Conventional Lithium-ion batteries
Dr. Michael Roscher imk automotive GmbH Chemnitz
New generation battery systems for PHEV and BEV applications: Advantages and Challenges
Contents
Introduction of the imk automotive GmbH Battery- and hybrid-electric-vehicles State-of-the-art Lithium-ion battery systems technologies based on rare materials advantages and drawbacks in use New trends in battery technologies next generation Lithium-ion systems alternative technologies and future prospects Conclusion
Page: 2
Version: 04/05/2011
Company ímk automotive GmbH
address
Annaberger Straße 73 09111 Chemnitz
phone fax
+49 (0) 371 400 97 0 +49 (0) 371 400 97 19
e-mail internet
[email protected] www.imk-automotive.de
Headquarter Chemnitz
Page: 3
Version: 04/05/2011
Company imk automotive Inc.
Headquarter Greenville, SC
address 5 Research Drive Greenville, SC 29607 phone +1 (423).903.5220 e-mail [email protected] internet www.imk-automotive.com
Page: 4
Version: 04/05/2011
imk automotive GmbH The company
Aim of the imk automotive: development of new concepts for automotive applications innovative projects in corporation with companies and faculties Optimization of products and production processes Personel development 40 35
total number
30 25 20 15 10 5
Project focus in 2010:
0 2002
2003
2004
Hochund Fachschulabschluß regular employees
2005
2006
2007
Auszubildende apprentices
2008
2009
Praktikanten trainees
2010
year
Diplomanden students
approx. 50% automotive customers approx. 50% others
Page: 5
Version: 04/05/2011
imk automotive GmbH The company
Controlling / Accounting
Quality Management Managing Director
Sales
Safety Engineer Dr. Jens Trepte Assistant / Purchase / Human Resources
Marketing
Product Development Dr. Jens Trepte
Production Process Development Carsten Otto
Information Technology Gerson Heuwieser
Consulting Ingolf Grüßner
Battery Electric Vehicles
Process Design
Software Development
Production Strategy
Mechatronic Systems
Production & Assembly
Training
Product & Production Optimization
Structural Components
Body In White
Support & Service
Ergonomics
Strategic Development Dr. Wolfgang Leidholdt
editor of human work Page: 6
Version: 04/05/2011
Electric Powertrains Architecture
Example: Battery electric vehicle
Page: 7
Version: 04/05/2011
Electric Powertrains Architecture
Battery electric vehicle: Battery supplies the power train and auxiliary components High voltage of the traction battery is transformed into 12 V on-board level (possible additional 12 V lead-acid battery) Charging via battery charger connected to the grid Full charge over night (> 8 hours) or fast-charge option (within 1 hour or faster)
12Von-board supply DC/DC
charger
Boost/ Recuperation
drive train
HVbattery
battery electric vehicle Page: 8
Version: 04/05/2011
Electric Powertrains Architecture
Hybrid electric vehicle: 2 separate power trains included in the vehicle, with two energy storages HV-battery covers short-termed power peaks and energy regeneration electric driving for several kilometers is possible with full hybrids and PHEVs (e.g. up to 60 km Opel Ampera)
12Von-board supply DC/DC
fuel tank
charger
Boost/ Recuperation
drive train
HVbattery
hybrid electric vehicle Page: 9
Version: 04/05/2011
Electric Powertrains Energy consumption and range
Battery electric vehicle: Gradually decreasing SOC Energy demand of approximately 14 – 20 kWh per 100 km (passenger car)
State-of-charge
Electric power
The battery capacity is the limiting factor operation window from SOC = 0…100%
Page: 10
Version: 04/05/2011
Electric Powertrains Additional on-board energy consumers Control systems Electric breaks and steering
Radio, HiFi
Lighting HVAC and comfort systems
In hot climates almost one half of the stored energy is used for air conditioning deduced range!
Page: 11
Version: 04/05/2011
Electric Powertrains The energy storage system
Battery system includes several tens or hundreds of battery cells to achieve: voltage of the power train (>> 100V) required energy content energy density of today automotive batteries cells is < 160 Wh/kg In comparison: conventional fuel 11900 Wh/kg (about 70 times higher), but efficiency of power conversion is 2…3 times better (ICE: 20-40%; electric power train > 80%)
(GS Yuasa)
Page: 12
(A123 Systems)
Version: 04/05/2011
Lithium-ion batteries How does it work?
loadILade / charger e-
e-
UZelle Ucell
Exchange of the lithium between the electrodes (Faradaic current), electrons migrate in the outer circuit Exchange of 1g lithium ≙ 3.86 Ah
Li +
No metallic lithium included (under normal conditions)
electrolyte Elektrolyt Anodenmaterial anode
Page: 13
Asymmetric design with anode and cathode
Kathodenmaterial cathode
Version: 04/05/2011
Lithium-ion batteries How does it work?
