International audienceThe broadband dielectric spectroscopy technique is applied, for the first time, to a composite material used as an electrode for lithium battery. The electrical properties (permittivity and conductivity) are measured from low (a few Hz) to microwave (a few GHz) frequencies. The results demonstrate that the broadband dielectric spectroscopy technique is very sensitive to the different scales of the electrode architecture involved in electronic transport, from interatomic distances to macroscopic sizes, as well as to the morphology at these scales, coarse or fine distribution of the constituents. This work opens up new prospects for a more fundamental understanding and more rational optimization of the electronic transport in composite electrodes for lithium batteries and other electrochemical energy storage technologies (including other batteries, supercapacitors, low- and medium-temperature fuel cells), electrochemical sensors and conductor-insulator composite materials

For various composite electrodes with the same composition 80͑73 wt % Li 1.1 V 3 O 8 , 8 wt % CB, 19 wt % PMMA͒-20͑EC-PC͒, and made by the solvent casting technique, the cycled capacity varies between 100 and 250 mAh/g depending on the initial volatile solvent concentration. For a concentration below the optimal one, the electrode dispersion exhibits a yield stress that inhibits flow and prevents homogeneous distribution of the constituents. Above the optimal concentration, settling of the particles in the low viscosity dispersion can create a concentration gradient. Below and above the optimal solvent concentration, the electrochemical performance is degraded due to poor electronic wiring of the active material. A generalization of this work to other materials and composite electrode formulations is discussed. In particular, satisfactory prediction of settling rate has been achieved using relations derived from Stokes' law and material parameters.