Design of a spatially resolved electro-thermal model for lithium-ion pouch cells

Transcription

1 ANSYS Conference & 31th CADFEM Users Meeting 2013 June 19-21, 2013 Rosengarten Mannheim Design of a spatially resolved electro-thermal model for lithium-ion pouch cells S. Stumpp, C. Günther, M.A. Danzer Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Ulm, Germany L. Kostetzer, E.Rudnyi CADFEM GmbH, Grafing bei München, Germany

2 Outline Introduction to lithium-ion cells Applications and requirements Theoretical background Functional principle and basic design Temperature influence on performance Safety risks Spatially resolved electro-thermal model for a large size lithium-ion pouch cell Parameterisation Sensitivity analysis Results of parameterisation - 2 -

3 Introduction to lithium-ion cells Applications Lithium-ion-technology for rechargeable batteries Highest energy- and power density of commercially available cells Applications Consumer electronics Mobile phones Laptop Energy storage systems Domestic Grid services Power tools and gardening tools Drill Chainsaw Electric vehicles BEV HEV Requirements Lightweight Low cost Long life Safe operation - 3 -

4 Introduction to lithium-ion cells Theoretical background Basic design of secondary batteries soaked with electrolyte Electro-chemical reactions anode/cathode: graphite/licoo charge Li + Li + discharge current collector (Al) cathode separator anode current collector (Cu) Anode: 0.6 C Li e LiC 6 Cathode: LiCoO 2 Li 0.4 CoO Li e Overall: LiCoO C 6 Li 0.4 CoO LiC 6 Transport mechanisms [1] Electrons Ohmic law Ions Migration zµ Fc ϕ Diffusion N = D c j el N mig diff = = σ ϕ [1]: Newman, Electrochemical Systems, Wiley,

5 Introduction to lithium-ion cells Temperature influence Performance Temperature-dependent parameters like ionic conductivity [2] Arrhenius-equation: Parameter P Degradation at elevated temperatures Increase of internal resistance [3,4] Decrease of capacity [3,5] Safety risks through Thermal runaway Temperature as trigger for exothermic reactions [6] Rate of reaction R P = P e 0 E A 1 R Tref 1 T RT R ~ c e Triggering of reactions with higher activation energy due to temperature rise induced by heat release of reactions E A [2]: Gu et al., J Electrochem Soc, 147, p. 2910, 2000 [3]: Amine et al., Electrochemistry Comm, 7, p , 2005 [4]: Amine et al., J Power Sources, 97-98, p , 2001 [5]: Amine et al., J Power Sources, 129, p.14-19, 2004 [6]: Kim et al., J Power Sources, 170, p ,

6 Introduction to lithium-ion cells Temperature influence Inhomogeneous degradation caused by cooling strategy: Accelerated aging in hotter regions of the cell [7] Electro-thermal interaction in cells and modules Increased current through hotter cells/regions Inhomogeneous distributions Current density State of charge Cell potential Heat generation [8, 9] Battery management systems with thermal management [10] Electro-thermal models for design of battery packs [7]: Gerschler et al., VPPC, Dearborn, 2009 [8]: Fleckenstein et al., J Power Sources, 196, p , 2011 [9]: Verbrugge, AlChE Journal, 41, p , 1995 [10]: Bandhauer, J Electrochem Soc, 158, p. R1,

7 Spatially resolved electro-thermal model for a large size lithium-ion pouch cell Schematic of cell Schematic of electrodes I Bat U Bat Electrical model [11,12] Network of resistors Discretisation of conducting components Reproduction of current paths Electro-chemical subcells Lumped model for electro-chemical impedance [7] subcell R tab,pos. R elec.,i,pos. R elec.,j,pos. [7]: Gerschler et al., VPPC, Dearborn, 2009 [11]: Stumpp et al., Advanced Battery Power, Münster, 2012 [12]: Stumpp et al., Modval, Bad Boll, 2013 R tab,neg. R elec.,i,neg. R elec.,j,neg

8 Spatially resolved electro-thermal model for a large size lithium-ion pouch cell Thermal model [11,13] Geometry Implemented in ANSYS Mechanical Thermal analysis FEM T r Heat equation [14] ρc p σ t Isotropic heat conductivity Tabs Orthotropic heat conductivity of composite materials Pouchbag foil Stack of electrodes Boundaries Temperatures at tabs Convection at surface ( T ) = hvol + q& surf Geometry of the cell Cell Tabs Pouchbag foil Stack of electrodes [11]: Stumpp et al., Advanced Battery Power, Münster, 2012 [13]: Kostetzer, Battery Pack Electro-thermal Simulation, Master thesis, Ingolstadt-Landshut, 2011 [14]: ANSYS Release 14 Theory Reference,

