The Battery and Electrochemistry Simulation Tool (BEST) is our software environment for the physics-based three-dimensional simulation of lithium-ion batteries.
»Physics-based« means that the cell behavior is not described by an adapted, phenomenological, but by a physical partial differential equation model which describes the charge, ion and energy transport in the cell. This is based on only one set of material parameters which can be determined experimentally.
Apart from the material parameters, their geometrical parameters are also relevant for the behavior of a battery cell. This is a multiscale problem because both the microstructure of the electrodes (eg particle sizes and arrangement) as well as the macroscopic dimensions (eg layer thickness or extent) are influencing.
For both levels, BEST offers the best solution with its BESTmicro and BESTmeso modules. In both cases the battery behavior is calculated fully three-dimensionally in order to be able to reproduce the geometrical factors as accurately as possible.
BEST not only calculates the time curve of the cell voltage for a given (de-) charging current. It is also possible to consider more complex time-dependent loads and CC / CV phases and to examine the behavior of the virtual cell. The calculated time and space varying ion and potential distribution allows a detailed study of the observed effects. By combining with thermal or mechanical effects or by calculating the Li-Plating risk, BEST also provides a solid basis for aging calculations.
Simulations that account for the three dimensional microstructure of electrodes are very expensive because of the fine spatial discretization required. BESTmicro can sometimes take several days of computing time on common work stations. In many standard cases, the recently developed BESTmicroFFT software-module provides the remedy. Similar to ITWM’s mechanical solver FeelMath, the new solver is also based on a Fourier method (FFT) and requires significantly less computing and storage effort for simulations. The user can now decide between the two micro-solvers depending on the current requirements.
Fraunhofer Institute for Industrial Mathematics ITWM
