Recent Progress in Lithium-Sulfur-Batteries

Prof. Dr. S. Kaskel

Fraunhofer Institute for Material and Beam Technology IWS

AABC Europe 2017

January 31, 2017, Mainz

© Fraunhofer IWS

Overview

Progress in Lithium-Sulfur-Batteries

Introduction

Status of Li-S-technology

Technology development

Cathode chemistry

Anode materials

Separator

Role of electrolyte

Conclusion

© Fraunhofer IWS

ALT: 23.02.2016 Netzwert/BamoSa

© Fraunhofer IWS

500 1000 1500 2000

capacity (mAh/g)

1 V

2 V

3 V

4 V

5 V

Si/C-Komposite

Hardcarbon

Graphite

Li4Ti5O12

Li2S

Po

ten

tial

vs L

i/Li+

4000

Si Li

Cathode materials

Anode materials

inte

rcala

tio

n

Theor. specific cathode energy (Voltage x capacity)NMC: ca. 630 Wh/kgLi2S: 2.550 Wh/kg

CostsNMC: 23 €/kgSulfur: << 1 €/kg

Sulfur as next generation battery material

LiFePO4

LiCo1/3Ni1/3Mn1/3O2

Future potential:

high energy plus cost savings

Li+e-

Components of Li-S cell

Status of Li-S technology

Li-S-cell (330 Wh/kg)

Electrolyte

Separator

Lithium Metal

Current collector (+)

Polymer-Binder

Conductive additive

Sulfur/carbon

composite

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ALT: 23.02.2016 Netzwert/BamoSa

© Fraunhofer IWS

Li-S-Battery: Introduction

Cathode properties

25 % cathode porosity (discharged)

47 % cathode porosity (charged)

Electrolyte excess for volume change

1000 mAh/g (Li2S), 2,1 V

65 wt-% Li2S content in cathode

Areal capacity: 5 mAh/cm2

Li-Anode: 100 % excess

Li+

Achievable energy density: Basic estimationson stack level

Li2S

S8

Status of Li-S technology

Energy density (charged state): 672 Wh/kg / 840 Wh/L

Examples of existing prototype cells

Status of Li-S technology

Li-S-cell (up to 330 Wh/kg)Li-S-cell (350 Wh/kg) Li-S-cell (up to 325 Wh/kg,

320 Wh/L)

Energy density is far from it‘s theoretical limit

Cycle life is limited to < 50 cycles for the high energy cells

However, applications are already there:

High Altitude Pseudo-Satellite (HAPS)

http://www.droneuniversities.com/drones/the-zephyr-high-altitude-pseudo-satellite-haps-aircraft-gets-lithium-sulfur-li-s-batteries/

Main cause of low cycle life:Lithium anode surface reactions

Degradation mechanisms

Depletion of org. electrolyte, cells dry out

Dendritic or porous structure causes shortcuts

Self-discharge and active material loss throughpolysulfide shuttle Anode Degradation

Status of Li-S technology

fresh Li

0.7 mm

cycled Li

0.7 mmLi+

Polysulfide Shuttle:Chemical reduction of dissolved PS at anode surface

LiNO3-Additive suppresses shuttle

© Fraunhofer IWS

Lithium Sulfur Batteries

Focus topic Li-S-Battery at Fraunhofer IWS, Dresden

Cathodes SeparatorsAnodes Electrolytes

Coating Laser-Cutting AssemblyMixing Tests

© Fraunhofer IWS

Cathode Materials Development

Chemical Surface and Battery Technology

Lee, J. T.; Zhao, Y.; Thieme, S.; Kim, H.; Oschatz, M.; Borchardt, L.; Magasinski, A.; Cho, W. I.; Kaskel, S.; Yushin, G.:

Advanced Materials 2013, 25(33), 4573-4579; M. Oschatz, S. Kaskel et al. Chem. Commun. 2013, 49(52), 5832-5834. M.

Oschatz, S. Kaskel et a. Advanced Energy Materials 2014, C. Hoffmann, S. Kaskel et al. ACS Nano, 2014.P. Strubel, S. Thieme et al., Adv. Funct. Mater., 2014, 10.1002/adfm.201402768

5 μm

Adam, Kaskel et al.

J. Mater. Chem. A, 2015, 3, 24103.

1 μm

Oschatz , Kaskel et al.

