Report

Dr. Song-Yul Choe Professor Auburn University High Resolution Modeling of Lithium Ion Battery and its Applications Auburn University Mechanical engineering Advanced Propulsion Research Lab. Song-Yul (Ben) Choe Ben Choe, [email protected] ; Research on HEV&EV 2 Copying this presentation is illegal and strictly forbidden. Trend of advanced propulsion systems Fuel Improvement Mass E-Drive (40miles) Toyota “PRIUS” Proto Test GM “Chevy-Volt” 50% Power support Toyota “PRIUS” GM “Tahoe” Honda 30% Nissan “INSIGHT” “TINO” VW GOlf Daimler Reneaut “S-400” Toyota “Twingo” Power Assist 15% “S-Class”Ford “Focus 2.0, GM Explorer 4.0” “Epsilon” GM(Subaru) Idle Stop Functionality Level of Voltage “THS-M” DCX Regen. Starter Alternator Ford “ESCAPE” “Elten-Custom” Conv. vehicle 12V 1-3kW Soft HEV Mild HEV 42V 5-10kW Ben Choe, [email protected] ; Research on HEV&EV 96-144V 20-30kW 3 Hard/Split HEV Plug-In HEV 288V <<40kW >288V Voltage(Power) >40KW) Copying this presentation is illegal and strictly forbidden. Energy storage with battery Nominal Capacity (Amp-hours): Nominal Cell Voltage 3.73 Cell Dimensions (mm) 5.27 Cell Dimensions w/ terminals (mm) Maximum Cell Temperature (°C) Positive Negative Electrolyte Separator Ben Choe, [email protected] ; Research on HEV&EV 4 15.7 164.2 X 249.6 75 Lithium Metal Oxide Carbon Organic Material SRS Copying this presentation is illegal and strictly forbidden. Typical models for battery • Models base on equivalent electrical circuit Statics: resistors in series to a voltage source Dynamics: a capacitor connected in parallel to a resistor R dch_d R dch_h V oc R cha_h I dch R cha_d C dch V b (t) I cha C cha Ignored effects : 1. Electrical behavior of the terminal as a function of SOC , T and material degradation, and O CV as a function of hysteresis and SOC. 2. Battery calendar life as a function of cycles and load profile 3. Heat generation as a function of SOC , change of entropy and I (charge and discharge), heat tr ansfer 4. Various temperature effects caused by gradients of ion concentrations and side reactions Ben Choe, [email protected] ; Research on HEV&EV 5 Copying this presentation is illegal and strictly forbidden. Modeling of LiPB cell Positive electrode area • T L Electrolyte LixC6 Current collector (Al) Negative electrode area Separato r • ce • Φe • Φs • ηSEI • cs Current collector (Cu) Y LiyMO2 Electrode particle Ben Choe, [email protected] ; Research on HEV&EV X 6 Copying this presentation is illegal and strictly forbidden. Principle: Current, Concentration and State of Charge • Current in micro cell - current + = Ion current - + + Electron current - + Credit: huangqing • SOC (state of charge) and cs (concentration in solid) - + - + - + Credit: huangqing Low SOC Medium SOC charging Ben Choe, [email protected] ; Research on HEV&EV 7 High SOC Copying this presentation is illegal and strictly forbidden. Electrochemical Thermal Mechanical Model Charging and discharging processes: Heat generation, Elasticity and Degradation Multi scale and Multi-physics coupled problems Ben Choe, [email protected] ; Research on HEV&EV 8 Copying this presentation is illegal and strictly forbidden. Overview of model Single cell model Initial conditions: •Initial SOC •Load profile •Initial temperature distribution •Ambient temperature Temperature distribution •Cell voltage •Temp. distribution •Energy conservation •Heat transfer •Charge conservation Potential distribution •SOC •Overpotentials •Reaction rate •Concentration •Efficiency Micro cell model Micro cell model Micro cell model Parameters: •Battery geometry •Maximum capacity •Concentration •Activity coefficient •Diffusion coefficient •Change of enthalpy •Conductivity Heat source Reaction rate Standard potential •Butler-Volmer Current Overpotential Nernst equ. etc. Concentration Ben Choe, [email protected] ; Research on HEV&EV Mass balance •In electrolyte •In solid 9 Copying this presentation is illegal and strictly forbidden. Static and dynamic behavior of the battery Characteristics at different current rates (T=300K and SOC=100%) Current (A) 4.0 3.8 0 -72 3.4 0 20 40 60 80 4.0 3.2 3.9 3.0 1C 2.8 10C 2.6 20C Terminal Voltage (V) Terminal Voltage (V) 3.6 72 5C 20C 2.4 50C 2.2 3.8 3.7 3.6 70% SOC 60% SOC 50% SOC 40% SOC 30% SOC 3.5 3.4 3.3 2.0 3.2 0.0 0.2 0.4 0.6 0.8 1.0 0 40 60 Time (s) DOD=1-SOC Ben Choe, [email protected] ; Research on HEV&EV 20 10 Copying this presentation is illegal and strictly forbidden. 80 Transient behavior of ion concentration (Discharging behavior at a step current of 10C) At 1secConcentration in solid (1s, discharge at 10C) Concentration in solid (80s, discharge at 10C) At 80 sec 1 1 0.9 0.8 0.9 1 0.8 0.7 Cs/Cs,max Cs/Cs,max 1 0.6 0.5 0.5 0.6 0.5 0.5 0.4 0 0 0.4 0 0 0.7 0.3 0 0.2 0.3 0 0.2 0.2 0.2 0.4 0.6 L 0 r 1 0.8 0.8 1 L 0.8 1 0.1 0.6 0.1 0.6 0.8 At 20 sec 0.4 0.4 0.6 0.2 0.2 0.4 0 r 1 Concentration in solid (180s, discharge at 10C) 1 Concentration in solid (20s, discharge at 10C) 1 At 180 sec 0.9 0.8 0.9 1 0.7 Cs/Cs,max Cs/Cs,max 0.8 1 0.7 0.6 0.5 0.5 0.3 0.2 0.4 0.4 0.3 0 0.2 0 0.2 0.5 0 0 0.4 0 0 0.6 0.5 0.2 0.4 0.2 0.6 0.6 0.4 0.6 0.6 0.8 L 0.8 1 1 r 0.2 0.4 0.8 0.1 L 0.8 1 1 r 0.1 0 0 As 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. Ben Choe, [email protected] ; Research on HEV&EV 11 Copying this presentation is illegal and strictly forbidden. Potentials/Current density at positive and negative current collector 15 3.6122 3.6124 3.612 3.6122 10 3.612 3.6118 3.6118 3.6116 3.6114 5 3.6116 3.6112 15 10 8 5 0 4 2 0 10 6 3.6114 0 -2 0 2 4 6 8 10 12 -4 x 10 -2 15 -4 x 10 0 -3 10 -2 -4 -4 -6 -5 5 -8 15 -6 10 8 5 0 0 2 4 6 10 0 -2 Ben Choe, [email protected] ; Research on HEV&EV 4 6 8 10 12 -7 0 2 12 Copying this presentation is illegal and strictly forbidden. Validation of a single pouch cell at 1C/2C/5C discharge/charge Terminal voltage comparison @ 1C/2C/5C discharge simulation experiment Temperature, K 4 Voltage, V Temperature comparison @ 1C/2C/5C discharge 320 simulation experiment 315 3.5 3 310 305 300 295 2.5 0 1000 2000 Time, s 290 0 3000 4 3.5 0 simulation experiment 500 1000 1500 2000 2500 Time, s Current comparison @ 20A/40A/60A/80A charge 0 -20 -40 simulation -60 experiment -80 0 500 1000 1500 2000 2500 Time, s Ben Choe, [email protected] ; Research on HEV&EV 2000 Time, s 3000 4000 Temperature comparison @ 20A/40A/60A/80A charge 308 simulation experiment 306 Temperature, K Current, A Voltage, V Terminal voltage comparison @ 20A/40A/60A/80A charge 1000 304 302 300 298 0 13 500 1000 1500 2000 Time, s 2500 3000 Copying this presentation is illegal and strictly forbidden. Thermal validation – 5C cycle 2D Ben Choe, [email protected] ; Research on HEV&EV 14 Copying