exploring the interfacial nanostructures of litfsi in ... · exploring the interfacial...

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


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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


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Introduction

Ionic

Liquids

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


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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;


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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.


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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


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

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

Cis

Trans


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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


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Cyclic Voltammetry

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


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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


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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)


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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


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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


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

Ge deposit

After Cycling


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Charge-Discharge Cycle and AFM

60 µA


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XPS (Ge and F)


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XPS (C and Li)


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XPS (O and S)


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IR and Raman of electrolyte


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1M LiTFSI in [Py1,4]FSI

[Py1,4]TFSI

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


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

CN= 0.71CN= 0.7


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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


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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


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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


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Symposium on Material Synthesis in Ionic liquids and Interfacial

Processes

April 13-15th

2016, Goslar, Germany

Organising Team

Natalia Borisenko ([email protected])

Abhishek Lahiri ([email protected])

• Material Synthesis in Ionic Liquids

• Electrochemistry in Ionic Liquids

• Interfacial Processes in Ionic Liquids


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Thank you for your attention

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