Angewandte Chemie 2012,51, 7577.

500 nmHoffmann, Kaskel et al.

ACS Nano 2014, 8, 12130.

100 nm

Borchardt et al.

Phys. Chem. Chem. Phys .2016,

100 nm100 nm

20 nm

Borchardt, Kaskel et al.

Carbon 2012, 50, 3987.

S. Dörfler, M. Hagen, S. Kaskel et al, Chem. Commun., 2012, 48, 4097.

Up to SA = 3000 m2/gPV = 3-4 cm3/g

2e–

Li+

Li+

I

Li+

Reducing PS Shuttle by Tailoring porous carbons

© Fraunhofer IWS

Hard carbons form stable SEI in ether electrolytes

4000 reversible cycles achieved

Recommended for cathode evaluation

Chemical Surface andBattery Technology

Anode materials development

Hard carbon

ether

molecule

lithium ion

SEI

J. Brückner, S. Kaskel et al., Adv. Funct. Mater., 2014 24 9, 1284–1289, DOI:10.1002/adfm.201302169

0 1000 2000 3000 40000

200

400

600

800

1000

1200

1400

1600

1 C

0.5 C

Dis

ch

arg

e c

ap

ac

ity

/ m

Ah

g-1 S

Cycle number

0.1 C

E/S = 12.00

20

40

60

80

100

CE

/ %

0 10 20 4080 4090 41000

400

800

1200

1600

S. Thieme et al., J. Mater. Chem. A 2015, 3, 3808 - 3820, DOI: 10.1039/C4TA06748G

Projected:up to 190 Wh/kg

© Fraunhofer IWS© Fraunhofer IWS

Nafion as cation-selective polymer coating to reduce polysulfide shuttle

Chemical Surface and Battery Technology

Ion-selective separator coatings

I. Bauer et al., J. Power Sources, 2014 251, 417–422, DOI:10.1016/j.jpowsour.2013.11.090

SEM Nafion@Celgard

1 µm1 µm

SEM Celgard 2500

Cathode mechanism in ether electrolyte requires dissolution ofpolysulfides

Most studies use >> 5 µl Electrolyte / mg S

S

Li2S

Poly-sulfides

Status of Li-S technology

The role of electrolyte

Saturated PS-solution in DME/DOL

DOL

DOL Gn (n ≥ 1); DME (n = 1)

LiNO3: SEI former LiTFSI: salt

© Fraunhofer IWS

Michael Kohl, 27. April 2015 14© Fraunhofer IWS

The role of LiNO3

Standard electrolyte additive in DME/DOL

LiNO3: Directing SEI formation in Li-S cells

Surface film: inorganic and organic species (LiNxOy, ROLi + ROCO2Li)

Compact and homogenous surface film formed with LiNO3

Enhanced stability of lithium anode and improved cycle life

S. Xiong et al. / Journal of Power Sources 246 (2014) 840-845

Electrolyte depletion and LiNO3 consumption is major cause for low cycle life

Excess electrolyte can enhance cycle life drastically

0 50 100 150 2000

200

400

600

800

1000

1200

1400

1600

E/S = 5.0

E/S = 6.5

E/S = 8.0

E/S = 12.0

Dis

ch

arg

e c

ap

acit

y / m

Ah

/g

Cycle number

50 cycles100 cycles

150 cycles

> 200 cycles

0

20

40

60

80

100

CE

/ %

C/10, LiTFSI/LiNO3 DME/DOL

S. Thieme et al., J. Mater. Chem. A, 2015, 3, 3808–3820, DOI: 10.1039/C4TA06748G

Electrolyte content determines cycle life

LiNO3 is consumed during cycling

M. Hagen et al. „Lithium–Sulfur Cells: The Gap between the State-of-the-Art and the Requirements for High Energy Battery Cells”DOI 10.1002/aenm.201401986

