53. Superhydrophobic Surface by Laser Ablation of PDMS  

Anustup Chakraborty, Narayana R. Gottumukkala, and Mool C. Gupta* 

Mool C. Gupta − Charles L. Brown Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904, United States

Anustup Chakraborty − Charles L. Brown Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904, United States

Narayana R. Gottumukkala − Charles L. Brown Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904, United States

Superhydrophobic surfaces have important applications in generating anti-icing properties, preventing corrosion, producing anti-biofouling characteristics, and microfluidic devices. One of the most commonly used materials to make superhydrophobic surfaces is poly(dimethylsiloxane) (PDMS). Various techniques, including spin-coating, dip-coating, spray coating, surface etching, and laser-textured mold methods, have been used to make superhydrophobic surfaces. However, all these methods require several steps, the usage of multiple chemicals, and/or surface modifications. In this paper, a one-step, low-cost method to induce superhydrophobicity is described. This was done by the pulsed laser deposition of laser-ablated PDMS micro/ nanoparticles, and the method applies to a variety of surfaces. This technique has been demonstrated on three important classes of material-glass, poly(methyl methacrylate) (PMMA), and aluminum. Water contact angles of greater than 150° and roll-off angles of less than 3° were obtained. Optical transmission value of as high as 90% was obtained on glass or PMMA coated with laser-ablated PDMS micro/nanoparticles. Furthermore, this method can also be used to make micron-scale patterned superhydrophobic PDMS surfaces. This would have potential applications in microfluidic microchannels and other optical devices. 

52. Rapid fabrication of microfluidic PDMS devices from reusable PDMS molds using laser ablation  

Ziya Isiksacan 1, M Tahsin Guler 2, Berkan Aydogdu 1, Ismail Bilican 2,3 and Caglar Elbuken 1 

1 UNAM—National Nanotechnology Research Center, Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey

2 Department of Physics, Kirikkale University, 71450 Kirikkale, Turkey

3 Science and Technology Application and Research Center, Aksaray University, 68100 Aksaray, Turkey

The conventional fabrication methods for microfluidic devices require cleanroom processes that are costly and time-consuming. We present a novel, facile, and low-cost method for rapid fabrication of polydimethylsiloxane (PDMS) molds and devices. The method consists of three main fabrication steps: female mold (FM), male mold (MM), and chip fabrication. We use a CO2 laser cutter to pattern a thin, spin-coated PDMS layer for FM fabrication. We then obtain reusable PDMS MM from the FM using PDMS/PDMS casting. Finally, a second casting step is used to replicate PDMS devices from the MM. Demolding of one PDMS layer from another is carried out without any potentially hazardous chemical surface treatment. We have successfully demonstrated that this novel method allows fabrication of microfluidic molds and devices with precise dimensions (thickness, width, length) using a single material, PDMS, which is very common across microfluidic laboratories. The whole process, from idea to device testing, can be completed in 1.5 h in a standard laboratory. 

51. Optical properties of polydimethylsiloxane (PDMS) during nanosecond laser processing 

N.E. Stankova a,∗, P.A. Atanasov a, Ru.G. Nikov a, R.G. Nikov a, N.N. Nedyalkov a, T.R. Stoyanchov a, N. Fukata b, K.N. Kolev c, E.I. Valova c, J.S. Georgieva c, St.A. Armyanov c

a Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsaridradsko shose Boul., Sofia 1784, Bulgaria 

b International Center for Materials for NanoArchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan 

c Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 11, Sofia 1113, Bulgaria 

This article presents experimental investigations of effects of the process parameters on the medical grade polydimethylsiloxane (PDMS) elastomer processed by laser source with irradiation at UV (266 and 355 nm), VIS (532 nm) and NIR (1064 nm). Systematic experiments are done to characterize how the laser beam parameters (wavelength, fluence, and number of pulses) affect the opticalproperties andthe chemical compositioninthe laser treatedareas. Remarkable changes of the optical properties and the chemical composition are observed. Despite the low optical absorption of the native PDMS for UV, VIS and NIR wavelengths, successful laser treatment is accomplished due to the incubation process occurring below the polymer surface. With increasing of the fluence and the number of the pulses chemical transformations are revealed in the entire laser treated area and hence decreasing ofthe opticaltransmittance is observed. The incubation gets saturation after a certain number of pulses and the laser ablation of the material begins efficiently. At the UV and VIS wavelengths the number of the initial pulses, at which the optical transmittance begins to reduce, decreases from 16 up to 8 with increasing of the laser fluence up to 1.0, 2.5 and 10 J cm−2 for 266, 355 and 532 nm, respectively. In the case of 1064 nm the optical transmittance begins to reduce at 11th pulse incident at a fluence of 13 J cm−2 and the number of the pulses decreases to 8 when the fluence reaches value of 16 J cm−2. The threshold laser fluence needed to induce incubation process after certain number of pulses of 8 is different for every wavelength irradiation as the values increase from 1.0 for 266 nm up to 16 J cm−2 for 1064 nm. The incubation and the ablation processes occur in the PDMS elastomer material during its pulsed laser treatment are a complex function of the wavelength, fluence, number of pulses and the material properties as well. 

50. The influences of ambient humidity on laserinduced breakdown spectroscopy

Jiacen Liu a, Zongyu Hou *ab and Zhe Wang *ab 

a State Key Laboratory of Power System Operation and Control, International Joint Laboratory on Low Carbon Clean Energy Innovation, Department of Energy and Power Engineering, Institute for Carbon Neutrality, Tsinghua University, Beijing, 100084, China.

b Shanxi Research Institute for Clean Energy, Tsinghua University, Shanxi, 030032, China 

The poor long-term repeatability of laser-induced breakdown spectroscopy (LIBS) is a barrier to its general adoption. To date, its causes and the mechanisms involved are poorly understood. Despite the potential impact of variations in ambient operating conditions such as ambient temperature and humidity, these factors have not been thoroughly investigated, especially ambient humidity. This study investigates the influence of ambient humidity on LIBS spectra. The ambient humidity of a pure copper sample was adjusted in real-time and the LIBS spectra were acquired. The results indicate that the H I 656.28 nm intensity increased with humidity, whereas the variation of the Cu I line intensity with humidity depended on the laser energy. The intensity of the Cu I 510.55 nm decreased with humidity at 8 mJ and 13 mJ, and increased with humidity at 18 mJ, 30 mJ, and 50 mJ. An investigation of the underlying mechanism suggested that at a high ambient humidity, sample ablation increased, but the lifetime of the induced plasma was reduced. The two mechanisms increased and decreased the spectral intensity, respectively, and determined the variation in the Cu I line intensity with humidity. This study demonstrates that ambient humidity affects the LIBS spectral intensity and should be considered especially for long-term LIBS measurements or open-air measurements. 

49. Manufacturing of anti-fogging super-hydrophilic microstructures on glass by nanosecond laser

Liang Yang a , Xichun Luo b, *, Wenlong Chang b , Yankang Tian b , Zhengjian Wang b , Jian Gao b , Yukui Cai c , Yi Qin b , Mark Duxbury d 

a School of Mechanical Engineering, Dalian Jiaotong University, PR China 

b Centre for Precision Manufacturing, DMEM, University of Strathclyde, Glasgow G1 1XJ, UK 

c School of Mechanical Engineering, Shandong University, PR China 

d Department of Surgery, Glasgow Royal Infirmary, UK 

Nanosecond laser processing method with the support of light-absorption auxiliary materials was developed to fabricate anti-fogging super-hydrophilic microstructures on glass substrate surfaces. Through adjusting the focal point offset, the laser was focused on the auxiliary material layer, thus the laser energy required for micromachining was precisely controlled. As a processing example, a bionic honeycomb structure was successfully manufactured by this method. The effects of laser processing parameters on the size and integrity of the fabricated microstructures and on the light transmission of the machined surface were investigated through laser machining experiment. The results indicate that lower power and frequency is the key to obtaining regular honeycomb structures in laser machining. The laser focal point significantly affects the light transmittance of glass, while the feed rate has little effect. The water droplet contact angle was measured to evaluate the hydrophilicity of glass specimens with different dimensions of microstructure. It was found that the contact angle decreased with reduction of the honeycomb structure size. 

