The combination of thick film electrodes with the three-dimensional (3D) battery concept enables increased energy densities while maintaining high power densities at the lithium-ion battery (LIB) cell level. On the one side, 3D electrode architectures allow a rapid and homogeneous wetting of the electrodes with liquid electrolyte through the implementation of tailored capillary structures. On the other side, key electrochemical properties, including high-rate capability and cell lifetime, can be significantly enhanced, particularly under operation at elevated C-rates. For instance, fast charging up to 80% state-of-charge at C-rates of up to 6C has been reported using laser structured graphite anodes, without the occurrence of lithium-plating.
Recently, a variety of electrode designs based on line and hole patterns have been reported for cathodes and anodes. However, most studies to date have focused on the structuring of one electrode, with electrochemical analyses typically carried out using a laser-structured electrode paired with an unstructured electrode in full-cell or with Li foil in half-cell configuration. Thus, the interaction between electrodes structured with different pattern types has not yet been systematically investigated. Furthermore, the laser ablation rates reported in the literature remain insufficient to match typical roll-to-roll (R2R) coating line speeds of ≥ 30 m/min. Upscaling the structuring process with advanced and industrially reliable high-power ultrashort pulse (USP) lasers is therefore essential for bringing this technology into battery production and achieving technology readiness level of at least 6.
In the present work, NMC 811 cathodes and graphite anodes were fabricated and subsequently structured with either line or hole patterns using ultrafast laser ablation. Various laser parameters such as average laser power were investigated to increase process efficiency while optimizing electrochemical performance. Meanwhile, the mass loss induced by laser structuring was taken into consideration and the N/P ratio was kept constant to enable a meaningful comparison of the impact of different patterns on the electrochemical properties. The electrodes were assembled into full-cells and characterized electrochemically, including rate capability analyses, lifetime analyses, as well as electrochemical impedance spectroscopy. Line patterning exhibited an order-of-magnitude higher processing rate compared to hole patterning. Moreover, all cells with laser structured electrodes exhibited enhanced rate performance, reduced ionic resistance, faster charging capability, and a shift in the onset of lithium plating toward higher C-rates relative to reference cells with unstructured electrodes. Besides, among the various combinations of line- and hole-structured cathodes and anodes, the best electrochemical performance was achieved when both electrodes were structured using line patterns at high average laser power.