Most research papers useE/S >> 5 or not even mention it

E/S =Electrolyte Volume

Sulfur Mass

Inactive materials dominate the mass of Li-S cells

Li-S cathode Li-Ion cathode

Status of Li-S technology

Coating (NCA): 100 µm

Areal capacity: 5 mAhPorosity: 25 %Cell voltage: 3,7 V

Coating (S/C): 100 µm

Areal capacity: 5 mAhPorosity: 65 %Cell voltage: 2,1 V

76 wt-% active material17,5 wt-% active material

Weight distribution

~ C/7, 1.8 mgS/cm2,IWS electrolyte

IWS stacked

3.7 Ah pouch cell

Li-S pouch cell with ref. cathode, IWS elelctrolyte

3.4 µL/mgS vs. 2.5 µL/mgS

New electrolyte shifts the limit for minimum electrolyte content!

real capacity ~ 2.5 Ah

36 h rest

ref. cathode

3.4 µL/mgS

2.5 µL/mgS

12 h rest

real capacity ~ 2.7 Ah

0 20 40 60 80 1000

400

800

1200

1600

Cycle

Cap

acit

y / m

Ah

/g

E

44.4 %

Li

S

Li

S

E

37.7 %

3.4 µL/mgS 2.5 µL/mgS

Patent pending

New Electrolytes with low PS

solubility (without LiNO3)

Reducing electrolyte content

1.5M LiTFSI / 0.25M LiNO3

in DME/DOLIWS electrolyte

Work in progress

Li anode, 89 cycles, DME/DOL

50 µm

50 µm

Li anode, 100 cycles, new El.

Electrolytes with low PS solubility

Reduced anode degradation Improved safety

Smooth Lithium deposition

Low flammability

Work in progress

Safety of LiS-Cells

Safety Tests: Lithium-Sulfur Pouch Cell

(IWS electrolyte)

▪ Standardized Tests by SGS Germany GmbH (München)

▪ Thermal Stability (130 °C), Overcharge,Simulated Internal Short Circuit, Nail Penetration,Short Circuit

▪ no „Thermal Runaway“

▪ max. Hazard Level (according to EUCAR): HL 3

▪ Significantly improved safety of Li-S-Cells, as compared to Li-Ion-Cells with same cell format

▪ Li-Metal burning at T > 190 °C;only if externally heated

Li-metal burning

Cell after Nail Penetration

Status of Li-S technology

Li-S-cells reach 350 Wh/kg lightest accumulator today

Volumetric energy density currently lower than Li-Ion

Cycle life in high energy cells is limited today to 50-100 cycles

Available cells not yet suitable for automotive

Potential for step-change

Anode

Cathode

Electrolyte

Separator

Niche markets are growing and may expand

Conclusions

Related projects

Thanks to co-workers, partners and funding agencies!

Li-S-Battery-Team at IWS

Acknowledgements

6th Workshop »Lithium-Sulfur Batteries«

201420132012 2015

Annual conference in Dresden

More than 150 participants from industry and academia

Save the date: November 6–7, 2017

20162016

Prof. Dr. S. Kaskel

Dr. Holger Althues

Fraunhofer IWSWinterbergstraße 2801277 Dresden, Germany

Phone +49 351 83391-3476 Fax +49 351 83391-3300E-Mail holger.althues@iws.fraunhofer.de

www.iws.fraunhofer.de

Thank you for your attention!

© Fraunhofer IWS

Status and Potential of Li-S-Technology

SoA (LIB) SoA (Sion-Li-

S)

Prognosis

(Li-S) – GM*

Prognosis

(Li-S)BMW**

Prognosis

(Li-S) - IWS

Grav. Energy density

(Cell)

140 - 250

Wh/kg

350

Wh/kg

550

Wh/kg

419

Wh/kg

490

Wh/kg

Vol. Energy density

(Cell)

280 - 670

Wh/L

320

Wh/L

620

Wh/L

644

Wh/L

685

Wh/L

Panasonic 18650 (Tesla):

243 Wh/kg Sion-Power:

350 Wh/kg (cell)260 Wh/kg (pack)

Li-Ion-Cells (examples) Li-S-cells

LG Pouch-Cell (Opel Ampera):

140 Wh/kg

* T. Greszler, GM Beyond Lithium Ion 5, Berkeley, CA 2012 ** Dr. P. Oberhumer, BMW Li-S-Battery-Workshop 2013, Dresden

Oxis-Energy: -5 – 80°CULC: 300 Wh/kg, 200 Wh/LDemonstrated: 400 Wh/kgLLC: 180 Wh/kg, 170 Wh/L

Li-S-Battery SeminarIntroduction

ULC = Ultralight Cell

LLC = Long life cell