4 Energy storage with battery Nominal Capacity (Amp-hours): 15.7Nominal Cell Voltage 3.73Cell Dimensions (mm) 5.27Cell Dimensions w/ terminals (mm) X 249.6Maximum Cell Temperature (°C) 75Positive Lithium Metal OxideNegative CarbonElectrolyte Organic MaterialSeparator SRS
5 Typical models for battery Models base on equivalent electrical circuitStatics: resistors in series to a voltage sourceDynamics: a capacitor connected in parallel to a resistorIgnored effects :Electrical behavior of the terminal as a function of SOC , T and material degradation, and OCV as a function of hysteresis and SOC.Battery calendar life as a function of cycles and load profileHeat generation as a function of SOC , change of entropy and I (charge and discharge), heat transferVarious temperature effects caused by gradients of ion concentrations and side reactions
6 Modeling of LiPB cell ce Φe Φs ηSEI T cs Y Separator LixC6 LiyMO2 Current collector (Cu)Current collector (Al)ElectrolytePositive electrode areaNegative electrode areaElectrode particleLTX
7 Principle: Current, Concentration and State of Charge Current in micro cellcurrent=Electron current-+-Ion current+-+Credit: huangqingSOC (state of charge) and cs (concentration in solid)-+-+-+Low SOCMedium SOCchargingHigh SOCCredit: huangqing
8 Electrochemical Thermal Mechanical Model Charging and discharging processes: Heat generation, Elasticity and DegradationMulti scale and Multi-physics coupled problems
9 Overview of model Single cell model Initial conditions: Initial SOC Load profileInitial temperature distributionAmbient temperatureCell voltageTemp. distributionSOCOverpotentialsReaction rateConcentrationEfficiencyEnergy conservationHeat transferCharge conservationTemperature distributionPotential distributionMicro cell modelMicro cell modelMicro cell modelButler-VolmerHeat sourceParameters:Battery geometryMaximum capacityConcentrationActivity coefficientDiffusion coefficientChange of enthalpyConductivityetc.Reaction rateStandard potentialCurrentOverpotentialNernst equ.Mass balanceIn electrolyteIn solidConcentration
10 Static and dynamic behavior of the battery Static and dynamic behavior of the batteryCharacteristics at different current rates (T=300K and SOC=100%)
11 Transient behavior of ion concentration (Discharging behavior at a step current of 10C) At 1secAt 80 secAt 20 secAt 180 secAs lithium ion leaves from negative electrode and deposited in positive electrode, concentration at the interface of the negative electrode drops rapidly when compared with that of inners, while opposite phenomena occurs in the positive electrode.
12 Potentials/Current density at positive and negative current collector
13 Validation of a single pouch cell at 1C/2C/5C discharge/charge
15 Heat generation using the model and calorimeter
16 Measurement of Thickness 4/10/2017Measurement of ThicknessThe change of battery thickness caused by the volume change of electrodes is calculated by the model.In experiment, thickness of the battery is measured by measuring both sides of the battery during cycling.
17 Mechanical stress of cells at 0.5C, 1C and 2C cycling 4/10/2017Mechanical stress of cells at 0.5C, 1C and 2C cycling
18 4/10/2017Maximum Stress as a Function of Position during discharge (at one instant)SeparatorAnode current collectorCathode current collectorThe plotted stress at each position is the maximum value of the stress in the local electrode particle.The highest stress is found in the electrode near the separator.
19 Fracture is Observed near the Separator 4/10/2017Fracture is Observed near the SeparatorQ. Horn and K. White, 2007 J. Christensen, 2010 Other researchers took SEM images at the cross-section of cell, where fractures are found in the electrode near the separator  .Our simulation shows that the highest stress locates at the electrode near the separator, where fractures are most likely to happen.
