In-situ measurement and design of the electronic conductivity at all scales of a composite electrode for lithium battery – CALICE

The development of new lithium batteries with high energy density, high power and high cyclability is targeted. To reach this long-term goal, a fundamental understanding of the so called “formulation” of the composite electrode, i.e. the relationships between its processing, its morphology at different scales, its electrical and mechanical properties and its electrochemical performance, is a prerequisite. Indeed, since IMN (coordinator of this project) provided exhaustive experimental proofs regarding the impact of the electrode formulation on electrical and electrochemical properties, a more rational and smart optimization of lithium battery performance should be expected. On these bases, the CALICE project propose, for the first time, a fundamental study dedicated to the optimization of the efficiency of electronic pathways (which is one of the two major properties of a composite electrode, the other one being the ionic counterpart) with respect to the electrochemical performance. To this end, we intend to extract the electronic conductivities of a composite electrode at all the scales of its architecture (from interatomic distances to macroscopic lengths), using broad band dielectric spectroscopy (BDS) measurements. Indeed, preliminary results of the IMN-LCMCP-LGEP-UMICORE partners demonstrate that BDS is very sensitive to the different scales of the electrode architecture involved in the electronic transport, i.e. above the MHz for, the interatomic scale (charge motion within active material (AM) and carbon (C) grains), the nanoscale (grains boundaries within AM and C clusters), the micronic scale (binder (B) boundaries between AM and C clusters), and below the MHz, for the macroscopic size (the C network and the electrode / current collector interface). Moreover, we will develop a new BDS cell to be able to achieve for the first time, in-operando BDS measurements on cycling the battery. Finally, as a possible and attractive breakthrough, we will evaluate the possibility to tailor nanoscale electronic pathways by introducing molecular junctions (MJ) in between all constituents of the electrode. After having selected the most efficient chemistries to implement MJ, engineered molecules with optimized high electron transfer (HET) ability will be synthesized by the CIMA partner in order to achieve optimized MJ. The industrial company UMICORE will bring to this project well designed active materials for practical lithium battery applications. It is a guaranty that this fundamental research will be developed with composite electrodes that integrate active materials with pertinent physical characteristics for application and therefore, that results will be fully relevant to research applied to the industrial development of lithium batteries.