Energy Science and Technology III Lecture Winter Term 2015/16. Battery Safety 28 January 2016

Transcription

1 Energy Science and Technology III Lecture Winter Term 2015/16 Battery Safety 28 January 2016 Harry Döring, Harald Brazel, Mario Wachtler Zentrum für Sonnenenergie- und Wasserstoff-Forschung (ZSW) Baden-Württemberg

2 Accidents with Batteries -2-

3 Potential Risks of Battery, Supercap, etc. Functional: Electrical: Mechanical: Chemical: Thermal: Worst case: Unreliable / unsafe function of device powered by battery Voltage, current Mass Leakage of cell materials (electrolyte, gas, solid materials) Heat generation, sparks Fire / flame, explosion -3-

4 Chemical Hazards of Cell Components Corrosive H 2 SO 4 (Pb), KOH (Ni-MH, Ni-Cd, RAM), LiPF 6 (LIB), Toxic Pb, PbO 2 (Pb), Cd (Ni-Cd), LiPF 6 after hydrolysis to HF (LIB), Ni-based cathode materials (LIB), acetonitrile (EDLC), Mutagenic, cancerogenic, sensitising Pb, PbO 2 (Pb), Cd (Ni-Cd), Ni-based cathode materials (LIB), Flammable H 2 (Pb, Ni-MH, Ni-Cd, RAM), organic electrolytes (LIB, EDLC), Explosive H 2 (Pb, Ni-MH, Ni-Cd), electrolyte vapours (LIB, EDLC) Hazardous to aquatic environment Pb, PbO 2 (Pb), Cd (Ni-Cd), Ni-based electrode materials (LIB) Pb = lead-acid, LIB = Li-ion, EDLC = electrical double layer capacitor, RAM = rechargeable alkaline manganese -4-

5 Potential Safety Risks of Lead-Acid Batteries Charge / overcharge Overdischarge Short circuit H 2 formation, thermal runaway, pressure increase, fire, explosion H 2 formation H 2 formation Crash Acid leakage (approx. 38% H 2 SO 4 ) Heating Pb vapours (Heating is not very critical due to high specific heat capacity) -5-

6 Potential Safety Risks of Ni-MH Batteries Charge / overcharge Overdischarge Short circuit Crash H 2 formation, temperature increase (thermal runaway), pressure increase, fire, explosion electrochemical H 2 formation electrochemical and chemical H 2 formation Alkaline solution leakage (approx. 7 M KOH) Heating chemical H 2 formation (MH M + ½ H 2 ) (1 Wh = ~ 0.35 L H 2 ) -6-

7 Potential Safety Risks of Li-Ion Batteries Charge / overcharge Overdischarge Short circuit Crash Heating decomposition of layered cathode materials (LCO, NCA, NMC) with O 2 formation, electrolyte oxidation (gas formation), Al current collector corrosion, Li metal deposition at anode, Cu dissolution followed by dendrite formation (see heating) Electrolyte leakage (LiPF 6 can form HF in combination with H 2 O vapour) Exothermal decomposition of cathode materials (LCO, NCA, NMC), electrolyte decomposition (gas formation: CO, CO 2, PH 3, ), electrolyte inflammation, LiPF 6 decomposition (HF), melting of separator (short circuit), -7-

8 Potential Safety Risks of Li-Ion Batteries Li dendrites Particles Cu dendrites Exothermal reaction Heating Gassing Crash Internal short circuit External short circuit Thermal runaway Fire Heating Overcharge -8- Overdischarge Overcurrent External heating Explosion

9 Thermal Runaway of Li-Ion Batteries During Abuse Tests -9-

10 Thermal Behaviour of Li-Ion Cell Components exo Anode Graphite (charged, + electrolyte) DSC signal / a.u. Cathode NCA (charged, + electrolyte) NMC (charged, + electrolyte) Electrolyte 1 M LiPF 6 / EC-DMC Separator PP/PE/PP Temperature / C -10-

