Lithium Battery

Safety and Performance

Applications of Calorimetry

Thermal Hazard Technology

October 2012

1. The effect of heat on batteries…

2. Quantifying heat produced by batteries… -----------------------------------------------------------------------------------------------------------------------------------------

Well known hazards:

temperature exposure, over-voltage charging and over-discharge, shorting, crush, nail penetration

Performance issues:

effect of rapid charge/discharge, thermal management, efficiency, cell ageing and lifecycle variation-----------------------------------------------------------------------------------------------------------------------------------------------------------------------

Applications of Calorimetry in the area of Lithium Batteries

Battery Development Battery Safety Battery Lifecycle & Efficiency Battery Performance

Determine what is the hazard and how can it be reduced

Thermal Issues with Li Batteries

Accelerating Rate Calorimeter technology

has become the benchmark for lithium battery testing in all areas requiring thermal information

Why? The ARC gives quantitative empirical data

•Quantifies the heat and pressure

•Gives a ‘worst case’ assessment

•Will allow connection to leads for in situ electrical cycling

•Test components and coin-cells to large cells and modules

•Safe and easy to use

•Proven technology world wide with very many household name users

•Also measures heat capacity and surface temperature variation

Quantifying Thermal Issues by the ARC

Options & Modifications to allow…•In situ cycling of batteries with integrated/stand-alone cyclers

•Automated heat capacity measurement

•Shorting, over-voltage charging / over-discharging

•Abuse tests in situ; Nail Penetration, Crush (variable speed)

•EV/HEV Battery testing / fast discharge

•Sub-ambient testing of batteries

•Quantify gas Gas collection from battery disintegration

• Find spatial variation of temperature with MultiPoint

•And extra-large volume calorimeter (for large batteries as used in HEV, PHEV, EV, bicycle, plane, space, military…)

•Video monitoring of battery tests to observe cell damage

ARC advantages with Li Batteries

Methodology – the ARC; ARC Technology for Battery testing…

Bomb Sensor

Top Sensor

Middle Sensor

Bottom Sensor

Pressure

Sensor

Cartridge Heater Radiant Heater

The ARC - an Adiabatic Safety Calorimeter

…what is ADIABATIC?

Adiabatic is the condition of NO HEAT LOSS or gain… therefore –

the sample temperature is ALWAYS followed by calorimeter

If the sample gives out heat…

its temperature increases

So …

the ARC makes the

Calorimeter temperature rise

to match it

The traditional sample is a chemical

in a sample holder

In battery calorimetry the sample is

a cell, module, or cell components

ADIABATIC Calorimetry

With conditions of NO HEAT LOSS or gain, heat release …data showing heat release ie exotherm reaction.... is given as ‘WORST CASE’ DATA

a SIMULATION of what may happen

WORST CASE data may then be extrapolated to any LARGER scale

Sample

Calorimeter

Options & Modifications allow

•Abuse tests in situ; Nail Penetration, Crush

•Shorting, Over-voltage charging / discharging

•In situ Cycling of batteries

•EV/HEV Large format Battery testing / fast discharge / drive cycle simulation

•Measurement of heat release over surface for Thermal Management

•Determination of thermal properties – eg Specific Heat Capacity

All THT ARCs are

SAFE IN USE• Large Blast-proof Chamber of

3mm Reinforced Steel

• 3 secure locks

• Space to add options and apparatus

• Door Safety interlock

• Automatic fume extraction

• Compressed air for rapid cooling

• Simple thermocouple and gas line

connections

• Built in Vacuum, Gas and Pressure

lines

•Thermolock system – automated

cut-out of heaters to avoid runaway

SIMPLE IN USE

HEAT-WAIT-SEEK (adiabatic)

Automatically increases temperature in small steps to find the EXOTHERM… then follow (or track) this reaction ADIABATICALLY to finish, then H-W-S again to end temperature.

OR

Isothermal Operation

How the ARC Works…

ARC testing on battery components: Cathode,

Anode, Electrolyte, SEI. Specialized test cells

are available for component testing.

