compete with batteries• Larger voltage window that traditional electrolytes provides much greater

energy density• Still need to understand capacitance mechanisms and possibly increase the

voltage window even more

Ionic Liquids

0

10

20

30

40

50

60

0 1 2 3 4 5 6

Ene

rgy

dens

ity (W

-h k

g-1)

Voltage (V)

Aqueouselectrolytes

Organicelectrolytes

Ionicliquids


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• TiC-CDC tested with EMI-TFSI ionic liquid• Results show that, again, ionic liquids have larger capacitance in carbons with

smaller pore size • Question: How to match a porous electrode with an ionic

liquid (select from hundreds)?. Largeot, C. Portet, J. Chmiola, P.L. Taberna, Y. Gogotsi, P. Simon, J. Am. Chem. Soc. (2008) in press


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Challenge: Modeling Filled Porous Carbon StructuresSolution:Energetics of series of filled pores. Carbon nanotubes may serve as idealized models. Variation of ions and solvent molecules, relative stabilities with respect to empty pores and pores filled with solvent only and their effect on the work function of the pore walls.Affinities of various pore shapes to solvents vs. solutes.Primarily quantum mechanical calculations.

Difficulties:The following components put competing requirements on the modeling:

-Electrochemical potential.-Redox processes at the surface, role of specific solute ions, solvent’s role.

These have to be treated together and for different pores.


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Theory and Modeling Challenges• Structure and behavior/properties of solvent and ions inside pores.• Ion transport near electrified surfaces and inside mesopores and

micropores to predict capacitance energy and charging dynamics.• Wetting phenomena and desolvation of ions at high voltages and

high rates.• Use modeling tools that include both chemistry and dynamics (e.g.,

ab initio molecular dynamics and electronic structure of carbon).• Modeling of new capacitor electrolytes (e.g., ionic liquids and new

solid electrolytes).• Identify model experimental systems for validation of simulations

(e.g., ion transport in a CNT).• Multi-scale modeling of electrochemical capacitors (electronic

interfacial structure → pore-scale dynamics → charging profiles).


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• Mathematical theory (beyond equivalent circuits)– Derivation of nonlinear transmission line models for large voltages– Modified Poisson-Nernst-Planck equations (steric effects,

correlations…)– Continuum models coupling charging to mechanics, energy

dissipation,…• Physics and chemistry of solvent and ions in nanopores

– Develop accurate models for MD and MC simulations– Entrance of ions into nanopores -- desolvation energy and kinetics.– Ion transport, wetting, surface activation, and chemical modification.

• Physics and chemistry of electrode materials– Electron and ion transport in capacitor electrodes.– Theory of capacitance of metal oxides and conducting polymers.

• Validation against simple model experiments– Ordered arrays of monodisperse pores, single carbon nanotubes.– Vibrational spectroscopy, neutron and x-ray analysis of ions and

solvent in confined spaces

Research Directions for Theory & Modeling

Documents

Chicago Kiev Karlsruhe, Philadelphia Tokyo, Germany Japan ...computing.ornl.gov/workshops/peta08/presentations/y_gogotsi.pdf · Pore volume (cc/nm/g) Pore size (nm) Ti 3SiC 2-CDC