Personal web page : http://iramis.cea.fr/nimbe/Phocea/Membres/Annuaire/index.php?uid=herlin
Laboratory link : http://iramis-i.cea.fr/nimbe/ledna/
More : https://www.researchgate.net/profile/Benoit_Mathieu
Facing the energy transition, the storage of energy is a major issue. However, it appears necessary to increase the battery storage capacity and one way could be the use of silicon in addition to graphite for the negative electrode of Li-ion accumulators. The development of accumulators based on these materials is however slowed by their instability, related to the swelling of silicon during the insertion of lithium. Thus, the understanding of the phenomena occurring during the first cycles of operation appear fundamental to master the operation over the long term.
This thesis project aims to understand and model the mechanical behavior of these new silicon-graphite electrodes. It is based on 3 teams: in Saclay, we will synthesize custom materials: silicon nanoparticles, silicon / germanium alloys, core @ shell where the shell will be carbon. Commercial silicon / graphite materials will also be used as reference. The behavior of materials will be studied in Grenoble using a laboratory diffractometer allowing in-situ and operando analyzes and large instruments such as ESRF or SOLEIL. These measurements will provide information on the stress inside the silicon but also on the state of lithiation of the graphite and will allow the modeling of the electrochemistry of the insertion of the lithium in the silicon, in particular the dependence in time of the hysteresis, still poorly understood. The aim of the thesis is to build a physics-based battery model allowing: "simple" experiments of swelling measurements, electrical cell performance measurements, early-life and model cycling and modelization, to deduce the mechanical and electrochemical behavior of cells at the scale of grains and agglomerates. This, in order to predict the aging of cells in the long term, in relation with their mechanical properties.