Multiscale characterization and modeling of charge transport properties and their influence on rate performance of high energy density composites electrodes for lithium batteries – PEPITE

In opposition to most of academic research on material development, this proposal addresses the issue of electrode technology, and its relation to limitation of power and energy of Li-ion batteries, reaching only 50 % of theoretical capacity. Indeed, in commercial batteries, practical electrodes must be made thin to show acceptable power as a consequence of charge transport limitations. As a result, 50% of batteries weight and volume are non electroactive parts or materials (collectors, separators, and electrolyte). To increase the energy density and decrease the cost of the stored kWh for Li-ion batteries, it is needed to overpass charge transport limitations and design thick electrodes.

To reach this goal it is mandatory to work on composite electrode engineering in order to understand and optimize charge transport in these complex multi- and hierarchical materials. Despite decades of work, this topic is still poorly understood and efficient models of battery performance are limited.
The novelty of our approach resides in multiple measurements and simulations with the use of new advanced measuring (high field NMR, broad band EIS from mHz to GHz) and imaging (R-Ray and FIB/SEM computed tomography) techniques, and their intended feedback for simulations. Some studies of real electrodes have already been published worldwide, but most of the time with a single method (e.g. tomography). It is rare that both the electronic and the ionic conduction systems are studied with in the same project.

Our commitment in this project is to (i) allow a rigorous interpretation of the observations, and study the influence of key parameters (thickness, porosity, tortuosity, composition...), and (ii) to lever simulation with new and reliable experimental data. Our ultimate aim is providing cell level understanding based on mesoscale modeling.
We will also search to create innovative electrode architectures with significantly improved kinetics, allowing the design of much higher energy density lithium ion batteries for automotive applications. We target the design of a 10mAh/cm² positive electrode (96% active material, 25% porosity) keeping at 1C 90% of its capacity at room temperature and 80% at 0°C, to push higher energy density whilst meeting power performances of end users.

This project fills a gap in the current work-flow of knowledge within the field of Li-ion batteries:
- The fundamental approach and the new tools will bring new scientific knowledge and short term improvements to practical batteries. As the focus is on commercial materials of today, the results will then be feasible to lead to breakthroughs and fast application.
- The ambition is to provide a tool to the industrials to optimize their today and future formulations.

The consortium regroups leading labs in the field (IMN, CEMHTI, GeePs, MATEIS, ICMMO), having specific expertise on the various advanced analysis techniques proposed, accustomed to collaborate in projects, and the modelling and evaluation expertise of two industrials partners (RENAULT, AUROCK).