Automotive Battery EGVI Expert Workshop Dr. Ulrich Mhr Volkswagen - - PowerPoint PPT Presentation

Automotive Battery – EGVI Expert Workshop

• Dr. Ulrich Mähr

Volkswagen AG, Group Research Battery

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High voltage lines Electrical brake power assist Cooling Cross-linking of components Heating Power electronics E-Motor and transmission Traction battery and battery managment Infotainment Remote-steering / online services

Spectrum of new technologies for electric vehicles

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Battery activities Volkswagen Group Research

Air cathode before and after discharge Li-ion batteries gen. 1 and 2 Gen 1:

• Benchmark (energy and power, safety)
• Analytics
• Aging models

Gen 2:

• New materials, new cell types

After Li-ion technologies

• Li – sulfur
• Li – oxygen

Safety

failure, accident, abuse, maintainance, comfort, reliability

Costs

profitability, market acceptance recycling

Energy

electrical driving range, availability of comfort devices charging time and infrastructure driving power, performance, dynamics

Power Durability

cycles, lifetime

Battery requirements for automotive applications

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Safety

failure, accident, abuse, maintainance, comfort, reliability

Costs

profitability, market acceptance recycling

Energy

electrical driving range, availability of comfort devices charging time and infrastructure driving power, performance, dynamics

Power Durability

cycles, lifetime

Battery requirements for automotive applications

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Hazard Level Description No effect 1 Passive protection devices activated 2 Defect / damage 3 Leakage 4 Venting 5 Fire or flame 6 Rupture 7 Explosion

Requirements for the cell: Hazard Level ≤ 4

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Challenges

• Used materials are sufficient

safe, for improvement of life time and energy density also new safe materials have to be developed

• Today safety is ensured by

large efforts on system level

Safety of Li-Ion technology

Research necessity

• Further development of protective mechanisms (cell, module, system)
• Development of intrinsically safe materials

Simulation of a rear-crash

time [ms] Acceleration [g] 7

Lithium-plating and dendrite growth

Intact area Molten and recoagulated fibre Separator

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Damages on cell level during applicationrare but normal use

• Short cut of anode and cathode by

Lithium dendrites

• Closed pores in the separator
• Melting and recoagulation of the

polymer

Damaged area

Safety

failure, accident, abuse, maintainance, comfort, reliability

Costs

profitability, market acceptance recycling

Energy

electrical driving range, availability of comfort devices charging time and infrastructure driving power, performance, dynamics

Power Durability

cycles, lifetime

Battery requirements for automotive applications

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Challenges

• Consideration of special ambient conditions
• Temperature (e.g. South Africa, Northern

Sweden)

• Driving strategy (current, Depth of discharge,

SOC, etc.)

• Reliable durability prognosis is needed

(10 …15 years)

• Combination of aging effects in the highly complex

system of a Li-ion cell

Life time of Lithium-Ion cells

Research necessity

• Enhanced life time by materials research
• Development of prediction models for aging behaviour

Laboratory for cell and battery testing (VW Gorup Research)

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Aging effects in lithium-ion cells

Influencing parameters for aging of Li-ion cells

• Temperature
• Time
• Voltage (SOC)
• Current, power
• Charge- and discharge

levels

• Anode, cathode material
• Electrolyte, additives
• Cell type (pouch

prismatic, cylindrical)

• …

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Relative capacity [%] Relative capacity [%] Cycle number Cycle number

Status / Challenges

• Temperature requirements of automotive

applications differ from consumer electronics:

• Consumer electronics: 0°C to 50°C
• Automotive requirement: -30°C to 60°C
• Physics of electrolyte/solvent systems is

limiting factor (cristallization)

Power capability at low temperatures

Research necessity Considerable expansion of operating temperatures by novel electrolytes

Schematic graph: abrupt power decrease of known Li-ion cells at low temperatures. Temperature

• 30°C 23°C 60°C

Power Minimum requirement EV Typical behaviour of a Li-Ion cell

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Voltage (SOC) Current, power Temperature Time Charge and discharge levels

20 40 60 80 100 100 200 Cycle number Energy / Power

rate



Cell chemistry Cell type (pouch, prism., cyl.)

Aging model

Application

Voltage (SOC)

• 80 -60 -40 -20

20 40 1k 2k 3k 4k 5k 6k

Count

P_Batt [kW]

Power / currents Temperature Recovery time Charge and discharge levels

Target

• Reliable life time prediction in real vehicle operation on basis of

laboratory measurements and simple technical operation data Frequency of … Verification

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Thank you!

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