The Effect of Thermal Management Material on Thermal Runaway - PowerPoint PPT Presentation

The Effect of Thermal Management Material on Thermal Runaway Propagation Greg Wilk, Siddique Khateeb, Stephen Wilke, Greg Albright, Said Al-Hallaj R&D Engineer, AllCell Technologies http://www.allcelltech.com Compact | Lightweight | Long Lasting Confidential

Lithium-Ion Battery Fires Compact | Lightweight | Long Lasting 2 Confidential

Lithium-Ion Battery Fires  Lithium ion battery fires serious threat  Hoverboards  Galaxy Note 7  Safety concern for aerospace companies  Dreamliner grounded due to battery fire  Jet propulsion laboratory prototype robot destroyed by 98 cell explosion  Must engineer lithium ion packs assuming one cell will short  Boeing with the best BMS and fusing still had a failed cell cause a catastrophic fire Compact | Lightweight | Long Lasting 3 Confidential

Thermal Runaway, Cell Level  Thermal runaway: Cell Raw Data - Temperature vs Time ( 2.9 Ah) chemistry reacts 800 rapidly generating 700 heat 0146 600  Accelerating Rate Temperature (°C) 0153 500 Calorimetry 400  See what temperature 300 cell enters TR 200 Threshold: 100°C  Depends on cell and 100 state of charge 0  90°C to 120°C 0 500 1000 1500 Total Test Time (min) Compact | Lightweight | Long Lasting 4 Confidential

Thermal Runaway Propagation: Heat transfer Success Criteria: Adjacent cell temperature T c < 100°C  Q: Cell heat generation from TR  Cell energy Q  Parallel welds  Combustion  Conduction to adjacent cells  Pack material thermal diffusivity  Cladding thickness T c < 100°C  Contact resistance  Convection to surroundings 𝑙  Thermal diffusivity a function of 𝑈 𝑑 ≈ 𝐸 = temperature in phase change materials 𝜍𝐷 𝑞 (𝑈) Compact | Lightweight | Long Lasting 5 Confidential

Research Overview  Evaluate what cell packaging materials can prevent the propagation of thermal runaway in a small pack of 18650 style cells.  Air  Graphite  Wax  Graphite and Wax (PCC)  Evaluate the importance of battery configuration and weld strength on thermal runaway propagation  Nail penetration test Compact | Lightweight | Long Lasting Confidential

Battery Pack Materials Evaluated Temperat erature ure  Phase Change Composite (PCC) With h No PCC  20 wt.% graphite Temper erat ature e with  80 wt.% wax PCC  Wax micro-encapsulated Melti ting g Point  Melts at 55°C Temperature ure Remain ins Const stant nt Durin ing g Meltin ing  ½ Latent heat of ice  Graphite only (90% porous) Time  Wax (100%)  Air PCC Materia ial Li-io Li ion n Cells Compact | Lightweight | Long Lasting 7 Confidential

Different Material Properties Graphite Only PCC Wax Only Air Air Graphite ite Only Wax Only PCC Conductivity (W/m-K) 0.024 13.77 (in-plane) 0.15 17.21 (in-plane) Density (kg/m 3 ) 1.23 200 775 935 Specific Heat (J/kg-K) 1005 725 2384 1837 Latent Heat (J/g) N/A N/A 211 153 Diffusivity (mm 2 /s) 19.42 94.96 0.08 10.02 Compact | Lightweight | Long Lasting 8 Confidential

Battery Pack Specifications Pack k speci ecificati ication ons Cell speci ecificatio ications ns Specif cificati ication on Value Specif cificati ication on Value Config igurat uratio ion 10s4p Form Fact ctor 18650 Ene nergy gy (Wh) h) 413 Capacit acity, nominal inal (Ah) 2.85 Voltag age, nominal nal (V) 36.2 Voltag age, nominal nal (V) 3.62 Mass ss (kg) 2.75 Specif cific ic Energy gy (Wh kg -1 ) 224 Specific cific Ene nergy gy (Wh h kg -1 ) 150 Ene nergy gy Densi sity ty (Wh h L -1 ) 603 Dimen ension sions s (cm) 32 x 9 x 13 Chemis mistry ry Graphite anode, NCA Casi sing ng Aluminum & plastic cathode Compact | Lightweight | Long Lasting 9 Confidential

Pack Build Procedure 6 welds on trigger cell (normally 4) Hole drilled in casing for nail penetration Compact | Lightweight | Long Lasting 10 Confidential

Air Pack TRP Video https://youtu.be/vmUpbou8VtA  Compact | Lightweight | Long Lasting 11 Confidential

