Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka
AVL List GmbH (Headquarters)
Confidential
Cost and performance
penalty of mitigation
measuresSession 5 – Thermal Propagation Workshop @JRC
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 2Confidential
• Introduction
• Mitigation measures for different cell types
• Performance Penalties?
• Comparison on energy density (efficiency) of various measures
• Cost?
• Are safe cells available?
• Summary
Content
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 3Confidential
Serviceability
Production Capability
Efficiency
Performance
Driver Experience
Cost
EngineeringRequirements
Safety
8 attributes of traction batteries as key factor for success.
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 4Confidential
Chevrolet BOLT Mitsubishi Outlander PHEVTesla Model X
Mitigation measures for different cell types
2,3mm
PC isolation 0,3mm
Cooling pipe1mm
Compressionpad 2,1 mm
Cartridge cover0,5 mm
Picture source: SAE Matthe 2016
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 5Confidential
Venting Strategies compared
Chevrolet BOLT Mitsubishi Outlander PHEVTesla Model X
Front sideLeft side
4 pressure equalization & ventingmembranes
Venting plugs assembly
3 pressure equalization & venting membranes Nitto Denko
15 fluorosilicone venting plugs
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 6Confidential
Safety CRITERIA RATING Cell Level – EUCAR Hazard Levels
Parameter TESLA Model X BOLTMitsubishi
OUTLANDER PHEV
Overcharge 1CEUCAR Hazard Level
2 3 6
Nail (GB/T)EUCAR Hazard Level
6 3 4
Max Temp. @ Nail 767 °C 56 °C 369 °C
Thermal stabilityEUCAR Hazard Level
4 4 4
Thermal stabilitycell temperature @event
130°C 120°C 145°C
Short circuitEUCAR Hazard Level
3 3 3
Overcharge protection is easily handled on pack level
G/NCA vulnerable to damage
--- 1--- 1--- 1
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 7Confidential
Safety Parameters: Venting strategy and fire protection measures
Parameter TESLA Model X Chevrolet BOLTMitsubishi
OUTLANDER PHEV
Distances cell to cell0.3 mm isolation
1 mm cooling pipe2.1 mm foam
0.5 mm Aluminum2.3 mm air
Materials between cells
PC (Polycarbonat)Aluminum
FoamAluminum
Air gap with centralfoam pad
Containment measures between modules
MICA plates - -
Cross section venting elements
15 times 530 mm² 4 times 289 mm² 3 times 72 mm²
Battery cover materialSheet metal
(DX51D)PP GP3156F PP GF40
Battery to vehicle isolation
Insulating Blanket 9,3mm
Air gap Air gap
Widely varying venting cross sections
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 8Confidential
What is a performance penalty for cell integration into module or pack?
▪ Increased cost (€/kWh)
▪ Loss of energy density (Wh/L)
▪ Increased weight (Wh/kg)
▪ Increase in assembly complexity (€/kWh)
▪ durability/reliability
▪ Lifetime
▪ Field failures
▪ …
Performance Penalty?
Joining of cooling
elements
BMS Unit
Tab cooling on opposite ended tabs
Cell frames, one form only, forces pouches in
position
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 9Confidential
▪ Insulation foils between cells
▪ For prismatic & pouch the foils are also used to position and glue the cells together
▪ In cylindrical modules weaved in foils are possible usually collides with cooling
interface
Cell2Cell conductionceramic insulators
adhesive isolation layer
EXAMPLE: AVL MODULE FOR PRISMATIC CELLS
Penalty:▪ Cost▪ Assembly complexity
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 10Confidential
▪ Intumescent foils between cells
▪ For prismatic & pouch the foils are also used to position and glue the cells together
Cell2Cell conductionintumescent material
cells
intumescentmaterial
compressionpads
housing
Pouch cells movePrismatic cells material expands into
surrounding
Penalty:▪ Cost▪ Weight▪ Assembly complexity▪ Reliabiltiy
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 11Confidential
▪ Fire insulation foils and channel over directed vents
▪ For pouch the venting is not directed / no so energy dense not needed
Directed venting conductionprotective measures
Penalty:▪ Energy Density▪ Assembly complexity▪ Cost!!
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 12Confidential
Safety Critical Cell BehaviorInternal short circuit & thermal runaway simulation
Simulation of internal short circuits with electrochemical and electro-thermal battery model
• Implemented FIRE (AVL software)release 2016
Necessary input
• Cell abuse tests
• Cell deformation simulation in crash/crush case
SOC @ 500sec. Temp @ 500sec.
Simulating internal short circuits in AVL FIRE
Test Simulation
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 13Confidential
Safety Critical Cell BehaviorDirected venting conduction pack level simulation
Optimized venting flow
guidance
No venting flow guidance
Cell in thermal runaway and venting
Additional heat input to the cell above by venting leads to fast temperature rise
animation
Neighboring cells are heated via radiation & venting gas input
Design strategy:Guiding and separating of the venting flow to distribute the heat source of all cells
Cell in thermal runaway
Neighboring cells
Optimized venting gas flow distribution by design controlled guiding allows avoiding of propagation
Propagation safe
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 14Confidential
Cost of introduced measures
Cell 2 cell insulation:
▪ Ceramic material
~10% of module cost excl. cells
▪ Intumescent material
~15% of module cost excl. cells
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 15Confidential
Cost Summary on module level in benchmark vehicle Tesla Model X
Additional cost on battery housing=15% of housing frame cost
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 16Confidential
Just a recap of yesterdays presentations:
▪ LFP might be safer or not?
▪ Fire good or not?
▪ Directed venting preferable or not? In Sim yes in reality no? ☺
My experience:
▪ Cells with more than EUCAR Hazard Level 4 in GB/T 31487-2015 are not used in automotive
▪ Cells with higher hazard levels are sold by cell manufactures to small scale applications!
▪ Triggering external induced thermal runaway in real application is very different for prismatic, cylindrical and pouch!
Safe Cells? – many influences!
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 17Confidential
C
Comparison: conventional Lithium-Ion Cell vs. All-Solid-State Cell
All-solid-state cell with conventional C/Si anode
Liquid electrolyte in porous electrodes replaced by solid (orange cycles)
Electrolyte soaked separator is completelyreplaced by solid (orange cycles)
Possible increase in volumetric energy density by using silicon anodes
No significant change in energy density
No flammable liquids, reduced ageing
Conventional Li-ion cell
Liquid electrolyte in pores of electrodes and separator
porous anode (graphite grey circles)
porous cathode (metal oxide, e.g. NMC violet circles)
separator
2023?
Good for
BEV!
No base material
for thermal runaway
PHEV?
Dr. Bernhard Brunnsteiner, Dr. Wenzel Prochazka | Global Battery Competence Team | 09 März 2018 | 18Confidential
▪ Current automotive packs have a host of mitigation measures included
▪ Mitigation measure development needs to be done in view of cell & module & pack & application!
▪ Defining measures on cell level, module level or pack level – independent of each other may lead to high cost, but maybe not to an increase in safety (weakest link principle!)
▪ Future cells (solid state) might decrease the risks
reduced risk BEV
but small PHEV stay in need of low resistance cells with liquid electrolyte for the time horizon foreseeable
Summary
www.avl.com
Thank You