法国新能源和原子能委员会电子能谱学博士后职位

In order to improve Li-ion batteries (LIB) performances, many studies concerning the electrode active materials, the electrolyte, or the battery architecture, are thoroughly studied. In particular, it is necessary to understand the physical and chemical phenomena affecting the active material performances during electrochemical cycling. Two of those phenomena are overwhelming with respect to battery performance and ageing, and need to be better understood and controlled.

1. The lithiation mechanisms of an electrode in the whole volume – The influence of surface modification, electrode formulation or test conditions on Li distribution in the electrode, and on the SEI formation, needs to be studied. This will be allowed thanks to preparation tools which are implemented on the Nanocharacterization Center at Minatec Campus, in particular an in situ FIB attached to an “Ion-Tof 5” ToF-SIMS. Li distribution in a single particle, or throughout the entire electrode, needs to be determined, by using ToF-SIMS, and also Auger spectroscopy, with the help of a UHV transfer suitcase. The results will help in understanding the electrode behavior.

1. The formation of a Solid Electrolyte Interphase (SEI) at their surface, which is the result of the reactivity and degradation of the electrolyte at the surface of the electrode materials during electrochemical cycling – This interface has a critical influence on the electrode performance and durability. This is generally studied by X-Ray Photoelectron Spectroscopy (XPS). However, new etching tools dedicated to surface analysis are recently implemented on surface-dedicated instruments in order to study softer materials. Indeed, Gas Cluster Ion Source (GCIS) is well adapted to the study of polymers and organic molecules by allowing softer and more homogeneous sputtering. Coupled with ToF-SIMS and also to a brand new XPS spectrometer, suitable and complementary information should be obtained on the SEI structure, nature and localisation of organic/polymer molecules and also inorganics products, as a function of different parameters such as the active material surface nature, the state of charge, depth of discharge, or the electrolyte composition.

The offered “postdoc/fixed-term contract” position is in line with two European projects, HIC and BACCARA, both of which are devoted to the development of efficient electrode materials (anodes and cathodes) for LIB applications. Considering the projects above, the main directions for the research work will consist in 1) developing, optimizing and using the XPS/ToF-SIMS cross-analysing for the characterization of the lithiation mechanisms of electrode materials developed within the context of the projects, and 2) developing knowledge on the use of GCIS coupled with an XPS and with a ToF-SIMS spectrometer, with the aim to apply this knowledge and optimize its use for the study of SEI on different electrode materials. In a first step, simpler “model” materials will be studied as references. Real systems, typically negative electrodes based on graphite or silicon, will allow demonstrating the interest of this technique for the study of the SEI in different cases, also showing its complementarity with XPS.

This work will be achieved at the Nanocharacterization Center (PFNC) at the MINATEC Campus in Grenoble, in close collaboration with the LITEN laboratories involved in the development of innovative electrode materials and electrolytes for LIB applications, and within the collaborative mesh existing between LITEN and LETI teams working on the same instruments. The candidate should have the best knowledge of surface science and characterization, as well as strong skills in ToF-SIMS and electron spectroscopy techniques. He or she must be able to work in a collaborative manner and strengthen links between different teams that have different interests in this work: electrode behavior for the battery department, generic information for GCIB technique for LETI, SEI characterization for our team). This work should be achieved in a 2 to 3 years period (1 to 1.5 year, renewable).