Batteries & Fuel Cells Module Updates

For users of the Batteries & Fuel Cells Module, COMSOL Multiphysics® version 5.5 brings a single-ion conductor charge balance option for solid-state battery modeling, an interface for equilibrium potential calculation using the Nernst equation, and generation of concentration-dependent Butler–Volmer kinetics from chemical equations. Read more about these battery and fuel cell features below.

Single-Ion Conductor Charge Balance Option for Solid-State Battery Modeling

A new Single-ion conductor charge balance model has been added to the Lithium-Ion Battery interface, together with a new Lithium-Ion Battery, Single-Ion Conductor model wizard entry. The single-ion conductor charge balance model can typically be used for modeling solid-state electrolytes. You can see the new charge balance option in the Lithium-Ion Battery with Single-Ion Conduction Solid Electrolyte model.

Lumped Battery Interface Improvements

  • Three new operation modes are now available in the Lumped Battery Interface: Potentiostatic, Power, and Circuit Voltage Source
  • A Short Circuit node has been added to the Lumped Battery interface
  • New user-defined and From definitions options for the open circuit voltage input
    • Available in the:
      • Cell Equilibrium Potential node in the Lumped Battery interface
      • Battery Open Circuit Voltage node in the Electric Circuit interface
    • These new features allow for specifying the equilibrium potential data only once in a model featuring multiple batteries

The above features are demonstrated in the following models:

Equilibrium Potential Calculation Using the Nernst Equation

In the Electrode Reaction and Porous Electrode Reaction features, the equilibrium potential of electrode reactions can be defined using the new Nernst Equation option, making it easier to set up thermodynamically consistent models. In physics interfaces solving for multiple concentrations, such as the Tertiary Current Distribution and Chemistry interfaces, the equilibrium potential will automatically be concentration dependent, based on the reaction stoichiometry. All models in the Application Libraries featuring Nernstian equilibrium potentials have been updated to use the new feature.

Concentration-Dependent Butler–Volmer Kinetics

In the Electrode Reaction and Porous Electrode Reaction features, the exchange current density of the Butler-Volmer and Linearized Butler-Volmer kinetics expressions can now be automatically defined to be concentration dependent, based on reaction stoichiometry. The option is available if the Nernst equation option is used when defining the equilibrium potential. In the Tertiary Current Distribution, Nernst-Planck interface, the options Mass action law and Lumped multistep are available for the exchange current density type. All models in the Application Libraries featuring Nernstian equilibrium potentials and concentration-dependent kinetics have been updated to use the new feature.

The Porous Electrode Reaction feature settings with the Electrode Kinetics section open and the Butler-Volmer expression type selected. Porous Electrode Reaction feature: Electrode Kinetics Settings section for the Electrode kinetics in the Tertiary Current Distribution, Nernst-Planck interface. The exchange current density will be calculated automatically from the reaction stoichiometry and species concentrations.

Electrode Reactions in the Chemistry Interface and Thermodynamics

The Chemistry interface, added to the Batteries and Fuel Cells Module in version 5.5, now features Electrode Reactions and Electrode Reaction Group nodes. The Chemistry interface allows for defining multiple species and electrode reactions, as well as ordinary chemical reactions. Also, mixture and thermodynamic properties, such as equilibrium potentials, can be calculated automatically by the Chemistry interface. Variables defined by these features, such as local current densities and equilibrium potentials, can be coupled to any other applicable physics interface. Additionally, the Thermodynamics feature has been added to the Batteries & Fuel Cells Module in version 5.5. The Thermodynamics node can be used to calculate mixture properties, and other thermodynamic properties, such as equilibrium potentials and heat of reaction. You can see this new functionality in the Solid Oxide Electrolyzer model.

New Mass Flow Rates Inflow Condition

In the Transport of Concentrated Species interface, you can specify mass flow rates with the Inflow feature. Also, the Darcy's Law interface now allows for setting the total mass flow rate at the Inlet node. This new feature facilitates investigating fuel cell performance versus a given cell current and gas flow rate (gas stoichiometry). You can see this feature demonstrated in the Solid Oxide Electrolyzer model.

New Adsorption Models

The Transport of Diluted Species in Porous Media and Transport of Diluted Species in Fractures interfaces include two new adsorption isotherms to predict the adsorption of dissolved species onto porous media. The Brunauer–Emmett–Teller (BET) and Toth isotherms are added to the existing Langmuir and Freundlich isotherms.

New Tutorial Models

Version 5.5 brings several new tutorial models.