In Li-ion batteries, ion diffusion kinetics represents a limitation to combine high power and high energy. To bypass this limitation, textured electrodes have been demonstrated to increase the active surface, decrease the ion tortuosity and accelerate the electrolyte wetting. Amongst the structuring technologies, ultrashort pulse laser processing may represent the key option enabling at the same time high precision, negligible material deterioration and high throughput.
Here we report a study on laser structuring of electrodes (NMC and graphite) with both holes and grooves reaching the metallic collector. Electrochemical models emphasize the importance of holes and lines dimensions on the performances of the cell. Thus, the impact of the main process parameters (fluence, repetition rate, pulses overlapping) on the topography of the laser generated surface features has been investigated jointly with the strategies required to sensibly reduce the takt-time. We demonstrate that we can control the hole and line width by adjusting the applied fluence. In addition, results show that it is possible to drill 65 µm deep and ~15 µm wide holes in nearly 100 µs resulting in up to 10,000 holes/s. For the grooving, we obtained the same width with a takt-time of 2 s/m. Moreover, we show how to reduce more the takt-time by using the burst technology. Effects of average power and burst length (number of pulses per burst) have been studied. We show that it exists a power threshold beyond which the process in burst regime becomes faster than in a single pulse. Above 2 W, the process time decreases by increasing the burst length and can be reduced by a factor up to 4. In addition, we show experimentally that the process time can be shorter than expected considering the number of pulses in the bursts. Therefore, the burst mode appears as a promising method for high-rate electrode structuring.