this presentation is illegal and strictly forbidden. Voltage, V Current, A Heat generation using the model and calorimeter 110 0 -110 4 3.5 7C 6.3C 5.7C 5C 4.1C 3 Heat, W 2.5 120 90 Measured (OCV-Vt)I+Qrev 60 30 0 0 200 400 600 Discharging time, s Ben Choe, [email protected] ; Research on HEV&EV 0 15 200 400 Chargeing time, s 600 Copying this presentation is illegal and strictly forbidden. Measurement of Thickness • The 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. Ben Choe, [email protected] ; Research on HEV&EV 16 Copying this presentation is illegal and strictly forbidden. Mechanical stress of cells at 0.5C, 1C and 2C cycling Ben Choe, [email protected] ; Research on HEV&EV 17 Copying this presentation is illegal and strictly forbidden. Maximum Stress as a Function of Position during discharge (at one instant) • The 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. Ben Choe, [email protected], Research on HEV and Fuel cell 18 Copying of this presentation is strictly forbidden. Cathode current collector Separator Anode current collector • Fracture is Observed near the Separator Q. Horn and K. White, 2007 [8] J. Christensen, 2010 [7] • Other researchers took SEM images at the cross-section of cell, where fractures are found in the electrode near the separator [7] [8]. • Our simulation shows that the highest stress locates at the electrode near the separator, where fractures are most likely to happen. Ben Choe, [email protected], Research on HEV and Fuel cell 19 Copying of this presentation is strictly forbidden. Block Diagram for battery management system (BMS) Battery Pack/Module Predefined Map Current Voltage SENSOR Temperature Ri(SOC) Ri(Charging) TRAY Temp. Voc(SOC) Voc(Charging) Thermal Management Imean Cooling Control Charging/Discharging Control HCU Aging Coefficient & SOC Calculation Accumulated SOC Error Comp. I,V(SOC) Health monitoring & Protection Vaverage & Temp. Compensation Temperature Charging/Discharging power User Interface Diagnosis Search IVSOC by IV Voltage MAP Voltage Imbalance detection Ben Choe, [email protected] ; Research on HEV&EV 20 Copying this presentation is illegal and strictly forbidden. Review of models for Battery High Improvement of cell designs Intermediate BMS Functionalities Full 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 elasticity Reduced order of Electrochemical thermal Model (ETM: ROM ): Empirical OCV Polynomial, State space, Páde approx., POD, Galerkin Reformulation and others Electric equivalent circuit Model (EECM): Randles models with the 1st, 2nd and 3rd order Low Empirical Model: Peukert’s equation Comp. time Accuracy Low Ben Choe, [email protected] ; Research on HEV&EV Moderate 21 High Copying this presentation is illegal and strictly forbidden. Reduced order of the model (ROM) for real time applications Input: Parameters: • Cell geometry • Kinetic and transp ort properties Initial conditions: • Terminal voltage • Load profile • Ambient temperat ure Steps Approaches Order reduction • • • Battery : Ion concentration in electrolyte Ce Output Ion concentration in electrodes Cs • • • : voltage Cell Temperature SOC Potentials Φ SOC estimation Results Ce State space approach Cs Polynomial approach Φ Parameters simplification Ben Choe, [email protected] ; Research on HEV&EV 22 • • • Higher accuracy with less computational