Topic 01-08 : Multiscale characterization of positive electrodes for Li-ion batteries: from ex situ to operando study

The control of the composition, stoechiometry and morphology of positive electrode materials is a crucial point to design materials showing enhanced electrochemical properties and higher mechanical stability for Li-ion batteries. It is well known that the size and shape of the particles may play a key role on the Li diffusion paths within the material, having a main effect not only on the reaction mechanism itself but also on the reversibility of the Li insertion/extraction. Such phenomena are amplified depending on the stoechiometry and morphology, because the presence of different chemical/crystallographic phases and defects could affect the electronic and ionic conductivity and limit the structural reversibility upon cycling.

To shed light on the different factors influencing the electrochemical properties, we propose a multi-scale investigation on LiNi1/2Mn3/2O4 oxides with specific composition, stoechiometry, morphology and surface modification. Tomography, micro-tomography and coherent Bragg X-ray diffraction imaging are the suitable techniques for the proposed study thanks to their spatial resolution ranging from micron to nanometric scale, and providing insights on i) the chemical composition and crystallographic structure within particles, ii) the propagation of the reaction paths along the Li insertion/extraction reaction, and iii) the mechanical stability associated to defects and coexistence of different phases.

The PhD student will spend almost 1/2 of his/her time at ICMCB/LRCS to synthesize the pristine materials and for the physico-chemical and electrochemical characterizations; he/she will stay the remaining time at SOLEIL to perform the synchrotron imaging experiments and to develop a new setup dedicated to the proposed experiments.

Contact

PhD Supervisor : Laurence Croguennec (Laurence.Croguennec@icmcb.cnrs.fr)