Air Pack: Thermal Runaway Propagation 5 700 T1 2 600 3 Temperature (C) T2 1 500 4 T3 400 300 T4 200 T5 Threshold Trigger String 100 Neighbor String 0 0 100 200 300 400 500 600 700 Time (s) 4 Trigger Voltage (V) 3 Neighbor 2 1 0 • TRP occurred slowly due to air low 0 100 200 300 400 500 600 700 thermal conductivity and low ability to Time (s) store heat Compact | Lightweight | Long Lasting 12 Confidential

Graphite Only: Thermal Runaway Propagation 1200 T/C-1 °C 5 Temperature (C) 1000 T/C-3 °C 3 1 4 800 T/C-4 °C 600 T/C-5 °C 400 Threshold 200 Trigger String 0 Neighbor String 0 50 100 150 200 250 300 Time (s) 4 Trigger Voltage (V) 3 Neighbor 2 1 • TRP occurred quickly due to high 0 0 50 100 150 200 250 300 thermal conductivity and low ability Time (s) to store heat Compact | Lightweight | Long Lasting 13 Confidential

Wax Only: Thermal Runaway Propagation 700 5 T1 600 T2 Temperature (C) 2 500 T4 1 400 4 T5 300 200 Threshold Trigger String 100 Neighbor String 0 0 50 100 150 200 250 300 350 400 450 500 Time (s) 5 4 Trigger 3 Voltage (V) Neighbor 2 1 0 • TRP occurred quickly due to liquid 0 50 100 150 200 250 300 350 400 450 500 -1 wax flow and wax combustion -2 Time (s) Compact | Lightweight | Long Lasting 14 Confidential

Phase Change Composite (PCC): Avoided Thermal Runaway Propagation 5 250 T1 T2 200 Temperature (C) T3 2 3 T4 150 1 T5 Threshold 4 100 50 Trigger String Neighbor String 0 0 50 100 150 200 250 300 350 400 Time (s) 4 Trigger Voltage (V) 3 Neighbor 2 1 • TRP was prevented due to phase 0 change absorbing thermal runaway 0 50 100 150 200 250 300 350 400 energy Time (s) Compact | Lightweight | Long Lasting 15 Confidential

Comparison Between Packs 350 700 Trigger Cell Air 600 Neighbor Cell Time to neighbor Temperature (C) 500 Neighbor Cell Peak Temperature (C) Graphite cell peak temp. 400 300 300 200 Wax Peak Temperature 100 0 250 PCC 50 100 150 200 250 300 Time (s) Pack k Thermal Runaway 200 Material ial Propagat gation ion? Air Fail Graphite Fail 150 Wax Fail PCC Pass 100 0 50 100 150 200 250 300 350 400 Time to Neighbor Cell Peak Temperature (s) Compact | Lightweight | Long Lasting 16 Confidential

Autopsy No o The hermal mal Run unaway ay Prop opagatio tion The herm rmal al Run unaway ay Prop opagati ation on *Pack was sprayed with water after second cell propagated in packs that propagated Compact | Lightweight | Long Lasting 17 Confidential

Nickel separation during cell venting Nickel Cladding can separate from venting cell isolating Not 100% reliable separation. Cells can vent outside of electrical energy available for thermal runway propagation side casing Compact | Lightweight | Long Lasting 18 Confidential

Ongoing Research with PCC Cell Ene nergy Pack k Con onfigur urati ation on The herm rmal al Run unaway ay Prop opagati ation on 2.9 Ah 10s4p Pass 3.2 Ah 10s4p Pass 3.5 Ah 10s4p Fail 3.5 Ah 10s0p Pass Compact | Lightweight | Long Lasting 19 Confidential

Conclusions and Future Work  PCC (graphite and wax) reliably prevented TRP in 2.9 Ah, 10s4p packs  Packs need to be engineered for TRP on a case by case basis  Cell energy (2.9, 3.2, 3.5 Ah…)  Material thermal properties  Parallel configuration and cladding separation  Future tests will investigate different cell energies and graphite densities for AllCell Battery Products: http://www.allcelltech.com/ Compact | Lightweight | Long Lasting 20 Confidential

Contact Information  http://www.allcelltech.com/  Greg Wilk, R&D Engineer, gwilk@allcelltech.com, 773-922-1155 (x244)  Siddique Khateeb, Head of R&D, Skhateeb@allcelltech.com  Greg Albright, VP of Business Development, galbright@allcelltech.com, 773-922-1155 (x211) Compact | Lightweight | Long Lasting 21 Confidential