PhD in Nanocharacterization with lithium tracing for Li-ion batteries (M/F)

Job Description

Thesis Subject

Thanks to their very high energy densities and their long lifetime, lithium-ion (Li-ion) batteries are one of the most promising energy storage technologies. Developing applications, such as the electric vehicle or intelligent power grids, require higher energy densities and retention of cycling capacities but also increased safety requirements.
Among the negative electrode candidate materials, silicon is one of the most attractive alternatives to graphite due to its natural abundance and its high energy density (3579 mAh.g-1 vs 372mAh.g-1 for graphite). For the past 10 years, silicon has been at the center of a growing number of studies. Previous studies have shown the continuous and uncontrolled degradation of the liquid electrolyte on the surface of silicon particles, playing a significant role in the failure mechanism and responsible the end of battery life. It appears therefore necessary to understand and control the parasitic side reactions degrading the salt and the solvents of the electrolyte as well as the composition of the passivation layer on the surface to optimize the behavior of the batteries.
The proposed PhD thesis is part of an ANR project, in collaboration with CEA-LITEN (Grenoble) and LIST (Luxembourg). During this thesis work, the dynamics of formation and evolution of passivation layers will be characterized by following the mobility and the trapping of Li ions, in the case of silicon cycled in half-cells and full cells. The impact of the pre-lithiation of silicon on the evolution of the passivation layer and electrochemical performance will then be evaluated for silicon/NMC full cells. The main objective of this thesis will be to combine different characterization techniques (MAS-NMR but also XPS, impedance measurements, microscopy and electrochemical measurements) to obtain both qualitative and quantitative information on the chemical composition and the physicochemical properties. of the passivation layer. The aim of the proposed research is to develop and use a methodology based on solid 7Li and 6Li NMR techniques and the tracing of lithium to better understand its mobility in the passivation layer / material of electrode and study its trapping through a detailed description of the phenomenon. XPS and SIMS spectroscopies as well as profilometry analyzes will be carried out on the surface of the electrodes in order to obtain additional information concerning the chemical structure of the passivation layer. In particular, high-resolution SIMS will also be challenged on the surface of samples and in cross-sections configurations (obtained by in situ FIB), in order to characterize the lithium isotopic ratio in different parts of the analyzed electrodes. This will lead to a better understanding of the failure mechanism of Si-based electrodes for lithium batteries cycled in full-cell configuration.

Your Work Environment

The research work will take place at IMN (Nantes, https://www.cnrs-imn.fr/) for 18 months then at CEA-LITEN during the second half of the thesis. Short stays at LIST are also planned. The student will be able to train and work with the following techniques: preparation and cycling of electrodes, electrochemical measurements, liquid and MAS NMR, XPS, SIMS, SEM.

Constraints and risks

The research work will take place at IMN (Nantes, https://www.cnrs-imn.fr/) for 18 months then at CEA-LITEN during the second half of the thesis.
No other identified constraints or risks

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

The research professions