Japanese Research for Thermal Propagation EVSGTR IWG 9

Japanese Research for Thermal Propagation EVS-GTR IWG #9 in China 14 th-18 th Sep, 2015 1

Background Japan will give a presentation as shown below. n The definition of thermal runaway and thermal propagation n The criteria of thermal propagation n Report for research about initiation method for thermal propagation EVS-08 -12 e-revised 2

Definition of Thermal Runaway and Propagation *Thermal Runaway “Thermal runaway” means the phenomena of uncontrollable heat generation with continuous temperature rise caused by exothermal chain reaction in the cell. **Thermal Propagation “Thermal propagation” means the sequential occurrence of thermal runaway within a battery system triggered by thermal runaway of a cell in that battery system. EVS-06 -23 3

Criteria of Thermal Propagation Criteria: No evidence of fire or explosion by visible validation. (Within 1 hour observation period since the test initiation) Note: The existing all criteria for REESS safety test are defined for protection for the persons inside or in the vicinity of the vehicle. The applicable criteria from the existing criteria should also be chosen taking account of the event assumed for thermal propagation test. The existing criteria for REESS Applicable / Not applicable Leakage Since thermal propagation test is premised on occurring the defect of a single cell, this criterion is not applicable. Rupture Since this criterion is for mechanical endurance , this criterion is not applicable. Isolation resistance Since this criterion is the protection from electric shock, this criteria is not applicable. Fire, explosion This criteria are appropriate to thermal propagation test. The thermal propagation test should be also provided with the observation period (1 hour) because the same thought for existing criteria should be consistently applied. 4

Research about initiation method of Thermal Propagation n Japan presented research results in IWG#6 and TF 5 meeting(Beijing). n Methods which can easily cause internal short circuit and thermal runaway of a cell in battery pack are different depending on cell type and battery structure. n We did research with additional initiation method for thermal propagation test. (Nail, Partial Heating, Overcharge, Heating) EVS-06 -23 5

Initiation method of in the research n Thermal propagation test is to confirm if vehicle or battery pack achieve occupant protection when a single cell internal short circuit and thermal runaway occurs in vehicle or battery pack. n We assumed to cause a single cell internal short circuit and thermal runaway for initiation method of propagation test. n We researched initiation methods which can achieve this with various battery packs. 　 Visible validation ・　 ・ Internal short circuit Thermal runaway cell ・　・　 Cell Vehicle/ Battery pack Image of thermal propagation test 6

Initiation methods Method Nail Test condition Image of test Insert nail until a single cell internal short circuit and thermal runaway occurred. Nail This includes prick, partial penetration, or full penetration of nail regardless the material of the nail. Partial Heating Heat a cell partially with the rate of 100゜C/min. Heater 【Spec of heater】 Size : 25 x 1. 75 mm Capacity : 100 V-555 W Overcharge Charge with the rate of 1 C Constant Current. Charge Current Heating Heat battery pack with the rate of 60゜C/min. 【Spec of heater】 Heater Size : 5, 000 x 40 mm Capacity : 100 V-1, 000 W 7

Test sample Sample Type of battery Type of cell SOC A HEV Prismatic cell hard case ㇾ ㇾ ㇾ － B BEV Prismatic cell hard case ㇾ ㇾ － ㇾ C PHEV Prismatic cell hard case ㇾ ㇾ ㇾ － D BEV Pouch cell － ㇾ ㇾ － 100 % Nail Partial Heating Overcharge Heating ㇾ : Administered － : Unadministered Sample C Sample A Sample B Sample D 8

Nail n In each sample, single cell internal short circuit and thermal runaway occurred. Cell Voltage Time / min Voltage / V Sample C(Prick) Temperature / ℃ Internal short circuit occurred Temperature / ℃ Time / min Sample B(Full penetration) Cell Temperature Cell Voltage Time / min Cell Voltage Internal short circuit occurred Cell Temperature Time / min Temperature / ℃ Cell Temperature / ℃ Voltage / V Internal short circuit occurred Voltage / V Sample C(Partial penetration) Sample A(Full penetration)

