Safety and Thermal Management for Li-ion Batteries in Transportation Applications
Said Al-Hallaj
Presented at: EV Li-ion Battery Forum 2012
AllCell Technologies LLC 2321 W. 41st Street Chicago, IL 60609
Presentation Outline
• Overview of lithium-ion batteries
• Importance of thermal management – Safety – Performance
• Passive thermal management with phase change material (PCM)
• Concluding remarks
2 Lithium-ion chemistry has large power/energy range
HEV
PHEV
EV
Cycle life and cost per kWh generally increase with specific power 3 Automotive applications require full range of lithium-ion batteries
Hybrid Plug-in Hybrid 0.5-1.5 kWh 4 -16 kWh
Priority Not Priority Not
Power Energy Density Energy Density
Shallow/Cycle life Cost
Full EVs LEV 20-70 kWh 0.5-10 kWh
Priority Not Priority Not Energy Density Power Cost Power Cost Deep cycle life Deep/ cycle life
4 Divas of the EV world
• Li-ion batteries have high performance, but very temperamental
• Key problem: dealing with heat generated by cells during charge, discharge and ambient conditions
• If cells get too hot, three problems: – Decreased battery life – Decreased performance – Risk of fire or explosion
5 Thermal degradation is a hot button issue
“As a result, the LEAF pack will have temperatures „all over the place,‟ “Thermal management of the system...all of causing it to suffer „huge degradation‟ in those little details go into effect to take it to cold environments and basically „shut the next level” – Jay Iyengar, Global Director & Chief Engineer for Electrified Powertrains, Chrysler off‟ in hot environments.” – Elon Musk, CEO Tesla “Thermal management of lithium-ion battery systems is critical to the success of all-electric vehicles because extreme temperatures can affect performance, reliability, safety and durability.” – V. Anand Sankaran, Executive technical leader, Ford Energy Storage & High Voltage Electrical Systems
“The different chemistries have different thermal characteristics and so we‟ve been able to incorporate how to make sure from a thermal perspective that we‟ve got it...” - Denise Gray, Advanced Battery Director of GM
6 Chemical reactions inside cell add complexity to the heat problem
heat accumulation in cell creates additional chemical reactions heat accumulation in cell creates burden on cooling
Heat Net Heat Heat accumulation in Entering/Leaving Generation Cell = + Cell
Insufficient heat transfer causes heat accumulation in cell Heat from Chemical reaction accumulates in cell
7 AllCell’s PCM Solution
• Phase change material (PCM) and PCM conductive matrix used to absorb and conduct heat to and from lithium-ion batteries
• PCM improves battery cost, efficiency, and weight when compared to active systems Cell • Phase change materials have a long track record in other applications: – Vehicle HVAC – Delphi, Behr – Building thermal systems Cell – Spacecraft thermal systems PCM – Medical supply shipping – Chemical reaction exotherm smoothing Cell
Why not apply PCM to batteries?
8 Safety issues still exist
Source: A. Pesaran/USDOE-NREL
9 Safety reputation bad for industry,
Chevy Volt Fire Prompts but... Federal Investigation Into Auto safety chief denies sitting on Lithium-Ion Batteries – NY Times Chevy Volt warnings in heated hearing – Fox News
Fisker Recalling 239 Karma Plug -In Hybrids for Fire Hazard – NY Times
Fisker Karma recall is official, 239 cars will need their battery packs swapped - engadget
Fire deals new setback to Navy's heralded mini-sub – navyseals.com
PC Notebook Computer Batteries Recalled Due to Fire and Burn Hazard - http://www.cpsc.gov/
10 ...it’s really about lives
Lithium Ion Batteries Faulted for Jet Crash - Gigaom
2 Die as Asiana Cargo Plane Crashes Off South Korea – NY Times
11 Safety improvements are being made on multiple fronts
Pack Level Cell Level
Active Cooling Passive Cooling Cell Design Cell Chemistry
Electrolytes Additives Liquid Cooling Phase Change Anode/ Air Cooling (refrigerant) Material Cathode
Shutdown Positive Thermal Coefficient Safety Vents Safety Circuits Electrode Coatings Separators Devices
Ceramic Conductive Materials Polymer
12 AllCell PCM prevents thermal runaway propagation
13 Operational performance must evolve to achieve mass adoption Gen 1 – Product Gen 2 – Mass market/cost Introduction sensitive Safety Must Must Low Cost Good to have Must Performance Good to have Must Gen 1 Chevy Volt uses 16 kWh battery to achieve 25-50 mi AER 11 kWh go to vehicle propulsion + 3.5 kWh oversize to limit SOC window and heat generation + 1.5 kWh oversize for thermal management power requirements 16 kWh
Gen 2 must meet more difficult technical goals at a lower cost 11 kWh still required for propulsion + 2.5 kWh oversize to limit SOC window and heat generation + 0.2 kWh thermal management (cabin air/PCM system) 13.7 kWh – (2.3 kWhr or 14% battery size reduction)
battery downsize translates to significant savings in vehicle cost
14 Optimal solution balances multiple methods
• Oversize battery • Curtail performance • Effective thermal management
• Must consider cost, efficiency, life and customer satisfaction when evaluating options
15 When is liquid cooling used?
High
Air cooling Liquid cooling Air cooling
C-rate
Energy Density
Heat Removal Without Intensity PCM With PCM
Low HEV PHEV EV (Prius) (Volt) (Leaf) Hybrid air/PCM cooling for hybrid and EV normal operation PCM eliminates the need for active cooling and heating during the majority of operating time – combined with cabin air system for remainder of situations Ambient EV HEV Cold Delays cool down. Adds minimal Delays cool down. Heat with engine heating time/energy. heat. Moderate No active management required Peak shaving of heat removal requirement Hot Keeps battery below ambient Peak shaving of heat removal during hot days requirement AllCell system simplifies design
Copper mesh enhances heat transfer to air
500 Wh LFP battery
Al air channel PCM-graphite Copper mesh
18 Battery can be used more aggressively without needing liquid cooling
45 Air only 40 35 30
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20 10 m/s air flow – 0.4 m3/s
2 m/s air PCM+Air
19 Concluding Remarks
• One size does not fit all...variety of cell types and applications necessitates customized solutions
• Chemistry advances are only one piece of solution...thermal management and intelligent electronics play significant role
• Safety problems still exist...high energy and toxic chemicals pose real risk
20 Company Contacts
Said Al-Hallaj, Chairman & CEO Tel: (+1) 773-922-1155 x201 [email protected]
AllCell Technologies LLC Corporate Headquarters 2321 West 41st Street Chicago, IL 60609 USA
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