Discrepancy in Cycle Life: Manufacturer specified and PyBaMM Simulated

[mlnsai]

Hi Team,

I am trying to validate manufacturer specified life cycle for LG M50 INR21700 cell with PyBaMM Simulated life cycle.

According to Datasheet:

The cycle life is 300 cycles (>= 80%) when followed the following protocol

"Cells shall be charged at constant current of 0.33C to 4.20V with end current of 1/20C.
Cells shall be discharged at constant current of 0.33C to 2.85V.
Cells are to rest 10 minutes after charge and 20 minutes after discharge at 25 ºC ± 2 ºC"

Source: https://www.batteryspace.com/prod-specs/11514.pdf

The cell must loose 20% of it's nominal capacity 5.013 Ah

From Pybamm:

I tried to subject the cell (O'kane 2022 parameter set : LGM50T cell) to same protocol:

cycle = 300
experiment = pybamm.Experiment(
[(
        "Charge at 0.33C until 4.2V",
        "Hold at 4.2V until 0.05C",
        "Rest for 10 minutes",
        "Discharge at 0.33C until 2.85V",
        "Rest for 20 minutes", 
)] * cycle,
)

But, the LLI, including electrolyte (%) I am getting is only 0.9522 % with all the default parameters after 300 cycles

Why is this difference? To get 20% fade, what are the required changes or parameter updating I need to do?
@brosaplanella @tinosulzer

Here's my complete code:

import pybamm
import numpy as np
import matplotlib.pyplot as plt
import pandas as pd
pybamm.set_logging_level("NOTICE")

option={
"SEI":"solvent-diffusion limited",
"particle mechanics": ("swelling and cracking", "swelling only"),
"particle" : "Fickian diffusion",
"SEI on cracks": "true",
"loss of active material": "stress and reaction-driven",
"thermal": "lumped",
"SEI film resistance": "distributed",
"SEI porosity change" : "true", 
"lithium plating": "reversible",
"x-average side reactions": "true"
}

model=pybamm.lithium_ion.SPMe(options=option)
param1 = pybamm.ParameterValues("OKane2022"):

tempK = 25 + 273.15
param1.update({"Ambient temperature [K]": tempK}) 
param1.update({"Initial temperature [K]": tempK})
param1.update({"Upper voltage cut-off [V]": 4.3}) 


cycle = 300
experiment = pybamm.Experiment(
[(
        "Charge at 0.33C until 4.2V",
        "Hold at 4.2V until 0.05C",
        "Rest for 10 minutes",
        "Discharge at 0.33C until 2.85V",
        "Rest for 20 minutes", 
)] * cycle,
)


solver=pybamm.CasadiSolver("safe",dt_max=200,max_step_decrease_count=20)
var_pts={"x_n": 40, "x_s":20, "x_p": 40, "r_n": 40, "r_p":40}
sim=pybamm.Simulation(model, experiment = experiment,parameter_values = param1,solver = solver,var_pts=var_pts)
solution=sim.solve(calc_esoh=False)

Note: I tried updating default parameters for accelerated fading. However I didn't get more than 3% fading in any of the cases after 500 cycles.

Lithium plating kinetic rate constant [m.s-1]
Lithium plating transfer coefficient
Dead lithium decay constant [s-1]
Outer SEI solvent diffusivity [m2.s-1]
SEI kinetic rate constant [m.s-1]