Electrode Surface
Use the Electrode Surface node to model an electrochemical electrode-electrolyte interface between an electrolyte domain and an electrode boundary where the electrode is not included explicitly as a domain in the model geometry. Set the electric potential of the electrode or specify a current condition that the potential of the electrode shall fulfill, and use subnodes to specify the Electrode Reaction and the Double Layer Capacitance at the interface.
This node can only be applied on outer boundaries to electrolyte domains. For internal boundaries between electrolyte and electrode domains, use the Internal Electrode Surface node.
Dissolving-Depositing Species
Use the settings of this section to define species that participate in dissolution-deposition electrode reactions, for instance metal deposition/dissolution or oxide formation.
Use the Add () and Delete () buttons as needed in the tables to control the number of species.
The Density and Molar mass, in conjunction with the reaction rates and stoichiometry, defined in the Electrode Reaction subnodes, determine the normal electrode growth rate. The growth rate can be used in conjunction with the Deforming Electrode Surface and Nondeforming Boundary multiphysics couplings to model geometry deformations.
When the Solve for species concentrations variables check box is checked, dependent variables for the molar surface concentration of the dissolving-depositing species are added. These can be used to model the thickness of an dissolving/depositing layer in a time-dependent simulation where the resulting deformation in the model geometry is small and will have negligible impact on the current distribution.
When solving for the species concentration variables, corresponding thickness variables are defined that you for instance can use to couple to the Film Resistance (see below).
Use The Surface Reactions Interface interface to model surface diffusion.
Species Conservation on Deforming Geometry
In Deforming Geometry simulations, the Compensate for Boundary Stretching adds a tangential convection term, based on the movement of the mesh, to the mass balance equations of the dissolving-depositing species surface concentrations.
Film Resistance
Use a film resistance if you want to include an additional potential drop due to an ohmic resistance at the interface between the electrode and the electrolyte, for instance due to build-up of insulating deposits.
Specify either a Surface resistance Rfilm (SI unit: Ω·m2) directly or choose the Thickness and conductivity option to calculate the surface resistivity based on a depositing film thickness.
Harmonic Perturbation
Use this section in conjunction with AC Impedance study types to control the perturbation amplitude in the frequency domain.
The perturbation parameter is either Electric potential, Electrode potential, Total current, or Average current density, based on the Boundary condition selected in the next section.
The frequency spectrum is specified in the study node.
Boundary Condition
This section specifies the potential in the electrode phase of the electrolyte-electrode interface. The electrode potential is used (via the overpotential) by the Electrode Reaction subnodes.
Electric potential and Electrode potential will set the potential value directly, whereas Total current, Average current density, and External short all add an extra global degree of freedom for the potential in the electrode phase, set to comply with the chosen condition.
When using the Total current option in 1D or 2D, the boundary area is based either on the Cross sectional area (1D), or the Out-of-Plane thickness (2D) properties, set on the physics interface top node.
See also the External Short node for further information about this boundary condition.
Constraint Settings
For primary current distributions, the use of weak constraints will in some cases give a more accurate value of the local current density during the solver process. This may in turn render more accurate results when coupling to the local current density variable to describe other phenomena in the model, for instance when modeling geometry deformation due to electrode dissolution/deposition.
The section is available in the Primary Current Distribution and Secondary Current Distribution interfaces when the Current Distribution Model property has been set to Primary.
This section is only available in the Primary Current Distribution and Secondary Current Distribution interfaces when the Current Distribution Model property has been set to Primary. To display this section, click the Show button () and select Advanced Physics Options.
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Electrode Reactions Theory
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Film Resistance