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Groupe 2 - Energie : Matériaux et batteries

Le Cras Frédéric

[ - ] publié le , mis à jour le

- CEA LETI personnel

- Senior researcher

- E-mail / - phone : +33 (0)540 006 638 Room E-36 (ENSCBP)

- Current research topics : All-solid-state lithium (micro)batteries, Li-ion batteries, Synthesis and properties of thin film electrode and electrolyte materials, (electro)chemical processes at the electrode/electrolyte interface

Education and scientific position

2007 – present : Senior researcher at CEA LETI, Grenoble, France, on secondment at ICMCB since 2012. Development of all-solid-state microbatteries for micro-devices and IoT.
1997 – 2007 : Engineer/Researcher at CEA LITEN, Grenoble, France. Development of Li-ion batteries and battery materials for automotive applications.
2013 : Habilitation à diriger des recherches, Université Grenoble Alpes, France
1992 – 1996 : PhD, Laboratoire de Cristallographie (Institut Néel), Université Grenoble I, France. Supervisors : Dr. Pierre Strobel and Dr. Michel Anne
1989 – 1992 : Engineering degree, M.Sc. in Electrochemistry, Institut Polytechnique de Grenoble (ENSEEG, PHELMA), France

Research activities

The sustained demand for “smart” and connected devices in the context of the development of the Internet-of-Things and an increased healthcare monitoring has induced a need for more miniaturized power sources. A complete integration of the power source in miniaturized devices comprising generally CMOS components and MEMS sensors or actuators is indeed an asset to optimize their compactness and security. All-solid-state thin-film lithium batteries are adapted solutions to this issue since they can be manufactured with small footprints by techniques commonly used in the microelectronics industry. These cells are manufactured through a bottom-up process, by using vacuum deposition techniques to place each material layer on the top of the previous one, to form at the end a monolithic component. Finally, at least ten different thin films are synthesized, hence forming at least as many solid−solid interfaces.

In this context, my research is currently focusing on the :

  • Design and synthesis of thin film electrode materials (mainly by sputtering) and inorganic ionic conductors for all-solid-state lithium or sodium microbatteries. Due to their particular specifications, manufacturing process and design, the selection of efficient active materials can be quite different from the one of common Li-ion batteries. Thus, specific electrode materials such as LxTiOS, FeS2, (Fe, Co, Ni)S, Li1+xMn2-xO4, Fe2(MoO4)3, CuO, Si1-xGex, Li alloys thin films have been recently developed for low-voltage, solder-reflow tolerant, 0 V tolerant Li(-ion) cells, thanks to a careful study of the influence of the sputtering conditions on the structural and chemical features of the films.
  • Electrochemical and physico-chemical characterization of all-solid-state thin film batteries and materials subsets during their manufacturing process and their operation. The particular structure, thickness and/or chemical composition of thin film electrodes prepared by sputtering, combined with their almost absence of reactivity with suitable solid electrolytes, such as LiPON, allows to achieve reversible electrochemical transformations involving conversion reactions, alloying reaction or anion-based electrode processes. Then, it is possible to carry out fine studies on the influence of the cycling parameters on the electrochemical response over extended periods of time, and to study the related chemical and structural changes of the electrode materials. Solid/solid interfaces play also a crucial role in the transportation of Li+, Na+ ions and electrons in these multilayer monolithic cells. Therefore, the knowledge of their chemical and morphological features, and the evolution of latter from the assembly of the cell to its end of life, is compulsory to develop high performance devices. To do so, numerous characterization techniques are used from electrochemical/electrical techniques (Low current cycling, sweep voltammetry, impedance spectroscopy) to FIB/STEM, HR-TEM, ToF-SIMS, Auger nano-probe, Rutherford Back-scattering Spectroscopy, XPS, Raman spectroscopy, Synchrotron X-ray diffraction,…

This research also opens the way to other studies outside the strict field of microbatteries, dealing with : the characterization of the SEI formation and other processes occurring at the liquid electrolyte / electrode interface in bulk-type Li-ion batteries by using thin film model electrodes, thin film solid electrolytes as artificial SEIs on electrodes in Li-sulfur batteries, new Li, Na layered sulfides as high capacity electrodes, electrode/electrolyte interfacial processes in bulk-type all-solid-state batteries…

Scientific production and supervision

Dr Frédéric LE CRAS authored about 65 publications & 25 patents

An updated list + citation metrics can be found here : Orcid, Scopus


Selected recent papers

  1. Nanoscale chemical characterization of solid state microbattery stacks by means of Auger spectroscopy and ion-milling cross-section preparation. A. Uhart, J.-B. Ledeuil, B. Pecquenard, F. Le Cras, M. Proust, H.Martinez. ACS Appl. Mater. Interfaces, 9, 33238−33249 (2017).
  2. Dual cation and anion-based redox process in lithium titanium sulphide thin film cathodes for all-solid-state lithium-ion batteries. V. Dubois, B. Pecquenard, S. Soulé, H. Martinez, F. Le Cras. ACS Appl. Mater. Interfaces, 9, 2275-2284 (2017).
  3. Comprehensive characterization of all-solid-state Li/LiPON/LiCoO2 thin films commercial microbatteries by Electrochemical Impedance Spectroscopy. S. Larfaillou, D. Guy-Bouyssou, F. Le Cras, S. Franger. J. Power Sources, 319, 139-146 (2016).
  4. All-solid-state lithium-ion microbatteries using silicon nanofilm anodes : high performance and memory effect. F. Le Cras, B. Pecquenard, V. Dubois, V. P. Phan. Adv. Energy Mater., 5, 1501061 (2015).
  5. Perfect reversibility of the lithium insertion in FeS2 : the combined effects of all-solid-state and thin film cell configurations. V. Pelé, F. Flamary, L. Bourgeois, B. Pecquenard, F. Le Cras. Electrochem. Comm., 51, 81-84 (2015).
  6. Study of the conversion reaction mechanism into CuO by a comprehensive XPS analysis of lithiated thin film electrodes. L. Martin, H. Martinez, D. Poinot, F. Le Cras, B. Pecquenard. J. Phys. Chem. C, 117, 4421-4430 (2013).
  7. Memory effect highlighting in silicon anodes for high energy density lithium-ion batteries. M. Ulldemolins, F. Le Cras, B. Pecquenard. Electrochem. Comm., 27, 22-25 (2013).
  8. Evolution of the Si electrode/electrolyte interface in lithium batteries characterized by XPS and AFM techniques : the influence of vinylene carbonate additive. L. Martin, H. Martinez, M. Ulldemolins, B. Pecquenard, F. Le Cras. Solid State Ionics, 215, 36-44 (2012).
  9. High-performance all-solid-state cells fabricated with silicon electrode. V. P. Phan, B. Pecquenard, F. Le Cras. Adv. Function. Mater., 22, 2580-2584 (2012).
  10. Investigation on the part played by the SEI on the electrochemical performances of the silicon electrode in lithium-ion batteries. M. Ulldemolins, F. Le Cras, B. Pecquenard, V. P. Phan, L. Martin, H. Martinez. J. Power Sources, 206, 245-252 (2012).