9 Spatially resolved electro-thermal model for a large size lithium-ion pouch cell Electro-thermal model Coupling of electrical and thermal model Transfer of heat release Calculated by electrical model Input for thermal model Heat generation Tabs Electrode stack Mechanisms Joule heat Reversible heat Similar work based on FEM: [15] [15]: Kostetzer et al., Simvec, Baden-Baden,

10 Spatially resolved electro-thermal model for a large size lithium-ion pouch cell Implementation of electro-thermal model Input signals Cell current Temperatures Tabs Ambient air Thermal model in ANSYS Mechanical MOR4ANSYS Classes of output signals Cell states Subcell branches Electrode branches Accessible properties Temperature { T } = { T 1 T 2 } Current SOC Heat release Potential In Electro-thermal model in Matlab { } { I} dt SOC = + C, N Elem { SOC } Electrical parameters f(soc,t) i { Q& } T T T tab, neg tab, pos amb u Thermal model MOR-matrices x& = Ax + Bu y = C x { T } y Out

11 Spatially resolved electro-thermal model for a large size lithium-ion pouch cell Parameterisation of model 1 Time domain measurements [16] In the range of interest SOC T Relaxed voltage: OCV(SOC,T) Analysis of cell voltage response due to cell current step using a lumped electrical model RC-circuits: (R 1,C 1 ) and (R 2,C 2 ) Series resistance: R s [7]: Gerschler et al., VPPC, Dearborn, 2009 [16]: Guenther et al., ISGT, Berlin, 2012 Scaling of electrical parameters [7] Volume fraction Distributed electrical parameters [7] Subcell capacity Subcell dynamics Subcell potential V f = V subcell How to parameterise the network? R electrodes R tabs R s,subcell C C cell N, subcell R1,2, subcell = R1,2, cell / 1,2, subcell OCV OCV subcell cell = CN, = C = Cell 1,2, cell ( SOC, T ) subcell f f f subcell

12 Spatially resolved electro-thermal model for a large size lithium-ion pouch cell Parameterisation of model 2 Approach based on cell voltage Sensitivity analysis in frequency domain Cell voltage U = f(r electrodes, R tabs, R s,subcell ) Results: Variation of impedance: f(r electrodes, R tabs, R s,subcell ) Response: qualitatively similar No information in cell voltage U for identification [12] R electrodes R tabs R s,subcell [12]: Stumpp et al., Modval, Bad Boll,

13 Spatially resolved electro-thermal model for a large size lithium-ion pouch cell Parameterisation of model 2 Approach based on distribution of cell surface temperature Thermal excitation using alternating current profile Thermal imaging of cell surface Identification of R electrodes, R tabs, R s,subcell Possible, if parameter variation affects different regions [12]: Stumpp et al., Modval, Bad Boll,

14 Spatially resolved electro-thermal model for a large size lithium-ion pouch cell Parameterisation of model 2 Approach based on distribution of cell surface temperature Parameter variation in steady state Variation of R elec,neg Highest influence on region near P1 Similar for remaining parameters High requirement on thermal model Capabilities of ANSYS Mechanical Quick implementation of geometry High detail of geometry Orthotropic conductivity Adaption of mesh P1 P2 P3 P4 [12]: Stumpp et al., Modval, Bad Boll, 2013 P5-14 -

15 Spatially resolved electro-thermal model for a large size lithium-ion pouch cell Parameterisation of model 2 Thermal model in ANSYS Mechanical Identification of R electrodes, R tabs, R s,subcell Using a pre-parameterised electrical model to predict the distributed heat generation Least squares optimisation with Matlab Objective function θ = (θ el, θ th ) f 5 ( m, i s, i, ) ( θ ) = T ( t) T ( θ t) t i= 1 2 θ θ th θ el In Electro-thermal model in Matlab { } { I} dt SOC = + { SOC i } C N, Elem Electrical parameters f(soc,t) { Q & } T tab, neg u T tab, pos T amb Thermal model MOR-matrices x & = A x + B u y = C x { T } y Out T s, i MOR4ANSYS Adaption of thermal parameters MOR4ANSYS Fast optimisation of FEM-models [13,17] min f ( θ ) Additional information to conserve electrical properties: Resistance of a network for a current step: Nodal analysis R DC,network = f(r tabs,r electrodes,r s,subcell ) R DC,network = R s,cell T m, i [13]: Kostetzer, Battery Pack Electro-thermal Simulation, Master thesis, Uni. Ingolstadt-Landshut, 2011 [17]: Bechtold et al., Fast simulation of electro-thermal MEMS efficient dynamic compact models, Springer, Berlin,

16 Results of parameterisation Input signals Cell states SOC start = 50 % Room temperature Alternating current pulses Voltage Temperature in the middle of the cell Overall heat release

