Image made using the COMSOL Multiphysics® software.
Temperature in a battery pack.
Modeling batteries requires different levels of detail depending on the purpose of the simulations. The Battery Design Module encompasses descriptions over a large range of scales, from the detailed structures in the battery’s porous electrode to the battery pack scale including thermal management systems.
The descriptions involve physics phenomena such as transport of charged and neutral species, charge balances, chemical and electrochemical reactions, Joule heating and thermal effects due to electrochemical reactions, heat transfer, fluid flow, and other physical phenomena that are important for the understanding of a battery system.
In this example, a heterogeneous NMC (Nickel-Manganese-Cobalt) electrode structure is generated from tomography data using a Model Method. Time-dependent discharge and electrochemical impedance spectroscopy (EIS) simulations are then made on the full 3D geometry. A solid mechanics simulation is also made to study the effect of electrode expansion/contraction on the particle and binder stresses.
This example simulates the heat profile in an air-cooled cylindrical battery in 3d. The battery is placed in a matrix in a battery pack. The thermal model is coupled to a 1d-battery model that is used to generate a heat source in the active battery material.
This model demonstrates the Lithium-Ion Battery interface for studying the discharge and charge of a lithium-ion battery for a given set of material properties. The geometry is in one dimension and the model is isothermal. Battery developers can use the model to investigate the influence of various design parameters such as the choice of materials, dimensions, and the particle size distribution of the active materials, in this case carbon on the negative electrode and lithium manganese oxide (LiMn2O4) on the positive electrode. You can also benefit from simulating battery performance under different operating conditions and in different devices, for example, cell phones or laptop computers.
In a cylindrical or prismatic battery cell, the active layers, current collector metal foils and separators are wound into a “jelly roll”. Additional tabs (metal strips) are welded to the current collector foils in order to conduct the current to the exterior of the cell can. The interplay of the various dimensions of the layers and the tabs, in combination with the magnitude of the cell current, governs the temperature and current distribution in the battery cell. This tutorial models the ohmic and activation losses, and the resulting temperature distribution, in a jelly roll for a pseudo-stationary case at a constant cell current.
Thermal management of a battery pack is simulated considering two scenarios, air (natural convection) and phase change material (PCM) in the gap between the batteries. The PCM considered is a composite material of paraffin wax and graphite additive. Graphite is typically added for improving the thermal conductivity of pure paraffin wax. In this model, the temperature of the battery pack during a discharge operation is monitored. It is observed that the battery pack is maintained at a lower temperature and at a more uniform temperature with PCM cooling than with air cooling. The thermal safety of a battery pack can be improved by using PCMs.
This 2D example of a vanadium flow battery demonstrates how to couple a secondary current distribution model for an ion-exchange membrane to tertiary current distribution models for two different free electrolyte compartments of a flow battery.
In a lithium metal battery, lithium metal is deposited during charging on the negative electrode. Mass transport and ohmic effects in the electrolyte cause small protrusions on the metal surface to be subjected to accelerated growth during charging. In worst case scenarios, this leads to the formation of dendrites, internal short circuits and thermal runaway scenarios. This tutorial model explores the method of reverse pulse charging for mitigating the formation of dendrites.