–
+
elektrolyte electrolyte
porous active materials high surface areas anode
additives and binder added
cathode
coated on the collector foils between the electrodes an porous separator is inserted pores filled with the electrolyte (from TradeKorea.com)
(Kesai Im&Ex Co. Ldt.)
separator
different housings:
Cu Al
cylindrical Page: 14
prismatic
Coffee-bag Version: 04/05/2011
Lithium-ion batteries How does it work?
Li/Li+ 5V
Li0,5CoO2 LiCoO2
potential
4V
cell voltage results from the different electrode potentials of the active materials involved electrode potentials depend on the lithium contents
3V
voltage at the terminals
2V
1V
No side reactions!!
C6
0
Page: 15
The OCV is under load superimposed by transient voltages drops at conductive parts
LiC6
SOC / %
100
Version: 04/05/2011
Conventional Lithium-ion batteries Supervising of an automotive battery
Voltages, currents and temperatures are to be measured to detect and avoid: U1
cell 1
over-charge, deep-discharge
U2
cell 2
temperature overload
U3
cell 3
over-current
U4
cell 4
Us
estimate energy content, power capability, and state-ofhealth
cell s
IBatt
current sensor
(BRUSA, www.brusa.biz) Page: 16
Version: 04/05/2011
Conventional Lithium-ion batteries Properties
Cathodes: metal-oxides (Co, Ni, Mn)
The “highest energy cell“ NCR18650A
Anodes: carbon (graphite, hard carbon, amorphous) voltage range approx. 2 … 4.2 V, nominal 3.7 V power density ≈ 400 … >5000 W/kg
(Panasonic)
energy density ≈ 80 … 250 Wh/kg
(I.-S. Kim, J. Pow. Sources 163)
actual SOC accessible through measured
measuring OCV integrating the current after full charge derived
Page: 17
Version: 04/05/2011
Conventional Lithium-ion batteries Battery for BEV applications
Typical battery requirements:
- 25 kWh energy content
cell 1
- lifetime > 12 years With conventional Li-ion cells: 400 V ÷ 3.7 V/cell
108 cells in series
25 kWh ÷ 400 V
62.5 Ah
25 kWh ÷ 130 Wh/kg
192 kg cell weight
cell s
s cells in serial connection
- 400 V nominal voltage
p cells in parallel
+ 30 % cooling, housing, electric,… 250 kg total weight
(Energy density on system level: 100 Wh/kg)
Page: 18
The number p of cells in parallel depends on the capacity of the cells available on the market.
Version: 04/05/2011
Conventional Lithium-ion batteries Drawbacks in use
short/moderate cycle and calendar lifetime high costs, due to the rare materials (cobalt, nickel) safety (flammable electrolytes and active materials)
Energy / Wh
Results from cycle lifetime testing (80% DoD)
Cycle number Page: 19
(Saft, www.saftbatteries.com) Version: 04/05/2011
Conventional Lithium-ion batteries Drawbacks in use
Safety drawbacks result from the exothermic decomposition reactions of the electrodes, initialized by thermal over load metal-oxide cathode releases the oxygen for Li-oxidation
Li/Li+
Flashing point of lithiated carbon (anode) ≈ 190°C, critical in case of thermal overload
Lithium-platting on carbon anodes at low temperatures and/or at high charging currents Electrode potentials beyond the stability window of electrolytes passivating layers on the electrodes (enables cyclability) gradual decomposition of active materials and electrolyte (reduces calendar lifetime) Deformation of active materials mechanical stress, cracking (reduces cycle life)
4V LiMn2O4
LiNiO2
3V LiMnO2 Li1+xV3O8
2V
1V
Li
Page: 20
LiCoO2
Stability window
Meltdown ( short) of common separators (PP, PE) at temperatures above 150°C thermal runaway
Graphit amorph. Carbon
Version: 04/05/2011
New technologies for Li-ion batteries Potentials
Fields of battery cell improvement
Electrode materials
Electrolytes
Separators
Higher thermal stability
Higher thermal stability
Longer cycle lifetime
Wider stability window
Higher meltdown temperature
Higher capacity
Not flammable
Mechanic stability
Higher voltage
Non toxic
Cost reduction
Page: 21
Version: 04/05/2011
New technologies for Li-ion batteries Potentials
Fields of battery cell improvement
Electrode materials
