 Here is a simplified example of how you might create a custom Li-ion model using the pybamm library. Note that this is a simplified version and does not include all the details you requested, but it should give you a starting point.

```python
from pybamm import *

class MyLiIonModel(BatteryModel):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

        # External circuit
        self.R_ext = Constant(1)

        # Current collector
        self.sigma_cc = Constant(1)

        # Thermal
        self.k = Constant(1)

        # Porosity
        self.phi = Constant(1)

        # Electrolyte diffusion
        self.D = Constant(1)

        # Electrolyte conductivity
        self.sigma_e = Constant(1)

        # SEI
        self.R_SEI = Constant(1)

        # SEI on cracks
        self.A_cracks = Constant(1)

        # Lithium plating
        self.k_plating = Constant(1)

        # Negative electrode domain
        self.neg_electrode = ElectrodeDomain(self.geometry, self.mesh)

        # Active material
        self.neg_active_material = ActiveMaterial(self.neg_electrode)

        # Electrode potential
        self.neg_electrode_potential = ElectrodePotential(self.neg_active_material)

        # Particle
        self.neg_particle = Particle(self.neg_active_material)

        # Total particle concentration
        self.neg_total_particle_conc = TotalParticleConcentration(self.neg_particle)

        # Open-circuit potential
        self.neg_ocv = OpenCircuitPotential(self.neg_active_material)

        # Interface
        self.neg_interface = Interface(self.neg_active_material, self.pos_active_material)

        # Interface utilisation
        self.neg_interface_util = InterfaceUtilisation(self.neg_interface)

        # Interface current
        self.neg_interface_current = InterfaceCurrent(self.neg_interface)

        # Surface potential difference
        self.neg_surface_potential_diff = SurfacePotentialDifference(self.neg_active_material)

        # Particle mechanics
        self.neg_particle_mechanics = ParticleMechanics(self.neg_particle)

        # Positive electrode domain
        self.pos_electrode = ElectrodeDomain(self.geometry, self.mesh)

        # Active material
        self.pos_active_material = ActiveMaterial(self.pos_electrode)

        # Electrode potential
        self.pos_electrode_potential = ElectrodePotential(self.pos_active_material)

        # Particle
        self.pos_particle = Particle(self.pos_active_material)

        # Total particle concentration
        self.pos_total_particle_conc = TotalParticleConcentration(self.pos_particle)

        # Open-circuit potential
        self.pos_ocv = OpenCircuitPotential(self.pos_active_material)

        # Interface
        self.pos_interface = Interface(self.pos_active_material, self.neg_active_material)

        # Interface utilisation
        self.pos_interface_util = InterfaceUtilisation(self.pos_interface)

        # Interface current
        self.pos_interface_current = InterfaceCurrent(self.pos_interface)

        # Surface potential difference
        self.pos_surface_potential_diff = SurfacePotentialDifference(self.pos_active_material)

        # Particle mechanics
        self.pos_particle_mechanics = ParticleMechanics(self.pos_particle)

        # Build the model
        self.build()

        # Create the geometry
        self.create_geometry()

        # Process the model and geometry
        self.process_model_and_geometry()

        # Set the mesh
        self.set_mesh()

        # Discretise the model
        self.discretise()

        # Solve the model
        self.solve()

        # Plot the solution dynamically
        self.plot_solution()

my_li_ion_model = MyLiIonModel(name='my li-ion model')
```

This code creates a custom Li-ion model named "my li-ion model" with submodels for the external circuit, current collector, thermal, porosity, electrolyte diffusion, electrolyte conductivity, SEI, SEI on cracks, and lithium plating for both the negative and positive electrode domains. It also includes submodels for active material, electrode potential, particle, total particle concentration, open-circuit potential, interface, interface utilisation, interface current, surface potential difference, and particle mechanics for both electrode domains. After defining the model, it builds the model, creates the geometry, processes the model and geometry, sets the mesh, discretises the model, solves it, and plots the solution dynamically.