SaBatAir ProjectContribution of the Sabatair project to the SAE

G27 working groupImpact Solutions

Les Atelier des Tanneurs, Brussels – November 14th, 2019

Note: the information included in this presentation are provisional, as the research

project is still on-going.

The content of the Sabatair consortium presentations does not reflect the official opinion

of the European Union nor EASA. Responsibility for the information and views expressed

in this presentation lies entirely with the author(s).

Review of three test methods from the draft SAE AS6413 (Nov 2018 version): Test(VIII) Reduced Cell configuration

Test (VII): Generic packaging Test (I) Cells and/or batteries in specific packaging Verify that reduced cell configuration test results match the results of

Test(I) and Test (VII) Construction of test rig inline with draft SAE AS6413 Review of available packaging and key failure modes Evaluation of repeatability of test results with focus on failures Recommendation of improvements

Initial objectives

Task 2: Phase I:Objectives: Understand key variables which affect the result under SAE AS6413 Test setup:

Task 2: Phase I:Observationso Control of heater band (leading to aggressive thermal events/inconsistent results)o Differences in temperature being observed o Thermocouple readings are affected by thermal runaway leading to unreliable readings

- Are they reading correctly? E.g. short circuit caused by heater band - Are the thermocouples damaged, giving wrong readings (refer to test 8, where there’s extreme

thermal reading)

o Differences between pouch cells and 18650- Does the construction of the battery affect the final result?

Task 2: Phase IIa:Purpose of Phase IIa :o Define type of heater, and position of heater for 18650 cellso Define how to ensure optimal amount of thermal energy is introduced to the initiation

cello Define how to prevent thermal energy being lost to the rest of the systemo Determine the optimal methodology for controlling the heating (temperature ramp rates,

max temperatures etc)

Task 2: Phase IIa:Set-up

Results:

• Single initiation cell @ 30%SOC• Heater held at set temperatures• No packaging

• Multiple runs showed consistent thermal runaway• Thermal runaway after 49, 51 and 61 minutes• Peak temperatures ~300C• Same severity explosion (visual)

Task 2: Phase IIa:Conclusiono Test results showed consistency, but less severe thermal runaway events than during

Phase I.o Rate of temperature ramp was non-linear due to heat transfer from initiation cell into

surrounding packagingo Rate of temperature rise in surrounding packaging was similar to initiation cello Design of heater meant heat was evenly distributed over whole 18650 cell, rather than as

a “pin point”

Task 2: Phase IIB:Objectives:o Can consistent thermal runaway be achieved by applying heat to side of cell?

o Design of heater/contact area (See example)o Rate of temperature rise needs agreed and critical to test result. Large difference between

5C and 12C (both within current limits). Testing commenced at 5C/min with a steady slope of T increase to be targeted.

o Decide placement of control thermocouple. Similar rise across cell (construction of cell dependant). Testing will control contact area, but record temperatures around circumference of cell. Validate against thermal model.

o Perform validation testing on box as prepared for transportation

Developed New Point Contact Method to Induce Thermal Runawayo Internal shorts, the major cause of cell thermal runaway, are characterized by intense

local heating o The heat is generated can be generated by a variety of spot defects like: dendrite

formation, defective or torn separators, misaligned electrodes, tab burrs, cell contamination, tab weld splatter, …

o A point heating method was developed and validated to simulate localized heating of a cell defect

o Factors that needed to be taken into account includeo geometry of the heating elemento contact area of the heating elementoposition of heating point on cello effect of cell SOC

The thermocouples positions (1, 2, 3, 4)Cross section of the cell

3

1

4

2

Cell outside polymer cover layer

Soldering iron tip

Point Contact Heating Method

Rationale of Point Heating Spot• Good simulation of localized

heating due to internal short• Location of heater: side of cell• Constant heating rate

Generation II Tip

Point contact

Original Heating Element

End base linear contact with cell

Higher contact area of the tip with cell surface,

conformal contact

Generation III Tip

Experiments used for ValidationsALGOLiON Experimentso Experimental Setup

o Heater with soldering tip atpoint 1

o Temperature measurementsat points 1,2,3 & 4

o Case A – 30% SOC, not well-insulated, no TR

o Case B – 100% SOC, well-insulated, TR occurs

Thermal Runaway Experiment on 18650 LGMJ1 D51

Thermocouple No.