Electrolytes
Separators
Higher thermal stability
Higher thermal stability
Longer cycle lifetime
Wider stability window
Higher meltdown temperature
Higher capacity
Not flammable
Mechanic stability
Higher voltage
Non toxic
Cost reduction
Page: 21
Version: 04/05/2011
New technologies for Li-ion batteries Cathodes based on iron phosphate (LiFePO4)
in LiFePO4 the compound PO4 is stable releases no oxygen at high temperatures intrinsically safe
Li/Li+
Potential within the stability window of electrolyte no chemical decomposition increases lifetime very high active surface possible high power
4V
Minor deformation during lithium insertion and extraction no mechanical stress long cycle lifetime
3V
LiMn2O4
LiCoO2
LiNiO2 LiFePO4
LiMnO2 Li1+xV3O8
2V
Stability window
No rare materials included low costs
1V
(B. Cooke, GreenCar Congress)
Page: 22
Li
Graphit amorph. Carbon
Version: 04/05/2011
New technologies for Li-ion batteries Cathodes based on iron phosphate (LiFePO4)
Lower electrode potential lower energy density (10-15% less in comparison to metal-oxides systems)
Nominal voltage (against carbon) 3.3V Very flat SOC-OCV-curves
3.8
> 0,4 V 3.6
OCV / V
Cathode’s specific capacities are similar to metaloxides
4
> 0,2 V
3.4 3.2
LiFePO4-Zelle
3
LiCoO2-Zelle
2.8
OCV / V
0
20
40 60 SOC / %
80
100
3.34
LiFePO4-carbon cells exhibit OCV hysteresis
3.32
Flat curves and hysteresis are critical for reliable SOC estimation through measuring the actual OCV
3.3 3.28 3.26 OCVcharge 3.24
OCVdischarge 0
Page: 23
20
40 60 80 100 SOC / % (Roscher et al., Int. J. Electrochem., 2011) Version: 04/05/2011
New technologies for Li-ion batteries Cathodes based on iron phosphate (LiFePO4) (Roscher & Sauer, J. Pow. Sources 196)
LiFePO4 comprises special electric characteristics
3.32
New methods and algorithms necessary to reconstruct several effect: Fuzzy logic systems artificial neural networks
3.29 3.28 3.27 3.26 3.25 20
25 SOC / %
30
SOC / %
In BEV the intermitted full charge enables SOC estimation through current integration only
3.3
OCV / V
model-based state observers
3.31
measured OCV modelled OCV
Connected to a charging station
Page: 24
Version: 04/05/2011
Conventional Lithium-ion batteries Cathodes based on iron phosphate (LiFePO4)
Typical battery requirements: - 400 V nominal voltage cell 1
s cells in serial connection
- 25 kWh energy content - lifetime > 12 years With LiFePO4-based cells (graphite anode): 400 V ÷ 3.3 V/cell
121 cells in series
25 kWh ÷ 400 V
62.5 Ah
25 kWh ÷ 110 Wh/kg
227 kg cell weight
cell s
+ 30 % cooling, housing, electric,… 295 kg total weight
(Energy density on system level: 85 Wh/kg)
Page: 25
p cells in parallel
The number p of cells in parallel depends on the capacity of the cells available on the market.
Version: 04/05/2011
New technologies for Li-ion batteries Anodes based on lithium titanate (Li4Ti5O12)
Anode material for very high charge current rates (no lithium platting!)
No mechanical strain during Li insertion and extraction very long cycle and calendar life possible
Li/Li+
4V LiMn2O4
With LiFePO4 cathode: nominal cell voltage ≈ 1.8 V
LiCoO2
LiNiO2 LiFePO4
3V LiMnO2 Li1+xV3O8
2V
Stability window
Electrode potential inside the stability window high surface areas (nano-particles)
Li4Ti5O12
1V
Li
Graphit amorph. Carbon
(Zaghib et al., J Pow. Sources 196) Page: 26
Version: 04/05/2011
Conventional Lithium-ion batteries Anodes based on lithium titanate (Li4Ti5O12)
Typical battery requirements: - 400 V nominal voltage cell 1
- 25 kWh energy content s cells in serial connection
- lifetime > 12 years With LiFePO4-cathode and titanate-anode Li-ion cells: 400 V ÷ 1.8 V/cell
222 cells in series
25 kWh ÷ 400 V
62.5 Ah
25 kWh ÷ 70 Wh/kg
375 kg cell weight
+ 30 % cooling, housing, electric,… 488 kg total weight
cell s
(Energy density on system level: 54 Wh/kg) p cells in parallel
Very heavy battery system (488 kg ↔ 250 kg of metal-oxide-carbon system) !!! Page: 27
Version: 04/05/2011
