Li-Ion Battery Cell Model: Cell Electrochemistry Analysis

In this tutorial, you model a Li-Ion battery cell at the microscale level. The simulation introduces the method for the prediction of the three-dimensional microstructure of porous battery electrodes.

In a production environment, such analysis results in speeding up the design process of a battery cell, and assessing the safety and life-span of a design.



Generally, the structure of the active materials is irregular and complex, and varies from one active material to another. The structure of the solid particles is often represented by a simpler, regular structure. In this tutorial, you are given randomly distributed spherical particles that represent a single structure, and reflect the desired porosity.

In this tutorial, you model the following:

  • electric potential in active materials, electrolytes, and current collectors

  • concentration of lithium in active materials and electrolytes

  • special conditions on the SEI (Solid Electrolyte Interface)

Note

To activate the Li-Ion battery cell, concentration, and electric potential models that are necessary for modeling the transport of Lithium ions, run a double-precision version of Simcenter STAR-CCM+.

The geometry consists of a sample across a pair of electrodes from a typical Li-ion cell. The CAD geometry that is provided is of a larger scale than in reality. For example, the anode collector is 1.0 m in CAD and 10 μm in reality. After meshing the geometry, you then scale the CAD by 1E-5. The included parts of the geometry are:

  • a cathode collector—1.0 m thick aluminum foil

  • an anode collector—1.0 m thick copper foil

  • electrolytes—a 50:50 mixture of ethylene carbonate/ethyl methyl carbonate, and LiFP6 (lithium hexafluorophosphate—a common electrolyte salt in lithium batteries)

  • a separator—1.0 m thick, with a porosity of 40%, and MacMullin number of 2.5.

    The MacMullin number is the ratio of the resistance of the separator when it is filled with electrolyte to the resistance of the electrolyte alone. This number describes the tortuosity when defining a homogeneous porous medium.

  • a cathode AM (Active Material)—3.5 m thick LiMn2O4 (lithium manganese oxide), with particle diameter equal to 1.8 m, and a target porosity of 40%

  • an anode AM—3.5 m thick graphite, with particle diameter equal to 2.0 m, and a target porosity of 40%

Each electrode is formed from a solid active material and the surrounding fluid electrolyte. These regions within an electrode are modeled separately. Chemical reactions occur at the SEI (Solid-Electrolyte Interfaces).



Note

The tutorial uses a simplified idealized microstructure of a LiMn2O4 electrode. The electrode structure is only represented by a few aggregated spherical particles and the electrolyte. The voluntary omission of the binders and conductivity aids is to speed up the computation for this tutorial. This case does not represent a commercially used electrode. However, it is relevant enough to compute a consistent solution and demonstrate the capabilities of the model.