BATTERY MODELING TECHNOLOGYA UNIQUE SIMULATION TOOL FOR THE ANALYSIS OF ELECTROCHEMICAL & THERMAL PERFORMANCE OF LITHIUM-ION BATTERIES

CD-adapco™

A NEW PROCESS

Battery Design Studio (BDS):This piece of software was specifically developed to provide a simulation environment for the design and analysis of electrochemical systems and detailed geometry of a single battery cell. A choice of three battery performance models is offered to the user, enhanced with significant developments relevant to contemporary cell design, such as multiple active materials or particle sizes. Through its integrated environment, BDS offers its users a faster battery design process and provides a standard platform connecting material suppliers, cell designers and battery users.

STAR-CCM+ Battery Simulation Module (BSM):Combining the electrochemical solver of BDS with the flow & thermal solver of STAR-CCM+, STAR-CCM+ BSM has the ability to calculate the 3D thermal, fluid and electrochemical properties of lithium-ion battery cells on several length scales, starting from each finite volume/e-cell within a battery cell, to the entire pack, including thermally-conducting parts such as metallic connectors at high discharge/charge rate. This is achieved through a closely coupled 3D simulation which returns the electrochemical and thermal properties as complex distributions over the electrodes and battery cells. The internal construction of each cell is taken into account without the need to resolve all its layers independently, balancing computation effort with appropriate detail.

THE TOOLBOX

Having the ability to compute both the thermal and the electrical/electrochemical solution within one code and ensure that all phenomena are included to achieve the correct overall performance, and hence distributions of temperature as well as integral values, is unique.

Steve Hartridge Director, Electric & Hybrid VehiclesCD-adapco

In November 2009, CD-adapco, which has 30+ years of experience with thermal-fluid simulations, partnered with Battery Design LLC, which has over 10 years of experience with the development of lithium-ion (Li-ion) battery analysis software and cell design consulting. From this close cooperation and combined expertise,which led to Battery Design Studio being acquired by CD-adapco in 2011, one working methodology was developed for the design and analysis of Li-ion battery cells, modules and pack installations.

A SUCCESSFUL PARTNERSHIP

This new battery technology allows the user to migrate from short length scale simulations, such as studies of a detailed single cell, to complex battery modules, packs or complete installations, including multiple hundreds of battery cells and their surrounding structure and cooling system.

The same battery performance model, including a range both empirical and physics based, can be used in any of the different length scale models. This removes the need for duplicating or simplifying the engineering tasks, thereby facilitating the division of labor: one engineer, probably part of the cell team, creates a battery cell model and begins running cell level simulations; this model can then be passed on to another analyst, maybe working in the application team, who uses it to create complex simulations of battery modules or packs. This process ensures that there is no duplication in the two engineers’ time while providing a high fidelity numerical model and coupled flow, thermal & electrochemical solution.

CD-adapco™

STEP 1: The complete battery definition, including all geometric details of the cell, details of the collector technology, number of electrodes, and finally a relevant numerical model of the battery’s performance under load is built in BDS.

STEP 2: The battery model is then tested under appropriate discharge and thermal conditions. This rapidly confirms the correct behaviour of the electrical model.

..::BATTERY MODELING TECHNOLOGY

Electrode Definition Electrochemical Composition Numerical Battery Model

SINGLE CELL STUDIES ARE CONDUCTED IN BATTERY DESIGN STUDIO (BDS)

Battery Definition, Response to load, Parametric studies, Form Factor Studies

Time Step 1

Time Step 2

Time Step 3

THE BATTERY CELL DEFINITION CAN BE MODIFIED AND RE-TESTED UNTIL A SATISFACTORY DESIGN SOLUTION IS FOUND.

STEP 3: The model can then be used to study the cell response to load and to understand its limiting factors.

Cell voltage response

Concentration of lithium in the electrolyte

Battery Design Studio®

MODULE AND PACK ANALYSES ARE CONDUCTED IN STAR-CCM+ BATTERY SIMULATION MODULE (BSM)

Module/Pack Performance, Installation effects, Test Cooling Systems, Individual Cell response, Detailed 3D Geometry

STEP 4: The satisfactory battery cell design is imported in STAR-CCM+ BSM, where an equivalent 3D CAD model is automatically generated and meshed with finite volumes.

STEP 8 : The electrochemical and thermal performance of the design can be analysed and understood.

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STEP 5: A module can be automatically created from the single cell. This process can also be applied to spiral cells.

STEP 6: Modules can then be added together with surrounding CAD to create a complete pack.

STEP 7: A closely coupled solution is computed.

Electrical Solver:Calculates the batteries performance within

the computed thermal environment

Flow/Thermal Solver:Calculates the heat generation due to

electrical loading

THE BATTERY MODULE CAN BE MODIFIED AND RE-TESTED UNTIL A SATISFACTORY DESIGN SOLUTION IS FOUND.

