Researchers at the Karlsruhe Institute of Technology (KIT) have developed and successfully tested an innovative concept for simultaneous coating and drying of two-layered electrodes. Drying times can be reduced to less than 20 seconds, which corresponds to half down to one-third of the usual production time, without capacity losses of the battery.

With the help of this concept, lithium-ion batteries could be produced more rapidly and at lower cost. The results are reported in an open-access paper in the journal Energy Technology.

KIT Scanning electron microscopy of a multi-layered electrode cross section: Different active materials are used for the layers and applied simultaneously. (Figure: Joyce Schmatz, MaP - Microstructures and Pores GmbH, and Jana Kumberg, KIT)

In lithium-ion batteries, the coating and subsequent drying of electrodes cause most of the battery production costs. A big cost reduction potential thus lies in process engineering. Researchers of the Thin Film Technology (TFT) Group headed by Professor Wilhelm Schabel and Dr. Philip Scharfer have been conducting research in this area for years now. They already succeeded in considerably increasing coating speed and developed an innovative drying process. Now, the group has combined coating and drying in a simultaneous concept.

TFT develops technologies for electrode production within CELEST—Center for Electrochemical Energy Storage Ulm & Karlsruhe—one of the biggest battery research platforms worldwide.

Our work shows that in principle, we manage all process steps needed to produce batteries more rapidly and, hence, at lower cost in future without affecting quality.

—Professor Wilhelm Schabel

At usual electrode drying times of up to one minute and production speeds of one hundred meters per minute and more, long drying lines are needed. In case of electrodes with a high coating weight, this is hardly feasible and very expensive. The new concept is based on the idea of using different active materials for the layers and applying them simultaneously. One layer is responsible for adhesion, another for specific capacity. This layer structure enables manufacture at a very high drying rate, with drying times shortened to one-third.

In spite of the reduced drying time, no capacity losses occur. The range of the battery remains the same, even with 3C cycles (rapid charging times of twenty minutes).

Capcities of slowly dried single layer (Einzellage) and rapidly dried multilayer (Doppellage) electrodes at different rates. The rapidly dried single layer exhibits considerable losses at 2C and 3C. (Figure: Jana Kumberg, KIT)

Within their study, the scientists applied different active materials over the thickness of the anode, as a result of which different properties were distributed specifically in the electrode layers. In this way, electrodes can be customized and have better mechanical and electrochemical properties.

At the moment, the group is working on ways to transfer the simultaneous concept to the industrial scale. For this purpose, it is testing purely convective drying with high-performance nozzles and laser drying modules.

Studies are funded with more than €5 million by the German Federal Ministry of Education and Research (BMBF) within different research cluster projects. The results are now being transferred to other materials and used to optimize sodium-ion battery electrodes within the POLiS – Post Lithium Storage Cluster of Excellence.

Resources

• Jana Kumberg, Werner Bauer, Joyce Schmatz, Ralf Diehm, Max Tönsmann, Marcus Müller, Kevin Ly, Philip Scharfer, and Wilhelm Schabel (2021) “Reduced Drying Time of Anodes for Lithium-Ion Batteries through Simultaneous Multilayer Coating.” Energy Technology doi: 10.1002/ente.202100367