48. Hierarchical anti-reflective laser-induced periodic surface structures (LIPSSs) on amorphous Si films for sensing applications

A. Dostovalov,*a K. Bronnikov, a,b V. Korolkov,a S. Babin,a E. Mitsai,c A. Mironenko,d M. Tutov,e D. Zhang,f,g K. Sugioka, f J. Maksimovic,h T. Katkus,h S. Juodkazis,h,i A. Zhizhchenkoc and A. Kuchmizhak *c 

a Institute of Automation and Electrometry of the SB RAS, 1 Acad. Koptyug Ave., 630090 Novosibirsk, Russia.

b Novosibirsk State University, 2 Pirogova St., 630090 Novosibirsk, Russia 

c Institute of Automation and Control Processes, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690041, Russia 

d Institute of Chemistry, Vladivostok 690090, Russia 

e Far Eastern Federal University, Vladivostok 690090, Russia 

f RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan 

g Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China 

h Optical Sciences Center and ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), Swinburne University of Technology, John st., Hawthorn 3122, Victoria, Australia i World Research Hub Initiative (WRHI), School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152- 8550, Japan 

Here, we applied direct laser-induced periodic surface structuring to drive the phase transition of amorphous silicon (a-Si) into nanocrystalline (nc) Si imprinted as regular arrangement of Si nanopillars passivated with a SiO2 layer. By varying the laser beam scanning speed at a fixed pulse energy, we successfully tailored the resulting unique surface morphology of the formed LIPSSs that change from ordered arrangement of conical protrusions to highly uniform surface gratings, where sub-wavelength scale ripples decorate the valleys between near-wavelength scale ridges. Along with the surface morphology, the nc-Si/ SiO2 volume ratio can also be controlled via laser processing parameters allowing the tailoring of the optical properties of the produced textured surfaces to achieve anti-reflection performance or partial transmission in the visible spectral range. Diverse hierarchical LIPSSs can be fabricated and replicated over large-scale areas opening a pathway for various applications including optical sensors, nanoscale temperature management, and solar light harvesting. By taking advantage of good wettability, enlarged surface area and remarkable light-trapping characteristics of the produced hierarchical morphologies, we demonstrated the first LIPSS-based surface enhanced fluorescent sensor that allowed the identification of metal cations providing a sub-nM detection limit unachievable by conventional fluorescence measurements in solutions.

47. Characteristics of laser-induced plasma generated in water and in air with different nanosecond laser pulse durations 

Canxu Zhai, Ye Tian, * Longshang Wang, Ziwen Jia, Ying Li, Yuan Lu, Jinjia Guo, Wangquan Ye and Ronger Zheng 

College of Physics and Optoelectronic Engineering, Ocean University of China, Qingdao 266100, China

The formation of laser-induced plasma on a solid target depends strongly on the laser pulse parameters and the ambient conditions. In this work, the characteristics of laser-induced plasma generated in water and in air were investigated with two laser pulse durations of 6 ns and 17 ns. It was shown that the responses of laser-induced breakdown spectroscopy (LIBS) signals on the laser pulse duration in water and in air are different. In water, the 17 ns laser induces a brighter plasma and a stronger LIBS signal, whereas in air, the 6 ns laser is better. Such differences were attributed to the different plasma growth mechanisms in water and in air. The plasma growth in air is driven by strong laser-supported absorption waves, where the 6 ns laser with a higher peak irradiance corresponds to a stronger shock wave and more efficient heating on the plasma. Whereas for plasma growth in water, a great amount of laser energy is consumed in the material phase transitions, and in the mechanical effects of bubble expansion and shock wave propagation. The underwater plasma is far less heated by the laser pulse, and more easily suffers from the multiple breakdowns of water producing multiple shock waves and multi-plasmas. By using a longer laser pulse, which has a lower peak irradiance, the underwater plasma can absorb more laser energy over a longer laser pulse duration, and the multiple breakdown phenomenon can be suppressed. This results in a higher quality of underwater LIBS signals. The present work gives insights into the mechanism of plasma growth in water and in air, and provides suggestions for the choice of laser pulses in the relevant LIBS analyses. 

46. Direct Femtosecond Laser Processing for Generating High Spatial Frequency LIPSS (HSFL) on Borosilicate Glasses with Large-Area Coverage 

Rajeev Rajendran 1 , E. R. Krishnadev 1 and K. K. Anoop 1,2,* 

1 Department of Physics, Cochin University of Science and Technology, Kochi-22, Cochin 682022, Kerala, India; rajeevrajendran@cusat.ac.in (R.R.)

2 Inter University Centre for Nanomaterials and Devices (IUCND), Cochin University of Science and Technology, Cochin 682022, Kerala, India 

Large-area nanostructuring of glasses using intense laser beams is a challenging task due to the material’s extreme non-linear absorption of laser energy. Precise optimization of the process parameters is essential for fabricating nanostructures with large-area coverage. In this study, we report the findings on creating high-spatial-frequency LIPSS (HSFL) on borosilicate glass through direct laser writing, using a femtosecond laser with a wavelength λ = 800 nm, pulse duration τ = 35 fs, and repetition frequency frep = 1 kHz. We measured the single-pulse ablation threshold and incubation factor of Borosilicate glasses to achieve high-precision control of the large-area surface structuring. Single-spot experiments indicated that, when there was higher fluence and a larger number of irradiated laser pulses, a melt formation inside the irradiated area limited the uniformity of LIPSS formation. Additionally, the orientation of the scan axis with the laser beam polarization was found to significantly influence the uniformity of LIPSS generated along the scan line, with more redeposition and melt formation when the scan axis was perpendicular to the laser beam polarization. For large-area processing, the borosilicate glass surface was scanned line-by-line by the laser beam, with a scan orientation parallel to the polarization of the laser. The optical characterization revealed that the transmittance and reflectance of the borosilicate glass decreased significantly after processing. Additionally, the surface’s wettability changed from hydrophilic to super-hydrophilic after processing. These chemical contamination-free and uniformly distributed structures have potential applications in optics, microfluidics, photovoltaics, and biomaterials. 

45. Formation and Properties of Laser-Induced Periodic Surface Structures on Different Glasses 

Stephan Gräf *, Clemens Kunz and Frank A. Müller 

Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena, Germany 

The formation and properties of laser-induced periodic surface structures (LIPSS) was investigated on different technically relevant glasses including fused silica, borosilicate glass, and soda-lime-silicate glass under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. For this purpose, LIPSS were fabricated in an air environment at normal incidence with different laser peak fluence, pulse number, and repetition frequency. The generated structures were characterized by using optical microscopy, scanning electron microscopy, focused ion beam preparation and Fast-Fourier transformation. The results reveal the formation of LIPSS on all investigated glasses. LIPSS formation on soda-lime-silicate glass is determined by remarkable melt-formation as an intra-pulse effect. Differences between the different glasses concerning the appearing structures, their spatial period and their morphology were discussed based on the non-linear absorption behavior and the temperature-dependent viscosity. The findings facilitate the fabrication of tailored LIPSS-based surface structures on different technically relevant glasses that could be of particular interest for various applications. 

