In order to meet the challenge of a transition from fossil fuels to green energies, the rapid development of technology is crucial. A characteristic of energy produced from renewable sources is to be discontinuous in time (e. g. photovoltaic or wind turbines). So, as a result of the development of this kind of systems, it is really important to establish a reliable electric energy storage grid. Nowadays, advanced devices that convert and store energy are the focus of intensive attentions and lithium-ion batteries hold the promise of effective solution for a clean electric future.

Nevertheless, the needs to improve performances and reduce costs of Li-ion batteries encourage different research strategies. Among them, an increase in the basis weight of the electrodes active material allows to improve the energy density and to reduce the costs associated with the electrochemical inactive materials (current collectors and separator). The maximum loading achievable by the current industrial reference process, the coating, is limited by the migration of the binder during solvent evaporation phase. Thus, an innovative and effective process, the filtration, is here proposed for the production of ultra-thick electrodes (> 20 mAh / cm² or > 50 mg / cm²). In particular, this research is focused on the adaptation of filtration with the aim to obtain Li-ion battery electrodes and on the development of a pseudo 3D current collector. This innovative current collector is suitable for the filtration process, participates in the transversal electrical conductivity and improves the adhesion of the active layer. The active materials used in this research are commercial LiNiMnCo (NMC) for the cathode and graphite for the anode.

The mechanical properties of ultra-thick electrodes are, of course, critical and will be discussed. Moreover, the remarkable mechanical stability along with the improved adhesion of active material layer with the metallic current collector allows electrodes to be pressed and to attain low porosity, resulting in improved energy density and increased electrical conductivity due to a better contact between particles. The electrochemical performances of electrodes based on NMC/graphite and of a full cells composed of these ultra-thick electrodes will be presented.

These ultra-thick electrodes feature a volumetric energy density greater than the state of art Li-ion electrodes, making them particularly suitable for stock energy produced from renewable and natural sources, giving the possibility to increase the capacity of future electricity grid.

Fig. 1: Ambient temperature galvanostatic cycling behavior of a NMC/graphite ultra-thick cell at different C-rate. Inset shows typical potential vs. specific capacity profile.