Young researcher : Operando XPS study of Li-ion batteries: electrode/electrolyte interfaces in real working conditions – M/F

Job Description

Missions

Lithium-ion batteries have enabled the development of portable electronics and electric vehicles, due to their great gravimetric and volumetric energy densities. The tremendous success of these systems and the development of new battery chemistries (all-solid-state batteries for example) and large-scale applications require ongoing improvements. Proper functioning of a classical Li-ion battery requires the formation of the Solid Electrolyte Interphase (SEI) at the surface of the graphite negative electrode to reach good performances, long lifetime and safety. More generally, it is necessary to stabilize the electrode/electrolyte interface at both the positive and negative electrodes, which could be achieved by using an electrolyte having a voltage stability window compatible with the working potentials of the two electrodes. Unfortunately, due to the great voltage difference between the two electrodes, this is never achieved, and thus the interface can be ideally stabilized by a passivation layer formed by the electrolyte degradation products (like the SEI on graphite). Alternatively, coatings can be deposited at the surface of the electrodes (or the electrolyte, in the case of an all-solid-state battery) to stabilize this interface, if a spontaneous passivation layer cannot be obtained. It is therefore of prime importance to fully understand the reactivity between materials at interfaces, and to characterize efficiently the chemical species in the interphases for an in-depth understanding of the electrochemical processes that govern the next generation battery performances. Such a major effort is intimately linked to the use of advanced characterization techniques, with operando approaches allowing to monitor the behaviour of batteries under real working conditions. This is the objective of the present OPENSTORM project, belonging to the research program PEPR Battery France 2030.
Operando cells dedicated to the study of batteries with bulk-sensitive spectroscopies and diffraction techniques were first developed more than 15 years ago, enabling the study of thin batteries. In contrast, the development of operando cells for X-ray photoemission spectroscopy (XPS) studies is still challenging owing to the difficulty of designing a cell capable of approaching the real battery conditions while using a surface sensitive probe [2,3]. Nevertheless, XPS remains one of the most widely used techniques for investigating electrode/electrolyte interfaces in batteries by the identification of chemical species. Efforts are still required to design reliable operando cells for XPS investigation, as most of battery limitations originate from electrode/electrolyte interface reactivity, and for all new generations of batteries studied today. The objective of this postdoc project is to exploit the increased probing depth offered by HAXPES (the extension of XPS at high photon energies) to develop operando cells for the investigation of buried interfaces in batteries. These new operando cells will allow us to surpass existing designs used for standard XPS spectrometers which can only probe the top surface layers. Thanks to superior probing depth of HAXPES, it will be possible to closely reproduce the conditions existing in real batteries. We aim at developing two types of operando cells, for solid/solid interfaces on one hand, and for solid/liquid interfaces on the other hand, with the goal of characterizing the interfacial chemical species formed during the electrochemical process in operando conditions. We have already realized a first, operational prototype of the solid/liquid cell (Capone et al., J. Synchrotron Rad. 2024, 31, 1505).

Activity

This research project will be conducted in close collaboration between IPREM (Institute of Analytical Sciences and Physical Chemistry for Environment and Materials, University of Pau & Pays Adour, France: https://iprem.univ-pau.fr) specialized in surface/interface analysis of batteries, which is a lab of the French Research Network on Electrochemical Storage of Energy (RS2E https://www.energie-rs2e.com/en/our-organization), and the French synchrotron SOLEIL (Paris Region) https://www.synchrotron-soleil.fr/en.
The postdoc will be based mainly in Pau, with HAXPES experiments in SOLEIL during campaigns (about three weeks per year). Two additional labs of the RS2E will participate to the elaboration of the operando cells. The postdoc will have the opportunity to participate to this design in the partner labs. He(she) will devote an important part of his(her) research work to the elaboration of the cells, their electrochemical and spectroscopic assessment, and to the study of chemical processes taking place at electrode/electrolyte interfaces in order to understand and describe mechanisms existing in batteries.
The postdoc will benefit from the following surface characterization tools:
- in SOLEIL (Galaxies beamline): Hard X-ray Photoemission Spectroscopy (HAXPES).
- in IPREM: XPS, Auger electron spectroscopy (AES), time-of-flight secondary ions mass spectrometry (ToF-SIMS). All of them are the subject of operando developments in the lab. A participation to these developments is also possible.

Your Profil

Skills

- PhD degree in chemistry/physico-chemistry of materials
- Solid knowledge in chemistry and electrochemistry of solids, and/or in physical chemistry of surfaces and interfaces.
- Proactive character, ability to analyze scientific results and to write and speak in English will be important points to select the candidate.

Your Work Environment

IPREM (Institute of Analytical Sciences and Physical Chemistry for Environment and Materials), is a Joint Research Unit CNRS/University of Pau & Pays de l'Adour, https://iprem.univ-pau.fr), located in Pau (South-West of France). The expertise of IPREM lies in the knowledge and characterization of electrode materials surfaces and electrode/electrolyte interfaces in Li-ion batteries, microbatteries, and post-Li-ion batteries: Li-Sulfur, Sodium-ion, Potassium-ion, organic batteries, all-solid-state, etc. The laboratory has a world-class experimental platform in this specialty. It is active member of the French research network on electrochemical storage of energy (RS2E) and of the European Research Institute Alistore.

Compensation and benefits

Compensation

Between 3 041.58€ et 3 359.58€ gross monthly according experience

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