GeoDict provides standard materials in the GeoDict Material Database for electrolyte, active materials, and binder and carbon black.
The following material parameters are required to add new materials for electrochemical simulations to the GeoDict Material Database:
For all materials, save the changes in the Material Database by clicking Save Database. The new material can now be used like any of the standard materials delivered with GeoDict.
Electrical Conductivity (Electrical Conductivity tab, enter the ionic conductivity of your electrolyte)
For solid electrolytes no parameters need to be entered in the Electrochemistry tab, GeoDict automatically considers the transference number for solid electrolytes.
For all active materials that should be used together with the new electrolyte, the Maximum Exchange Current Density needs to be defined.
Maximum lithium concentration (Electrochemistry tab)
Ionic Diffusivity (Electrochemistry tab)
Open-circuit potential (OCV) function curve (Electrochemistry tab)
Maximum Exchange Current Density (Electrochemistry tab): This value depends not only on the active material, but also on the electrolyte. It can be therefore defined for different electrolyte materials.
To be able to use an active material in a degradation simulation with BatteryDict-Degradation, apart from the mandatory material parameters for a charging simulation (see above), the concentration expansion coefficient and the mechanical parameters need to be defined.
The GeoDict Material Database currently provides the materials Graphite, NMC333, NMC532, NMC622, NMC811, LNO and Silicone with these parameters.
To define the parameters for another material, in the GeoDict Material Database, select the material, e.g. Graphite in the example shown here. To avoid changing the material parameters delivered with GeoDict, first create a Copy of the material. Save it with a new name in the Material Database.
If all parameters are set as described below, save the database.
For other materials of the battery cell (electrolyte, in case of solid electrolyte, binder and carbon black, current collectors and separator), mechanical parameters need to be defined as well to be able to use them in a degradation simulation.
On the Mechanical Properties tab, add the name of a new Material Law and call it e.g., Lithium Intercalation and click Add.
On the Material Law tab below, choose the Type UMAT. Two UMAT files for concentration dependent expansion are provided in the UMAT folder of your GeoDict installation. For isotropic expansion, select the file IsotropicLithiumIntercalation.f, for transversal isotropic expansion the file LithiumIntercalation.f.
On the subtab UMAT Parameters, browse to the file you want to use. Set the appropriate UMAT Type and choose the Precision desired for the computation. We recommend using double precision.
On the subtab Material Parameters, define now Young’s Modulus, Poisson Ratio and Concentration Dependent Expansion Coefficient for the isotropic case. The lithium concentration expansion coefficient is used for volume expansion during lithiation with BatteryDict-Degradation, measured e.g. by electrochemical dilatometry.
For the transverse isotropic case, with the UMAT LithiumIntercalation.f, define the Young’s modulus and the Concentration Expansion Coefficient in longitudinal and transversal direction, the transversal plane and parallel plane Poisson Ratio and the Shear modulus.
