Computational Studies on Advanced Lithium Batteries for Electronic Devices and Electric Vehicles

Computational Studies on Advanced Lithium Batteries for Electronic Devices and Electric Vehicles. MC Masedi, HM Sithole and PE Ngoepe

1. Materials Modelling Centre, School of Physical and Mineral SciencesUniversity of Limpopo, Private Bag x 1106, Sovenga, 0727, South Africa2. CSIR, Meraka Institute, Meiring Naude, Brummeria, P. O. Box 395, Pretoria 0001South Africa CHPC Meeting 2013

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06/12/2013

The growing global energy demand of modern society is urging to find large-scale sources, which are more sustainable and environmentally friendly of the oil-based one. The increase of CO2 emissions of oil , call for the search for sources of clean energy.

Rechargeable lithium batteries are expected to play a key role also in future energy storage, including both stationary [1] and automotive applications [2- 4].

Li-ion batteries have transformed portable electronic devices [5]. However, even when fully developed, the highest energy storage that this batteries can deliver is too low to meet the demands of key markets, such as transportation.

Introduction

Reaching beyond the horizon of Li-ion batteries is a formidable challenge; it requires the exploration of new chemistry, especially electrochemistry and new materials [3].

Here we consider a study on: Lithium and Zinc – air batteries. All this batteries are potentially ultrahigh energy density chemical power sources, which could potentially offer higher specific energy and could address pressing environmental needs for energy storage systems .

In the current work we present a comparative study on stability, structural and electronic properties of discharge products formed in Lithium and Zinc – air batteries.

[1] B. Dunn, H. Kamath, J.-M. Tarascon, Science 334 (2011) 928-935.[2] P.G. Bruce, S.A. Frauberger, L.J. Hardwick, J.-M. Tarascon, Nat. Mater. 11(2012) 19-29.[3] M. Armand, J.-M. Tarascon, Nature 451 (2008) 652-657.[4] J.-M. Tarascon, M. Armand, Nature 414 (2001) 359-367.[5] D. Linden (Ed.), Handbook of Batteries, McGraw-Hill, New York, 1984

US Advanced Battery Consortium USABC Goals for Advanced Batteries for Evs (2006)

Frontiers of Electrochemical Energy Storage

Focus

Product:Li2O

Li

LiLi

O

O

Nanostructured Cathode

Li+

e- e- e-

e-

e-

e-

O -

O

Li+

Li+

Li+

Lithium Anode

Discharge phase

Li+

Li+

O -

O -

Li+e-

– +

Aprotic electrolyte

O2+e -> O2-

O2- + Li+ ->LiO2

LiO2 + Li+ + e->Li2O2Li -> Li++ e

Lithium Oxide (Li2O)

Operations Model: Li-Air battery

Catalyst:MnO2

Methodology

The calculations were carried out using ab initio Density Functional Theory (DFT) formalism as implemented in the VASP code [7] with the projector augmented wave (PAW) [8].

An energy cut-off of 500 eV was used, as it was sufficient to converge the total energy of all the systems and k-points of 8x8x8.

For the exchange-correlation functional, the generalized gradient approximation of Perdew, Burke and Ernzerhof (GGA-PBE) [9] was chosen.

Elastic properties were calculated with the strain of 0.003.

Phonon dispersions calculations the interaction range of 10.0Å and displacement of atoms of +/- 0.02Å were used.

[7] P. E. Blöchl, Phys. Rev. B 50, 17953 (1994)[8] H.J. Monkhorst and J.D. Pack, Phys. Rev. B 13, 5188 (1976).[9] J.P. Perdew, K. Burke and M. Ernzerhof. Phys. Rev. Lett. 77 , 3865 (1996)

Structures

(a) Li2S

(b) Li2O

Li

S

O

Li

Li2O and Li2S have a cubic anti-fluorite structure with Fm-3m symmetry.

Active materials in lithium batteries

10. W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, 91st edition (2010)

Discharge product of oxygen formed in Lithium- air battery

Results and Discussions Structure and Heats of Formation

[10] J.M Osollo-Guillen, B. Holm, R. Ahuja and B.A Johonsson. Journal 167, 221-227 (2004)[14][11] Bertheville J Phys. Cond Matt 10, 2155 -2169 (1998) (Exp thermal exp)[12] A. Golffon, J.C. Dumas and E. Phillippot. Journal 1, 1-123 (2002)[13] E. Zintl, A. Harder and B. Dauth, Z Elektorchem, 40 588 (1934)

Li2O and Li2S satisfy the necessary conditions for stability. C11>0, C11-C12>0, C44>0Hence Li2O and Li2S are mechanically stable.

Elastic Properties

Phonon Dispersions Calculations Phonon Dispersions, in condensed-matter physics, represents an excited state in the

quantum mechanical quantization of the modes of vibrations of elastic structures of interacting particles.They play a major role in determining a material's thermal conductivity, electrical conductivity and stability. Thus, the study of phonons is an important part of condensed-matter physics

Determining material’s stability.Lattice Vibrations – Phonons in Solid StateAlex Mathew, University of Rochester

Phonon Dispersions of Li2O and Li2S

-1

4

9

14

19

24

Brillouin Zone Direction

Freq

uenc

y (T

Hz)

Li2O

Phonon dispersion calculations for Li2O and Li2S structures, indicates that the structures are stable.

