Conductive and inductive drying processes for Li-ion electrode production towards higher throughput

Summary:

Aiming an efficient lithium-ion battery production all process steps have to be enhanced in terms of quality and performance. In this regard, the drying process of electrodes holds great potential for improvement. The main challenge of state-of-the-art convective drying methods is the negative impact of high drying rates on electrode properties for example, a destruction in cycle stability, due to binder and carbon black segregation. Therefore, conventional drying processes are limited to a certain drying rate, which limits the overall battery production speed. In order to decrease production costs by increasing the electrode drying speed without impairing the performance of the battery, the development of innovative drying methods is necessary.

This study focuses on the development and prototypical implementation of two new methods for drying electrodes through inductive and conductive heat input. By the means of induction, the conductive material of the coated current collector can be heated specifically using electromagnetic waves. This way, the coating is dried from the bottom up. Furthermore, induction allows the generation of complex heating zones with individual heat distributions, for example to prevent the formation of tensions inside the active material. With conductive drying the energy input – as with inductive drying – is carried out directly into the substrate by a current. Therefore, both methods enable the effective drying of the coating through the direct and targeted energy input into the metallic substrate. This in turn leads to a significant reduction of heating time and accordingly allows a significant energy saving compared to conventional convective methods respectively.

Within this study an electrically save test stand for the conductive drying of electrodes is being developed and built. Conductive drying experiments were carried out on freshly coated high-capacity SMG-A5 anodes at different current strengths and drying times. An infrared thermal imaging camera was used to determine the heat distribution of the coating during the drying process. Furthermore, the influence of the drying process on the mechanical and electrical properties of the film is investigated. A concept for the inductive drying of electrodes is further investigated.