TroPMelt -Dry powder melt calendering paves the way for sustainable battery production

Through the “TroPMelt” research project, Fraunhofer ISIT has been driving forward the development of a novel, solvent-free technology for the manufacture of battery electrodes since July 2023. The aim is to make production processes not only more cost-effective, but above all significantly more environmentally friendly. The technology can be used in industrial battery manufacturing and offers great potential for mobile and stationary energy storage solutions. The project thus addresses key challenges of the energy transition: resource efficiency, CO₂ reduction and competitiveness.

The project focuses on dry coating, a process that completely eliminates the use of solvents. Instead of energy-intensive drying processes, powder materials are processed directly and then compacted using a melt-calendering process. This approach not only significantly reduces energy consumption but also simplifies the entire process chain.

At the start of the project, the focus was on identifying suitable binder materials, which are crucial for dry processing and the subsequent mechanical stability of the electrodes. Building on this, various powder mixtures were developed and tested using different mixing technologies. In parallel, a comprehensive characterisation of the physico-chemical properties, such as particle size distribution, was carried out in order to draw conclusions about the processability and quality of the mixtures.

Significant progress was achieved through the iterative optimisation of mixing and coating processes. By adapting the spreading methods, it was possible to apply the powder mixtures evenly to current collector foils and specifically improve their adhesion. Analysis of the resulting electrode films provided important insights into structure-property relationships, enabling unsuitable material combinations to be ruled out at an early stage.

In parallel with material development, the processing technology has been continuously refined. In particular, the integration of a newly acquired calender into an existing coating line represented a crucial milestone. We have now succeeded in combining the individual process steps into a continuous roll-to-roll process, which is a key prerequisite for industrial-scale production. The current focus is on fine-tuning process parameters and transferring promising materials into continuous operation.

The quality of the electrodes produced was also thoroughly validated. In addition to macroscopic homogeneity, microscopic structures were analysed and mechanical and electrical properties were investigated. Of particular note are the low electrical resistance achieved and the high adhesive strength of the electrode films. In electrochemical tests, full cells demonstrated an efficiency of over 98 per cent over more than 100 charge cycles.

The project benefits significantly from close collaboration within the consortium. Together with partners such as UniverCell, Fraunhofer IFAM and AntonPaar, both materials and processes are being coordinated and further developed. This division of labour enables a holistic approach, from material development through to cell production and validation. To this end, “TroPMelt” is receiving €2.5 million in funding from the Federal Ministry for Economic Affairs and Climate Action (BMWK).

With the project set to run until mid-2026, work is now focusing on further process optimisation and the comprehensive validation of the electrodes within the continuous manufacturing process. Given the growing interest in dry coating processes in both research and industry, TroPMelt is positioning itself as a forward-looking approach. The project is thus making an important contribution to the development of sustainable, efficient and competitive battery technologies ‘Made in Germany’.