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Lithium & Safety webinar
July 2nd, 2019
Different cell types
2 ARTS ENERGY - CONFIDENTIAL & PROPRIETARY July 2nd, 2019
Types
Cylindrical Prismatic Pouch
Which failures?
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July 2nd, 2019
ARTS ENERGY - CONFIDENTIAL & PROPRIETARY
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ARTS ENERGY - CONFIDENTIAL & PROPRIETARY
What are the risks?
July 2nd, 2019
Risks
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Risks are :
Gaz emission
Smoke
Fire
Explosion
Possible causes :
over–temperature / over charge / over courant / internal short circuit, crush or
perforation
That leads to temperature increase
That leads to thermal runaway
ARTS ENERGY - CONFIDENTIAL & PROPRIETARY July 2nd, 2019
Why Thermal Runaway propagation is dangerous ?
A lithium cell can have an internal short-circuit like a nickel based cell. But with lithium technology, this internal short-circuit can be very dangerous.
If 1 cell have an internal short circuit, it’s not very sensible, but if this cell propagates to other battery cells we will have a Thermal Runaway Propagation. This phenomena can be very dangerous:
20 X =
Thermal Runaway
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Safety mechanism
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160°C-200°C
120°C-130°C
75°C-100°C
70°C
60°C
Gaz emission (CO2)
Gaz emission (O2)
Electrolyte ignition
Temperature
CID Opening
Vent Opening
Charge interruption
Discharge interruption
Current interruption
Gaz emission
Separator melting
450°C
Charge stopped
Discharge stopped
Current interruption
Fire/ explosion
Protections Effects
Irre
vers
ible
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ARTS ENERGY - CONFIDENTIAL & PROPRIETARY
At cell level
July 2nd, 2019
Safety component on cylindrical clls
9 ARTS ENERGY - CONFIDENTIAL & PROPRIETARY July 2nd, 2019
PTC (Polyswitch)
On some energy cells, a PTC is inserted between the
CID and the lid (top). In case of over current, the PTC
goes into high impedance mode; which has the effect
of reducing the current.
CID (Current Interrupt device)
In case of inappropriate use such as overload, the
pressure increases and the CID deforms. Following
this deformation, the connection between the cathode
and the CID is interrupted and the current no longer
flows.
Security event
If the pressure continues to increase after opening the
CID, the vent opens to prevent explosion. Then the
gases escape to the outside in a safe way.
Safety component on pouch and prismatic
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Prismatic cell
No TPC or CID.
Presence only of a vent.
This is why it is recommended to insert a PTC or a thermo fuse at the
battery level in this case.
Polymer cell
No PTCs, IDCs, or vent.
In case of pressure, the cell will inflate and take a form of rugby ball, the
cell can even, in some cases, eventually catch fire or explode.
Hence the addition of protection at the battery level (PTC, Thermo fuse,
fuse, ...)
ARTS ENERGY - CONFIDENTIAL & PROPRIETARY July 2nd, 2019
Difference between Li-Ion (Co,NMC,NCA,...) & LiFePO4
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Better thermal stability of cathod in LiFePO4
No O² generation => no thermal runaway
However, graphite anode same as Li-Ion Risk is still existing
PCM is needed
ARTS ENERGY - CONFIDENTIAL & PROPRIETARY July 2nd, 2019
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ARTS ENERGY - CONFIDENTIAL & PROPRIETARY
At Electronic level
July 2nd, 2019
Lithium Ion must be managed cautiously!
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Event •Over charge
•Over temperature
•External short circuit
•Over current
•Cell Internal short circuit
Run away start
•Temperature increase •Internal pressure increase
Effect • Fire
•Toxic or harmful gas escaping the battery (CO, organic electrolyte)
•Toxic or harmful liquids flowing out of the battery electrolyte, others)
•parts ejections from the battery
•Explosion
Protection Circuit
Mandatory into
battery pack
To keep voltage and current levels to secured levels and manage temperature, especially in charge
At hardware and software levels
14 ARTS ENERGY - CONFIDENTIAL & PROPRIETARY July 2nd, 2019
Hardware application level
Thermal cut-off?
Fuse for current
Software Application level
Voltage management
Temperature management
Current management
Battery level
Overcharge Overdischarge Overcurrent Short circuit Thermal cut
off?
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ARTS ENERGY - CONFIDENTIAL & PROPRIETARY
At pack design level
July 2nd, 2019
It is a matter of Probability!
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July 2nd, 2019
ARTS ENERGY - CONFIDENTIAL & PROPRIETARY
To improve our knowhow, AE had invested in:
Thermal camera Thermal analysis Software
Cabin to realize abusive test
Internal equipment and first results
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Results and Design factors
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Depends on cell technologies
Design impacts
July 2nd, 2019
Technologies Impact Conclusion
Nickel Cobalt Aluminum Very sensitive Must have safety design
Nickel Manganese Cobalt Sensitive Security levels must be adjust (capacity Vs power)
Lithium Phosphate Fer Safe No safety design is necessary
ARTS ENERGY - CONFIDENTIAL & PROPRIETARY
Factors with strong impact General impacts
Management of gas evacuation (Keeping « free » positive side of cell/ protecting of rejection/ Evacuating gas )
Take care with a sealed casing
Isolation of TR cell with fuse connection Design impact
Space between cells => Small design impact
It is a matter of Probability!
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If we are in the “Internal cell failures” case:
With Japan / Korean suppliers => 1 to 5 ppm with a particle => Hypo 2 ppm
With Chinese suppliers => 10 to 150 ppm with particle => Hypo 50 ppm
This will happen during charge!
ARTS ENERGY - CONFIDENTIAL & PROPRIETARY July 2nd, 2019
Battery configuration
Battery pack Probability of failure (2 ppm)
Battery pack Probability of failure (50 ppm)
2 cells 1/ 250 000 1/ 10 000
8 cells (4S2P) 1/ 62 500 1/ 2 500
39 cells (13S3P) 1/ 12 800 1/ 510
98 cells (7S14P) 1/ 5 100 1/ 200
It is a matter of Probability!
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Depending on customer case…
ARTS ENERGY - CONFIDENTIAL & PROPRIETARY July 2nd, 2019
+ -
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ARTS ENERGY - CONFIDENTIAL & PROPRIETARY
Conclusion
July 2nd, 2019
0 risk is not possible ! Only reducing risk!
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Respect the recommendations of the cell manufacturers
Voltage thresholds for overcharge, over discharge
Temperatures in charge and discharge
Acceptable currents
Prohibition of cold or hot load
Develop following methods that integrate risk management (EN61508, EN ISO 13849-1, IEC62061, ...)
Define with customer what are acceptable risks through their safety analysis
Design to avoid the spread of a failure
Run away test as a validation
ARTS ENERGY - CONFIDENTIAL & PROPRIETARY July 2nd, 2019
ARTS Energy support
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Electrical safety
Voltage protection level in accordance with cell manufacturers (design)
Current protection in accordance with cell manufacturers and application (design)
Short circuit protection in accordance with battery impedance (design)
Thermal run away propagation management
Mechanical & Electrical arrangements based on our tests (design)
Case vent dimensioning (design)
Validation of final product (test)
Thank you for your
attention
www.arts-energy.com
contact@arts-energy.com
Our Head Office / Manufacturing Site
ARTS ENERGY - CONFIDENTIAL & PROPRIETARY
ARTS Energy SAS
10 Rue Ampère
Zone industrielle
F-16440 Nersac
Tel. : +33 (0)5 45 90 35 52 / 53
Fax. : +33 (0)5 45 90 37 68
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