-1

4

9

14

19

24

Brillouin Zone Direction

Freq

uenc

y (T

Hz)

Li2S

Γ L W X Γ X W L

Phonon Dispersion for Li2S

Calculated Experimental – Bill et al (1991)

Good agreement of calculated and experimental, especially on acoustic modes.

AcousticAcousticLA

TA

LA

TA

Experimental-M Wilson et al (2004)

Phonon Dispersion for Li2O

Calculated ГXГ

Acoustic

Optical

LA

TA

Good agreement of calculated and experimental, especially on acoustic modes and lower optical modes.

Acoustic

Problems with Li-air batteries: Dendrite Formation on Charge

• In most lithium batteries, the anode is covered by a thin film called a Solid Electrolyte Interphase (SEI) [14].

• As a result, on charge, lithium deposits through the SEI in the form of lithium dendrites and mossy (sponge) lithium.

• This raises safety issues – the formation of internal short circuits by lithium dendrites.

[14]E. Peled. J. Electrochem. Soc. 126, 2047-2051 (2011).

Sodium–air battery

• We suggest here to replace the metallic lithium anode by liquid sodium and to operate the sodium–air (oxygen) battery.

• The theoretical specific energy of the sodium–air cell, assuming Na2O as the discharge product, is expected to be 1690 Wh/kg.

• The surface tension of the liquid sodium anode is expected to prevent the formation of sodium dendrites on charge.

Results and Discussions

Na2O and Na2S satisfy the necessary conditions for stability. C11>0, C11-C12>0, C44>0Hence Na2O and Na2S are mechanically stable.

Structure and Heats of Formation

Elastic Properties.

Phonon Dispersions of Na2O and Na2S

-1

1

3

5

7

9

11

13

Brillouin Zone Direction

Freq

uenc

y (T

Hz)

Na2S

Phonon dispersion calculations for Na2O and Na2S structures, indicates that the structures are stable.

-1

1

3

5

7

9

11

13

15

Brillouin Zone Direction

Freq

uenc

y (T

Hz)

Na2O

-1

1

3

5

7

9

11

13

Brillouin Zone Direction

Freq

uenc

y (T

Hz)

Na2SNa2S

Brillouin Zone Direction

Calculated Experimental-M Wilson et al (2004)

Phonon Dispersion for Na2S

-1

1

3

5

7

9

11

13

15

Brillouin Zone Direction

Freq

uenc

y (T

Hz)

Na2ONa2O

Calculated Experimental-M Wilson et al (2004)

Phonon Dispersion for Na2O

Structure Calca

)Å(

Exp a) Å(

Calcc

)Å(

Exp c

(Å)

Volume)Å3(

ΔH)kJ/mol(

ZnO 3.26 5.23 48.06 -280.43

ZnS 5.45 162.06 -139.92

Results and Discussion

Structure ZnO ZnSC11 C12 C13 C16 C33 C44 C66

230.28 124.32 107.51 231.60 43.79

96.81 57.42

55.19

ZnO and ZnS satisfy the necessary conditions for stability. C11>0, C11-C12>0, C44>0Hence ZnO and ZnS are mechanically stable.

Elastic Properties

Structure and Heats of Formation

Phonon Dispersions for ZnO and ZnS

-4

1

6

11

16

21

26

ZnO

Brillouin Zone Direction

Freq

uenc

y (T

Hz)

-4

1

6

11

16

21

26

ZnS

Brillouin Zone Direction

Freq

uenc

y (T

Hz)

Phonon dispersions calculations for ZnO and ZnS structures, indicates that the structures are stable.

• All discharge products formed Li–O2 and Zn–O2 batteries are stable because of low values of the heats of formations.

• Lattice parameters and elastic constants values are in good agreement with the experimental values especially for Li2O, Li2S, Na2O and Na2S structures.

• The elastic constants suggest mechanical stability of all discharge products .

• Our phonon dispersion calculations shows that all the discharge products are generally stable with the absence of vibrations in the negative frequency.

• Phonon dispersions are in good agreement with the experimental studies especially for Li2O, Li2S, Na2O and Na2S structure.

Summary

Acknowledgements

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Future Work

Battery Simulation using Battery Design Studio (BDS)

Require Improving Batteries Performances

The fundamental electrochemical reactions in Li-air batteries

MnO2 as a catalyst in Li-air batteries

Lithium-air Battery

Li

LiLi

e-

e- e-e-

Li+

Li+

Li+

Charging phase

Li+

Li+

Li+O -

O -Li+

O -

O -Li+Li+

MnO2e-

e-

e-

O

O -Li+

Li2O2 –> LiO2- + Li+

LiO2- –> LiO2 + Li+ +

eLi+ + e –> Li 0

LiO2 –> O2 + Li+ + eLi+ + e –> Li 0

O

O

e-

e- e-e-e-

e-

Lie-

Operations Model: Li-Air battery

Catalyst Particle

All-electric – the BMW i3 Concept.

BMW i3 CONCEPT COUPE. ELECTRICITY MEETS INTELLIGENCE.

South African Nissan Leaf 2013

Launched by Department of Environmental Affairs

If we succeed in developing this technology, we are facing the ultimate breakthrough for electric cars, because in practice, the energy density of Li-air batteries will be comparable to that of petrol and diesel.

Research Success

How does this study benefit us?

Thank you"One of the reasons people don’t achieve their dreams is that they desire to change their results without changing their thinking“ (Maxwell 2003)