Batteries & Fuel Cells Module Updates

For users of the Batteries & Fuel Cells Module, COMSOL Multiphysics® version 5.2a brings a new Reacting Flow multiphysics interface to couple fluid flow and reactions in gases and liquids and a new Single Particle Battery interface, which simplifies modeling lithium-ion and nickel-metal hydride batteries. Expanded functionality for the Lithium-Ion Battery and Battery with Binary Electrolyte interfaces includes a fast assembly option, improved solver defaults, and numerical stability for high and low SOCs. Browse all of the updates to the Batteries & Fuel Cells Module in more detail below.

New Single Particle Battery Interface

The new Single Particle Battery interface offers a simplified approach for modeling various kinds of batteries, including lithium-ion and nickel-metal hydride batteries. The governing equations, which describe the battery, are typically valid for low- and medium-current levels and may be defined either globally (resulting in a small computational load) or locally in the geometry. The local option can be used to study the effects of uneven temperature distribution in large battery packs.

The single-particle approach is computationally efficient and accurate at moderate loads. This allows for modeling complex 3D assemblies in battery packs at a relatively low computational cost, with the discharge and recharge behaviors supplied by the simple single-particle model at every point in the three-dimensional description of the battery pack.

Application Library path for an example that uses the new Single Particle Battery interface: Batteries_and_Fuel_Cells_Module/Batteries,_Lithium-Ion/li_battery_single_particle

New Reacting Flow Multiphysics Interface

To enhance the study of fluid flow and reactions in gases and liquids, the new Reacting Flow multiphysics interface combines the Single-Phase Flow and Transport of Concentrated Species interfaces. Previously available as a standalone interface, the new Reacting Flow multiphysics interface gives better control of the settings in each physics interface as well as the multiphysics coupling between them.

Using the new Reacting Flow coupling, the process of solving any of the coupled interfaces separately, or at the same time, has been significantly improved. For reacting flow, this is important in order to generate suitable initial conditions or to test how the results are affected by coupling. The Reacting Flow multiphysics interface supports both laminar and turbulent reacting flows, as well as flow and reactions in porous media.

Application Library path for an example that uses the new Reacting Flow multiphysics interface:

Chemical_Reaction_Engineering_Module/Reactors_with_Mass_and_Heat_Transfer/round_jet_burner

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New Functionality in Transport of Concentrated Species: Porous Media Transport Properties

The new Porous Media Transport Properties feature enables you to study multicomponent transport in a solution flowing through a porous medium. The new functionality includes models for computing effective transport properties that are dependent on the porosity of the material in combination with transport in concentrated mixtures.

Application Library path for an example that uses the new Porous Media Transport Properties feature in the Transport of Concentrated Species interface:

Chemical_Reaction_Engineering_Module/Reactors_with_Porous_Catalysts/carbon_deposition

The porosity distribution in a reactor for the thermal decomposition of methane on a solid Ni-Al2O3 catalyst is studied using the Porous Media Transport Properties feature. The porosity decreases as soot forms in the decomposition reaction. The porosity distribution in a reactor for the thermal decomposition of methane on a solid Ni-Al2O3 catalyst is studied using the Porous Media Transport Properties feature. The porosity decreases as soot forms in the decomposition reaction.
The porosity distribution in a reactor for the thermal decomposition of methane on a solid Ni-Al2O3 catalyst is studied using the Porous Media Transport Properties feature. The porosity decreases as soot forms in the decomposition reaction.

New Nernst-Planck-Poisson Equations Interface

The new Nernst-Planck-Poisson Equations multiphysics interface can be used to investigate charge and ion distributions within an electrochemical double layer, where charge neutrality cannot be assumed. The Nernst-Planck-Poisson Equations interface adds the Electrostatics and Transport of Diluted Species interfaces to a model, together with predefined couplings for potential and space charge density.

New External Short Boundary Condition

The new External Short boundary condition lets you short circuit Electrode Surfaces, Porous Electrodes, and Electrodes through an external lumped resistance. The new boundary condition is suitable for studying short circuiting in batteries, for instance, or for interconnecting large, electrochemically active objects in corrosion protection problems.

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New Electrochemical Heat Source Multiphysics Node

The new Electrochemical Heat Source multiphysics interface offers an optional way to couple the electrochemical heat sources with a heat transfer interface

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New Thermodynamic Equilibrium Kinetics Type

Electrode reactions now support a new Thermodynamic Equilibrium electrode kinetics type (known as Primary Condition in the Secondary Current Distribution interface), which assumes zero overpotential (negligible voltage losses).

