Porous Electrode Reaction
The Porous Electrode Reaction node defines the electrode kinetics for a charge transfer reaction that occurs at the interface between the pore electrolyte and the electrode matrix a porous electrode. The node can be added as subnode to a Porous Electrode node. Add multiple nodes to the same Porous Electrode node to model multiple reactions, for instance in self discharge or capacity fade problems.
See the Electrode Reaction node in Shared Physics Features in the Current Distribution Interfaces for a general description of the Equilibrium Potential, Electrode Kinetics and Stoichiometric Coefficients sections.
Electrode Kinetics
The battery interfaces have some tailor-made kinetic expressions types (see also Electrode Reaction).
Lithium Insertion
The charge transfer reaction can be described by the reaction at the surface of the electrode particles with subsequent lithium intercalation. This solves the charge transfer current density in the particles in combination with the diffusion of the intercalating species (see the theory section).
The Lithium insertion option is available for the Lithium-Ion Battery interface. The expression is suitable for any positive or negative intercalation reaction. The Reference exchange current density io,ref(T) (SI unit: A/m2) depends on the electrode material in use and the temperature.
Insertion Reaction
The Insertion reaction option is available for the Battery with Binary Electrolyte interface. It can be used for both the positive and the negative electrode main reactions of a NiMH battery. The Reference exchange current density io,ref(T) (SI unit: A/m2) depends on the electrode material in use and the temperature.
Lead-Acid Battery Charge and Lead-Acid Battery Discharge
These options are available for the Lead-Acid Battery interface. The kinetic section is equal between the Lead-acid battery charge or Lead-acid battery discharge, but the Active specific surface area equations differ.
Advanced Insertion Kinetics Settings
To display this section, click the Show More Options button () and select Advanced Physics Options.
By enabling Extrapolate insertion kinetics using first order kinetics for high and low socs numerical stability can be improved for solid concentration values close to 0 or the maximum concentration. The feature is enabled by default. Use the Extrapolation soc window width to specify how close to 0 or the maximum soc the extrapolated kinetics expression should be used.
The option is available both for the Lithium Insertion and the Insertion Reaction kinetics.
Active Specific Surface Area
The Active specific surface area av (SI unit: m2/m3) specifies the area of the electrode-electrolyte interface that is catalytically active for this porous electrode reaction. av is multiplied by iloc (defined in the Electrode Kinetics section) to produce a current source in the domain.
When using a Particle-based area the particle radius is taken from the parent node if using Intercalating particles (Lithium-ion and Battery with Binary Electrolyte interfaces).
For the Lead-Acid Battery interface the active surface area can also be calculated as a function of the porosity of the electrodes, which changes during discharge and recharge as defined by the Maximum active surface area, amax (dimensions L2/L3; that is, the SI unit is 1/m) and the Morphology number (dimensionless).