th Symposium on Energy Storage: 4 th Symposium on Energy Storage: 4 - - PowerPoint PPT Presentation

• Dr. R. Schmidt
• Dr. R. Schmidt, Dr. A. Panchenko, Dr. B. Ewald, Dr. S.

, Dr. A. Panchenko, Dr. B. Ewald, Dr. S. Ivanovici Ivanovici, Dr. , Dr.

• R. Oesten (BFB)
• R. Oesten (BFB)

BASF SE, 67056 Ludwigshafen, Germany BASF SE, 67056 Ludwigshafen, Germany

Electrode Development @ BASF for Electrode Development @ BASF for Lithium/Sulfur Batteries Lithium/Sulfur Batteries 4 4th

th Symposium on Energy Storage:

Symposium on Energy Storage: Beyond Lithium Ion Beyond Lithium Ion

Pacific Northwest National Laboratory June 8, 2011

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BASF Lithium/Sulfur Research Partner

Since 2009 joint development agreement with world-leading lithium/sulfur company Sion Power Sion Power major developer of Li/S battery systems and protected lithium anode technology Acceleration of Li/S research and development with BASF expertise as chemical solution provider

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Outstanding superiority of Li/S in respect of gravimetric energy density

Comparison Li-Ion vs. Li/S batteries

Li/S – The Battery System Beyond Li-ion

Today Future Theory

3000 2000 1000 Li-Ion Li/S

Gravimetric Energy [Wh/kg]

Li-Ion Li/S

Volumetric Energy [Wh/l]

Advantages: High gravimetric energy density Low cost and abundant raw materials Ideal battery system for full electric vehicle application Operability at very low temperatures High potential of improvement

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Potential and Challenges

“Life” of Li/S batteries ends currently too early after 50-100 cycles (< 800 mAh) Goal: > 500 cycles Observed capacity five times higher than lithium-ion batteries

Comparison of cycle data of Li/S cell (red = discharging, blue = charging) and lithium-ion battery (LIB).

Li/S Cycle no. 50 40 30 20 10 Capacity (mAh/g) 1.200 1.000 800 600 400 200 LIB

Five times higher capacity than Li-ion technology

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Discharging: Li is stripped from anode and lithium sulfides are formed in the cathode Charging: Re-plating of Li and re- formation of elemental sulfur Speciality of Li/S: (Partly) dissolving electrodes during cycling

Model of Lithium/Sulfur battery

Working Principle of Li/S System

• Separator

Li0 Li2S3 Li2S6 Li2S Li2S8 Polysulfide Shuttle Anode (–) Cathode (+)

Charge (Li plating) Discharge (Li stripping)

Li S S S S S S S S Li

• Li

S S S S S S S S Li Li S S S S Li Li S S Li Li S S S S Li Li S S S S Li Li S S S S S S Li S Li S S Li

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Discharge Curve

Second Stage

Precipitation of Li2S Formation of smaller polysulfides 65-75 % of sulfur usage

First Stage

Elemental sulfur is reduced Polysulfide up to Li2S4 are formed

2.4 Potential (V) vs Li/Li+ 2.3 2.2 2.1 2.0 1.9 1.8 Specific capacity (mAh/g Sulfur) 400 800 1200 1600 First stage Theoretical capacity Second stage

Speciality of Li/S: (Partly) dissolving electrodes during cycling

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State of the art Li/S battery with Teflon binder

Special requirements: Sulfur cathode sensitive to drying under vacuum Partly dissolving cathode Carbon particles responsible for structural stability

50 40 30 20 10 1.400 1.000 800 600 400 200 1.200 Cycle no. Capacity [mAh/g]

capacity drop ~ 50 %

Binder and carbon development is key factor for optimized cathode Approach: Utilization of new carbon materials Pretreatment of carbon and sulfur material

Cathode Development

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Intercalated graphites: Intercalation of Lewis acid guest molecules (e.g. SO3)

intercalate

Intercalated Graphite: Graphite:

Intercalation: e.g. + NOx / H2SO4 Intercalation: e.g. + NOx / H2SO4

Expanded Graphites

Intercalation is key to expansion

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Graphite Expanded Graphite “Pockets” for sulfur uptake Expanded graphites can lead to better cell performance Highly conductive and light material Fixation of sulfur in pockets

Expanded Graphites

Micropockets

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Temperature / gradient controlled expansion:

Expanded Graphites

Temperature is key factor for optimized structure

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Expanded Graphites

Highly stable performance for first 50 cycles Over 1100 mAh/g sulfur

• ver 50 cylces

Consumption of electrolyte responsible for cell failure after 60 cycles Testing in 110 mAh cells Up to 40% expanded graphites in cathode

50 40 30 20 10 1.400 1.000 800 600 400 200 1.200 Cycle no. Capacity [mAh/g]

Charge/discharge capacity of cell with improved cathode

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