Towards scaling up in the production of Silicon-rich anodes with water-based binders

Li-ion Batteries (LIBs) production presents an important gap between laboratory studies and the industrial level. This gap is considered one of the most important bottlenecks in the commercialization of new technologies and it is strictly related to the need of using and start new processes or optimization of the use of new materials on pilot lines at laboratory levels. The scale-up of the production process is strongly depending on the chemical composition of materials used of the electrodes production, the interphase between electrode and electrolyte, electrolyte composition, chemical-physical properties of the slurry, which is influenced by the final rheological properties, and finally all parameters used during the coating, calendering phases. While graphite anodes are already commercialized with water-based binders, significant efforts are still necessary for silicon-rich anodes to reach the same technology maturity. This is mainly related to the detrimental volume expansion of silicon during the charge and discharge processes, thus a deeper study about how the production process can affect this behavior is fundamental. The electrode production starts with mixing of the electrode components (active material, conductive additive, binder and solvent). The used techniques can be different in relationship on the technology used for its production: if this is performed at laboratory scale (commonly with a simple magnetic stirrer) or at industrial level with bigger slurry amount (e.g. in a planetary mixer). The use of this technology permits to increase the slurry stability, in particular for more environmental friendly water-based production, so avoiding unwanted phenomena such as aggregation and sedimentation, often due to hydrogen bonding formation between the binder’s chains. The increase of the slurry solid content can limit the sedimentation phenomena, even if it can lead to the increase of the viscosity so adding difficulties to get a well homogeneous coating of the electrode. Electrodes coating is the core step of the cells production, and it is strongly affected by the production scale: at the laboratory scale, the process is discontinuous, while, at industrial level, due to the high yield requested, the process is fully automated and continuous [3]. In particular, at the laboratory level, the main instrument chosen for the deposition is the tape casting (doctor blade), while at the industrial level the technology switches to slot die coater or others. Our research aims to better understand how innovative active materials, for instance silicon-rich materials, associated with aqueous binders perform at different TRL levels to anticipate and propose new solutions to overcome the challenges that the industry will face for electrode production.