How to change cathode material loading in pybamm

[Thiyaga2025]

hi all, sorry for this very basic question. I have some experience in battery modeling with commercial tools (GT-Autolion, BDS) but new to pybamm modeling. trying to build a model for cylindrical cell with parameters from Chen2020 dataset. I wanted to change the capacity loading(cathode), charge and discharge capacities of electrodes. how to do this and where to find this information in pybamm.
please help me here. thanks for your time.

[TomTranter]

You can change the capacity indirectly by changing a number of other variables that go into calculating it. electrode thickness and active material volume fraction. You have to be a bit careful when changing these though as you also have to consider porosity and don't want this + active material vf summing to more than 1. Also might want to adjust nominal cell capacity so that C-rates are calculated based on the updated capacity and also cell volume if you are changing thickness. The electrode height and length also affect the total capacity of the cell and nominal capacity but not the aerial capacity. I made a little app to help adjust things consistently and also let you balance the initial lithium concentrations and combine different half cells. It might help understand what changing things has an effect on and you can download the parameter set too. https://cellcombinator.streamlit.app/

[TomTranter]

You're right that density should probably also change as a volume averaged property of the electrode. Thickness affects the loading but is independent of the volume fractions

[Thiyaga2025]

Tom, thanks a ton the clarifications. this helps. will try and reach out for any help.

[Thiyaga2025]

@TomTranter , i was trying to understand the stoichiometries and got some idea from the relevant threads and "electrode state of health" pybamm worksheet. in this regard, can you please tell me how Q_p, Q_n and Q_Li are calculated in pybamm and in your ycombinator tool. thanks.

[TomTranter]

Have a look at the ElectrodeSOH model

[Thiyaga2025]

Thanks @TomTranter ,

Q_n = parameter_values.evaluate(param.n.Q_init)
Q_p = parameter_values.evaluate(param.p.Q_init)
Q_Li = parameter_values.evaluate(param.Q_Li_particles_init)

helped to calculate.