time Implicit method to solve PDEs Optimization of the ROM for real time applications Copying this presentation is illegal and strictly forbidden. Validation of the ROM 4.2 [email protected] 4 [email protected] Vt/V [email protected] 3.8 [email protected] 3.6 [email protected] [email protected] 3.4 2. Test condition: Mode: Depleting Cycle #: 2 Temperature: 25ºC Current: 1C, 2C, 5C Initial SOC: 0% 1. Test condition: Mode: Depleting Cycle #: 5 Temperature: 0ºC, 25ºC, 45ºC Current: 1C, 2C, 5C Initial SOC: 0% 3.2 3 Current/C 5 2.8 2.6 0 0.5 1 1.5 2 Time/s 2.5 3 3.5 x 10 60 0 -5 4 0 5 10 Time/h 15 20 0 5 10 Time/h 15 20 10 Time/h 15 20 [email protected] [email protected] 50 4 Vt/V [email protected] [email protected] 40 o 3.5 3 [email protected] C o [email protected] C T/ C 30 2.5 o [email protected] [email protected] 20 [email protected] 10 o [email protected] C T/ C 35 -10 [email protected] o 0 0 0.5 1 1.5 2 Time/s 2.5 3 0 4 Ben Choe, [email protected] ; Research on HEV&EV [email protected] 25 3.5 x 10 30 23 5 Copying this presentation is illegal and strictly forbidden. SOC estimation using Extended Kalman Filter • • Error of SOC 7-10% Initial errors of BMS Input: Feedback controls and real time model Output: I , T amb Vt Battery Time update with the ROM Vˆt Measurement update c s, ave Xueyan Li, [email protected] , Nov.,2012 SOC calculation xˆ k SOC 24 Copying this presentation is strictly forbidden. Results of the estimation based on ROM + EKF Current: Voltage: SOC: 1.1 4.3 70 Exp ROM ROM+EKF Exp 4.2 60 4.1 50 Exp ROM ROM+EKF Ah Ah w/o bias 1 0.9 0.8 3.9 30 0.7 3.8 20 10 0 0.6 3.7 0.5 3.6 0 200 400 600 800 1000 3.5 0 200 400 600 800 1000 0.4 0 200 400 Current: Voltage: 1000 Error of SOC: Exp ROM ROM+EKF 4.2 4 800 0.12 4.4 Exp 600 Time/s Time/s Time/s 6 4 ROM ROM+EKF Ah Ah w/o bias 0.1 0.08 3.8 0.06 3.6 0.04 0 SOC error Vt/V 2 Current/C Test condition: Mode: Depleting Temperature: 25ºC Initial SOC: 0% Initial error: 0.5V (6.5% SOC) SOC 40 Vt/V Test condition: Mode: JS Temperature: 25ºC Initial SOC: 100% Initial error: 0.2V (30% SOC) Current/A 4 3.4 3.2 -2 0 5 10 Time/h 15 0 3 -0.02 2.8 -0.04 2.6 -0.06 -4 -6 0.02 20 Xueyan Li, [email protected] , Nov.,2012 0 5 10 Time/h 15 20 -0.08 0 5 25 Copying this presentation is strictly forbidden. 10 Time/h 15 20 Health monitoring of battery Research interests for SOH SOHQ SOH Capacity fade SOHP Power fade Other mechanism Current i Battery pack Output states value (V T) Compare error ROM Model & SOH detection algorithm Ben Choe, [email protected] ; Research on HEV&EV 26 States estimation (Vt SOC T ) Aging parameters estimation ( as ɛs ) SOH Copying this presentation is illegal and strictly forbidden. Estimation of SOHQ 16 Experimental Simulation(Curve fitting) 15 14 Qmax (Ah) 13 12 11 10 9 8 7 • 0 50 100 150 200 Number of cycles 250 300 350 The simulation of Qmax is calculated by the semi-empirical model whose aging parameters are obtained from curve fitting. Ben Choe, [email protected] ; Research on HEV&EV 27 Copying this presentation is illegal and strictly forbidden. Fast charging: limiting factors The reaction on the negative electrode is described as: When operated improperly, Li-ions are deposited on the anode surface instead of intercalating during charging: C 6 x Li x e Li x C 6 Li e Li ( s) Cause of Lithium plating: Large current rate during