Linking the flow, thermal and electrochemical simulations into one environment enables producing highly accurate solutions. The models span multiple computational domains from systems models to highly resolved complex 3D models.

Top: Predicted cell voltage during an automotive drive cycle (scale removed). Bottom: Predicted cell temperature during an automotive drive cycle. Left: Plot of temperature on the surface of a cell within the simulated module compared to an experimental measurement. Right: Position of the temperature sensors in the tested module. Click to enlarge.

Continued progress developing and linking physics-based models of batteries allows developers and designers to better understand the internal behavior of batteries in electric drive vehicles and explore new designs in a virtual environment, reducing the number of prototypes and tests required by a traditional build-break design cycle. The outcome of this project is expected to enable scientists and engineers to further improve the performance, cost, and lifetime of advanced lithium ion batteries in support of the DOE’s EV Everywhere Grand Challenge.

—Ahmad Pesaran, Energy Storage Group Manager in NREL’s Transportation and Hydrogen Systems Center

CAEBAT. The objective of CAEBAT is to incorporate existing and new models into design suites/tools with the goal of shortening design cycles and optimizing batteries (cells and packs) for improved performance, safety, long life, and low cost.

After a competitive selection process, NREL awarded subcontracts worth $7 million to the following three industry teams:

• EC Power, Penn State University, Johnson Controls, Inc., and Ford
• General Motors, ANSYS, and ESim
• CD-adapco, Battery Design LLC, A123 Systems, and Johnson Controls Inc.

Each team worked independently to develop and to validate modeling and design tools for EDV batteries, with an emphasis on integrating electrochemical, electrical, mechanical, and thermal physics. Teams also explored different chemistries, cell geometries, and battery pack configurations.

These industry partners contributing 50% of project costs, bringing the overall budget to $14 million for three years.

In support of the CAEBAT project, Oak Ridge National Laboratory (ORNL)developed an open-architecture software interface to link the models developed by different teams into the CAEBAT suite of tools. ORNL is also developing input-output interfaces to allow utilization of models across different platforms.

CAEBAT and CD-adapco. Total project funding for the CD-adapco-led project was $2.74 million over three years. The specific objectives of this project were:

• To produce electrochemical, electrical, and thermal simulation models applicable for spirally wound lithium ion cell designs, both cylindrical and prismatic;

• To validate the results of the simulation across a range of lithium ion cell chemistries;

• To generate best practice methods for the timely generation of future electrochemical models by users; and

• To include the created simulation models and best practice into the readily available 3D multi-physics code STAR-CCM+, for combined flow, thermal & electrochemical simulation across a range of length scales.

The team created an electrochemical and thermal model has been created which can be applied to wound electrode battery types. The model is applicable at both the cell and module and pack level of analysis; users can control the fidelity of the model depending on desired output and level of accuracy.

The project team used five cells from the two different manufacturers (spanning the 3 cell form factors, i.e., stacked, cylindrical and prismatic wound electrodes) to validate the computational model developed using real world drive cycles. This also included a “blind” validation using a WLTC drive cycle on one module.

The researchers also added a database incorporating 12 contemporary electrolyte formulations, typical of those used in modern lithium ion batteries. This enables the a more complete physics based simulation to take place.

The team validated the process to generate the electrochemical model using cell information and controlled test work; it also created a complimentary calendar aging model which works alongside the created cell performance models preconditioning them to an “aged” stage.

We are pleased to have worked with our partners on the Department of Energy's CAEBAT project. CAEBAT has provided us with world-class capabilities to model the performance and safety of Lithium-ion batteries. These technologies have helped us design innovative battery systems and enable new fuel-saving technologies for vehicles.

—Brian Sisk, Johnson Control’s Director of Controls & Modeling

Resources

• R. Spotnitz, S. Hartridge, G. Damblanc, G. Yeduvaka, D. Schad, V. Gudimetla, J. Votteler, G. Poole, C. Lueth, C. Walchshofer, and E. Oxenham (2013) “Design and Simulation of Spirally-Wound, Lithium-Ion Cells Lithium-Ion Batteries: Modeling,” ECS Transactions 50 (26): 209-218 doi: 10.1149/05026.0209ecst

• R. Spotnitz, K. Gering, S. Hartridge, G. Damblanc (2014) “Simulation of Electrolyte Composition Effects on High Energy Lithium-Ion Cells,” ECS Transactions volume 58, issue 13, 25-36 doi: 10.1149/05813.0025ecst