New technologies for Li-ion batteries Anodes based on lithium titanate (Li4Ti5O12)
Very low energy density very heavy battery systems But: excellent cycle and calendar lifetime! optimal for BEV operation (full cycle load; 1-2 full cycle each day) also able to cover additional functionality, e.g. peak shaving (vehicle-to-grid) LiFePO4-titanate cells are not available on the market yet In the next years maybe a good solution for smart grid stabilization systems (high cycle numbers, weight not relevant)
Results from cycle lifetime testing (100% DoD)
(Zaghib et al., PPFC, 2009) Page: 28
Version: 04/05/2011
Next generation batteries 5-Volt cathodes for Li-ion batteries
Target of next generation of Li-ion batteries is to increase the operational voltage up to 5 V
Electrode potentials far beyond the electrolytes’ stability window Very poor conductivities of the cathode materials ( doping; small particles)
LiCoPO4
4V LiMn2O4
LiCoO2
LiNiO2 LiFePO4
3V
Problems with stability and power capabilities not solved yet No commercials cells available
LiNiPO4 LiMnMO4
LiMnO2 Li1+xV3O8
2V
Stability window
Cathodes based on metal-phosphates (electrode potentials > 5V)
„5V-cathodes“
Li/Li+
Li4Ti5O12 1V
Li
Page: 29
Graphit amorph. Li-Si Carbon
Version: 04/05/2011
Next generation batteries Limitations of Li-ion systems
Very good efficiency of storing energy: > 90 % (in most cases) Potentials for further improvement by optimizing the active materials are limited due to high fraction of passive components (> 50% of a battery cell) 5-times higher capacity of the anode
+12% energy density
+0.4V increased cell voltage
+11% energy density
(in comparison to a standard high-power Li-ion cell) Target of Li-ion batteries < 500 Wh/kg in the next years (today 250 Wh/kg) For further improvement a new battery technology is necessary
Weight% of components of a battery cell Electrolyte
Separator Copper
Housing Aluminum
Cathode
Anode (M. Wohlfahrt-Mehrens, ZSW)
Page: 30
Version: 04/05/2011
Next generation batteries Lithium-sulphur systems
Reaction:
S + 2Li ⇌ Li2S
Nominal voltage of 2.1 V (< Li-ion) Theoretical energy density: 2862 Wh/kg (without passive components)
5 voltage / V
New technology with sulphur cathode and anode based on metallic lithium or Li-alloy
4 3
5V-Li-ion
metal-oxid Li-ion
LiFePO4-graphite
2
Li-sulphur LiFePO4-titanate
1
Problems with cyclability and safety unsolved yet
0
500
1000 1500 2000 capacity / Ah·kg-1
today the energy density of Li-S cells is < 500 Wh/kg Low power capability Energy storing efficiency: 80 – 90% Promising alternative to Li-ion systems in the next years (SionPower website)
Page: 31
Version: 04/05/2011
Next generation batteries Lithium-air systems
Reaction lithium with oxygen form the ambient air cathode is not part of the battery
Li
Li2O2
Highest theoretical capacity > 10000Wh/kg (equal to metallic lithium) in the charged state Anodes: Li, Li-Si, Li-Zn
E = 11500 Wh/kg
E = 3400 Wh/kg
Operating voltage 3.1 V Today: problem of reversibility of the discharge process
voltage / V
5 4
5V-Li-ion
metal-oxid Li-ion Li-air
3
LiFePO4-graphite (MIT via www.gas2.org)
2
Li-sulphur LiFePO4-titanate
1 0
Page: 32
500
1000 1500 2000 capacity / Ah·kg-1 Version: 04/05/2011
Conclusion
The battery system is the most critical component of an PHEV or BEV (cost, weight, lifetime) Conventional Li-ion batteries comprises high energy densities but limited lifetime and safety New active materials can significantly improve the batteries’ power, lifetime and safety, energy content is reduced (lower operating voltage)
but:
With “5V-Li-ion-batteries” this drawback might be overcome, but technology is not available yet Li-sulphur and Li-Air are promising for next generation batteries, but also not available yet The invention of new technologies (i.e. Li-S, Li-air) will take several years
Li-ion
2010
Li-S
2020
Li-air
2030 (redrawn from Jossen, TUM)
Page: 33
Version: 04/05/2011
Thank you very much for your attention!
