M.A.P.L.E. Lab

A code to help you predict and understand the impedance behaviour of your battery!

Would you like to understand your battery cells better? Would you like to link your impedance data to the physical processes inside your battery? If so, this impedance simulation program (download here for half cell and here for full cell) may help you. It is ready to go on any Windows PC without software installation.

The impedance program takes a set of design variables and material properties as input and calculate the real and imaginary impedance over a range of user-specified frequencies. The result generated can be viewed as prediction of the impedance response as a result of the coupling of all the physical processes at the given frequency range. The values obtained can be used to generate the Bode plot or Nyquist plot commonly used to represent the impedance data. Detailed instruction for executing the program is given below. 

1. Download the program files from the Subramanian group’s website and unzip all the files into a single folder.

2. Modify the parameters for cell design and chemistry in the “pars.txt” file if needed. The parameters are given as a 1 by 28 array in the following order:

1. Bruggeman coefficient,
   electrolyte diffusivity (m²/s),
   solid phase diffusivity in the negative electrode (m²/s),
   solid phase diffusivity in the positive electrode (m²/s),
   electrolyte conductivity (S/m),
   particle radius of the negative electrode (m),
   particle radius of the positive electrode (m),
   temperature (K),
   electrolyte concentration (mol/m³),
   first derivative of open circuit potential versus state of charge in the negative electrode (Vm³/mol)
   first derivative of open circuit potential versus state of charge in the positive electrode (Vm³/mol)
   negative electrode filler fraction,
   positive electrode filler fraction,
   negative electrode thickness (m),
   positive electrode thickness (m),
   separator thickness (m),
   electronic conductivity of the negative electrode (S/m),
   electronic conductivity of the positive electrode (S/m),
   transference number,
   double layer capacitance outside the particles in the negative electrode (F/m²),
   double layer capacitance outside the particles in the positive electrode (F/m²),
   anodic charge transfer coefficient,
   cathodic charge transfer coefficient,
   porosity of the negative electrode,
   porosity of the positive electrode,
   porosity of the separator,
   exchange current density of the negative electrode (A/m²),
   exchange current density of the positive electrode (A/m²).
   
   
The values used in this paper are given in the txt file as an example.

 

3. Change the frequencies to the desired values in “freq.txt” (0.5mHz to 30kHz as an example, the maximum number of frequencies is 1000). Double click and run the “EIS_half.exe” program for half cell or “EIS_full.exe” program for full cell. Let the program run and no action is required while executing. These results are using 25 collocation points. To confirm that the number of node points is enough to get 6 decimal accuracy, "EIS2_half.exe" and "EIS2_full.exe" are provided as references. They provide results with 23 collocation points.

4. The real and imaginary impedance can be found in the “EIS_half.txt” file or "EIS_full.txt". The first column is the real part and the second column is for the imaginary part (in Ohm-m2). These two columns can be used to generate the Nyquist plot.

These codes given should be viewed as providing an estimate for the impedance behaviour. Other important phenomena, such as degradation mechanism, which requires more detailed models, are not included here.

**Code released with restrictions. Free for academic use but not for commercial purposes.**
**For details on restrictions please contact mananp@uw.edu or vsubram@uw.edu**