44. Laser-enabled high-conductivity solid electrolytes boost performance of solid-state sodium metal batteries 

Xiong Xiao a,1 , Shuaishuai Yang a,1,* , Runqing Miao a , Debao Fang a,b , Yang Zhao c,* , Changxiang Shao d , Ying Wang e , Chengzhi Wang a,b,* , Jingbo Li a , Yuefeng Su a,b , Haibo Jin a,b 

a School of Materials Science and Engineering, Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, Beijing Key Laboratory of Environmental Science and Engineering, Beijing Institute of Technology, Beijing 100081, China 

b Chongqing Innovation Center, Beijing Institute of Technology, Chongqing 401120, China 

c Key Laboratory of Cluster Science Ministry of Education of China Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China 

d School of Chemistry & Pharmaceutical Engineering, Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan 250117, China 

e Department of Chemistry, Key Laboratory of Organic Optoelectronics & Molecular Engineering, Ministry of Education, Tsinghua University, Beijing 100084, China 

Solid-state sodium metal batteries (SSBs) are pivotal for next-generation energy storage due to their high safety, energy density, and resource sustainability. However, most SSBs show poor performance at room temperature, critically induced by the large interfacial resistance and unstable contact between the solid electrolyte and the sodium metal anode. Herein we demonstrate a facile laser etching process by removing the insulating impurities on the surface of the conventional Na3Zr2Si2PO12 solid electrolyte (SE) to promote a highly conductive and coarse surface with nanoscale protrusions. The laser-treated SE shows enhanced interfacial contact with the sodium metal electrode with a low interfacial resistance of 83 Ω⋅cm2 reduced from the 28666 Ω⋅cm2 for the untreated SE. Moreover, without any wetting agents and stacking pressure, a high critical current density of 1.0 mA cm-2 is achieved at room temperature. The corresponding all-solid-state Na||Na symmetrical cells exhibit excellent sodium plating/stripping cycling performance at 0.2 mA cm-2 over 4000 h with flat voltages of around 50 mV. Solid-state Na3(VO)2(PO4)2F||Na cells deliver a high capacity of 116.0 mAh g-1 at a 1 C rate with a 68.6 % retention after 1000 charge/discharge cycles. These results underscore the transformative potential of laser processing in advancing high-performance SSBs for practical applications 

43. Picosecond laser texturing of Al current collector to improve cycling performances and simplify recycling of Lithium-ion batteries 

Paolo Tallone a, Silvia Spriano a, Daniele Versaci a, Sara Ferraris a, Alice Tori b, Silvia Bodoardo a 

a Politecnico di Torino, Department of Applied Science and Technology, Corso Duca degli Abruzzi, 24, 10129 Turin, Italy

b Osai Automation Systems SpA, Via della Cartiera 4, 10010 Parella TO, Italy 

Lithium-ion batteries (LIBs) are one of the main energy storage technologies currently in use and recycling them offers significant economic, environmental, and material recovery benefits. Despite various recycling processes, separating the metallic current collector from the electrode composite film remains a crucial challenge. In this framework, the present study focuses on laser texturing of aluminum current collectors (CCs) to introduce a microscale surface architecture. The asymmetric surface pattern facilitated a controlled and directional adhesion, enhancing attachment to manage the significant volume variation of the active material (NMC811) during charging and discharging cycles. Additionally, it enabled an easy separation of the electrode composite layer from the current collector, during recycling, by applying a force in a specific direction. As a result, the laser-treated cathodes displayed low electrode polarization and increased cycling performances, with a capacity retention of 67.6% after 300 cycles at 1C, thanks to the increased interfacial adhesion that reduced the active material delamination from the current collector upon cycling.

42. Bio-Inspired Functional Surfaces Based on Laser-Induced Periodic Surface Structures

Frank A. Müller *, Clemens Kunz and Stephan Gräf

Otto Schott Institute of Materials Research (OSIM), Löbdergraben 32, Jena 07743, Germany

This paper explores how nature combines material properties with periodic micro/nanostructures to solve surface-related challenges and how ultra-short pulsed lasers can mimic these natural designs through Laser Induced Periodic Surface Structures (LIPSS). The paper first explains the physical principles behind LIPSS formation and surface phenomena such as wettability, reflectivity, and friction. It then presents biological examples like lotus leaves, springtails, moth eyes, and shark skin to show nature’s solutions to technical problems. A detailed overview of recent advances using LIPSS to create superhydrophobic, anti-reflective, colored, and drag resistant surfaces is provided. The paper concludes by discussing future directions and potential applications of LIPSS based surface technologies. 

41. Ten Open Questions about Laser-Induced Periodic Surface Structures

Jörn Bonse 1,* and Stephan Gräf 2,*

1 Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, D-12205 Berlin, Germany 

2 Otto-Schott-Institut für Materialforschung (OSIM), Löbdergraben 32, D-07743 Jena, Germany

LIPSS is a simple yet powerful method for creating nanostructures on solid surfaces, enabling functional surfaces for diverse applications in optics, medicine, tribology, and energy. While current laser technologies offer high processing speeds, industrial implementation faces challenges such as the complex interaction between surface chemistry and nanoscale topography, difficulties in process control, and limited long-term stability of surface functions. This article reviews these technical limitations and the current state of theoretical modeling, proposing directions for future research and technological advances to promote the industrial adoption of LIPSS.

40. Influence of femtosecond laser produced nanostructures on biofilm growth on steel

Nadja Epperlein, Friederike Menzel, Karin Schwibbert, Robert Koter, Jörn Bonse, Janin Sameith, Jörg Krüger ∗, Jörg Toepel 

Bundesanstalt für Materialforschung und −prüfung (BAM), Unter den Eichen 87, D-12205 Berlin, Germany 

Biofilm formation poses high risks in multiple industrial and medical settings. However,the robust nature of biofilms makes them also attractive for industrial applications where cell biocatalysts are increasingly in use. Since tailoring material properties that affect bacterial growth or its inhibition is gaining attention, here we focus on the effects of femtosecond laser produced nanostructures on bacterial adhesion. Large area periodic surface structures were generated on steel surfaces using 30-fs laser pulses at 790 nm wavelength. Two types of steel exhibiting a different corrosion resistance were used, i.e., a plain structural steel (corrodible) and a stainless steel (resistant to corrosion). Homogeneous fields of laserinduced periodic surface structures (LIPSS) were realized utilizing laser fluences close to the ablation threshold while scanning the sample under the focused laser beam in a multi-pulse regime. The nanostructures were characterized with optical and scanning electron microscopy. For each type of steel, more than ten identical samples were laser-processed. Subsequently, the samples were subjected to microbial adhesion tests. Bacteria of different shape and adhesion behavior (Escherichia coli and Staphylococcus aureus) were exposed to laser structures and to polished reference surfaces. Our results indicate that E. coli preferentially avoids adhesion to the LIPSS-covered areas, whereas S. aureus favors these areas for colonization.