director address phone fax e-mail internet
Page: 34
imk automotive GmbH Dr.-Ing. Jens Trepte Annaberger Straße 73 09111 Chemnitz +49 (0) 371 400 97 0 +49 (0) 371 400 97 19 [email protected] www.imk-automotive.de
imk automotive Inc. CEO Dr. rer. nat. Lars Fritzsche address 5 Research Drive Greenville, SC 29607 phone +1 (423).903.5220 e-mail [email protected] internet www.imk-automotive.com
Dr. Michael Roscher, +49 (0) 371 400 9762, [email protected]
Version: 04/05/2011
New generation battery systems for PHEV and BEV applications: Advantages and Challenges
Contents
Introduction of the imk automotive GmbH Battery- and hybrid-electric-vehicles State-of-the-art Lithium-ion battery systems technologies based on rare materials advantages and drawbacks in use New trends in battery technologies next generation Lithium-ion systems alternative technologies and future prospects Conclusion
Page: 2
Version: 04/05/2011
Company ímk automotive GmbH
address
Annaberger Straße 73 09111 Chemnitz
phone fax
+49 (0) 371 400 97 0 +49 (0) 371 400 97 19
e-mail internet
[email protected] www.imk-automotive.de
Headquarter Chemnitz
Page: 3
Version: 04/05/2011
Company imk automotive Inc.
Headquarter Greenville, SC
address 5 Research Drive Greenville, SC 29607 phone +1 (423).903.5220 e-mail [email protected] internet www.imk-automotive.com
Page: 4
Version: 04/05/2011
imk automotive GmbH The company
Aim of the imk automotive: development of new concepts for automotive applications innovative projects in corporation with companies and faculties Optimization of products and production processes Personel development 40 35
total number
30 25 20 15 10 5
Project focus in 2010:
0 2002
2003
2004
Hochund Fachschulabschluß regular employees
2005
2006
2007
Auszubildende apprentices
2008
2009
Praktikanten trainees
2010
year
Diplomanden students
approx. 50% automotive customers approx. 50% others
Page: 5
Version: 04/05/2011
imk automotive GmbH The company
Controlling / Accounting
Quality Management Managing Director
Sales
Safety Engineer Dr. Jens Trepte Assistant / Purchase / Human Resources
Marketing
Product Development Dr. Jens Trepte
Production Process Development Carsten Otto
Information Technology Gerson Heuwieser
Consulting Ingolf Grüßner
Battery Electric Vehicles
Process Design
Software Development
Production Strategy
Mechatronic Systems
Production & Assembly
Training
Product & Production Optimization
Structural Components
Body In White
Support & Service
Ergonomics
Strategic Development Dr. Wolfgang Leidholdt
editor of human work Page: 6
Version: 04/05/2011
Electric Powertrains Architecture
Example: Battery electric vehicle
Page: 7
Version: 04/05/2011
Electric Powertrains Architecture
Battery electric vehicle: Battery supplies the power train and auxiliary components High voltage of the traction battery is transformed into 12 V on-board level (possible additional 12 V lead-acid battery) Charging via battery charger connected to the grid Full charge over night (> 8 hours) or fast-charge option (within 1 hour or faster)
12Von-board supply DC/DC
charger
Boost/ Recuperation
drive train
HVbattery
battery electric vehicle Page: 8
Version: 04/05/2011
Electric Powertrains Architecture
Hybrid electric vehicle: 2 separate power trains included in the vehicle, with two energy storages HV-battery covers short-termed power peaks and energy regeneration electric driving for several kilometers is possible with full hybrids and PHEVs (e.g. up to 60 km Opel Ampera)
12Von-board supply DC/DC
fuel tank
charger
Boost/ Recuperation
drive train
HVbattery
hybrid electric vehicle Page: 9
Version: 04/05/2011
Electric Powertrains Energy consumption and range
Battery electric vehicle: Gradually decreasing SOC Energy demand of approximately 14 – 20 kWh per 100 km (passenger car)
State-of-charge
Electric power
The battery capacity is the limiting factor operation window from SOC = 0…100%
Page: 10
Version: 04/05/2011
Electric Powertrains Additional on-board energy consumers Control systems Electric breaks and steering
Radio, HiFi
Lighting HVAC and comfort systems
In hot climates almost one half of the stored energy is used for air conditioning deduced range!
Page: 11
Version: 04/05/2011
Electric Powertrains The energy storage system
Battery system includes several tens or hundreds of battery cells to achieve: voltage of the power train (>> 100V) required energy content energy density of today automotive batteries cells is < 160 Wh/kg In comparison: conventional fuel 11900 Wh/kg (about 70 times higher), but efficiency of power conversion is 2…3 times better (ICE: 20-40%; electric power train > 80%)
(GS Yuasa)
Page: 12
(A123 Systems)
Version: 04/05/2011
Lithium-ion batteries How does it work?
loadILade / charger e-
e-
UZelle Ucell
Exchange of the lithium between the electrodes (Faradaic current), electrons migrate in the outer circuit Exchange of 1g lithium ≙ 3.86 Ah
Li +
No metallic lithium included (under normal conditions)
electrolyte Elektrolyt Anodenmaterial anode
Page: 13
Asymmetric design with anode and cathode
Kathodenmaterial cathode
Version: 04/05/2011
Lithium-ion batteries How does it work?
