Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Exploring the Interfacial Nanostructures of LiTFSI in Ionic Liquids on Different Substrates

Abhishek Lahiri, Timo Carstens, Natalia Borisenko, Andriy Borodin, Frank Endres

Institute of Electrochemistry, Clausthal University of Technology, Arnold-Sommerfeld-Str. 6, D-38678 Clausthal-Zellerfeld, Germany

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Introduction

Ionic liquid Interface

Importance of understanding IL interface in electrochemistry

LiTFSI on Au(111) and on Electrodeposited Ge

Conclusions

Contents of the talk

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Introduction

Ionic

Liquids

http://lem.ch.unito.it/didattica/infochimica/Liquidi%20Ionici/ApplicationsMap.html

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Ionic Liquid Interface

Ionic liquids / electrode interface

Electric Double Layer Multilayer model

Aqueous electrolyte / electrode interface

(from Wikipedia)

RTIL / Electrode interfaces Layered structure; strong interaction;

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Various experimental techniques to explorethe interface

HE X-ray reflectivity/SFA

Mezger et al, Science, 2008, 322, 424

Perkin, PCCP, 2012, 14, 5052-62

XPS/UPS

Lovelock et al, Chem Rev, 2010, 110, 5158-5190

SPM

Carstens et al, J. Phys. ChemC, 2014, 118, 10833-43

Elbourne et al, ACS Nano, 2015, 9, 7608-7620

Uhl et al, Beilstein J Nanotechnol, 2013, 4, 903-918

SFG/ Impedance spectroscopy

Baldelli, Acc. Chem. Res, 2008, 40, 421-431

Fabregat-Santiago et al, PCCP, 2011,13, 9083-9118

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Importance of understanding the interface

N+N-

S

O O

S

O O

CF3F3C[Py1,4]TFSI

[EMIM]TFSIN-

S

O O

S

O O

CF3F3C

N+N

Pulletikurthi et al, J. Solid. State. Electrochem, 2013, 17, 2823-2832Endres et al. PCCP, 2010, 12, 1724-1732Lahiri et al, Angew. Chem. Int. Ed, 2015, 54, 11870-11874

[Py1,4]TFSI

The structure and dynamics of the interfaciallayer influence the electrochemical reactions, deposit morphology and material property.

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Ionic liquids as battery electrolytes

MacFarlane et al, Energy. Environ. Sci. 2014, 7, 232-250

Armand et al, Nature Mater, 2009, 8, 621-629

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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LiTFSI in [Py1,4]TFSI (Raman Spectroscopy)

Lahiri et al, J. Phys. Chem. C, 2015, 119, 16734- 16742

Cis

Trans

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Raman Spectroscopy (Quantitative analysis)

Coordination number N =

𝐴𝐼𝐼𝐼(𝐴𝑡𝑜𝑡𝑎𝑙)

x

N= 2

N= 1N= 0.53

[Li(TFSI)2]-

[Lim(TFSI)n](n-m)-

n/m < 2

[Lim(TFSI)n](n-m)-

n/m < 2

Pitawala et al, Faraday Discussion, 2012, 154, 71-80Lahiri et al, J. Phys. Chem. C, 2015, 119, 16734- 16742

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Cyclic Voltammetry

Lahiri et al, J. Phys. Chem. C, 2015, 119, 16734- 16742

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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In situ AFM Principle

Schematic view of an AFM tip approaching a solid surface in the presence of ILand corresponding approach curves

Schematic diagram ot the vertical tip movement during the approach

A practical guide to AFM force spectroscopy and data anylsis, JPK Instruments – www.jpk.com

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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In situ AFM of [Py1,4]TFSI

Lahiri et al, J. Phys. Chem. C, 2015, 119, 16734- 16742Lauw et al, Langmuir, 2012, 28, 7374-7381

Au (111)

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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In situ AFM of 0.1M LiTFSI in [Py1,4]TFSI

0.5 nm

LiTFSI

~ 0.2 nm

[Li(TFSI)2]-

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In situ AFM of LiTFSI in [Py1,4]TFSI at -1.0 V (Different Concentrations)

0.1 M 0.5 M 1.0 M

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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1M LiTFSI-[Py1,4]TFSI on Electrodeposited Ge

N= 0.53

Lahiri et al, Phys.Chem.Chem.Phys, 2015, 17, 11161-11164

N= 0.75

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Cyclic Voltammetry of 0.5 M LiTFSI-[Py1,4]TFSI on electrodeposited Ge

Ge deposit

After Cycling

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Charge-Discharge Cycle and AFM

60 µA

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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XPS (Ge and F)

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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XPS (C and Li)

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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XPS (O and S)

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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IR and Raman of electrolyte

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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1M LiTFSI in [Py1,4]FSI

[Py1,4]TFSI

Lahiri et al, Phys.Chem.Chem.Phys, 2015, 17, 11161-11164

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Raman of 1M LiTFSI in [Py1,4]FSI

CN= 0.71CN= 0.7

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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The interfacial nanostructure of LiTFSI in [Py1,4]TFSI and[Py1,4]FSI on Au(111) and on Ge was evaluated.

Multilayered nanostructure was observed for both [Py1,4]TFSIand [Py1,4]FSI on Au(111)

On addition of LiTFSI in [Py1,4]TFSI, the [Py1,4]+ cation wasreplaced by Li+ ion on the Au(111) surface. However, onaddition of LiTFSI in [Py1,4]FSI, a decrease in rupture force isnoted.

With increase in concentration of LiTFSI in [Py1,4]TFSI, thenumber of interfacial layers decreased.

At -1.0 V, for 1M LiTFSI-[Py1,4]TFSI, an underpotentialdeposition of Li might have taken place as no prominentinterfacial layers could be oberved.

Conclusions

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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On electrodeposited Ge, Li intercalation and deintercalationprocesses took place.

AFM analysis of LiTFSI in [Py1,4]TFSI showed that the SEIlayer is inhomogeneous and changes during the first charge-discharge cycles. However, the SEI layer was found to bestable after 10 charge-discharge cycles.

From IR spectroscopic analysis, it was shown that both thecation and anion is affected during the charge-dischargecycles

From Raman and AFM analyses it was shown that > 0.5 MLiTFSI- [Py1,4]TFSI is not ideal as an electrolyte for LIBs.

Conclusions

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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AcknowledgementProf. Dr. Frank Endres Dr. Timo Carstens Dr. Natalia Borisenko Dr. Andriy Borodin

Workgroup of Prof Endres

Financial Support

DFG

BMBF

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Symposium on Material Synthesis in Ionic liquids and Interfacial

Processes

April 13-15th

2016, Goslar, Germany

Organising Team

Natalia Borisenko (natalia.borissenko@tu-clausthal.de)

Abhishek Lahiri (abhishek.lahiri@tu-clausthal.de)

• Material Synthesis in Ionic Liquids

• Electrochemistry in Ionic Liquids

• Interfacial Processes in Ionic Liquids

Institute of Electrochemistry, Clausthal University of Technology, Germany (www.iec.tu-clausthal.de)

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Thank you for your attention