39. Biocompatible nano-ripples structured surfaces induced by femtosecond laser to rebel bacterial colonization and biofilm formation

Xiao Luo a,1, Shenglian Yao b,1, Hongjun Zhang a, Mingyong Cai a , Weijian Liu a, Rui Pan a, Changhao Chen a, Xiumei Wang c, Luning Wang b, Minlin Zhong a,⁎ 

a Laser Materials Processing Research Centre, School of Materials Science and Engineering, Tsinghua University, Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Beijing 100084, PR China

b State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, PR China

c School of Materials Science and Engineering, Tsinghua University, Beijing 100084, PR China 

This work explores the behavior of bacteria (E. coli) and cells (MSCs) on three types of nano-ripples including LIPSS (Type 1 texture), columns with overlapped LIPSS (Type 3 texture) and partially developed type 3 structures (Type 2 texture), among which the last two morphologies are composite structures consisting of nano-ripples and micro-grooves. In detail, the period of LIPSS is about 400 nm and achieves a 43% anti-bacterial property for E. coli. Type 2 texture has ripples with period of 400 nm and grooves with width of 1 μm, yielding reductions of 49%. IR has 500-nm-wide ripples and 1-μm-wide grooves. However, compared with the depth of grooves on type 2 texture, the grooves on type 3 texture are about 200 nm deeper. The deeper grooves make benefits for better antibacterial activity – a reduction of 56%. The bacterial cells attach to the laser-treated surfaces and the membranes stretch between ripples and grooves leading to the rupture and deformation of bacteria. It is possible that possessing deep grooves, as displayed on type 3 texture, could potentially improve the performance of anti-bacteria. Besides the excellent performance of anti-bacteria, the laser-treated specimens exhibit good biocompatibility. The MSCs can survive, adhere and proliferate well on the laser-tectured surfaces. Furthermore, the spreading areas of MSCs are larger and the orientation of the cell is consistent with nano-ripples rather than micro-grooves because of the contact-guided cell alignment. The results suggest that using femtosecond laser to fabricate nano-ripples and grooves on titanium is likely to be a promising candidate for improving the long-term performance of implant material.

38. Size matters: how periodicity and depth of LIPSS influences E. coli adhesion on ferritic stainless steel  

J. Outon´ a,b,* , M. Carbú c , M. Domínguez a,b , M. Ramírez-del-Solar a,b , G. Alba d , M. Vlahou e,f , E. Stratakis e,g , V. Matres h , E. Blanco a,b

a Department of Condensed Matter Physics, Faculty of Sciences, University of Cadiz, ´ 11510, Puerto Real, Cadiz, ´ Spain 

b IMEYMAT: Institute of Research on Electron Microscopy and Materials of the University of Cadiz, ´ Spain 

c Microbiology Laboratory, Department of Biomedicine, Biotechnology and Public Health, Faculty of Marine and Environmental Sciences, University of Cadiz, ´ 11510, Puerto Real, Cadiz, ´ Spain 

d Department of Materials Science, Metallurgical Engineering and Inorganic Chemistry, Faculty of Sciences, University of Cadiz, ´ 11510, Puerto Real, Cadiz, ´ Spain 

e Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology (FORTH), N. Plastira 100, Vassilika Vouton, 70013 Heraklion, Crete, Greece 

f Department of Materials Science and Technology, University of Crete, 70013 Heraklion, Crete, Greece g Department of Physics, University of Crete, 71003 Heraklion, Crete, Greece 

h Corrosion Laboratory, Technical Department, ACERINOX Europa S.A.U., 11379, Palmones-Los Barrios, Cadiz, ´ Spain 

This research establishes that surfaces featuring LIPSS with spatial periods smaller than the size of the E. coli bacteria effectively reduce bacterial adherence due to their topographical  characteristics, independent of wettability. In contrast, surfaces where the spatial period aligns with bacterial dimensions facilitate adherence. Moreover, it has been observed that deeper LIPSS structures correlate with higher relative bacterial adherence. These findings underscore the nuanced interplay between nanostructure dimensions, surface properties, and bacterial behaviour, providing insights critical for the design of antibacterial surfaces.

37. Effect of surface treatment for aluminum foils on discharge properties of lithium-ion battery 

Shigeki NAKANISHI1 , Takashi SUZUKI1 , Qi CUI1 , Jun AKIKUSA2 , Kenzo NAKAMURA2 

1. Products Research and Development Department, Mitsubishi Aluminum Co., Ltd., 85 Hiramatsu, Susono-city, Shizuoka-pref., 411-1127, Japan 

2. Central Research Institute, Electronic Components Department, Mitsubishi Materials Corporation, 1002-14 Mukohyama, Naka-city, Ibaraki-pref., 311-0102, Japan 

A chemical etching surface treatment was used to prepare roughened foil for Li-ion battery cells and investigate the effect of surface morphology on battery performance. Evaluation of the cell performance with two active materials (LCO and LFP) was conducted, and there is no significant difference between two types of aluminum foils with LCO because the particles are large and become embedded on the foil by compression. On the other hand, for the cells with the LFP active material and roughened foils, significant difference was confirmed to affect high-rate cycle properties. It is believed that the cathode electrode sheet with roughened foil exhibits improved performance because contact with the surface over the active and conductive material is increased 

36. Femtosecond laser-indced peridic surface structures

J. Bonse, J. Kru¨ger, S. Ho¨hm, A. Rosenfeld 

J. Bonse and J. Kru¨ger

BAM Bundesanstalt fu¨r Materialforschung und—pru¨fung, Unter den Eichen 87, D-12205 Berlin, Germany 

S. Ho¨hm and A. Rosenfeld

Max-Born-Institut fu¨r Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Max-Born-Straße 2A, D-12489 Berlin, Germany 

The successful generation of sub-100 nm LIPSS on titanium surfaces using a simple one-step processing approach in air environment was demonstrated. In semiconductors and dielectrics, the intrapulse transient changes of the optical properties play an important role in the formation of LIPSS and accounting for fluence and pulse number dependent spatial periods as well as their subwavelength characteristics. Temporal pulse shaping using ultrashort laser pulses/sequences offers a new way to control LIPSS patterns.

35. Quo Vadis LIPSS?-Recent and Future Trends on Laser-Induced Periodic Surface Structures

Jörn Bonse

Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, D-12205 Berlin, Germany 

Nanotechnology and lasers have been among the most successful and actively researched technological fields that have boomed over the past 20 years. Many advancements are based on the controlled fabrication of nanostructures, enabling customized material functionalization for a wide range of industrial applications, electronics, and medicine, and have already become part of our daily lives. One of the attractive approaches for fabricating these nanostructures in a flexible, durable, fast, and non-contact single-step process is based on the generation of Laser-Induced Periodic Surface Structures (LIPSS). This paper presents a review of the literature and recent trends in LIPSS. Additionally, it discusses future directions and unresolved issues related to LIPSS. 

34. Generation of laser-induced periodic surface structures (LIPSS) in fused silica by single NIR nanosecond laser pulse irradiation in confinement

Martin Ehrhardt b, Bing Hanb,⁎, Frank Frosta, Pierre Lorenza, Klaus Zimmera,⁎ 

a Leibniz Institute of Surface Engineering (IOM), Permoserstraße 15, 04318 Leipzig, Germany 

b Advanced Launching Co-innovation Center, Nanjing University of Science and Technology, #200 XiaoLingWei, 210094 Nanjing, Jiangsu, People’s Republic of China 

This study conducted experiments on the formation of Laser-Induced Periodic Surface Structures (LIPSS) on a SiO₂ substrate using a single nanosecond laser pulse (λ = 1064 nm, tₚ = 2–50 ns). In the experiment, the substrate was covered with a material stack consisting of an intermediate layer, an absorption layer, and a confinement layer. The LIPSS period varied depending on the laser parameters (pulse energy, pulse duration) and the specific properties of the material stack (film thickness, material). The experimental results showed that the LIPSS period ranged from 400 to 600 nm, with a peak-to-valley value of up to 140 nm. Additionally, the LIPSS orientation was always perpendicular to the polarization direction of the laser beam. The researchers proposed that this formation is based on a Surface Plasmon Polariton (SPP) mechanism. When the laser pulse excites the SiO₂ surface, it induces heating, high pressure, and plasma shock, leading to the transformation of SiO₂ into a metallic state, which then forms an interface with the dielectric substrate, enabling SPP generation. LIPSS formation is defined within a specific process window (pulse energy, pulse duration, and confinement conditions). It can be explained by the generation of SPPs, localized material removal due to the modified intensity distribution of the laser beam's SPP, and the final freezing of the localized height distribution after removal. 