charging, especially at high Li ion concentration Low temperature Observed Li plating Effects of Lithium plating: Reference: C. J. Mikolajczak, J. Harmon, From Lithium plating to Capacity Lithium –ion cell runaway Exponent [Ex(40)]annual report, 2009 • Irreversible loss of active Lithium Safety • Dendrites can cause shorting within the electrodes Heat generation • A mat of dead lithium and dendrites can increase the chances minor shorts will lead to thermal runway Ben Choe, [email protected] ; Research on HEV&EV 28 Copying this presentation is illegal and strictly forbidden. Comparison of simulation results and experimental results: Charging Test condition: Temperature=25°C Initial Vt= 2.9V Charge current: 1C/2C/5C rate Surface Concentration (mol/cm3) Terminal Voltage (V) 0.04 4.2 4 Sim1C Sim2C Sim5C 0.035 Sim1C Exp1C Sim2C Exp2C Sim5C Exp5C Vt/V 3.6 3.4 3.2 Surface concentration 3.8 0.03 0.025 0.02 3 0.015 2.8 2.6 0.01 0 500 1000 1500 2000 2500 3000 time/s 3500 4000 4500 5000 Ben Choe, [email protected] ; Research on HEV&EV 29 0 500 1000 1500 2000 2500 3000 time/s 3500 4000 4500 Copying this presentation is illegal and strictly forbidden. 5000 New Charging method Charging/Discharging current i(t) Positive Terminal + Negative Terminal Battery Ambient Temperature; T Terminal Voltage: VT ROM Model Estimated concentrations, SOC and temperature Pulse generator • Two level or • Three level Reference: Maximum allowed concentrations and temperature, and desired SOC Ben Choe, [email protected] ; Research on HEV&EV 30 Copying this presentation is illegal and strictly forbidden. Experimental Data for Charging at 4C 1 4.4 0 4.2 4 -2 Pulse CC/CV Vt/V current/A -1 -3 Pulse CC/CV sim 3.6 3.4 -4 -5 3.8 3.2 0 500 1000 time/s 3 1500 0 500 1000 time/s 1500 Qmax by CC and CV charging and the proposed charging method Ben Choe, [email protected] ; Research on HEV&EV 31 Copying this presentation is illegal and strictly forbidden. Fast Charging Algorithm Test conditions: Cell No. 1 2 Ambient temperature (°C) 25 25 CC/CV Pulse Charging current (C) 4 4 Discharging current (C) 2 2 Rest time (min) 10 10 Cycles 100 100 Charging method Benefits: 1. Less capacity losses after 100 cycles; • 0.34Ah by the CC and CV. • 0.24Ah losses by the proposing method • Estimate losses at 500 cycles: 0.5 Ah 2. Less temperature rise 3. Reduction of charging time Experiment Estimation 15.9 16 CC/CV-exp Pulse-exp CC/CV-est Pulse-est 15.7 If there is no significant degradation, 15.6 Qmax = Cycle*P1 + P2 15.5 Qmax/Ah Qmax/Ah 15.8 15 14.5 15.5 15.4 0 20 40 60 80 14 100 Ben Choe, [email protected] ; Research on HEV&EV 0 100 200 300 400 500 cycle cycle 32 Copying this presentation is illegal and strictly forbidden. Summary Multi-scale and Multi-physics high resolution electrochemical, thermal and mechanical modeling considering degradations of materials. Modeling 1. Cell design 2. System design • Series and parallel connection 3. Cooling systems Health monitoring (Growth of SEI, Change of conductivities, Losses of active materials and others) Diagnosis • • Power fade Capacity fade and Prognosis Design 4. Controls 1. SOC estimation 2. Temperature controls 5. Rapid charging and discharging Ben Choe, [email protected] ; Research on HEV&EV 33 Copying this presentation is illegal and strictly forbidden. Dr. Song-Yul Choe Professor Auburn University