17 Results of parameterisation Surface temperatures Surface temperatures at steady-state Good overall trend Small deviations in distribution Distribution qualitatively reproduced Possible causes: Discretisation of electrical model Inhomogeneous convection [11] [11]: Stumpp et al., Advanced Battery Power, Münster, 2012 P1 P2 P3 P4 P5-17 -

18 Summary Temperature influence on lithium-ion-cells Requirement of BMS with thermal management Application-oriented cooling strategies Model-based layout of cooling system Design and parameterisation of a spatially resolved electro-thermal model Requirements on thermal model Implementation and combined application Matlab ANSYS mechanical MOR4ANSYS Results Good overall trend Temperature distribution qualitatively reproduced

19 Thank you for your kind attention! Stefan Stumpp

20 References [1] J. S. Newman und K. E. Thomas-Alyea, Electrochemical systems. Hoboken, N.J.: J. Wiley, [2] W. B. Gu und C. Y. Wang, Thermal-Electrochemical Modeling of Battery Systems, Journal of The Electrochemical Society, Bd. 147, Nr. 8, S. 2910, [3] K. Amine, J. Liu, und I. Belharouak, High-temperature storage and cycling of C-LiFePO4/graphite Li-ion cells, Electrochemistry Communications, Bd. 7, Nr. 7, S , Juli [4] K. Amine, C. H. Chen, J. Liu, M. Hammond, A. Jansen, D. Dees, I. Bloom, D. Vissers, und G. Henriksen, Factors responsible for impedance rise in high power lithium ion batteries, Journal of Power Sources, Bd , S , Juli [5] K. Amine, J. Liu, S. Kang, I. Belharouak, Y. Hyung, D. Vissers, und G. Henriksen, Improved lithium manganese oxide spinel/graphite Li-ion cells for high-power applications, Journal of Power Sources, Bd. 129, Nr. 1, S , Apr [6] G.-H. Kim, A. Pesaran, und R. Spotnitz, A three-dimensional thermal abuse model for lithium-ion cells, Journal of Power Sources, Bd. 170, Nr. 2, S , Juli [7] J. B. Gerschler, F. N. Kirchhoff, H. Witzenhausen, F. E. Hust, und D. U. Sauer, Spatially Resolved Model for Lithium-Ion Batteries for Identifying and Analyzing Influences of Inhomogeneous Stress Inside the Cells, in 5th International IEEE Vehicle Power and Propulsion Conference, Dearborn, Michigan, USA, 2009, S [8] M. Fleckenstein, O. Bohlen, M. A. Roscher, und B. Bäker, Current density and state of charge inhomogeneities in Li-ion battery cells with LiFePO4 as cathode material due to temperature gradients, Journal of Power Sources, Bd. 196, Nr. 10, S , Mai [9] M. W. Verbrugge, Three-dimensionai temperature and current distribution in a battery module, AIChE Journal, Bd. 41, Nr. 6, S , Juni [10] T. M. Bandhauer, S. Garimella, und T. F. Fuller, A Critical Review of Thermal Issues in Lithium-Ion Batteries, J. Electrochem. Soc., Bd. 158, Nr. 3, S. R1, [11] S. Stumpp, L. Kostetzer, E. Rudnyi, M. Kellermeyer, R. Kuhn, und M. A. Danzer, Evaluation of thermal modelling approaches for lithium-ion pouch cells, in Advanced Battery Power 2012, Münster, [12] S. Stumpp, L. Kostetzer, C. Günther, E. Rudnyi, und M. A. Danzer, Critical review of parameterisation methods for equivalent circuit based, spatially resolved models of lithium-ion cells, gehalten auf der 10th Symposium on Fuel Cell and Battery Modelling and Experimental Validation, Bad Boll, Germany, [13] L. Kostetzer, Battery Pack Electro-thermal Simulation, Master thesis, Landshut University of Applied Sciences, Ingolstadt University of Applied Sciences, [14] ANSYS,Inc., ANSYS Release 14 Mechanical APDL Theory Reference, [15] L. Kostetzer und S. Stumpp, Electro-thermal battery modeling at the level of finite elements, in 16. Kongress mit Fachausstellung. SIMVEC Berechnung, Simulation und Erprobung Fahrzeugbau 2012, Baden-Baden, [16] C. Guenther, J. Klee Barillas, S. Stumpp, und M. A. Danzer, A Dynamic Battery Model for Simulation of Battery-to-grid Applications, in 3rd IEEE PES Innovative Smart Grid Technologies (ISGT) Europe Conference, Berlin, Germany, [17] T. Bechtold, J.G. Korvink, E.B. Rudnyi, Fast simulation of electro-thermal MEMS efficient dynamic compact models, Springer, Berlin; New York,