Y. Zheng1, Z. An1, P. Smyrek1, H.J. Seifert1, W. Pfleging1, P. Smyrek2, W. Pfleging2, T. Kunze3, V. Lang3, A.F. Lasagni3, V. Lang4, A.F. Lasagni4

1 Institute for Applied Materials – Applied Materials Physics Karlsruhe Institute of Technology (KIT) Karlsruhe, Germany 

2 Karlsruhe Nano Micro Facility Eggenstein-Leopoldshafen, Germany 

3 Surface Functionalization Fraunhofer Institute for Material and Beam Technology Dresden, Germany 

4 Institute for Manufacturing Technology Dresden University of Technology Dresden, Germany 

In this work, the formation of periodic surface structures using ultra-fast laser material processing was systematically investigated as a function of laser parameters. They were able to successfully create well-defined nanoripples (LIPSS) and hierarchical surface structures on copper surfaces. DLIP was applied to form line-like surface structures on aluminum and copper current collectors with different cycles. Subsequently, measurements of adhesion were performed on the laser-deformed metal current collectors. The film adhesion of the deformed aluminum current collectors was greatly improved. Ultra-fast laser processing allows the fabrication of various surface patterns such as dots, lines, or grids coupled to LIPSS. For copper, the hierarchical surface structure with line patterns provided the best results with respect to graphite anode film adhesion. 

Yanan Liu1†, Ye Ding2†, Zeping Liu3 , Xingchen Li4 , Sichao Tian5*, Lishuang Fan3*, Jichang Xie6 , Liangliang Xu7 , Jinwoo Lee7*, Jian Li8 and Lijun Yang1* 

1 Zhengzhou Research Institute, Harbin Institute of Technology, Zhengzhou 450000, P. R. China 

2 Suzhou Research Institute, Harbin Institute of Technology, Suzhou 215104, P. R. China 

3 School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China 

4 Defense Innovation Institute, Chinese Academy of Military Science, Beijing 100071, P. R. China 

5 Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100193, P. R. China 

6 Laboratoire Roberval, UTC, Sorbonne Universités, Université de Technologie de Compiègne, Centre de recherche Royallieu, CS60319, 60203 Compiègne Cedex, France 

7 Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea 

8 School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China 

Aqueous zinc-ion batteries provide a most promising alternative to the existing lithium-ion batteries due to their high theoretical capacity, intrinsic safety, and low cost. However, commercializing aqueous zinc-ion batteries sufer from dendritic growth and side reactions on the surface of metallic zinc, resulting in poor reversibility. To overcome this critical challenge, here, we report a one-step ultrafast laser processing method for fabricating three-dimensional micro-/nanostructures on zinc anodes to optimize zinc nucleation and deposition processes. It is demonstrated that the three-dimensional micro-/nanostructure with increased specifc surface area signifcantly reduces nucleation overpotential, as well as preferentially absorbs zinc ions to prevent dendritic protuberances and corrosion. As a result, the presence of threedimensional micro-/nanostructures on the zinc metal delivers stable zinc plating/ stripping beyond 2500 h (2 mA cm-2/1 mAh cm-2) in symmetric cells, a high Coulombic efciency (99.71%) in half cells, and moreover an improved capacity retention (71.8%) is also observed in full cells. Equally intriguingly, the pouch cell with three-dimensional micro-/nanostructures can operate across various bending states without severely compromising performance. This work provides an efective strategy to construct ultrafne and high-precision three-dimensional micro-/nanostructures achieving highperformance zinc metal anodes and is expected to be of immediate beneft to other metal-based electrodes. 

Johannes Kriegler,* Heiko Ballmes, Serge Dib, Ali Gökhan Demir, Lucas Hille, Yunhao Liang, Lovis Wach, Steffen Weinmann, Josef Keilhofer, Kun Joong Kim, Jennifer L. M. Rupp, and Michael F. Zaeh 

J. Kriegler, L. Hille, Y. Liang, L. Wach, J. Keilhofer, M. F. Zaeh Technical University of Munich; TUM School of Engineering and Design Department of Mechanical Engineering Institute for Machine Tools and Industrial Management Boltzmannstr. 15, 85748 Garching, Germany 

H. Ballmes Schaeffler Technologies AG & Co. KG 91074 Herzogenaurach, Germany 

S. Dib, A. G. Demir Department of Mechanical Engineering Politecnico di Milano Via La Masa 1, Milan 20158, Italy

S. Weinmann, K. J. Kim, J. L. M. Rupp TUM School of Natural Sciences Department of Chemistry Technical University of Munich 85747 Garching, Germany 

J. L. M. Rupp TUMint. Energy Research GmbH Lichtenbergstr. 4, 85748 Garching, Germany 

Incorporating lithium metal anodes in next-generation batteries promises enhanced energy densities. However, lithium’s reactivity results in the formation of a native surface film, affecting battery performance. Therefore, precisely controlling the chemical and morphological surface condition of lithium metal anodes is imperative for producing high-performance lithium metal batteries. This study demonstrates the efficacy of laser treatment for removing superficial contaminants from lithium metal substrates. To this end, picosecond-pulsed laser radiation is proposed for modifying the surface of lithium metal substrates. Scanning electron microscopy (SEM) revealed that different laser process regimes can be exploited to achieve a wide spectrum of surface morphologies. Energy-dispersive X-ray spectroscopy (EDX) confirmed substantial reductions of ≈80% in oxidic and carbonaceous surface species. The contamination layer removal translated into interfacial resistance reductions of 35% and 44% when testing laser-cleaned lithium metal anodes in symmetric all-solid-state batteries (ASSBs) with lithium phosphorus sulfur chloride (LPSCl) and lithium lanthanum zirconium oxide (LLZO) solid electrolytes, respectively. Finally, a framework for integrating laser cleaning into industrial battery production is suggested, evidencing the industrial feasibility of the approach. In summary, this work advances the understanding of lithium metal surface treatments and serves as proof of principle for its industrial applicability. 

Hui Li, Gang Wang, Jin Hu, Jun Li, Jiaxu Huang, and Shaolin Xu* 

Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen 518000, China 

The practical application of lithium (Li) metal anodes in high-capacity batteries is impeded by the formation of hazardous Li dendrites. To address this challenge, this research presents a novel methodology that combines laser ablation and heat treatment to precisely induce controlled grain growth within laser-structured grooves on copper (Cu) current collectors. Specifically, this approach enhances the prevalence of Cu (100) facets within the grooves, effectively lowering the overpotential for Li nucleation and promoting preferential Li deposition. Unlike approaches that modify the entire surface of collectors, our work focuses on selectively enhancing lithiophilicity within the grooves to mitigate the formation of Li dendrites and exhibit exceptional performance metrics. The half-cell with these collectors maintains a remarkable Coulombic efficiency of 97.42% over 350 cycles at 1 mA cm2 . The symmetric cell can cycle stably for 1600 h at 0.5 mA cm2 . Furthermore, when integrated with LiFePO4 cathodes, the full-cell configuration demonstrates outstanding capacity retention of 92.39% after 400 cycles at a 1C discharge rate. This study introduces a novel technique for fabricating selective lithiophilic three-dimensional (3D) Cu current collectors, thereby enhancing the performance of Li metal batteries. The insights gained from this approach hold promise for enhancing the performance of all laser-processed 3D Cu current collectors by enabling precise lithiophilic modifications within complex structures. 

