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 transmissionTraction 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

Energyelectrical driving range,

availability of comfort devices

charging time and infrastructure

driving power,

performance,

dynamics

Power

Durabilitycycles, lifetime

Battery requirements for automotive applications

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Safety

failure, accident,

abuse, maintainance,

comfort, reliability

Costs

profitability,

market acceptance

recycling

Energyelectrical driving range,

availability of comfort devices

charging time and infrastructure

driving power,

performance,

dynamics

Power

Durabilitycycles, lifetime

Battery requirements for automotive applications

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Hazard

Level

Description

0 No effect

1Passive 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-crashtime [ms]

Accele

ratio

n [g]

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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

Energyelectrical driving range,

availability of comfort devices

charging time and infrastructure

driving power,

performance,

dynamics

Power

Durabilitycycles, 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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Re

lative

ca

pa

city [%

]

Re

lative

ca

pa

city [%

]

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

necessityConsiderable 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

Po

we

r

Minimum requirement EV

Typical behaviour of

a Li-Ion cell

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Voltage (SOC)

Current, power

Temperature

Time

Charge and discharge levels

0

20

40

60

80

100

0 100 200Cycle number

En

erg

y/ P

ow

er

rate

Cell chemistry

Cell type (pouch, prism., cyl.)

Aging model Application

Voltage (SOC)

-80 -60 -40 -20 0 20 400

1k

2k

3k

4k

5k

6k

Cou

nt

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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