Targeting new ways for large-scale, high-speed surface functionalization using direct laser interference patterning in a roll-to-roll process

Abstract

Direct Laser Interference Patterning (DLIP) is used to texture current collector foils in a roll-to-roll process using a high-power picosecond pulsed laser system operating at either fundamental wavelength of 1064 nm or 2nd harmonic of 532 nm. The raw beam having a diameter of 3 mm @ 1/e² is shaped into an elongated top-hat intensity profile using a diffractive so-called FBS®-L element and cylindrical telescopes. The shaped beam is split into its diffraction orders, where the two first orders are parallelized and guided into a galvanometer scanner. The deflected beams inside the scan head are recombined with an F-theta objective on the working position generating the interference pattern. The DLIP spot has a line-like interference pattern with about 15 µm spatial period. Laser fluences of up to 8 J/cm² were achieved using a maximum pulse energy of 0.6 mJ. Furthermore, an in-house built roll-to-roll machine was developed. Using this setup, aluminium and copper foil of 20 µm and 9 µm thickness, respectively, could be processed. Subsequently to current collector structuring coating of composite electrode material took place. In case of lithium nickel manganese cobalt oxide (NMC 622) cathode deposited onto textured aluminum current collector, an increased specific discharge capacity could be achieved at a C-rate of 1C.For the silicon/graphite anode material deposited onto textured copper current collector, an improved rate capability at all C-rates between C/10 and 5C was achieved. The rate capability was increased up to 100 % compared to reference material. At C-rates between C/2 and 2C, the specific discharge capacity was increased to 200 mAh/g, while the reference electrodes with untextured current collector foils provided a specific discharge capacity of 100 mAh/g, showing the potential of the DLIP technology for cost-effective production of battery cells with increased cycle lifetime.

Optimizing Fast Charging and Wetting in Lithium-Ion Batteries with Optimal Microstructure Patterns Identified by Genetic Algorithm

“…12 Chen et al, also demonstrated this new manufacturing technique for industrially relevant cell format (>2 Ah pouch cells). 13 Direct laser interference patterning 14 and laser in hollow cylinders 15 have been also demonstrated in a roll-to-roll system, respectively, with web speed of 1.3 m min −1 with a web width of 150 mm and 2.6 m min −1 with a web width of 120 mm. Additionally, laser ablation offers relative fine control of the channel geometry, which is essential to maintain manufacturing uniformity.…”

Functional microfluidics: theory, microfabrication, and applications

“…Among which, polymers, including PDMS [102,126,[138][139][140][141], PMMA [14,128,[142][143][144][145], epoxy resins [15], hydrogels [110,146,147], etc [19], are increasingly used for microfluidic devices because of their merits of low cost and outstanding formability [126]. PDMS is one of the most widely used materials for microfluidic devices [126] with the merits of high elasticity, low viscosity variation with temperature, water resistance, 10 µm [41,122,132] Photosensitive resin [41], Negative Hydrogel [133] Two-photon polymerization (TPP) 50 nm [119,123] Photoresist [123], Negative Sol-gel [119] small surface tension, weather resistance, high shear resistance, low cost, well-operated mold, excellent clarity, natural hydrophobicity, biological compatibility [111], and electrical insulation [102]. Thus, various microfluidic devices made of PDMS have been well developed, including topologically complex 3D microfluidic devices [138], hydrophilic PDMS devices treated with oxygen plasma [139], glass coated PDMS microfluidic channels for generating emulsion [140], microfluidic devices with electronic components [141], and so on.…”