–
+
elektrolyte electrolyte
porous active materials high surface areas anode
additives and binder added
cathode
coated on the collector foils between the electrodes an porous separator is inserted pores filled with the electrolyte (from TradeKorea.com)
(Kesai Im&Ex Co. Ldt.)
separator
different housings:
Cu Al
cylindrical Page: 14
prismatic
Coffee-bag Version: 04/05/2011
Lithium-ion batteries How does it work?
Li/Li+ 5V
Li0,5CoO2 LiCoO2
potential
4V
cell voltage results from the different electrode potentials of the active materials involved electrode potentials depend on the lithium contents
3V
voltage at the terminals
2V
1V
No side reactions!!
C6
0
Page: 15
The OCV is under load superimposed by transient voltages drops at conductive parts
LiC6
SOC / %
100
Version: 04/05/2011
Conventional Lithium-ion batteries Supervising of an automotive battery
Voltages, currents and temperatures are to be measured to detect and avoid: U1
cell 1
over-charge, deep-discharge
U2
cell 2
temperature overload
U3
cell 3
over-current
U4
cell 4
Us
estimate energy content, power capability, and state-ofhealth
cell s
IBatt
current sensor
(BRUSA, www.brusa.biz) Page: 16
Version: 04/05/2011
Conventional Lithium-ion batteries Properties
Cathodes: metal-oxides (Co, Ni, Mn)
The “highest energy cell“ NCR18650A
Anodes: carbon (graphite, hard carbon, amorphous) voltage range approx. 2 … 4.2 V, nominal 3.7 V power density ≈ 400 … >5000 W/kg
(Panasonic)
energy density ≈ 80 … 250 Wh/kg
(I.-S. Kim, J. Pow. Sources 163)
actual SOC accessible through measured
measuring OCV integrating the current after full charge derived
Page: 17
Version: 04/05/2011
Conventional Lithium-ion batteries Battery for BEV applications
Typical battery requirements:
- 25 kWh energy content
cell 1
- lifetime > 12 years With conventional Li-ion cells: 400 V ÷ 3.7 V/cell
108 cells in series
25 kWh ÷ 400 V
62.5 Ah
25 kWh ÷ 130 Wh/kg
192 kg cell weight
cell s
s cells in serial connection
- 400 V nominal voltage
p cells in parallel
+ 30 % cooling, housing, electric,… 250 kg total weight
(Energy density on system level: 100 Wh/kg)
Page: 18
The number p of cells in parallel depends on the capacity of the cells available on the market.
Version: 04/05/2011
Conventional Lithium-ion batteries Drawbacks in use
short/moderate cycle and calendar lifetime high costs, due to the rare materials (cobalt, nickel) safety (flammable electrolytes and active materials)
Energy / Wh
Results from cycle lifetime testing (80% DoD)
Cycle number Page: 19
(Saft, www.saftbatteries.com) Version: 04/05/2011
Conventional Lithium-ion batteries Drawbacks in use
Safety drawbacks result from the exothermic decomposition reactions of the electrodes, initialized by thermal over load metal-oxide cathode releases the oxygen for Li-oxidation
Li/Li+
Flashing point of lithiated carbon (anode) ≈ 190°C, critical in case of thermal overload
Lithium-platting on carbon anodes at low temperatures and/or at high charging currents Electrode potentials beyond the stability window of electrolytes passivating layers on the electrodes (enables cyclability) gradual decomposition of active materials and electrolyte (reduces calendar lifetime) Deformation of active materials mechanical stress, cracking (reduces cycle life)
4V LiMn2O4
LiNiO2
3V LiMnO2 Li1+xV3O8
2V
1V
Li
Page: 20
LiCoO2
Stability window
Meltdown ( short) of common separators (PP, PE) at temperatures above 150°C thermal runaway
Graphit amorph. Carbon
Version: 04/05/2011
New technologies for Li-ion batteries Potentials
Fields of battery cell improvement
Electrode materials
Electrolytes
Separators
Higher thermal stability
Higher thermal stability
Longer cycle lifetime
Wider stability window
Higher meltdown temperature
Higher capacity
Not flammable
Mechanic stability
Higher voltage
Non toxic
Cost reduction
Page: 21
Version: 04/05/2011
New technologies for Li-ion batteries Potentials
Fields of battery cell improvement
Electrode materials
Electrolytes
Separators
Higher thermal stability
Higher thermal stability
Longer cycle lifetime
Wider stability window
Higher meltdown temperature
Higher capacity
Not flammable
Mechanic stability
Higher voltage
Non toxic
