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1、Institute of New Energy Technology, INET, Tsinghua UniversityUS-China Electric Vehicle and Battery Technology Workshop from 30 Aug. to 1 Sep., Argonne, USATest of Li-ion battery for self-heating & lifetime EvaluationTsinghua UniversityInstitute of New Energy Technology, INET, Tsinghua University1. S
2、elf heating evaluation2. Life time evaluation3. State of health evaluationContentsInstitute of New Energy Technology, INET, Tsinghua University3Self heatingSelf heating effects 1.In order to provide sufficient capacity, a large-scale lithium-ion battery generally consists of many individual cells th
3、at are connected in parallel. This configuration inherently increases the thermal resistance of a battery, so thermal management becomes critical for operation. 2.Choose two LiFePO4 batteries and two LiMn2O4 batteries which are typically representative.Institute of New Energy Technology, INET, Tsing
4、hua University4Temperature effects on equilibrium potential Temperature effects on kinetic processes and relative parameters Temperature effects on diffusion processes and relative parameters Dynamic thermal energy balance. The temperature of the battery should be solved dynamically so that it can b
5、e used to predict the effects of temperature on equilibrium potential, kinetic and diffusion processes. The effects of ohmic heating, heat generation due to entropy change, phase change, heat capacity change, mixing processes, as well as heat exchange to surroundings will be considered and compared
6、to see which heat effects can be neglected to simplify the evaluation. Self heatingInstitute of New Energy Technology, INET, Tsinghua UniversityEvaluation formulationsTransient balance equations of equivalent circuit ohmohmVti t R kk k kd dVtVtCi ttR dd d dd dVtVtCi ttR ohmkdOCVV tVtVtVt Dynamic ene
7、rgy balance equation pcamb( )( )dT tmcQh A T tTtHeat source termConvective heat transfer 222 ohmkdohmkdKinetic polarization heatOhmic heatDiffusion polarization heatVtVtVtQRRR Institute of New Energy Technology, INET, Tsinghua University00.20.40.60.811.21.41.61.82x 104298299300301302303304Battery Te
8、mperature/KparametersParameterUnitElectrode materialLiNi1/3Mn1/3Co1/3O2LiFePO4Highmm67104Widthmm7070Thicknessmm2727Weightk kg0.0.2750.0.410CapacityAh1011.5Surface areamSurface aream2 216.778e-323.956e-3Heat capacityJ.kg16.778e-323.956e-3Heat capacityJ.kg-1-1K K-1-1925925Ambient temperature925925Ambi
9、ent temperatureC2525C252500.20.40.60.811.21.41.61.82x 104-3-2-10123Time/sCurrent/ACurrent00.20.40.60.811.21.41.61.82x 1043.53.553.63.653.73.753.83.853.93.954Time/sVoltage/VVsimK = K = hAhA = 1.6778e= 1.6778e- -2 200.20.40.60.811.21.41.61.82x 104-0.04-0.03-0.02-0.0100.010.020.030.04Time/sPolarization
10、/VOhmic polarization/V Kinetic polarization/V Diffusion polarization/Vh = 1 Wmh = 1 Wm- -1 1K K- -1 1Institute of New Energy Technology, INET, Tsinghua University00.20.40.60.811.21.41.61.82x 104298299300301302303304305306307308Time/sTemperature/CK = 1.6778 K = 1.6778e-1 K = 1.6778e-2Effects of param
11、eter K = hAK value affect the performance and temperature much especially when K value is relatively small. Cruicial for battery geometry deisign and cooling system designh = 100 Wmh = 100 Wm- -1 1K K- -1 1h = 10 Wmh = 10 Wm- -1 1K K- -1 1h = 1 Wmh = 1 Wm- -1 1K K- -1 100.20.40.60.811.21.41.61.82x 1
12、043.53.553.63.653.73.753.83.853.93.954Time/sVoltage/VK = 1.6778 K = 1.6778e-2 K = 1.6778e-2Institute of New Energy Technology, INET, Tsinghua UniversityBattery temperature predictionSummary 1. Battery temperature can be simply predicted during operation with acceptable error. 2. The most important f
13、actor is the cooling & Radiating . 3. The battery self heating evaluation is helpful for the battery design and battery pack design.12345678354045505560657075temperatureTime (Min.)negative Tabpositive Tabbatterybattery0200040006000800010000 12000 140002.502.753.003.253.503.754.00Voltage10C discharge
14、自制高安全性12Ah动力电池NCM based 12Ah power batteryInstitute of New Energy Technology, INET, Tsinghua UniversityLife time evaluationConsidering (1) self discharge (2) SEI film growthThe effects of SEI growth was represented in additional resistance of ohmic resistance and kinetic polarization resistance. The
15、 self discharging process will be represented as a parallel resistance. Cycle life evaluation : Choose 10Ah-rated LiFePO4 batteries and 10Ah-rated LMO batteries which are typical. Testing duration is 1 year. Calendar life evaluation : Choose 10Ah-rated LiFePO4 batteries and 10Ah- rated LMO batteries
16、. These two kinds of batteries shall go fifty-fifty on shelfing at room temperature and on shelfing at 55in constant temperature box during day time. The 1C rate current charging-discharging capacities of batteries will be measured every half month. OCV of batteries will be measured every day. The duration is 1 year. Experimental methodology Institute of New Energy
