Problems encountered when the output variable is discharge capacity

[wjh346]

Hi,I encountered a problem when simulating liionpack. When I used the discharge capacity as the output variable, the following error occurred. I would be very grateful if you could answer my question!

import pybamm
import liionpack as lp
import numpy as np
import matplotlib.pyplot as plt

I_mag = 30.0
OCV_init = 4.0 # used for intial guess
Ri_init = 5e-2 # used for intial guess
R_busbar = 1.5e-3
R_connection = 1e-2
Np = 4
Ns = 1
Nbatt = Np * Ns
netlist = lp.setup_circuit(Np=Np, Ns=Ns, Rb=R_busbar, Rc=R_connection, Ri=Ri_init, V=OCV_init, I=I_mag)
cycle_number = 100
experiment = pybamm.Experiment(
["Charge at 15 A for 10 minutes", "Rest for 10 minutes", "Discharge at 15 A for 10 minutes", "Rest for 10 minutes"]*100,
period="30 seconds",)

parameter_values = pybamm.ParameterValues("Chen2020")
output_variables = [
'Discharge capacity [A.h]',
'Total capacity lost to side reactions [A.h]',
'Total lithium capacity [A.h]',
'Voltage [V]',
'Resistance [Ohm]',
'Loss of capacity to negative SEI [A.h]',
'Loss of capacity to positive SEI [A.h]',
]
def SEI_degradation(parameter_values=None):
"""
Create a PyBaMM simulation set up for integration with liionpack

Args:
    parameter_values (pybamm.ParameterValues):
        The default is None.

Returns:
    pybamm.Simulation:
        A simulation that can be solved individually or passed into the
        liionpack solve method

"""
# Create the pybamm model
model = pybamm.lithium_ion.SPM(
    options={
        "SEI": "ec reaction limited",
        "SEI film resistance": "distributed",
        "SEI porosity change": "true",
    }
)

# Add events to the model
model = lp.add_events_to_model(model)

# Set up parameter values
if parameter_values is None:
    parameter_values = pybamm.ParameterValues("Chen2020")

# Set up solver and simulation
solver = pybamm.CasadiSolver(mode="safe")
sim = pybamm.Simulation(
    model=model,
    parameter_values=parameter_values,
    solver=solver,
)

return sim

parameter_values.update({"EC initial concentration in electrolyte [mol.m-3]": "[input]"})
EC_conc=np.array([4000.0, 3500.0, 3000.0, 2500.0])
inputs = {"EC initial concentration in electrolyte [mol.m-3]": EC_conc}
output = lp.solve(
netlist=netlist,
parameter_values=parameter_values,
experiment=experiment,
sim_func=SEI_degradation,
output_variables=output_variables,
initial_soc=0.5,
inputs=inputs,
)
lp.plot_output(output)
lp.show_plots()

NotImplementedError: <class 'pybamm.expression_tree.unary_operators.ExplicitTimeIntegral'> does not implement _unary_evaluate.