Partial Heating n In sample A and D, a single cell internal short circuit and thermal runaway occurred. n In sample B and C, a single cell internal short circuit did not occurred. Because cells in sample B and C have high thermal conductivity, heat from the heater was diffused and couldn’t cause internal short circuit in a cell. Sample C Sample A Break down of heater Cell Temperature / ℃ Voltage / V Internal short circuit occurred Temperature / ℃ Cell Voltage Cell Temperature Time / min Break down of heater Voltage drop Cell Temperature (heated cell) Stop heating Cell Voltage Internal short circuit occurred Thermal propagation occurred Time / min Temperature / ℃ Cell Temperature / ℃ Voltage / V Cell Voltage / V Sample D Sample B 10

Overcharge Cell Temperature Time / min Cell Voltage Current Cutoff system operated Cell Temperature Time / min Temperature / ℃ Voltage / V Sample C Cell 1&2 Voltage Cell 1 Temperature Cell 2 Temperature / ℃ Burning of plastic parts Voltage / V Cell Voltage Internal short circuit occurred Temperature / ℃ Voltage / V n In sample A, a single cell internal short circuit and thermal runaway occurred. n In sample C, current cutoff system operated and couldn’t cause internal short circuit. n In sample D, simultaneous internal short circuit and thermal runaway of multiple cells occurred because cells are parallel-connected in sample D. Sample A Sample D Time / min Multiple cells thermal runaway occurred 11

Heating n In sample B, simultaneous internal short circuit and thermal runaway of multiple cells occurred because multiple initiation were heated by simultaneous heating. Cell 1 Voltage Cell 2 Voltage Multiple cells thermal runaway occurred Temperature / ℃ Voltage / V Sample B Cell 1 Temperature Cell 2 Temperature Time / min 12

Summary of test result n For prismatic cells(Sample A, B, C), Nail is suitable. n For pouch cell(Sample. D), Partial Heating is suitable. n Overcharge is unsuitable for the battery with cutoff system and parallel connecting structure. n Heating is unsuitable because multiple cell initiation occurred ㇾ: Able to cause a single cell internal short circuit and thermal runaway simultaneously. (M): Unable to cause “a single cell” internal short circuit and thermal runaway （Multiple cells thermal runaway occur） (X) : Unable to cause internal short circuit and thermal runaway － : Unadministered Test Results Sample Nail Partial Heating Overcharge Heating A ㇾ ㇾ ㇾ － B ㇾ (X) － (M) C ㇾ (X) － D － ㇾ (M) － ・Inapplicable to cells with shutdown device ・Inapplicable to　the battery multiple cells are parallelconnected. Whole battery is heated and multiple cells are damaged. Inapplicable to cells with high heat conductivity 13

Initiation methods n It is necessary to consider several parameters battery pack as shown below in deciding initiation methods of thermal propagation. n We assume Nail and Partial Heating may be applicable. n Even though these initiation methods still have remaining technical issues. Type of Cell Configuration Structure of electrode Cylindrical Winding Prismatic Stacking Winding Pouch Stacking Structure of Battery Protection device Series connecting With 　 Without Parallel connecting 　 With Sample C Without Sample B　 With Sample A 　⇒Nail Without 　 　 Without ⇒Nail? 　 　 ⇒Partial　Heating Sample D ⇒Partial Heating? 14

Technical issues for Initiation methods n If there are chassis or bracket around cells of testeddevice, it is necessary to process / modify them in order to insert nail or to set a heater. n We need to consider the influence of processing effect on test result. Hole made for inserting nail Bracket around cells Enlarged view Battery pack sample Battery pack drilled a hole for nail insertion 15

Summary and Proposal Summary n We investigated appropriate initiation methods. For Prismatic cell : Nail , For Pouch cell : Partial heating n Suitable initiation method should be selected based on battery type and connecting structure. n There are still remaining technical issues as mentioned below. <Technical issues> 1)Applicability of initiation methods for all batteries. To confirm the applicability for the batteries other than our tested devices. To justify the reason for choosing the initiation method for the battery. 2)Appropriateness as GTR. To consider the influence of actual processing for certification test. 3)Repeatability and reproducibility of tests. Proposal n To ask TF 5 validates test methods for variety of batteries to establish test method as GTR. n To request TF 5 to address the technical issues as shown in above. 16