锂离子电池安全问题
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Li-ion Safety, IEEE Operating WindowInternal Short and HS-Lithium Deposition (CLTF 2009, Shenzhen, China)Zhengming (John) ZHANG, Ph. D. 张正铭博士Chairman of Cell sub-Group, IEEE (P1625) VP & CTO, Celgard LLC Sr. Fellow and Council Chairman, Polypore Inc.世界IEEE P1625 电池规范-电池组主席; 美国Celgard 公司首席技术官和副总裁; 美国 Polypore 公司Sr. Fellow 和Council主席 and Dr. Shriram Santhanagopalan Dr. Prem RamadassContents• Main Issue of Field Incidents – Lithium Deposition and Internal Short • Summary of Internal Shorts • IEEE P1625 Operating Window • Lithium Deposition when Operating Outside of Window • Factors Affecting Lithium Deposition (Material, Process, Electrode, System Design, Separator Oxidation) • SummaryLi-ion Field Incident Safety Short w/o HS Li-Depo Cell with HS Li-DepoNo HS CarbonCycling Out of WindowNo Al/Carbon ShortLT, HT, HVSlow Down Thermal Propagation (Thermal Conduction) on AWrong DesignPorosity, Crystal Orientation Balance, H2O, ERWrong MaterialSEP, Flat Particle, SEIComparison of Power Generated at ShortNo Particle1. 2. 3.4.5.Al Æ LiC6 Al Æ C6 Al Æ Cu LCO Æ LiC6 Cu Æ LCOEasier Explode and FireVery Difficult to Explode and FireImpossible???Ni Particle1. 2. 3. 4. AM (Al+LCO) Æ LiC6 Al Æ LiC6 Al Æ C6 Al Æ Cu LCO Æ LiC6 Cu Æ LCOEasier Explode and FireVery Difficult to Explode and Fire5.6.Anode (w/ or w/o Li) Thermal PropagationLiC610 W/m-KCathode Thermal PropagationLCO or LNO0.3 W/m-KField Internal Short of Normally Designed CellSepLarge Area IR HeatEl HeatInternal ShortSpot HeatAnode Propagation (Heat)SepCathode Propagation (Heat 200%)SepIR Heat Safe CellThermal Runawayppb??Thanks to BAJ and IEEE (P1625) for the Support(Tested by BAJ Internal Short and 130oC Oven)Effect of Charge Rate (Cycling) and Temperature (Celgard Sep)45oC, C/2 45oC, 1C0oC, C/20oC, 1CCycling of LCO/C (or typical) Li-ion SystemElectrode Potential (V) LiCoO23% Vol + 1st Charge 1st Discharge 2nd Charge and DischargeSEI7% Vol +GraphiteCapacity (mAh)Position Polarization ElementsCarrier Affecting Factors Liquid DiffusionionPorosity, σi, C-layoutIonic Conduction in SEI ion σiCharge Transfer ion, e E-chemSolid Diffusion ion C-size, D-coeffElectronic Condusction e σeA n o d eInterface of Anodeion Li2CO3 Depo, Reduction (very t&T dependent)Bulk Separatorion σi, etc.Interface of Cathodeion Oxidation, Solid-Depo (very t&T dependent)Liquid Diffusion ionPorosity, σi, C-layout Charge Transfer ion, e E-chemSolid DiffusionionC-size, D-coeff Electronic Condusction eσeSe p & El C a t h o d eFactors that Lower the Electrode Potentials (Polarizations)2 CSOC = 0.031 CSOC = 0.230.5 C SOC = 0.7Influence of Temperature: Li Deposition is Significant Even at Low Rates Note: Li-Depo before 4.2V!!!CC Charge at 0C (Model Prediction)EXPT Data—Ref Electrode for Prismatic CellNeg. Electrode Potential at C/2 and 1C00.511.522.533.544.5100200300400500600700Time (min)C e l l V o l t a g e (V )-0.20.20.40.60.81N e g a t i v e E l e c t r o d e P o t e n t i a l (V v s L i /L i +)C/21C0 o CDon’t Operate Li-ion Outside of Your WINDOW for Normal Li-ion Cell with Common Graphite Anode.Anode•Effect of Diffusion Coefficient of the Anode •Effect of Particle Size of the Anode•SEI Layer Resistance on the AnodeMax. current (mA/cm 2) with RSEI = 0.001ohm m2Stage 2-1 for Max Capacity (ΔV=85mV)60.87113.57133.571e-1320.8775.5788.871e-14-0.40.81e-1520 microns Radius10 microns Radius 2 microns Radius DiffusionCoefficient(m 2/s)Electrode Porosity and CathodeSEI will not affect Li-DepoCarbon Diffusion (T and Size) is the KEYFast Charge w/o Li-Depo Can Only Be Done by Using High Potential “Carbon”ÎTransition 2’-2Separator InfluencesTrickle ChargeTrickle Charge Data (18650 Com m ercial Cells) - 60C, 4.25V00.0020.0040.0060.0080.010.0120.0140.0160.0180.020200000400000600000800000100000012000001400000Tim e (sec)C u r r e n t (A )00.511.522.533.544.55V o l t a g e (V )Celgard 25um Celgard 25um Comp2 25um Comp1 25um Comp1 25 um Comp2 25 um Voltage4.25 V12.71 mA0.9 mA 0.6 mA15.46 mA15 D ay s7 Day Trickle Charge, 4.25V, 65 °C, Interface with Cathode(HT and/or HV Cycling will Give Same Results) Comp 2CelgardComp 1For Normal Designed Cells •Trickle Charge at HT and/or HV Will Oxidize PE Separators ÎLi-depo•HT Storage Will Oxidize PE Separators ÎLi-depoAvoid HS Li-DepoMaterial Cell Design Cell Process Cell UseAnode:Size, D, Shape Separator: Oxidation, ERA/C Balance& ElectrodeThicknessVol Change of A/CHT operationElectrodePorosity &C-orientationEl Injection& FormationIn the WindowSame V(BMU)Cell WindingEl Additives Summary。
