Fast charging of lithium-ion batteries (LIBs) is indispensable for the application of electric mobility. A high C-rate performance of LIBs is required to approach charging durations comparable to refueling times of internal combustion engine vehicles. However, the rate capability of LIBs is limited by transport mechanisms such as the ion transport in the electrolyte liquid. Especially, the graphite anode exhibits an elevated ionic resistance due to the flake-like structure of the active material, which comes along with a high tortuosity.
Implementing structures such as cylindrical and cone-like geometries into electrodes is a proven approach to decrease the ionic resistance. The rate capability of LIBs increases as a result. Because of their high precision and flexibility, lasers are a versatile tool for this structuring process. It has been shown that the accessible capacity during the discharge of a lithium-ion cell can be increased by up to 20 % via laser structuring. However, laser structuring has disadvantages such as limited process speed and active material loss. Therefore, electrode-structuring using a laser is still not implemented in continuous electrode production processes.
A method to structure lithium-ion electrodes mechanically via an embossing roller is presented. The method has a high integration potential into roll-to-roll processes enabling a low cost and high throughput production of structured electrodes. The results of optical analyses to investigate the created three-dimensional structures are shown. Both, mechanically structured and unstructured electrodes, are characterized by electrochemical impedance spectroscopy as well as rate tests. It is shown, that the rate capability of moderately loaded electrodes increases by roughly 20 %.