Xueke Wang a,b , Sitong Chen a,b , Zhaohu Fan c , Weiwei Li b , Shubo Wang b , Xue Li b , Yang Zhao b , Tong Zhu a,**, Xiaofeng Xie b,* 

a School of Mechanical Engineering and Automation, Northeastern University, Shenyang, 110819, Liaoning, China 

b Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084, China 

c Department of Industrial Engineering, Pennsylvania State University, University Park, PA, 16802, USA 

A laser was used to perforate gas diffusion layer (GDL) that enhances liquid water transport from the electrodes to the gas channels. The generated holes diameter is from 80 to 200 mm, and center-to-center spacing is from 1 to 3 mm. A three-dimensional numerical model, based on a level set method, was built to investigate the water transport characteristics through the perforations with different diameters and spacing. Experiments and simulation results show that there is a better correlation among the diameter, spacing of the perforation and the power density. When the perforation diameter is 100 mm and the perforation pitch is 2 mm, the water transfer effect is the best which enhances the water discharge effectively and avoids the liquid droplets obstructing the gas flow channel at the same time. These results may assist in the design of GDL for water management in the operation of proton exchange membrane fuel cells 

Weitong Pan a , Xueli Chen a , Fuchen Wang a,* , Gance Dai b,** 

a Institute of Clean Coal Technology, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China 

b State Key Laboratory of Chemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China 

A comprehensive understanding of gas channel (GC)-gas diffusion layer (GDL) interrelations incorporating the mass transfer coefficients, resistances, and areas provides guidelines for the flow channel design. This paper is based on the “flow field analysis scheme” that combines theoretical analysis and numerical simulation. In the analysis, transport-reaction interactions are clarified using multiple resistances in series approach. Results indicate that the external mass transfer resistance is primarily confined to the GDL; and instead, the GC-GDL interface should be highlighted for a uniform transport flux. It is further revealed that the reconciliation of the mass transfer area and coefficient is the key to enhanced transport capability. On this basis, the analytical solution of optimal channel width is obtained; and its coordination with the flow rate is established. Next, a typical single-channel fuel cell model is investigated with various geometric and operating parameters, further validating and quantifying the theoretical analysis. 

E. Audouarda,*, M. Fleureaua , D. Pallarèsb , J.-M. Romanob , F. Mermetb 

a Amplitude - 11 avenue de Canteranne, 33600 Pessac, France 

b IREPA laser – Parc d’innovation, 67400 Illkirch, France 

The implementation of femtosecond laser processing in batteries fabrication is of high interest for automotive industry. The laser ablation mechanisms of composite materials used for batteries is a key knowledge for the laser processing optimization. In this work, we provide new results on fs ablation efficiencies for materials used in lithium-ion batteries. A very high value is obtained for specific ablation rates of graphite, up to 12 mm3/min/W, while the value is next to 0.2 mm3/min/W for the metallic substrate. The results show less benefit for MHz and GHz bursts of pulses in the case of graphite. Nevertheless because of the huge ablation efficiency difference between the active material and the metallic substrate, electrode cutting time is dominated by the metallic substrate cutting for which a significant benefit of GHz bursts is evidenced. 

D. Redka a,b,* , C. Gadelmeier c , J. Winter a,d , M. Spellauge a , C. Eulenkamp a , P. Calta b , U. Glatzel c , J. Minar´ b , H.P. Huber a,* 

a Department of Applied Sciences and Mechatronics, Hochschule München University of Applied Sciences, Lothstr. 34, 80335 Munich, Germany 

b New Technologies-Research Center, University of West Bohemia, Univerzitní 8, 306 14 Plzeň, Czech Republic 

c Metals and Alloys, University of Bayreuth, Prof.-Rüdiger-Bormann-Str. 1, 95447 Bayreuth, Germany 

d Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universitat ¨ Erlangen-Nürnberg, Paul-Gordon Straße 6, 91052 Erlangen, Germany 

In recent years, high entropy alloy research has experienced increased interest and it was found that some of these materials have extraordinary properties. High entropy alloys also show an increased damage resistance to high-energy particle irradiation, mainly due to effects caused by the increased configuration entropy. So far, no detailed studies have been carried out regarding the interaction with high-energy electromagnetic radiation, particularly by means of lasers. In this work, we compare results of ultrashort-pulse laser-matter interaction of the CrMnFeCoNi alloy (Cantor alloy), the most researched representative of this material group, with the con ventional alloy stainless steel AISI 304. Since metals can in general be processed efficiently with ultrashort pulses, which is of particular interest for industrial applications, we performed our experiments with single infrared sub-picosecond pulses. The crater surface morphology and process energetics are discussed in detail and the validity of established ablation models is investigated. We find that the damage threshold of the CrMnFeCoNi alloy is slightly lower than that of AISI 304 and consequently CrMnFeCoNi alloy shows an increased ablation volume. Therefore, the high entropy alloy CrMnFeCoNi can be processed efficiently with ultrashort-pulse lasers 

Er-Chieh Cho a , Cai-Wan Chang-Jian b,***, Yen-Ju Wu c , Szu-Han Chao d , Jen-Hsien Huang e , Kuen-Chan Lee f,****, Huei Chu Weng g,**, Shih-Chieh Hsu d,h,* 

a Department of Clinical Pharmacy, School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wuxing Street, Taipei City, 110, Taiwan 

b Department of Mechanical and Automation Engineering, I-Shou University, No.1, Sec. 1, Syuecheng Rd., Dashu District, Kaohsiung City, 84001, Taiwan 

c International Center for Young Scientists (ICYS), National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan 

d Department of Chemical and Materials Engineering, Tamkang University, No. 151, Yingzhuan Road, Tamsui District, New Taipei City, 25137, Taiwan 

e Department of Green Material Technology, Green Technology Research Institute, CPC Corporation, No.2, Zuonan Rd., Nanzi District, Kaohsiung City, 81126, Taiwan 

f Department of Science Education, National Taipei University of Education, No.134, Sec. 2, Heping E. Rd., Da-an District, Taipei City, 106, Taiwan 

g Department of Mechanical Engineering, Chung Yuan Christian University, No. 200, Chungpei Road, Chungli District, Taoyuan City, 32023, Taiwan 

h Water Treatment Science and Technology Research Center, Tamkang University, No. 151, Yingzhuan Road, Tamsui District, New Taipei City, 25137, Taiwan 

In this study, the graphene-modified Al foils are prepared to assemble lithium ion batteries (LIBs) through a three-step approach comprising: (1) deposition of the polyamic acid (PAA) on the Al substrate; (2) curing the PAA to form the polyimide (PI)-coated Al foils; (3) converting the PI into porous graphene by CO2 laser irradiation. With integration of the PI derived graphene (PDG) in the LIBs, the inserted PDG layer can enhance the adhesion and interface resistance between the active layer and Al electrode. The LiNi0.5Mn1.5O4 (LNMO)// Li4Ti5O12 (LTO) full cells with PDG layer are also fabricated to evaluate the effect of the modified layer on the cell performance. Compared to the pristine Al electrode, the modified current collector can improve the rate performance and reduce the temperature rise during the charge/discharge process leading to better cycling stability.

