To meet future customer demands for lithium-ion batteries (LIBs), it is necessary to increase their power density without sacrificing energy density. However, thicker electrodes, as necessary to reach this target, come with disadvantages such as limited Li-ion transport in the porous electrode structure.1 These limitations not only reduce the power capabilities of LIBs, but also cause safety-related problems. For instance, during charging of graphite-based anodes, the potential may drop below the Li+/Li0 equilibrium potential, leading to lithium deposition.2
To enhance lithium-ion mobility in porous electrodes, particularly anodes, laser structuring is a versatile and useful technology. Introducing pits in the electrode surface reduces the tortuosity of the anode, facilitating more efficient lithium-ion transport, which improves charge performance and mitigates lithium deposition.3–5 Today, most studies focus on investigating laser-structured anodes on a laboratory scale, without considering their transfer into industry-relevant cell formats.3–7 Furthermore, they often only examine the charging behavior of such structured anodes without further analysis of its behavior during discharge.3, 7, 8

In this work, we therefore present a full investigation of laser-structured anodes, beginning with systematic considerations of the structuring pattern involving pit dimensions, initial characterization in coin cells, and arriving at a successful implementation in 3.4 Ah 21700-type cylindrical cells. The influence of the structured anode on both the charging behavior and the discharging behavior is investigated.
Systematic considerations of the structuring pattern and pit dimensions were made to achieve low tortuosities, whereby laser parameters required for this purpose were successfully determined. The anode structuring resulted in a significant reduction in electrode tortuosity, as demonstrated by initial tests in symmetrical coin cells. Additionally, half-cell studies showed no damage to the active material due to the structuring process. The anode’s low tortuosity enhances both charging and discharging performance, as demonstrated in bi-layer pouch cells. The cells with the structured anode exhibit good long-term stability, despite the very low N/P ratio. The effectiveness of the anode-structuring concept is further showcased by its successful implementation in an industry-relevant 21700 cylindrical cell format. The 3.4 Ah cylindrical cells containing the structured anode demonstrated a significant improvement in charging performance compared to the unstructured reference. Specifically, they showed a 42% increase in CC charging capacity at 20 A, and, as evidenced by the post-mortem analysis, showed no lithium deposition after the charge C-rate test, unlike the unstructured anode. Additionally, the structured anode improved the cell discharge performance by 21% at 30 A and 11% at 35 A and resulted in a lower temperature rise at high discharge rates. The long-term cycling stability measurements showed comparable cell stability to the unstructured reference.

References
1. M. Weiss, R. Ruess, J. Kasnatscheew, Y. Levartovsky, N. R. Levy, P. Minnmann, L. Stolz, T. Waldmann, M. Wohlfahrt‐Mehrens, D. Aurbach, M. Winter, Y. Ein‐Eli and J. Janek, Adv. Energy Mater., 11(33), 2101126 (2021).
2. A. Tomaszewska, Z. Chu, X. Feng, S. O’Kane, X. Liu, J. Chen, C. Ji, E. Endler, R. Li, L. Liu, Y. Li, S. Zheng, S. Vetterlein, M. Gao, J. Du, M. Parkes, M. Ouyang, M. Marinescu, G. Offer and B. Wu, eTransportation, 1, 100011 (2019).
3. R. Dubey, M.-D. Zwahlen, Y. Shynkarenko, S. Yakunin, A. Fuerst, M. V. Kovalenko and K. V. Kravchyk, Batteries & Supercaps, 4(3), 464–468 (2021).
4. J. B. Habedank, J. Kriegler and M. F. Zaeh, J. Electrochem. Soc., 166(16), A3940-A3949 (2019).
5. L. Hille, H.-C. Toepper, C. Schriever, J. Kriegler, J. Keilhofer, M. P. Noecker and M. F. Zaeh, J. Electrochem. Soc., 169(6), 60518 (2022).
6. J. B. Habedank, J. Endres, P. Schmitz, M. F. Zaeh and H. P. Huber, Journal of Laser Applications, 30(3) (2018).
7. M.-J. Kleefoot, S. Enderle, J. Sandherr, M. Bolsinger, T. Maischik, N. Simon, J. Martan, S. Ruck, V. Knoblauch and H. Riegel, Int J Adv Manuf Technol, 118(5-6), 1987–1997 (2022).
8. K.-H. Chen, M. J. Namkoong, V. Goel, C. Yang, S. Kazemiabnavi, S. M. Mortuza, E. Kazyak, J. Mazumder, K. Thornton, J. Sakamoto and N. P. Dasgupta, Journal of Power Sources, 471, 228475 (2020).