Simultaneous coating and drying for fast electrode production
Researchers at Germany’s Karlsruhe Institute of Technology (KIT) have developed 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. With the help of the concept, lithium-ion batteries can be produced more rapidly and at lower cost.
In lithium-ion batteries, electrode layers are of decisive importance, as these active materials store the energy. However, coating and subsequent drying of electrodes cause most of the battery production costs. A big cost reduction potential lies in process engineering.
Researchers from KIT’s 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, which they have published in the journal Energy Technology.
“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,” Prof Schabel said.
At usual electrode drying times of up to one minute and production speeds of 100 m/min 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 and another for specific capacity. This layer structure enables manufacture at a very high drying rate, so drying times are shortened to one-third.
In spite of the reduced drying time, no capacity losses occur and the range of the battery remains the same. The scientists also 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 customised and have better mechanical and electrochemical properties.
“Our research demonstrates that it may be possible in principle to increase battery production speed by 200–300%,” Prof Schabel said.
At the moment, the group is working on ways to transfer the simultaneous concept to the industrial scale. For this purpose, it tests purely convective drying with high-performance nozzles and laser drying modules. The results are also being transferred to other materials and used to optimise electrodes of sodium-ion batteries within Germany’s Post Lithium Storage Cluster of Excellence (POLiS).
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