Zhaopeng Tong, Huaile Liu, Jiafei Jiao, Wangfan Zhou, Yu Yang, Xudong Ren* 

School of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013, PR China 

In this study, laser shock peening (LSP) was employed to change the stress state and microstructure of the surface layer of CrMnFeCoNi HEA fabricated by laser directed energy deposition (LDED) and improve its mechanical properties. The surface morphology, residual stress, and tensile properties of the CrMnFeCoNi HEA with and without LSP were investigated. Furthermore, we characterized the microstructure evolution of the specimen treated by LSP along the depth direction before and after conducting a tensile test. Results indicated that LSP transformed the surface-stress state from tensile to compressive stress, and the pores in the surface layer were closed after undergoing severe plastic deformation. Additionally, LSP resulted in the development of a gradient microstructure along the depth direction. The formation of a sandwich structure with a hardened surface layer and soft core improved the strength and ductility of the specimens treated by LSP. The underlying mechanisms that improved the strength and ductility were proposed. 

Srinagalakshmi Nammi1,*, Nilesh J Vasa1, Balaganesan G1 and Anil C Mathur2

1 Indian Institute of Technology, Madras, India. 

2 Indian Space Research Organization, Ahmedabad, India. 

A comparative study has been made for micro-scribing of copper and aluminum thin films in air and underwater using 355 nm, 532 nm and 1064 nm wavelengths of a Q-switched Nd3+: YAG laser with 6 ns pulse duration. For aluminum in air medium, the channel depth obtained is high for 355 nm wavelength, whereas for copper coated on a polyimide substrate, 532 nm wavelengths produced higher depth. In underwater scribing, with increase in the pulsed laser energy, the depth of micro channel was increased and remained unchanged at higher energy. The influence of beam profile on the micro channel cross-section has also been discussed. Further, theoretical modeling of the lasermaterial interaction in air and underwater ambience conditions to estimate the recession rate has been discussed by incorporating the laser ablation temperature measured using the laser induced breakdown spectroscopy technique. 

Wei-wei Liu1 • Heng Zhang1 • Li-hong Liu1 • Xiao-chuan Qing1 • Zi-jue Tang1 • Ming-zheng Li1,2 • Jin-song Yin3 • Hong-chao Zhang1,4 

1 School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, People’s Republic of China 

2 School of Engineering, University of Liverpool, Liverpool L69 3GH, UK 

3 Zhangjiagang Furui Special Equipment Co., Ltd., Zhangjiagang 215637, People’s Republic of China 

4 Department of Industrial Engineering, Texas Tech University, Lubbock, TX 79409, USA 

The electric vehicle industry has been rapidly developing internationally. Electric vehicle batteries (EVBs) are perceived as a low environmental impact energy storage technology. While the service life of an EVB is relatively long, a significant number of battery packs will reach the end of their service lives eventually. The end-of-life (EOL) EVBs may still have appreciable residual value for remanufacturing and secondary use. Some solid-electrolyte interface (SEI) layers will persist on the surface of electrodes deposit after a period of continuous cycling, causing the battery degradation and failure. An approach to battery end-of-life management was introduced involving remanufacturing of the cathode from EOL lithium-ion battery electrodes, and a recent study on remanufacturing process of the degraded EVBs using pulse laser to radiate SEI on the electrode surface was presented in this paper, here on a laboratory scale. Based on experimental data, the SEI film removal was carried out with laser energy intensity ranging from 0.035 to 0.169 J/mm2 . The remanufactured cathodes were characterized through a combination of scanning electron microscopy, Fourier transform infrared spectroscopy, and wavelength dispersive spectrometer, respectively. The experimental results indicated that the remanufacturing treatments were successful in removing the EOL by-products (e.g., SEI films) and upgrading the cathode to its pre-cycling functionality. It is suggested that the fade capacity of a lithium-ion battery can be recovered by using laser radiation method 

Elisa Ravesio a, Adrian H.A. Lutey b, Daniele Versaci a,*, Luca Romoli c, Silvia Bodoardo a 

a Politecnico di Torino, Department of Applied Science and Technology, Electrochemistry Group, Corso Duca degli Abruzzi, 24, 10129 Turin, Italy 

b Universita ` degli Studi di Parma, Dipartimento di Ingegneria e Architettura, Parco Area delle Scienze, 181/A, 43124 Parma, Italy 

c Universita ` di Pisa, Dipartimento di Ingegneria Civile e Industriale, Largo Lucio Lazzarino, 56122 Pisa, Italy 

Lithium-ion batteries (LIBs) have emerged as the primary energy storage solution for numerous portable electronic devices, electric vehicles, and renewable energy systems. However, enhancing the performance and longevity of LIBs is of paramount importance to meet the increasing demand for efficient and sustainable energy storage solutions. To improve the performance of current LIBs, one of the most interesting aspects is to study and optimize the so-called inactive materials which constitute the battery. Within this context, the present work focuses on laser texturing of aluminium current collectors (CCs) to improve the electrochemical performance of lithium iron phosphate-based cathodes. Two different nanosecond laser treatments were used to increase the wettability of metallic CCs and improve adhesion between this element and the other components of the electrode. Both laser treatments enhanced adhesion between the active material and CC, exhibiting good electrochemical performance at high C-rates compared to cells with untextured CCs, as well as good rate capability. Interestingly, one of the two pattern geometries exhibited significant cycling stability, with a capacity retention of >86% after 500 cycles. 

Hyunbin Nama, Chulho Parka, Jongun Moonc, Youngsang Nab, Hyoungseop Kimc, Namhyun Kanga,⁎ 

a Department of Materials Science and Engineering, Pusan National University, Busan 46241, Republic of Korea 

b Titanium Department, Korea Institute of Materials Science, Gyeongnam 51508, Republic of Korea 

c Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673, Republic of Korea 

Laser similar welding of cast and rolled high-entropy alloys (HEAs) was performed using the cantor system (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2). As the welding velocity was increased from 6 to 10 m min−1 , the shrinkage voids, primary dendrite arm spacing, and dendrite packet size decreased, thus improving the mechanical properties of the cast and rolled HEA welds. The cast HEA welds showed tensile properties comparable to those of the base metal (BM). In all the specimens fracture occurred near the heat-affected zone and BM at 298 K. However, the rolled HEA welds showed lower tensile strength than the BM, and fracture occurred in the weld metal (WM). This can be attributed to the larger dendrite packet size of the WM than the grain size of the BM. In addition, the tensile properties of the specimens at the cryogenic temperature were superior to those observed at 298 K, regardless of the cast and rolled HEA welds. This is because the formation of deformation twins and dislocations was predominant at 77 K. Therefore, the laser similar welds of cast and rolled HEAs are suitable for cryogenic applications. 