11 Safety Features in Li-Ion Batteries Small cells (consumer applications) PTC (positive temperature coefficient discs) CID (current interruption device) Shut-down separator (PP-PE-PP) Temperature-stable ceramic coatings of electrodes (e.g. HRL = heat resistant layer) Safety vents (to release overpressure) Large cells (automotive and stationary applications) Ceramic separator Thermally stable cathode materials Flame-retardant electrolyte additives Thermal design of cell (good heat conduction / cooling) Safety vents (to release overpressure) Externally (BMS = battery management system) Voltage control of single cells Cooling Look for safer chemistry! Safer anode / cathode / electrolyte materials (e.g. LTO / LFP) Overcharge protection -11-

12 Safety Features in Li-Ion Batteries Safety vents PTC Current interruption device (CID) Source: Varta Source: Sony Gas pressure builds up in cell and disrupts CID -12-

13 Safety Features in Li-Ion Batteries Tri-layer separator (polypropylene polyethylene polypropylene) Upon heat increase, PE melts and shuts cell down, whereas PP remains solid and maintains separator function PP (mp = ~ 160 C) PE (mp = ~ 130 C) PP (mp = ~ 160 C) P. Arora, Z.M. Zhang; Chem. Rev. 104 (2004), Temperature-stable ceramic coatings of electrodes (e.g. HRL = heat-resistant layer in Panasonic cells) Cathode separator / electrolyte HRL Anode -13-

14 Safety Features in Li-Ion Cells Ceramic separator Nail penetration test Polymer separator melts Large area internal short circuit Thermal runaway Source: Evonik Higher thermal and mechanical stability than for polymer separators Ceramic separator does not melt Short circuit / discharge is restricted to small area No thermal runaway -14-

15 Processes During Heating of Li-Ion Cells and Activation of Safety Features Source: BMZ Batterie-Montage-Zentrum -15-

16 Safety / Abuse Test Procedures Numerous safety / abuse test procedures: IEC (International Electrotechnical Commission) UL 1642 (Underwriter Laboratories) SAND (FreedomCar abuse test manual EV / HEV) VDA Li-Ionen-Batterien für HEV (Verband der Automobilindustrie, Germany) SAE J2464 (EV/HEV, Society of Automotive Engineers) UN Transport Tests (UN 38.3) etc -16-

17 Safety / Abuse Test Procedures Electrical Tests: Overcharge Overdischarge (forced discharge) External short circuit Thermal Tests: Heating Thermal cycling Fire test Mechanical Tests: Low pressure test Vibration test Shock test (acceleration test) Crash test Nail penetration test -17-

18 Hazard Levels Results of abuse tests are classified according to Hazard Levels (Different definitions, e.g. EUCAR or SAE J2464) Level EUCAR No effect (no loss of functionality) Passive protection activated (cell reversibly damaged, repair of protection device) Defect / damage (cell irreversibly damaged) Leakage (<50% electrolyte loss, no venting) Venting (>50% electrolyte loss) Fire / flame (no rupture / explosion) Rupture (no explosion, but flying parts of active mass) Explosion SAE J2464 No effect Passive protection activated (cell reversibly damaged, repair of protection device) Defect / damage (cell irreversibly damaged) Minor leakage / venting (<50% electrolyte loss) Major leakage / venting (>50% electrolyte loss) Rupture Fire / flame Explosion -18-

19 Recommended Literature J. Garche (ed.): Encyclopedia of Electrochemical Power Sources; Elsevier, Amsterdam (The Netherlands), 2009, Vol. 4. A. Jossen, W. Weydanz: Moderne Akkumulatoren richtig einsetzen; Leipheim and Munich (Germany), (Book in German language). -19-

20 Thank you for your attention! Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg Helmholtzstraße 8, Ulm Stuttgart Photovoltaics & Solab -20- Energy Policy & Energy Carriers Widderstall Solar test-field Ulm Electrochemical Energy Technologies Ulm elab (Battery research centre) FPL (Battery production research)