The Battery with Binary Electrolyte (batbe) interface (), found under the Electrochemistry > Battery Interfaces branch () when adding a physics interface, is used to compute the potential and current distributions in a generic battery. Multiple intercalating electrode materials can be used, and voltage losses due to film formation on the porous electrodes can also be included.

The cs variable is solved for in an extra dimension, using an internal discretization in the particle dimension, not visible in the ordinary model geometry. The cs variable can be referred to as batbe.cs_surface, batbe.cs_center, or batbe.cs_average. The concentration variation along the extra dimension can be plotted along the solid electrode phase using the comp1.xdim1.atxd2 operator. See also Using Extra Dimensions and Plotting Results in Extra Dimensions in the COMSOL Multiphysics Reference Manual.

When this physics interface is added, these default nodes are also added to the Model Builder — Electrolyte, Insulation, No Flux, and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, Porous Electrodes and nonporous Electrodes, and boundary conditions. You can also right-click Battery with Binary Electrolyte to select physics features from the context menu.

The Label is the default physics interface name.

The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.

The default Name (for the first physics interface in the model) is batbe.

This section contains some global settings for the electrolyte which are used in the Insertion Reaction type kinetics in the Porous Electrode Reaction node to calculate the concentration of water in the electrolyte. The default values correspond to a KOH electrolyte.

In this section, the Define cell state of charge (SOC) and initial charge inventory checkbox can be ticked, which activates the global SOC and Initial Charge Distribution node.

Convection can be added as an additional transport mechanism. By default, the checkbox Convection is not selected. Select the checkbox to enable convective transport.

To display this section, click the Show More Options button () and select the Advanced Physics Options. This section is not applicable if the Single-ion conductor option is selected in the Charge Balance Model section.

With the Use logarithm formulation for electrolyte salt concentration enabled the interface will solve for the logarithm of the electrolyte salt concentration. This option improves the numerical stability if the electrolyte salt concentration is expected to be close to zero. See Logarithm Formulation of Electrolyte Salt Concentration for more information.

The Electrolyte salt material balance form can be either Conservative or Nonconservative (the default). The differences between the two forms are in how the time derivative of the electrolyte volume fraction (porosity), εl, and the divergence of the velocity are handled. In the absence of convection, solvent mass sources and electrolyte volume fraction changes, the choice between the conservative and nonconservative form is arbitrary. For problems including convection, given that solvent concentration variations and molar solvent sources or sinks can be neglected, both the conservative and nonconservative will give equivalent results (when combined with a proper model for the solvent velocity). However, the nonconservative form is usually preferred due to a slighter lower computational load. See Electrolyte Salt Material Balance Formulation for more information.

The Physics vs. Materials Reference Electrode Potential setting on the physics interface node can be used to combine material library data for current densities and equilibrium potentials with an arbitrary reference electrode scale in the physics. The setting affects the electrode potentials used for model input into the materials node, as well as all equilibrium potential values output from the materials node.

Note that the setting will only impact how potentials are interpreted in communication between the physics and the Materials node. If the From material option is not in use for equilibrium potentials or electrode kinetics, the setting has no impact.

This section is available when the Advanced Physics Options is selected in the Show More Options dialog shown when the Show More Options button () is clicked.

To display these sections, click the Show More Options button () and select Stabilization from the Show More Options dialog. These sections are applicable only if Convection is selected in the Transport Mechanisms section. There are two consistent stabilization methods available and selected by default — Streamline diffusion and Crosswind diffusion. There is one inconsistent stabilization method, Isotropic diffusion, which is not selected by default.

This physics interface defines the dependent variables (fields) the Electrolyte potential, the Electrolyte salt concentration, and the Electric potential. The name can be changed but the names of fields and dependent variables must be unique within a model. The Intercalating species concentration in the electrode particles is another, hidden, dependent variable. This variable is solved for locally and with an independent variable for the particle radius.