Vladislav Ivaništšev a, Luis M. Varela b, Ruth M. Lynden-Bell c and Maxim V. Fedorov d

a University of Tartu, vi@ut.eeb Universidade de Santiago de Compostela

c University of Cambridged Strathclyde University

Mass transport at electrified ionic liquid–electrode interfaces

COST 1206 – EXIL workshop, Prague, 2015 2

Table of contents

ApplicationsInterface

Chemical spaceComputer simulations

ResultsChallenges

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Current developments

Computer power, top500.orgEnergy sources, AVICCENNE

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The battery market and materials trends

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Ionic liquid–electrode interfaceEl

ectro

de

Surfa

ce ElectricalDouble

Layer (3 nm)Electrolyte

Mass&Charge transport

Computational screening:(1) 2185 Li intercalation and 18226 Li conversion electrodesbuild-a-battery.meteor.com(2) 11000 electrolytesM. Korth, PCCP 16 (2014).(3) Few studies of interfaces

Mass&Charge transport

Adsorption

Intercalation

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Chemical space of ionic liquidsM.V. Fedorov, A.A. Kornyshev, Chem. Rev. 114 (2014) 2978.

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Matrix of electrolyte compositions

[BMIm]+ [BMPyr]+ [BPy]+

[BF4]− c11 c12 c13

[DCA]− c21 c22 c23

[FSI]− c31 c32 c33

[TFSI]− c41 c42 c43

Li+ Na+ K+

F− h11 h12 h13

Cl− h21 h22 h23

Br− h31 h32 h33

I− h41 h42 h43

××

Variables:Electrode material

Surface chargeTemperature & Pressure

+

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NaRIBaS: A scripting framework for computational modelling of Nanomaterials & Room Temperature

Ionic Liquids in Bulk and Slab

NaRIBaS workflow:1. System preparation2. Equilibration

10 ns3. Production run

2 ns × n replica4. Data management5. Analysis

sourceforge.net/projects/naribas

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A naive view on the interface

3 nm 30 nm

Model interface Realistic interface

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Mass transport and Free energy profiles

Mass transport

A(z)

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Mass transport and Free energy profiles Probability method

Potential of mean force method ΔA

k=B exp(−Δ A /RT )

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Li+ ion approaching negative (left) and positive (right) graphene wallsσ = ∓1 e nm−2, cmol = 10%

dashed line – A(z)=−RTln(c/c0); solid line – from the pulling results

There is no contact minimum for Li+

adsorbing at negatively charged graphene from 10%

ionic liquid mixture

There is a very high barrier and a contact minimum

for Li+ adsorbing at negatively

charged graphene from 10% ionic liquid mixture

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Charged probe in [MMIm]Cl and [BMIm]BF4

+1

0

−1

Probecharge

+1

0

−1

Surfacecharge

×

anode − +

cathode + −

[A]− [C]+

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Solvation layers and the solvation shell

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Cylindrically averaged charge density

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Li+ and K+ at Graphite | BMImBF4 interface

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Li+ and K+ at Graphite | BMImBF4 interface

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Li+ and K+ at Graphite | BMImBF4 interface

metal-ion–anion bindinganion size

electrolyte densityJ.B. Haskins, et al., J. Phys. Chem. B 118 (2014) 11295.

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Conclusions The interfacial mass-transport of a probe ion (Li+, K+) is related to the

free energy profiles fom translation of the ion in direction perpendicular to the surface.

The structure of solvation layers at the electrodes determines the positions of the minima and maxima on the free energy profiles.

At those positions where these solvation structures enhance each other, the free energy profile is lower, whereas at those positions where they distort each other, the free energy is higher.

Barrier for K+ is lower than for Li+ in BMImBF4 + MeBF4 mixtures. The method presented can be applied for ionic liquids screening.

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Some preliminary results

Unpublished results

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Challenges

Potential scalePolarisable force fields

Constant potential simulations

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References V. Ivaništšev, M.V. Fedorov, R.M. Lynden-Bell, J. Phys. Chem. C 118 (2014) 5841. A.I. Frolov, K. Kirchner, T. Kirchner, M.V. Fedorov, Faraday Discuss. 154 (2012)

235. T. Méndez-Morales, J. Carrete, M. Pérez-Rodríguez, Ó. Cabeza, L.J. Gallego,

R.M. Lynden-Bell, L.M. Varela, Phys. Chem. Chem. Phys. 16 (2014) 13271.

See also● S.K. Reed, P.A. Madden, A. Papadopoulos, J. Chem. Phys. 128 (2008) 124701. ● V. Nikitina, S.A. Kislenko, R.R. Nazmutdinov, M.D. Bronshtein, G.A. Tsirlina, J.

Phys. Chem. C 118 (2014) 6151.● V. Ivaništšev, S. O’Connor, M.V. Fedorov, Electrochem. Commun. 48 (2014) 61.

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Acknowledgements

Maxim V. FedorovRuth M. Lynden-BellLuis Miguel Varela Cabo

Trinidad Méndez-MoralesIsabel Lage Lage-EstebanezKathleen & Tom Kirchner

Sean O'Conner

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Thank you for your attention!

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