SEM pictures of three LiCoO2 with different particle sizes (0.8um,2um, and 5um,respectively)

Electrochimica Acta 49 (2004)2661-2666

Self-heating rate vs. temperature for the three Li0.5CoO2 samples with 1M LiPF6 EC/DEC

Self-heating rate vs. temperature for the three Li0.5CoO2 samples with EC/DEC solvent

Stopped at 220℃

Self-heating rate vs. temperature of 100mg of Li[(Ni0.5Mn0.5)0.2Co0.8]O2(900,1000, and 1100℃) charged to 4.2V(solid line) or 4.4V(dashed line) with 100mg of 1.0M LiPF6 EC/DEC electrolyte

Complete single 18650 battery:

Heat-wait-seek testing

Establishes:

Rate of cell reaction against temperature Reaction onset temperature

Maximum cell self-heating rate

Total heat of reaction

etc.

New Chemistries – four generations of development

J Power Sources 137 (2004) 117-127

Temperature vs. time and self-heat-rate vs. temperature for full cell at 50-200% SOC. All batteries went to thermal runaway except the one at 50% SOC.

Battery A: Sn-LCO/ MCMF

Battery B: LCO/ Graphite

Measurement of Internal Pressure

Cylinder or prismatic, large or small, sample must be prepared in an inert environment

Data reproduced with permission of ZSW, Ulm

After Battery disintegration the calorimeter is dirty due to carbon residue, but totally

undamaged. Gas/fumes are extracted via a fan in the blast box (max speed 30m2/min).

Short circuiting

an 18650

battery; open

or with gas

collection

High Impedance

Low Impedance

Overvoltage charging

Before

After

Automated nail penetration & crushing system

EV or Standard calorimeter compatibility – large or small

cells with voltage monitoring

Replaceable piston heads –

large and small

crushing heads or nails

Custom holders for

various sizes

of battery

Nail penetration data

Nail penetration in adiabatic conditions –

cell response is different compared to a open test.

In a non-adiabatic environment, the cells illustrated by red and black would not have

fully decomposed, however in the ARC the reaction continues after the penetration

and the cell self-heats to decomposition. ARC isothermal mode allows comparison

of nail penetration under adiabatic and non-adiabatic conditions.

Four different

commercial cells

tested by nail

penetration from

ambient temperature

in the ARC.

Control speed nail penetration

The newest abuse option is nail penetration with controlled speed this option can be

used without a calorimeter – it may be used as a stand-alone option (however the PSU

and control cards are still required)

It can also be elegantly integrated into the calorimeter (EV or EV+) for in situ nail

penetration tests

Speed range: 1mm per second to 200mm per second, 17nm maximum torque

Automated Specific Heat Capacity Measurement

…this is necessary to convert temperature data to units of Heat (Joules) and Power (Watts) to consider thermal management

Plot heat capacity against temperature

Test data show good

agreement

(< 5%)

with establish

literature values

Battery Performance – Efficiency and Lifecycle Testing

Efficiency is measured as the ratio of electricalenergy stored (or released) by the cellcompared to the heat generated. Cells arecycled in the ARC so heat release is directlyquantified (using heat capacity to convert kelvinto joules)

Old vs. new battery, heat release rate and voltage against time at the same constant current (1C)

CryoCool and Environmental Testing

Cooling of the EV and BPCARCs to -30°C or lower allows all

testing to be carried out at sub-ambient temperatures

Achieved using a liquid nitrogen flow system or circulating bath.

• 3600mAh LiFePO4

battery

• Charged/discharged at

1C

• Operating temps: -30oC

to 60oC

• Test shows poor sub-

ambient performance

Surface Area Thermal Variation

Battery has multiple surface mounted thermocouples and is within calorimeterMultiPoint Options are available with 8, 16 or 24 extra thermocouples. 2 extra thermocouple measurements as standard.MPO TCs used with the EV+ are pressure sealed.

18650 battery exampleHeat is primarily released at the positive terminal (the top of the battery)

Variation of Temperature over Surface

large prismatic battery multipoint example test

100 amp constant-current dischargeTab temperature 90oC+Bulk temperature 65oC

∴ ∆T = 25o C+

Multitrack feature allows tracking from the hottest thermocouple at all times.

Multipoint can also be used with safety tests.

Clamping batteries and modules for High-power discharge

New clamp

design with

holders

customized for

large prismatic

or cylindrical

batteries.