- Two-hour test- Temperature stepped 10 degrees / 6 minutes- Cell label removed at area of contact with point heater- Early warning diagnostic software tracked cell changes

Thermocouple at tip of point heater

Other thermocouples

180°C

3

1

4

2

Cell outside polymer cover layer

Conclusion: The temperature of the cell adjacent to the heating element (initiationtemperature) is the primary factor determining thermal degradation – not the temperatureat other locations.

Typical ResultsCell Type Heater Location TR temperature, C at TC118650, LG MH1 base 15018650, LG MH1 side 130Pouch, AET side 212Pouch, AET side 225Pouch, ATL side 197

All cells at 100% SOC in this seriesMH1 – graphite/Ni rich NMC, 3.2 AHAET Pouch – graphite/NMC, 0.83 AhATL Pouch – graphite/Ni rich NMC, 0.83 Ah

Achieved reproducible thermal runaway by thermal degradation using an external point heating contact. The point contact method was optimized as a simulation of localized heating from an internal short defect.

Heating conditions that should be adjusted for cell size, capacity and SOC are: 1) area of contact (heating tip area)2) heating tip geometry (conformal to cell geometry, e.g., cylindrical, pouch) 3) temperature ramp rate 4) dwell time5) and thus the amount of heat injected into the system.

There is no ‘one size – fits all’ protocol for reproducible, repeatable thermal runaway results

Conclusions

Task 2: Phase IIB:Test setup:

Metal Contact

Gap for Thermocouple to ensure good contact and no interference with contact between heater and cell

Thermocouple

Task 2 Phase IIB:Results:

Task 2: Phase IIB:Conclusiono Phase IIB testing showed consistent resultso Results showed that a 30%SOC 18650 cell would go into thermal runaway, leading to the

failure of a standard fibreboard boxo A 5 – 20C/min ramp rate was achieved, when averaged over the length of the test,

however this was non linear.

Task 2: Phase IIIObjectives:

o Does a linear heating rate effect the severity and position of the thermal runaway event?

Task 2: Phase IIIResults:

~1C/Min ramp rate

~3C/Min ramp rate

o Linear ramp produces a consistent thermal runaway event.

o Rate of ramp appears to be proportional to ramp speed.

o Control of ramp rate is easier from a thermocouple close to the heat source.

o Linear ramp rate appears to produce a slightly lower peak temperature, however the “event” seems as severe.

Task 2: Improvement of draft SAE AS6413o Thermal runaway after 34 minutes. Voltage drop after 28 mins.o 200°C reached after 30 minutes: ramp rate on TC3 (backside of the initiation cell)

achieved at 6.6°C/min.o Difficult to achieve a higher temperature increase rate on TC3o Similar results obtained in subsequent tests with similar temperature increase rates

Task 2: Conclusions The proposed test setup ensures that:

o repeatable results (thermal runaway events) are generated using linear temperature increase;

o a thermocouple close to the contact surface with the heater can be used to monitor the temperature of the initiation cell;

o the amount of energy transferred by the heater to the packaging and to the cells adjacent to the initiation cell is minimized;

o a tighter range of the rate of temperature increase could be specified.

The area of the contact surface between the initiation cell/battery and the heater adapter may be function of the size/design of the cell/battery to be tested.

Monitoring voltage drop does not significantly help determining if thermal runaway of the initiation cell is on-going.

Task 2: Other observations Small changes in the way heating is introduced can effect the severity of thermal

runaway. Consistency and control of heating is key to any future testing. Tests have showed even 30% SOC cells can produce large thermal runaway events

which can cause failure of package.

Task 2: Next Stepso Phase III testing can be considered finalized.

o Phase IV testing will consist in performing a series of tests using the reduced cell test method (test (VIII) of draft SAE AS6413.

o Tests will be run cells at 30% SOC and at 100% SOC.

o Further tests runs will be performed using cells at 100% SOC, implementing mitigating measures (packaging material change, individual cells/batteries isolation, etc.) as prototype solutions with the objective to reduce the severity of the fire event.

Thank you!

Questions?