Cost reduction
Page: 21
Version: 04/05/2011
New technologies for Li-ion batteries Cathodes based on iron phosphate (LiFePO4)
in LiFePO4 the compound PO4 is stable releases no oxygen at high temperatures intrinsically safe
Li/Li+
Potential within the stability window of electrolyte no chemical decomposition increases lifetime very high active surface possible high power
4V
Minor deformation during lithium insertion and extraction no mechanical stress long cycle lifetime
3V
LiMn2O4
LiCoO2
LiNiO2 LiFePO4
LiMnO2 Li1+xV3O8
2V
Stability window
No rare materials included low costs
1V
(B. Cooke, GreenCar Congress)
Page: 22
Li
Graphit amorph. Carbon
Version: 04/05/2011
New technologies for Li-ion batteries Cathodes based on iron phosphate (LiFePO4)
Lower electrode potential lower energy density (10-15% less in comparison to metal-oxides systems)
Nominal voltage (against carbon) 3.3V Very flat SOC-OCV-curves
3.8
> 0,4 V 3.6
OCV / V
Cathode’s specific capacities are similar to metaloxides
4
> 0,2 V
3.4 3.2
LiFePO4-Zelle
3
LiCoO2-Zelle
2.8
OCV / V
0
20
40 60 SOC / %
80
100
3.34
LiFePO4-carbon cells exhibit OCV hysteresis
3.32
Flat curves and hysteresis are critical for reliable SOC estimation through measuring the actual OCV
3.3 3.28 3.26 OCVcharge 3.24
OCVdischarge 0
Page: 23
20
40 60 80 100 SOC / % (Roscher et al., Int. J. Electrochem., 2011) Version: 04/05/2011
New technologies for Li-ion batteries Cathodes based on iron phosphate (LiFePO4) (Roscher & Sauer, J. Pow. Sources 196)
LiFePO4 comprises special electric characteristics
3.32
New methods and algorithms necessary to reconstruct several effect: Fuzzy logic systems artificial neural networks
3.29 3.28 3.27 3.26 3.25 20
25 SOC / %
30
SOC / %
In BEV the intermitted full charge enables SOC estimation through current integration only
3.3
OCV / V
model-based state observers
3.31
measured OCV modelled OCV
Connected to a charging station
Page: 24
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Conventional Lithium-ion batteries Cathodes based on iron phosphate (LiFePO4)
Typical battery requirements: - 400 V nominal voltage cell 1
s cells in serial connection
- 25 kWh energy content - lifetime > 12 years With LiFePO4-based cells (graphite anode): 400 V ÷ 3.3 V/cell
121 cells in series
25 kWh ÷ 400 V
62.5 Ah
25 kWh ÷ 110 Wh/kg
227 kg cell weight
cell s
+ 30 % cooling, housing, electric,… 295 kg total weight
(Energy density on system level: 85 Wh/kg)
Page: 25
p cells in parallel
The number p of cells in parallel depends on the capacity of the cells available on the market.
Version: 04/05/2011
New technologies for Li-ion batteries Anodes based on lithium titanate (Li4Ti5O12)
Anode material for very high charge current rates (no lithium platting!)
No mechanical strain during Li insertion and extraction very long cycle and calendar life possible
Li/Li+
4V LiMn2O4
With LiFePO4 cathode: nominal cell voltage ≈ 1.8 V
LiCoO2
LiNiO2 LiFePO4
3V LiMnO2 Li1+xV3O8
2V
Stability window
Electrode potential inside the stability window high surface areas (nano-particles)
Li4Ti5O12
1V
Li
Graphit amorph. Carbon
(Zaghib et al., J Pow. Sources 196) Page: 26
Version: 04/05/2011
Conventional Lithium-ion batteries Anodes based on lithium titanate (Li4Ti5O12)
Typical battery requirements: - 400 V nominal voltage cell 1
- 25 kWh energy content s cells in serial connection
- lifetime > 12 years With LiFePO4-cathode and titanate-anode Li-ion cells: 400 V ÷ 1.8 V/cell
222 cells in series
25 kWh ÷ 400 V
62.5 Ah
25 kWh ÷ 70 Wh/kg
375 kg cell weight
+ 30 % cooling, housing, electric,… 488 kg total weight
cell s
(Energy density on system level: 54 Wh/kg) p cells in parallel
Very heavy battery system (488 kg ↔ 250 kg of metal-oxide-carbon system) !!! Page: 27
Version: 04/05/2011
New technologies for Li-ion batteries Anodes based on lithium titanate (Li4Ti5O12)
Very low energy density very heavy battery systems But: excellent cycle and calendar lifetime! optimal for BEV operation (full cycle load; 1-2 full cycle each day) also able to cover additional functionality, e.g. peak shaving (vehicle-to-grid) LiFePO4-titanate cells are not available on the market yet In the next years maybe a good solution for smart grid stabilization systems (high cycle numbers, weight not relevant)