20 Block Diagram for battery management system (BMS) Block Diagram for battery management system (BMS)BatteryPack/ModuleSENSORCurrentVoltageTemperaturePredefined MapRi(SOC)Ri(Charging)TRAY Temp.Voc(SOC)Voc(Charging)Cooling ControlThermal ManagementImeanCharging/Discharging ControlAging Coefficient &SOC CalculationAccumulated SOC Error Comp.HCUI,V(SOC)Vaverage &Temp.CompensationHealth monitoring & ProtectionTemperatureCharging/Discharging powerUserInterfaceVoltage Imbalance detectionDiagnosisSearch IVSOCbyIV Voltage MAP
21 Review of models for Battery HighIntermediateLowImprovement of cell designsFull order of Electrochemical, thermal and mechanical Model (ETMM: FOM): Electrochemical kinetics, Potential theory, energy and mass balance, and charge conservation , Ohm’s law, Empirical OCV and elasticityBMS FunctionalitiesReduced order of Electrochemical thermal Model (ETM: ROM ): Empirical OCVPolynomial, State space, Páde approx., POD, Galerkin Reformulation and othersElectric equivalent circuit Model (EECM): Randles models with the 1st, 2nd and 3rd orderEmpirical Model:Peukert’s equationComp. timeAccuracyLow Moderate High
22 Reduced order of the model (ROM) for real time applications Parameters:Cell geometryKinetic and transport propertiesInitial conditions:Terminal voltageLoad profileAmbient temperatureCell voltageTemperatureSOCIon concentration in electrolyte CeIon concentration in electrodes CsPotentials ΦSOC estimationInput:Output:Battery :StepsApproachesResultsOrder reductionCe State space approachCs Polynomial approachΦ Parameters simplificationHigher accuracy with less computational timeImplicit method to solve PDEsOptimization of the ROM for real time applications
23 Validation of the ROM 1. Test condition: 2. Test condition: Mode: DepletingCycle #: 5Temperature: 0ºC, 25ºC, 45ºCCurrent: 1C, 2C, 5CInitial SOC: 0%2. Test condition:Mode: DepletingCycle #: 2Temperature: 25ºCCurrent: 1C, 2C, 5CInitial SOC: 0%
24 SOC estimation using Extended Kalman Filter Error of SOC 7-10%Initial errors of BMSFeedback controls and real time modelOutput:BatteryMeasurement updateTime update with the ROMSOC calculationInput:
25 Results of the estimation based on ROM + EKF Current: Voltage: SOC:Current: Voltage: Error of SOC:Test condition:Mode: JSTemperature: 25ºCInitial SOC: 100%Initial error: 0.2V(30% SOC)Test condition:Mode: DepletingTemperature: 25ºCInitial SOC: 0%Initial error: 0.5V(6.5% SOC)
26 Health monitoring of battery SOHSOHQSOHPCapacity fadePower fadeOther mechanismResearch interests for SOHSOHCurrent iBattery packROM Model&SOH detection algorithmOutput states value( V T )States estimation(Vt SOC T )CompareAging parameters estimation( as ɛs )error
27 4/10/2017Estimation of SOHQThe simulation of Qmax is calculated by the semi-empirical model whose aging parameters are obtained from curve fitting.
28 Fast charging: limiting factors Fast charging: limiting factorsThe reaction on the negative electrode is described as:When operated improperly, Li-ions are deposited on the anode surface instead of intercalating during charging:Reference: C. J. Mikolajczak, J. Harmon, From Lithium plating to Lithium –ion cell runaway Exponent [Ex(40)]annual report, 2009Observed Li platingCause of Lithium plating:Large current rate during charging, especially at high Li ion concentrationLow temperatureEffects of Lithium plating:CapacityIrreversible loss of active LithiumSafetyDendrites can cause shorting within the electrodesHeat generationA mat of dead lithium and dendrites can increase the chances minor shorts will lead to thermal runway
29 Comparison of simulation results and experimental results: Charging Test condition:Temperature=25°CInitial Vt= 2.9VCharge current: 1C/2C/5C rateSurface Concentration (mol/cm3)Terminal Voltage (V)
30 New Charging method - Battery i(t) + ROM Model Positive TerminalEstimated concentrations, SOC and temperature+-ROM ModelAmbient Temperature; TTerminal Voltage: VTCharging/Discharging currentNegative TerminalReference: Maximum allowed concentrations and temperature, and desired SOCPulse generatorTwo level orThree level
31 Experimental Data for Charging at 4C Qmax by CC and CV charging and the proposed charging method
32 Fast Charging Algorithm Test conditions:Benefits:Less capacity losses after 100 cycles;0.34Ah by the CC and CV.0.24Ah losses by the proposing methodEstimate losses at 500 cycles: 0.5 AhLess temperature riseReduction of charging timeCell No.12Ambient temperature (°C)25Charging methodCC/CVPulseCharging current (C)4Discharging current (C)Rest time (min)10Cycles100If there is no significant degradation,Qmax = Cycle*P1 + P2
33 Diagnosis and Prognosis SummaryMulti-scale and Multi-physics high resolution electrochemical, thermal and mechanical modeling considering degradations of materials.ModelingDesignDiagnosis and PrognosisCell designSystem designSeries and parallel connectionCooling systemsControlsSOC estimationTemperature controlsRapid charging and dischargingHealth monitoring (Growth of SEI, Change of conductivities, Losses of active materials and others)Power fadeCapacity fade