New Drying Process for Battery Production

Landshut University of Applied Sciences is researching and developing a new concept for the final drying of battery electrodes and separators - could save battery manufacturers time and money

Among other things, lithium batteries have the advantage of being able to be stored for a very long time due to their low level of self-discharge. However this is countered by water vapour, which, in the form of residual water in the cells, leads to rapid loss of power and premature ageing. For this reason, thorough drying and re-drying of the materials is an important step in the production of battery electrodes and separators. As part of the InTenZ (Intensive Final Drying of Components for Lithium-Ion Cells in Discontinuous Drying Ovens) research project, Landshut University of Applied Sciences hopes, in cooperation with TU Braunschweig and the Karlsruhe Institute of Technology, to design a more efficient drying process and thus make the production of batteries more cost-effective. The first project meeting took place in January at the Energy Technology Centre in Ruhstorf an der Rott.

Conventional final drying extremely costly
Conventionally, electrodes and separators are produced in roll-to-roll processes, i.e. the material for the anode and cathode is mixed into a liquid paste (slurry), which then - in a similar way to screen printing - is then applied to a copper or aluminium film. The layered films pass through ovens to dry, are then compressed using several rotating rollers (calendering) and finally rolled up into large coils (electrode coils). As, however, this process leaves residual moisture in the material, the rolls, which weigh between 30 and 125 kg, must be unrolled, re-dried and then rolled up again.

New process for effective final drying
With the new process, the partners involved in the InTenZ project aim to simplify this final step by, over a short period of time, drying the large roll in rolled up form right to the pore structure in the drying oven. “With the conventional process, final drying takes approximately five to six hours,” explains Professor Dr. Karl-Heinz Pettinger, Project Manager at Landshut University of Applied Sciences. “With the new drying concept we can achieve this in under an hour. This means enormous time savings in the production of batteries. Furthermore, it will also enable us to prevent possible film damage and impurities, which can result from the unrolling and re-rolling process.

Faster and more cost-effective production
To this end, Landshut University of Applied Sciences is developing a functional model of the new drying oven in the Energy Technology Centre in Ruhstorf, which simulates the new process in the laboratory as a test model. Using this, the project partners are examining how, through certain pressure profiles and heat inputs using pulsed IR-emitters, water molecules can quickly be extracted from the material and thus moisture gradually removed. “Our aim is, after a short time, to achieve 99.999 per cent drying,” says Pettinger. The preliminary simulation is used to understand the effect of final drying on the material being dried and to optimise the process in terms of time and energy expenditure. The project partners have until 2020. If the research project is a success, the new technology can then be developed as a prototype and be utilised in industrial applications - and battery manufacturers might soon benefit from this time and money-saving process.

About the Project
The InTenZ project, under the auspices of the VDMA’s specialist Battery Production group, will run until May 2020 and is funded by the Forschungskuratorium Maschinenbau e.V. (research association for the mechanical engineering industry). The Project Managers at Landshut University of Applied Sciences are Professor Dr. Karl-Heinz Pettinger and Professor Dr. Tim Rödiger; Landshut University of Applied Sciences has overall responsibility for managing the project. Industry meetings are organised by the team led by Professor Arno Kwade from TU Braunschweig. The project is financed by the Federal Ministry for Economic Affairs and Energy. The overall project size is around Euro 790,000.


Project partner:

TU Braunschweig
Karlsruhe Institute of Technology (KIT)
Landshut University of Applied Sciences / Energy Technology Centre

Overall Project Management:

Landshut University of Applied Sciences

Landshut University of Applied Sciences Project Manager:

Professor Dr. Karl-Heinz Pettinger, Professor Dr. Tim Rödiger

Funding - Landshut University of Applied Sciences:

Euro 265,000

Overall project size:

Euro 790,500

Financing:

Federal Ministry for Economic Affairs and Energy

Funded by:

Forschungskuratorium Maschinenbau e.V. (German Federation of Industrial Research Associations; AiF)