Pipeline and Hazardous Material Administration - PowerPoint Presentation

Slide1

Pipeline and Hazardous Material Administration(PHMSA)Department of Transportation AN OVERVIEW OF INTERNAL SHORT CIRCUIT SCREENING TEST METHODS FOR LITHIUM BATTERIES and a Proposal for Test T.6 Modification Presented at 1st Workshop on Lithium Batteries, Brussels, Belgium March 17-18, 2015Steve Hwang, Ph.D. steve.hwang@dot.gov

1Slide2

1. No leakage, no venting, no disassembly, no rupture, no fire, <90% of V2. Not exceeding 170 oC, no disassembly, no rupture, no fire3. disassembly, no fireTests

Test Name

Purpose Requirement Primary Secondary Cell Battery Cell Battery T1 Altitude Vacuum @ 11.6 kPa 1 yes yes yes yes T2 Thermal -40 – 72 oC 1 yes yes yes yes T3 Vibration 7 Hz – 200 Hz 1 yes yes yes yes T4 Shock Small 150 g 6 ms 1 yes yes yes yes Large 50 g 11 msT5 External Short External short 2 yes yes yes yes T6 Impact/Crush Internal short by 2 yes no yes no applying external impactT7 Overcharge <18 V 3 no no no yes > 18 V x 1.2 T8 Forced Discharge Maximum discharge 3 yes no yes no current

UN Test Guidelines

2Slide3

Causes of Internal Short-CircuitingCauses Why can this Can it be managed? happen?Shock or Dropping Physical Abuse Strong casing by designFormation of Dendrite Lithium Plating New Techniques neededExistence of Impurities Manufacturing New Techniques needed due to Poor Quality Control defects during Manufacturing

Imbalance of Voltage

Voltage

BMS among Cells ImbalanceHigh Charging Voltage High Charging BMS applied to a cell Voltage6. Propagation of Thermal Damaged Cell Proper venting, insulation Runaway can raise temp. of surrounding cellsSeparator Failure Temp, Defects, wear- T control, quality out, puncture, degrad. control, struct. 3Slide4

Cases of Thermal Runaway as it relates to Internal ShortsNail Penetration - Did not cause thermal runaway Manufacturing Defects – Possible thermal runawayCell Crushing - Can cause massive internal shorts and thermal runaway

Metal Plating (Dendrite) - Can reach 200 oC with

thermal runaway Elevated Temp - Can cause thermal runaway @ >170 oC (Metal particle in cathode slurry)4Slide5

Comparison of Internal Shorts Screening Tests How Applied Method for As a Test Requirement Inducing ISC for PreventionNREL During Manufacturing Heat to ~55 oC Can reduce IS with 1 ISC Device Process to Melt Wax Shut-down Separator UL Indentation Rounded Tip Pressure Safety Level req’d 1

Induced ISC Nail in the Market

IEC (62133) Nickel Powder Pressure Safe Cell Design 1

Forced ISC TechNail Nail Piecing Safety Level req’d 1 Penetration in the MarketImpact/Crash Small: Steel Bar Drop weight Survival of 2 (UN 38.3) Large: Flat Surface Force applied DeformationPropagation Insulated Heating of a Proper Venting 3 Test Thermal Chamber Cell 1. No Fire 2. No fire, No disassembly , not exceeding 170 oC 3. No external fire, No battery case rupture5Slide6

6Slide7

7Slide8

Cell Separator Deformation from Indentation Test8Slide9

Data Search Test Type (Li Ion cells) % of Explosion or FireIndentation ISC 58Forced Nickel Powder NoneNREL ISC Device Depending on existence

of shut-down separator

Techniques9Slide10

DENDRITEGROWTHPATTERN-10 oC5

o

C

20 oC10Slide11

Mechanical Interaction: Compressive StressPolymer Property: BrittleFailure Mode*: Crack Propagation & GrowthDesire Property: High Bulk Modulus; Low CompressibilityIdeal Material: Large Pore Size OK; High DuctilitySeparator vs. Dendrite11Slide12

SUMMARYMany companies are testing cells and batteries to determine their integrity as it relates to ISC using the test methods of their choosing.None of the ISC screening methods can address the basic concern on IS prevention.It is not clear why these tests are conducted by he manufacturers.No recommendable test methods for preventing occurrence of ISC can be identified from literature search.Though many field failures are reported to be caused by IS resulting from manufacturing defects or impurities inadvertently incorporated during manufacturing, no tools presently exist to detect or mitigate these defects.

12Slide13

Recent research information indicates that dendrite formed at the anode migrates to the cathode through the separator membrane to cause an internal short circuiting.A corollary to the finding is that the integrity of separator membranes plays a significant role in retarding or preventing the dendrite penetration through the membrane.It is important to test for the desired mechanical properties of the separator membranes to mitigate the occurrence of internal short-circuiting and thermal runaway

.

SUMMARY

(cont’d)13