4 symposium on energy storage: beyond lithium ion bli4... · basf se, 67056 ludwigshafen, germany...
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Dr. R. SchmidtDr. R. Schmidt, Dr. A. Panchenko, Dr. B. Ewald, Dr. S. , Dr. A. Panchenko, Dr. B. Ewald, Dr. S. IvanoviciIvanovici, Dr. , Dr. R. Oesten (BFB)R. Oesten (BFB)BASF SE, 67056 Ludwigshafen, GermanyBASF SE, 67056 Ludwigshafen, Germany
Electrode Development @ BASF for Electrode Development @ BASF for Lithium/Sulfur BatteriesLithium/Sulfur Batteries
44thth Symposium on Energy Storage: Symposium on Energy Storage: Beyond Lithium IonBeyond Lithium IonPacific Northwest National LaboratoryJune 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
0
3000
2000
1000
Li-Ion Li/SGravimetric Energy
[Wh/kg]
Li-Ion Li/SVolumetric Energy
[Wh/l]
Advantages:
� High gravimetric energydensity
� Low cost and abundantraw materials
� Ideal battery system for fullelectric vehicle application
� Operability at very lowtemperatures
� High potential of improvement
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Potential and Challenges
� “Life” of Li/Sbatteries endscurrently too earlyafter 50-100 cycles (< 800 mAh)
� Goal: > 500 cycles
� Observed capacityfive times higherthan lithium-ionbatteries
Comparison of cycle data of Li/S cell (red = discharging, blue = charging)and lithium-ion battery (LIB).
Li/S
Cycle no.5040302010
Capacity (mAh/g)1.200
1.000
800
600
400
200
00
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
Li+
Li+
Li+
Li+
Li+
Li+
Li+
Li+
Li+
Li+
Li+
Li+
Sep
arat
or
Li0
Li2S3
Li2S6
Li2S
Li2S8
PolysulfideShuttle
Anode(–)
Cathode(+)
Charge (Li plating)
Discharge (Li stripping)
LiSS S S
S S SSLi
Carbon
Sulfur
Binder
LiSS S S
S S SSLiLiS
SS
SLi
LiSSLi
LiSS
SSLi
LiSS
SSLi
LiSS S
S SSLi
SLi
SSLi
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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)0 400 800 1200 1600
First stage
Theoreticalcapacity
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
5040302010
1.400
1.000
800
600
400
200
00
1.200
Cycle no.
Cap
acity
[mA
h/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
IntercalatedGraphite:
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 over 50 cylces
� Consumption of electrolyte responsiblefor cell failure after 60 cycles
� Testing in 110 mAh cells
� Up to 40% expandedgraphites in cathode
5040302010
1.400
1.000
800
600
400
200
00
1.200
Cycle no.
Cap
acity
[mA
h/g]
Charge/discharge capacity of cell with improved cathode
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