Imag

e Cou

rtes

y of

ASCS

Validation of a new simulation tool for the analysis of

electrochemical and thermal performance of lithium ion

batteries - by Damblanc et al., presented at the JSAE

Annual Congress on May 19th 2011

S. Fell, E. Schneider, M. Lindner, R. Immel, J. Kremser

SIMVEC – Berechnung, Simulation und Erprobung im Fahrzeugbau 2012, VDI-Berichte 2169, p.241-254; ISSN

0083-5560, ISBN 978-3-18-092169-3; VDI Verlag GmbH, Düsseldorf 2012

STAR-CCM+®

BATTERY PERFORMANCE MODELSThe user has a choice of three battery performance models to choose from:

• ELECTROCHEMICAL MODEL: A detailed electrochemistry model with enhancements to handle multiple active materials and particle sizes, as seen in contemporary cell design. It is based on the Newman model, which calculates Li-ion intercalation between electrolyte and active materials and simulates the current density, voltage and Li-ion transfer within the battery cell. In addition to performance prediction, the distributed model can also predict battery cell performance degradation as it includes an aging model.

SEI Growth Evolution due to aging process

• EQUIVALENT CIRCUIT MODEL (ECM):A tailored equivalent circuit model that predicts the battery cell behavior in varying temperature conditions with a circuit composed of of resistances (R) and capacitances (C). This can be used to simulate complex drive cycles or simple constant current loads in a short computation time.

CD-adapco is leading a pioneering simulation project (CAEBAT - Computer-Aided Engineering for Batteries), co-funded by the U.S. Department of Energy, which aims at developing modeling techniques for Li-ion batteries using industrial partners’ prototype batteries.

THE CORE TECHNOLOGYThe active material is represented by a number of finite volumes whose discretisation, controlled by the user, depends on the level of detail required for the analysis. As shown in the figure on the right, the selected battery performance model is then mono-dimensionally applied to the electrical mesh resolution, while each discretised element of the mesh interact with each other through the positive and negative collectors placed on their sides.

Selected battery performance model (Electrochemical or equivalent circuit model)

Thermal MeshElectrochemical Mesh Temperature Battery State of Charge

Collector Resistances

..::BATTERY MODELING TECHNOLOGY

In parallel to the aforementioned developments, a 3D electrochemistry solver has been created for micro-scale analyses.

This development extends the applicable length scales of battery simulation to unit cell on a micro-structural level. The method removes the macro-homogeneous elements with 1D or pseudo 2D electrochemistry models and chooses instead to represent the various phases within the electrodes as distinct regions: active material, electrolyte, conductivity aid, separator and collector. The now greatly simplified fundamental equations have been added to STAR-CCM+’ solver capabilities, thereby enabling the computation of the following quantities:

• Salt concentration in the electrolyte region;• Lithium concentration in the positive and negative active materials;• Potential in both the solid and electrolyte regions;• Thermal energy within the entire regions.

Using this technology, cell designers and material specialists can explore and optimize active material packing ratio, particle shape and size distribution, electrolyte properties and other aspects under various charge and discharge conditions. This is a bold development which CD-adapco is first to bring to market.

3D MICROSTRUCTURAL ELECTROCHEMISTRY

CUTTING EDGE MODELING

Publications:Hutzenlaub, T., Thiele, S., Paust, N., Spotnitz, R., Zengerle, R., Walchshofer,

C. (2014). Three-dimensional electrochemical Li-ion battery modelling featuring a focused ion-beam/scanning electron microscopy based three-phase reconstruction of a LiCo2 cathode. Electrochimica Acta 115 131-139

Cooper, S.J., Eastwood, D.S., Gelb, J., Damblanc, G., Brett, D.J.L., Bradley, R.S., Withers, P.J., Lee, P.D., Marquis, A.J., Brandon, N.P., Shearing, P.R. (2014). Image based modelling of microstructural heterogeneity in LiFePO4 electrodes for Li-ion batteries. Journal of Power Sources 247 1033-1039

Spotnitz, R., Kaludercic, B., Muzaferija, S., Peric, M. et al., “Geometry-Resolved Electro-Chemistry Model of Li-Ion Batteries,” SAE Int. J. Alt. Power. 1(1):160-168, 2012

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STAR-CCM+ BSM is the most comprehensive battery modeling solution on the market. In addition to leveraging the full power of STAR-CCM+ features, such as a user-friendly interface, automatic meshing and best-in-class post-processing tools, it offers specific benefits, such as:

• Enables consistent information sharing between electrochemist and thermal engineers, even using encrypted files to protect sensitive data

• Everything is contained in a single analysis process which is applicable to all battery cell shapes - Pouch, cylindrical & prismatic

• Increase the accuracy of results through independent thermal and electrical meshing strategies, enabling the user to balance computation cost with required accuracy

• Expedite solutions through the deployment of massive parallel computing to scale simulations with hundreds of battery cells

• Visualise the evolution of quantities which are otherwise very difficult to measure experimentally (Such as heat generation or current density) or integrated quantities (such as total heat rejection)

• Enable the optimisation of the working process through the application of automation tools such as HEEDS

THE BENEFITS

..::BATTERY MODELING TECHNOLOGY

“Simulating lithium ion cell, modules and packs is now a daily task producing both electrochemistry and thermal results on highly detailed 3D geometries”Robert Spotnitz - President, Battery Design Llc

CD-adapco is the leading global provider of full-spectrum CAE simulation solutions for fluid flow, heat transfer, stress and more, including Computational Fluid Dynamics (CFD) software, CAD and PLM-embedded CFD tools and CAE consulting services and training.

Its principal offices are in New York, London and Yokohama with subsidiary offices across the world.

www.cd-adapco.com

For a full listing of our worldwide offices & resellers, please visit www.cd-adapco.com

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+1 631 549 2300info@cd-adapco.comwww.cd-adapco.com

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