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The Lithium-Ion Battery

Service Life Parameters

Geneva

May, 2013

JP. Wiaux & C. Chanson

RECHARGE aisbl

Advanced Rechargeable Batteries

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The battery life duration is generally limited by the ageing

of the Li-ion battery electrodes and chemistry.

It can be measured through the evolution of two performances criteria:

The evolution of the battery capacity

The evolution of the battery internal resistance

According usage conditions, other criteria may limit the performances of

the battery such as the effect of temperature and the shelf life,….

Li-ion battery ageing mechanisms

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The progressive reduction of the battery capacity over life

The progressive increase of the internal resistance of the battery:

it limits the battery power due to voltage reduction.

The ageing is often attributed to 2 cumulative mechanisms

Calendar life ageing: effect of time and temperature on performances.

Cyle life ageing: effect of charge and discharge cycles on performances.

Li-ion battery ageing mechanisms

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• The battery chemistry is characterized by the cathode material (LCO, NMC, LFP, etc…)* and the anode material ( Graphite, LTO, ..)**

Li-ion chemistries

*Cathode materials: LCO= Lithiated Cobalt Oxyde, NMC= Lithiated Nickel Manganese Cobalt

Oxyde, LFP= Lithium Iron Phosphate.

**Anode material: LTO= Lithium Titanate.

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Li-ion batteries key features

• Multiple Chemistries:

Li-Ion is a generic termc for rechargeable batteries

It overs several types of battery chemistries and several formats for various applications (see next slides).

• Improving technology:

This technology is still in an development phase

New chemistries and designs are progressively introduced on the market.

LCO LiCoO2

NCA LiNiCoAlO2

NMC LiNiMnCoO2

LMO LiMn2O4

LFP LiFePO4

LTO*

Li4Ti5O12

Si-C*

Cell Voltage,

100%/50% SOC

4.2V/

3.8V

4.0V/

3.6V

4.2V/

3.7V

4.2V/

3.9V

3.6V/

3.3V

2.8V/

2.4V

4.2V/

3.9V

Energy ++ +++ +++ + ++ - +++

Power ++ +++ ++ +++ ++ + ++

Calendar Life + +++ + - ++ - -

Cycle Life + ++ ++ ++ ++ +++ --

Safety + + + ++ +++ +++ +

Cost - + ++ ++ + - ++

* LTO and Si-C are anodes, which can be combined with any cathode.

Choices in Li-ion Chemistry

• The type of chemistry will impact performances and safety.

The selection of a chemistry for a given application is a trade off

Between various parameters

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1. The battery is also characterized by its format.

1. Button cells

2. Hard cases: cylindrical or prismatic (aluminium welded can) 3. Soft case or « pouch »

Li-ion batteries / Formats

Reference: IEEE 1725 Standard

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The industrial battery is independent of the cell format.

Li-ion packs technologies

Laptop Bicycle HEV

EV Battery

Management

System

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Li-ion ageing: power vs temperature and SOC

The battery power is impacted by the storage temperature and by the state of charge during storage

100

150

200

250

300

350

0 360 720 1080 1440 1800

Storage time, Days

Pu

issan

ce

(W

)

+20°C-100% SOC

+40°C-100% SOC

+60°C-100% SOC

+20°C-50% SOC

+40°C-50% SOC

+60°C-50% SOC

Ref: Saft Li-ion NCA/graphite, M. Broussely IMLB12

60°

C

40°

C

20°

C

10

0%

20%

40%

60%

80%

100%

120%

0 180 360 540 720 900 1080 1260

Days of storage @ 100% SOC

CA

PA

CIT

Y,

%

0%

20%

40%

60%

80%

100%

120%

EN

ER

GY

, %

capa +20°C

capa +40°C

capa +60°C

energy +20°C

energy +40°C

energy +60°C

60°C

40-20°C

Capacity and energy are impacted by the storage temperature

Ref: Saft Li-ion NCA/graphite, M. Broussely IMLB12

Li-ion ageing: capacity & energy vs temperature

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The cycle life duration is often measured with cycling at 100% depth of discharge: in this case -15% capacity after 1000 cycles

Ref: Saft Li-ion LCO/graphite, M. Broussely IMLB12

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4,5

5

5,5

6

0 100 200 300 400 500 600 700 800 900 1000 1100

Cycle number

Cap

acit

y (

Ah

)

Electrolyte "A"

-15%

But the large majority of applications do not use 100 % of the battery capacity at each cycle ( limited depth of discharge by the user or by the Battery Management System).

Li-ion ageing: capacity evolution with cycles

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The depth of discharge has a large effect on the number of cycle: 1 million cycles can be achieved at low DOD. => the battery management system can protect the battery while limiting the DOD

Ref: Saft Li-ion LCO/graphite, M. Broussely IMLB12

Typical cycle life of a

Li-ion cell

Li-ion ageing: cycle life vs depth of discharge

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The battery life duration is determined by 3 key factors

The battery design: type and quality of selected materials and components,

design of the product.

The application constraints: temperature of operation, type of usage ( from

high power permanent cycling to permanent charge for back-up).

The Battery Management System regulation mode: the more efficient is the

battery protection, the longer the service life.

Consequently, the service life expectation can be as short as 1 to 2 years,

(e.g. in cordless power tool) or up to 20 years (e.g. in in stationnary back-up

applications)!

Li-ion life duration by application