local variable 'j_sei' referenced before assignment

[Mykle99]

PyBaMM Version

22.3

Python Version

3.9.12

Describe the bug

Have tried all "SEI", "SEI porosity change" and "SEI film resistance" options. Documentation says "full electrode" should be used for DFN. ("x-average yields the same error, "interface" gives another error, makes sense since it is not meant for dfn)

Should I just build the model as usual and use dfn.update() instead?

submodel_options = {
    "thermal" : "lumped",
    "cell geometry" : "pouch",
    "electrolyte conductivity" : "full",
    "particle" : "Fickian diffusion", # default
    "intercalation kinetics" : "asymmetric Butler-Volmer",
    "loss of active material" : "stress and reaction-driven",
    "SEI" : "solvent-diffusion limited",
    "SEI porosity change" : "true",
    "SEI film resistance" : "distributed", # default
    "particle mechanics" : "swelling and cracking",
    "lithium plating" : "irreversible"
}

dfn = pybamm.lithium_ion.DFN(options = submodel_options, build = False)
dfn.submodels["sei"] = pybamm.sei.SEIGrowth(dfn.param, "full electrode")

dfn.build_model()

UnboundLocalError                         Traceback (most recent call last)
Input In [55], in <cell line: 22>()
     19 dfn.submodels["sei"] = pybamm.sei.SEIGrowth(dfn.param, "full electrode")
     21 # finish by building model
---> 22 dfn.build_model()

File ~\AppData\Local\Programs\Python\Python39\lib\site-packages\pybamm\models\full_battery_models\base_battery_model.py:850, in BaseBatteryModel.build_model(self)
    847 if self._built_fundamental_and_external is False:
    848     self.build_fundamental_and_external()
--> 850 self.build_coupled_variables()
    852 self.build_model_equations()
    854 pybamm.logger.debug("Setting voltage variables ({})".format(self.name))

File ~\AppData\Local\Programs\Python\Python39\lib\site-packages\pybamm\models\full_battery_models\base_battery_model.py:777, in BaseBatteryModel.build_coupled_variables(self)
    770 pybamm.logger.debug(
    771     "Getting coupled variables for {} submodel ({})".format(
    772         submodel_name, self.name
    773     )
    774 )
    775 try:
    776     self.variables.update(
--> 777         submodel.get_coupled_variables(self.variables)
    778     )
    779     submodels.remove(submodel_name)
    780 except KeyError as key:

File ~\AppData\Local\Programs\Python\Python39\lib\site-packages\pybamm\models\submodels\interface\sei\sei_growth.py:140, in SEIGrowth.get_coupled_variables(self, variables)
    137 else:
    138     alpha = 0.5
--> 140 j_inner = alpha * j_sei
    141 j_outer = (1 - alpha) * j_sei
    143 variables.update(self._get_standard_reaction_variables(j_inner, j_outer))

UnboundLocalError: local variable 'j_sei' referenced before assignment

[valentinsulzer]

You need to do

dfn.submodels["sei"] = pybamm.sei.SEIGrowth(dfn.param, "full electrode", dfn.options)

What are you trying to do here?

[valentinsulzer]

The reason I ask is because this code:

dfn = pybamm.lithium_ion.DFN(options = submodel_options, build = False)
dfn.submodels["sei"] = pybamm.sei.SEIGrowth(dfn.param, "full electrode", dfn.options)
dfn.build_model()

gives the same behavior as this code

dfn = pybamm.lithium_ion.DFN(options = submodel_options)

So I assume you're preparing your own SEI submodel or something?

[Mykle99]

Thanks for the explanation :) I am just looking through all the functionality of PyBaMM atm. Do you have any good examples as to when options (in dfn = pybamm.lithium_ion.DFN(options = submodel_options)) can/should not be used and submodels have to be added/swapped with something like this dfn.submodels["sei"] = pybamm.sei.SEIGrowth(dfn.param, "full electrode", dfn.options) instead? Is it just for when you are defining your own custom submodels (which do not exist as options)? And for when you are building a model from the pybamm.lithium_ion.BaseModel()? Which option changes electrolyte diffusion <pybamm.models.submodels.electrolyte_diffusion.full_diffusion.Full object at 0x0000027CF5007070> and negative (& positive) electrode potential <pybamm.models.submodels.electrode.ohm.full_ohm.Full object at 0x0000027CF6537AC0>?

[valentinsulzer]

Is it just for when you are defining your own custom submodels (which do not exist as options)?

Yes

Which option changes electrolyte diffusion <pybamm.models.submodels.electrolyte_diffusion.full_diffusion.Full object at 0x0000027CF5007070> and negative (& positive) electrode potential <pybamm.models.submodels.electrode.ohm.full_ohm.Full object at 0x0000027CF6537AC0>?

There are no options to change those, since there are no other submodels for those

[Mykle99]

Thank you for all your answers, very much appreciated!👍

[valentinsulzer]

Converted to discussion