The sustainable raw materials supply chain has been investigated and is now used for sourcing battery materials needed within the project to reduce the overall carbon footprint to a minimum, as the life cycle assessment of the state-of-the-art battery cell has proven that the raw materials are among the main contributor to the overall carbon footprint. A first version of a digital battery data space is ready and will be updated throughout the project cycle life with data from the life cycle assessment, that has started with state-of-the-art processes and materials, as well as real production energy consumption and electrochemical data of the final battery cell.
For the machine-learning supported methodology to derive manufacturing process parameters from targeted cell properties, parameters and potentially correlated output parameters have been investigated. Therefore, the individual production steps and machine parameters have been analysed at each stage of the manufacturing, including mixing, coating, drying, and calendaring. Within the context of these research activities based on machine learning, optimizing the battery formation process is also part of the scope of BatWoMan. For that purpose, comprehensive statistical analyses have been conducted to discern correlations between protocol parameters and performance, these analyses revealed crucial insights into the factors influencing formation protocol.
Abovementioned models are fed into a digital twin, which is constructed as a comprehensive digital representation of the electrode manufacturing and cell assembly process.
Within the work package for sustainable electrode manufacturing, particularly in the first year, the activity was focused on developing the baseline aqueous formulations for NMC622 cathodes and graphite anodes with as high as possible solid content at lab-scale. That means for the graphite anodes, where water-based processing is already state-of-the-art, increasing the solid content to a maximum to reduce the energy-intensive drying needs for electrode manufacturing. In the first reporting period, within BatWoMan we have successfully optimized the solids content of the graphite anode system for the conventional electrode coating process and worked on process development and parameter adjustment for extruder-processed anodes.
For water-based cathode manufacturing, where conventionally a toxic organic solvent is used for processing, the recipe development was the first step prior to upscaling and solid content increase. At the current state, the materials employed such as binders and additives as well as the composition of the NMC622 cathode have been varied and tested in different combinations to find the most suitable and performing one to achieve the project goals. For any modification in the formulation of the electrodes, the characterisation and consequent electrochemical testing were carried out to verify the validity of the change.
Both recipes, for water-based anode and cathode, have been successfully transferred to the research pilot lines and are to be further varied towards increasing the solid content in such way, that the drying unit can be attached to the compacter, as it has been already successfully designed within the project. Trials with attaching the slot-die head directly to this newly developed unit are currently ongoing. The produced electrodes from all trials at pilot scale will be used for the upcoming cell assembly activities at pouch cell level.
For introducing three-dimensional structures for enhanced wetting and current capability of the electrodes, the aqueously processed anodes and cathodes have been successfully laser-structured. Groove structures from electrode surface down to the current collector were generated without affecting the current collector. This was made possible with variation of laser parameters such as power, scanning speed and laser passes. With the aid of electrochemical modelling, the most promising structures will be further implemented in pouch cells to determine the electrochemical performance and improved electrolyte filling process. Besides the electrodes, also different types of separators have been structured and compared regarding their cycle life and capacity retention to choose the right materials to continue the BatWoMan activities.
Increasing the energy-efficiency as one of the main goals of BatWoMan means especially taking care of the drying processes, being among the main contributor to the energy needed for cell manufacturing. For that purpose, within the first project months, we have developed a drying model for electrode drying during manufacturing, that can be applied for optimizing the coating line drying settings depending on the needs. The formation process, being among the most crucial steps for battery cell production, especially considering their long duration and influence on the overall life time of the battery. Different formation procedures have been tested at coin and pouch cell level, with the focus on reducing the time and consequently costs.
For the industrialization part of the project, even though the activities have not officially started yet, some initial work was performed to determine critical parameters of cell assembly & finishing process. The target is to identify the most suitable technological solutions to measure and monitor the critical quality parameters of the cell assembly and finishing process.