Wires are

connected

inside the

calorimeter

chamber

through the

special collar

Fast Discharge…High power (short time)Driving cycle simulation

Options: stand –alone

EV Battery Test System (eg Bitrode ‘FTN’)

dSpace with programmable power supply and discharge units

Options: stand –alone

The EV ARC is available with Keisokuki cyclers (KSU)from 5V/0.1A to 50V/600A

The KSU can be fully integrated with ES ARC control software and ARCCal+ analysis software

High Power Discharge TestsARC testing with high power discharges using an electronic load:

50W, 100W, 200W, 300W...

200W discharge pulses

Each pulse is 60 seconds

MultiPoint measurement of temperature

variation across battery surface

250mm

High Power MultiPoint DischargeConstant

power

discharges

<= 300W

41oC rise

200W =>

38oC rise

<= 100W

25oC rise

50W =>

13oC rise

Using heat capacity, ΔT can be converted to ΔQ (heat).

High-Power Discharge Efficiency

Cell efficiency is reduced as rate of discharge is increased. When the discharge rate

is increased, more energy is wasted as heat due to the increased internal resistance.

Note that the heat produced results from a combination of the internal resistance and

the chemical process inside the cell.

Combined Safety/Performance Evaluation20Ah Lithium Iron Phosphate versus 20Ah Lithium Cobalt Oxide

Performance Safety

LiFePO4 onset = 135⁰C

LiCoO2 onset = 90 ⁰ C

EV+ Calorimeter

Designed to fulfil protocols outlined in Sandia Freedom Car and SAE Papers

3-zone calorimeter temperature control for adiabatic environment – standard

Cylindrical chamber 40cm diameter by 44cm depth – can take 38 cm wide prismatic cells

Sealed calorimeter to 1.5 bar above ambient (no gas escape)

Sealed, thermally guarded copper 12mm connectors for cycling (max 300amp) – standard

Inert calorimeter chamber with nitrogen or flush chamber with air – standard

Calorimeter chamber pressure measurement – standard

Video/image recording of sample during test – standard

Gas collection using Tedlar/Kynar bags – option

Gas collection using steel gas cylinders – option

Gas flow rate and total gas flow measurement – option

Liquid N2 delivery system for cryogenic testing – with LNFO option

Thermal surface variation (MultiPoint) – with MPO 8/16/24 option

Specific heat capacity measurement – with Cp option

Motorized speed-controlled nail penetration – with NPCO-SC option

EV+ Calorimeter

Internal view of the calorimeter:

12 o’clock – camera window

1 o’clock – NPCO port

6 o’clock – electrical connectors

7 & 8 o’clock TC ports

9 o’clock – gas removal port

External

views of

the

calorimeter

Battery Performance Calorimeter

Large volume performance testing calorimeter. Designed around high-current charge/discharge testing, and sub-ambient isothermal operation. Not designed for safety tests.

65cm x 45cm x 50cm chamber with elliptical cylinder shape

“Thermal Guard” design for direct electrical connection to calorimeter walls, allowing current supply/draw without thermal loses (500 amp max current rating)

Combined with refrigerated circulating bath for isothermal operation to -30⁰C.

Fast tracking at up to 20⁰C/min. Includes XL blast box for user safety.

THT ARCs – meeting the challenge of

MEASURING THE HEAT under a range of conditions

1997 2012

THT ARC Users

Summary

With Battery Safety and Cycler Options the ESARC EVARC and EV+ARC are the THT family of Battery Calorimeters, they may be used to study...BATTERY R&D, SAFETY, LIFECYLCE, EFFICIENCY, PERFORMANCE

battery components (anode, cathode, electrolyte, SEI) batteries (at various age or State of Charge) batteries of ‘any’ size, battery modules or packs batteries when shorted (internal or external), crushed (abuse) batteries when over-voltage charging and over-discharging (abuse) batteries when cycled to define their lifecycle and efficiency (use) batteries when tested to determine performance (use) cell, module pack testing video monitoring gas collection and pressure measurement environmental isothermal testing (-30 to +60C)measurement of specific heat capacity conversion of data to Enthalpy (Joules) and Power (Watts) testing with large, fast discharge or driving cycle simulation to be continued….!

The EndThe THT family of Battery Calorimeters... unique..World Benchmark ProductsBattery DevelopmentBattery Safety (Use & Abuse)Battery Efficiency & LifecycleBattery Performance

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