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New Support for Film Resistance and Dissolving-Depositing Species in Porous and Edge Electrodes

The Porous Electrode and Edge Electrode nodes now support the addition of Film Resistances and Dissolving-Depositing Species. Previously, this was only supported in the Electrode Surface feature. Film resistances and dissolving-depositing species in porous electrodes can, for instance, be used to model solid-electrolyte-interphase (SEI) formation in lithium-ion batteries.

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New Fast Assembly Option in the Lithium-Ion Battery and Battery with Binary Electrolyte Interfaces

By enabling Fast assembly in particle dimension in the Porous Electrode node, the computational time for some battery models using particle intercalation is significantly reduced. The effect is most pronounced in 1D models, when the number of mesh elements in the battery elements are comparable to the number of elements in the particle dimension. However, when using this option, it is not possible to postprocess data from the solution along the particle dimension axis, and the use of varying material properties, such as the solid diffusion coefficient in the particle dimension, is not supported.

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Improved Solver Defaults in the Lithium-Ion Battery and Battery with Binary Electrolyte Interfaces

In the 2D and 3D space dimensions, the intercalating concentrations are now put into separate groups in a segregated solver. This change reduces the memory requirements for large problems as well as the computation time for your simulations.

Improved Numerical Stability for High and Low SOCs in the Lithium-Ion Battery and Battery with Binary Electrolyte Interfaces

Numerical stability when using Lithium insertion kinetics in the Porous Electrode Reaction node has been improved for SOC values close to 0% and 100%. The improved kinetics formulation is used by default for new models. In order to use the new kinetics expression in an old model, enable it in the Advanced Insertion Kinetics Expression Settings section (only shown when Advanced Physics Options is enabled).

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New Tutorial Model: Internal Short Circuit of a Lithium-Ion Battery

During an internal short circuit of a battery, the two electrode materials are internally and electronically interconnected, giving rise to high local current densities. Internal short circuits may occur in a lithium-ion battery due to, for instance, lithium dendrite formation or a compressive shock. A prolonged internal short circuit results in self discharge in combination with a local temperature increase. The latter effect is important because the electrolyte may start to decompose by exothermic reactions if the temperature reaches above a certain threshold, causing thermal runaway with potential health and safety hazards.

This tutorial model investigates the local temperature rise due to the occurrence of a penetrating metallic filament in the separator between the two porous electrode materials. The physics are set up using the Lithium-Ion Battery interface coupled to the Heat Transfer interface. The battery chemistry consists of a graphite negative electrode and an NMC positive electrode with an LiPF6 electrolyte.

Application Library path for the Internal Short Circuit of a Lithium-Ion Battery tutorial model:

Batteries_and_Fuel_Cells_Module/Batteries, Lithium-Ion/internal_short_circuit

A cross section of the temperature distribution in a lithium-ion battery around a small penetrating filament and the temperature at the surface of the filament. A cross section of the temperature distribution in a lithium-ion battery around a small penetrating filament and the temperature at the surface of the filament.
A cross section of the temperature distribution in a lithium-ion battery around a small penetrating filament and the temperature at the surface of the filament.

Updated Tutorial Model: Capacity Fade

Side reactions and degradation processes may lead to a number of undesirable effects, causing capacity loss in lithium-ion batteries. Typically, aging occurs due to multiple complex phenomena and reactions that occur simultaneously at different places in the battery, and the degradation rate varies between certain stages during a load cycle, depending on potential, local concentration, temperature, and the direction of the current. Different cell materials age differently, and the combination of different materials may result in further accelerated aging due to, for instance, “crosstalk” electrode materials.

This tutorial demonstrates how to model aging in the negative graphite electrode in a lithium-ion battery, where a parasitic solid-electrolyte-interface (SEI) forming reaction results in an irreversible loss of cycleable lithium. The model also includes the effect of increasing potential losses due to the resistance of the growing SEI film on the electrode particles, as well as the effect of a reduced electrolyte volume fraction on the electrolyte charge transport.

This tutorial model has been updated from the previous version of COMSOL Multiphysics® to include more recent aging data from scientific literature. Additionally, a timescale factor has been introduced in order to reduce the simulation time for multiple cycles.

Application Library path for the Capacity Fade tutorial model:

Batteries_and_Fuel_Cells_Module/Batteries,_Lithium-Ion/capacity_fade

Cell voltage during a 1 C discharge for a different number of aging cycles. Cell voltage during a 1 C discharge for a different number of aging cycles.
Cell voltage during a 1 C discharge for a different number of aging cycles.