Mechanical/Electrochemical couplings in Li-ion batteries with composite Si/C electrodes

The last generation of anode for lithium-ion batteries are using silicon-graphite composite materials, for storing the lithium when charged. The composite is made of active material grains, glued together with a polymer binder. Those materials have the capacity to store important quantities of lithium, but at the cost of major volumetric swelling (up to 400% for silicon), which can potentially compromise the mechanical integrity and electrochemical performance of the system, at several levels (induced stress that damage components, loss of capacity due to material damage or porosity collapse).
The subject of the PhD work will be the modelling and understanding of couplings, between material dilation, mechanical damage, and electro-chemistry, from the electrode scale to the cell level. More precisely, the student will develop a micromechanical model of the negative electrode behaviour (dilation, and porosity evolution, damage generation) based on an original experimentation fit for purpose, to generate relevant data to be fed to battery models developed at IFPEN.
For that objective, the student  will work along three strong axis : (a) Macroscopic behaviour (capacity evolution and state of charge, expansion) of model batteries, for a variety of cycling conditions. (b) Imagery on electrodes, in order to visualize mechanical evolutions in the material. Two methods are under consideration : X-ray tomography for observing the dilation and porosity evolution, FIB-SEM for detailed imaging of damage in the polymer binder. (c) Numerical modelling of the mechanical behaviour (using FEM or DEM simulation). Models are going to be generated from imagery data, and relevant information is going to be extracted to feed higher level battery models. 

Keywords: Li-ion battery, X-ray tomography, material mechanics, numerical simulation, imagery

• Academic supervisor    Dr MAIRE Eric, MATEIS (INSA Lyon/Lyon 1 University/CNRS)
• Doctoral School    EDA 034 Matériaux de Lyon
• IFPEN supervisor    Dr ESNAULT Vivien, Solid mechanics department, Vivien.esnault@ifpen.fr
• PhD location    IFP Energies Nouvelles & MATEIS, Lyon, France  
• Duration and start date    3 years, starting in fourth quarter 2021
• Employer    IFP Energies Nouvelles, Lyon, France
• Academic requirements    University Master degree in relevant disciplines (solid mechanics, material sciences…)
• Language requirements    Fluency in French or English, willingness to learn French