Results from cycle lifetime testing (100% DoD)
(Zaghib et al., PPFC, 2009) Page: 28
Version: 04/05/2011
Next generation batteries 5-Volt cathodes for Li-ion batteries
Target of next generation of Li-ion batteries is to increase the operational voltage up to 5 V
Electrode potentials far beyond the electrolytes’ stability window Very poor conductivities of the cathode materials ( doping; small particles)
LiCoPO4
4V LiMn2O4
LiCoO2
LiNiO2 LiFePO4
3V
Problems with stability and power capabilities not solved yet No commercials cells available
LiNiPO4 LiMnMO4
LiMnO2 Li1+xV3O8
2V
Stability window
Cathodes based on metal-phosphates (electrode potentials > 5V)
„5V-cathodes“
Li/Li+
Li4Ti5O12 1V
Li
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Graphit amorph. Li-Si Carbon
Version: 04/05/2011
Next generation batteries Limitations of Li-ion systems
Very good efficiency of storing energy: > 90 % (in most cases) Potentials for further improvement by optimizing the active materials are limited due to high fraction of passive components (> 50% of a battery cell) 5-times higher capacity of the anode
+12% energy density
+0.4V increased cell voltage
+11% energy density
(in comparison to a standard high-power Li-ion cell) Target of Li-ion batteries < 500 Wh/kg in the next years (today 250 Wh/kg) For further improvement a new battery technology is necessary
Weight% of components of a battery cell Electrolyte
Separator Copper
Housing Aluminum
Cathode
Anode (M. Wohlfahrt-Mehrens, ZSW)
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Next generation batteries Lithium-sulphur systems
Reaction:
S + 2Li ⇌ Li2S
Nominal voltage of 2.1 V (< Li-ion) Theoretical energy density: 2862 Wh/kg (without passive components)
5 voltage / V
New technology with sulphur cathode and anode based on metallic lithium or Li-alloy
4 3
5V-Li-ion
metal-oxid Li-ion
LiFePO4-graphite
2
Li-sulphur LiFePO4-titanate
1
Problems with cyclability and safety unsolved yet
0
500
1000 1500 2000 capacity / Ah·kg-1
today the energy density of Li-S cells is < 500 Wh/kg Low power capability Energy storing efficiency: 80 – 90% Promising alternative to Li-ion systems in the next years (SionPower website)
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Next generation batteries Lithium-air systems
Reaction lithium with oxygen form the ambient air cathode is not part of the battery
Li
Li2O2
Highest theoretical capacity > 10000Wh/kg (equal to metallic lithium) in the charged state Anodes: Li, Li-Si, Li-Zn
E = 11500 Wh/kg
E = 3400 Wh/kg
Operating voltage 3.1 V Today: problem of reversibility of the discharge process
voltage / V
5 4
5V-Li-ion
metal-oxid Li-ion Li-air
3
LiFePO4-graphite (MIT via www.gas2.org)
2
Li-sulphur LiFePO4-titanate
1 0
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500
1000 1500 2000 capacity / Ah·kg-1 Version: 04/05/2011
Conclusion
The battery system is the most critical component of an PHEV or BEV (cost, weight, lifetime) Conventional Li-ion batteries comprises high energy densities but limited lifetime and safety New active materials can significantly improve the batteries’ power, lifetime and safety, energy content is reduced (lower operating voltage)
but:
With “5V-Li-ion-batteries” this drawback might be overcome, but technology is not available yet Li-sulphur and Li-Air are promising for next generation batteries, but also not available yet The invention of new technologies (i.e. Li-S, Li-air) will take several years
Li-ion
2010
Li-S
2020
Li-air
2030 (redrawn from Jossen, TUM)
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Thank you very much for your attention!
director address phone fax e-mail internet
Page: 34
imk automotive GmbH Dr.-Ing. Jens Trepte Annaberger Straße 73 09111 Chemnitz +49 (0) 371 400 97 0 +49 (0) 371 400 97 19 [email protected] www.imk-automotive.de
imk automotive Inc. CEO Dr. rer. nat. Lars Fritzsche address 5 Research Drive Greenville, SC 29607 phone +1 (423).903.5220 e-mail [email protected] internet www.imk-automotive.com
Dr. Michael Roscher, +49 (0) 371 400 9762, [email protected]
Version: 04/05/2011