Jingrun Chen1, Jing Zhang1,*, Ke Li1, Dongdong Zhuang2, Qianhao Zang3, Hongmei Chen3, Yandi Lu4, Bo Xu4 and Yan Zhang1 

1 School of Metallurgy and Materials Engineering, Jiangsu University of Science and Technology, Suzhou 215600, China 

2 School of Materials Science and Technology, Jiangsu University, Zhenjiang 212013, China 

3 School of Materials Science and Technology, Jiangsu University of Science and Technology, Zhenjiang 212100, China 

4 Suzhou Institute of Technology, Jiangsu University of Science and Technology, Suzhou 215600, China 

In this study, laser surface remelting of an AlCoCrFeNi2.1 high-entropy alloy was performed using a Yb:YAG laser. The effects of laser surface remelting on the phase structure, microstructure, Vickers hardness, frictional wear properties, and corrosion resistance of the high-entropy alloy were investigated. The remelted layer of the AlCoCrFeNi2.1 high-entropy alloy was produced by remelting at 750 W laser power and formed a good metallurgical bond with the substrate. The X-ray diffraction results showed that the 750 W remelted layer consisted of face-centered cubic and body-centered cubic phases, which were consistent with the phases of the as-cast AlCoCrFeNi2.1 high-entropy alloy, and a new phase was not generated within the remelted layer. Laser surface remelting is very effective in refining the lamellar structure, and the 750 W remelted layer shows a finer lamellar structure compared to the matrix. The surface hardness and wear resistance of the AlCoCrFeNi2.1 high-entropy alloy were substantially improved after laser surface remelting. In a 3.5 wt.% NaCl solution, the laser-remelted surface had a larger self-corrosion potential and smaller self-corrosion 

Lucas Hille*, Marc P. Noecker, Byeongwang Ko, Johannes Kriegler, Josef Keilhofer, Sandro Stock, Michael F. Zaeh 

Technical University of Munich, TUM School of Engineering and Design, Department of Mechanical Engineering, Institute for Machine Tools and Industrial Management, Boltzmannstr. 15, 85748, Garching, Gemany 

Despite the electrochemical benefits of laser electrode structuring, the process is not yet implemented in state-of-the-art industrial battery production due to a limited knowledge regarding its implementation into the manufacturing process chain. In this study, three process integration positions for laser structuring of graphite anodes, which are either after coating, after drying or after calendering, were experimentally evaluated. The obtained electrodes were analyzed regarding geometrical, mechanical and electrochemical characteristics. The results indicate that the material ablation process is governed by the evaporation of solvent and binder for wet and dry electrodes, respectively. As a consequence, electrodes structured in wet condition exhibited fewer particle residues on the electrode surfaces and a high coating adhesion strength. In contrast, laser structuring of dry electrodes significantly reduced the pull-off strengths of the electrode coatings. A tortuosity reduction and an increased discharge capacity at high C-rates by laser structuring were observed for all structured electrodes, but with higher performance improvements for electrodes structured in dry state. Although a partial clogging of the structures was observed in electrodes structured before calendering, laser structuring yielded a comparable electrochemical performance of electrodes which were structured in dry condition before and after calendering. 

Takashi TSUDA*,a Yuta ISHIHARA,a Tatsuya WATANABE,a Nobuo ANDO,b Takao GUNJI,a Naohiko SOMA,c Susumu NAKAMURA,d Narumi HAYASHI,e Takeo OHSAKA,b and Futoshi MATSUMOTOa 

a Department of Materials and Life Chemistry, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama, Kanagawa 221-8686, Japan 

b Research Institute for Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama, Kanagawa 221-8686, Japan 

c Wired Co., Ltd., 1628 Hitotsuyashiki shinden, Sanjo, Niigata 959-1152, Japan 

d Department of Electrical and Electronic Systems Engineering, National Institute of Technology, Nagaoka College, 888 Nishikatakai, Nagaoka, Niigata 940-8532, Japan 

e Industrial Research Institute of Niigata Prefecture, 1-11-1 Abuminishi, Chuo-ku, Niigata 950-0915, Japan 

The degradation of charging/discharging capacities in the rate-performance test of lithium iron phosphate (LFP) cathodes with different loading amounts of an active material on both sides of a current collector (i.e., “unbalanced” LFP/LFP cathodes) in a laminated cell (typically composed of anode/separator/unbalanced cathodes/separator/ anode) was not observed actually at low C-rates (e.g., 0.1 C). However, the rate-performance data obtained at high C-rates (e.g., >5 C) indicated that the imbalance of the loading amounts of an active cathode material on both sides of an Al current collector causes a significant capacity degradation. We have found that it is possible to prevent the capacity degradation observed at high C-rates by holing the unbalanced LFP/LFP cathodes in a micrometer-sized grid-patterned way (the percentages of the holed area are typically several %) using a pico-second pulsed laser: The non-holed unbalanced LFP/LFP cathodes exhibited a considerable capacity degradation at C-rates which are, for example, larger than 5 C, while the holed ones showed no degradation in capacity even at high C-rates (e.g., 5– 20 C). Forming micrometer-sized grid-patterned holes in the LFP/LFP cathodes leads to an improved capacity and high-rate performance of their charging/discharging processes. 

Shaoping Wu, Hongpeng Zheng, Xinyue Wang, Nan Zhang, Weizheng Cheng, Benwei Fu, Haochang Chen, Hezhou Liu, Huanan Duan* 

State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China 

A thick electrode with high areal capacity is a promising way to improve the energy density of batteries, but the development of a thick electrode is limited by poor mechanical stability and sluggish ion and electron transport. Here, we design a self-supporting cathode that consists of cellulose nanofibers, multi-walled carbon nanotubes, and lithium iron phosphate (LFP), and introduce a uniform microchannel structure to the cathode by laser drilling technology. The cellulose nanofibers and multi-walled carbon nanotubes construct a conductive network. The microchannel structure enables outstanding ion and electron transport and significantly improves the rate capability of the electrode. Meanwhile, the local heat by the laser produces an amorphous carbon layer on the inner surface of the microchannel, which helps form a stable cathode-electrolyte interface and enhances the capacity retention of the thick electrode. Notably, the drilled thick cathode with an LFP load of 40 mg cm−2 and an areal capacity of 5.33 mAh cm−2 exhibits substantially improved cycling stability at 0.5C than the undrilled samples. This work demonstrates a promising design concept for thick electrodes to high-performance energy storage devices

Dong Hyup Jeon

Department of Mechanical System Engineering, Dongguk University-Gyeongju, Gyeongju 38066, Republic of Korea

Wettability by the electrolyte is claimed to be one of the challenges in the development of high-performance lithium-ion batteries. Non-uniform wetting leads to inhomogeneous distribution of current density and unstable formation of solid electrolyte interface film. Incomplete wetting influences the cell performance and causes the formation of lithium plating in the anode, which leads to safety issue. Research has pointed out that insufficient wetting could be found in the electrode, and the wetting characteristics would be different in each electrode. Here we use lattice Boltzmann simulation to show the electrolyte distribution and understand the wetting characteristics in the cathode and anode. We develop a multiphase lattice Boltzmann model with the reconstruction of electrode microstructure using a stochastic generation method. We use a porous electrode model to identify the effect of wettability on the cell performance and to elucidate the dependence of capacity on the wettability. Our results would lead to more reliable lithium-ion battery designs, and establish a framework to inspect the wettability inside electrodes

Nathan Dunlap a, Dana B. Sulas-Kern a, Peter J. Weddle a, Francois Usseglio-Viretta a, Patrick Walker a, Paul Todd a, David Boone b, Andrew M. Colclasure a, Kandler Smith a, Bertrand J. Tremolet de Villers a, Donal P. Finegan a 

a National Renewable Energy Laboratory (NREL), 15013 Denver West Parkway, Golden, CO 80401, United States of America 

b Clarios, 5757 North Green Bay Avenue, Florist Tower, Milwaukee, WI 53209, United States of America 

Laser ablation is a scalable technique for decreasing the effective tortuosity of electrodes by selectively removing material with high precision. Applied to 

≈110μm thick electrode coatings, this work focuses on understanding the impact of laser ablation on electrode material properties at the beginning of life and synergistic impacts of ablated channels on cell performance throughout their cycle life. Post laser ablation, local changes in chemistry, crystallography, and morphology of the laser-impacted electrode regions are investigated. It is shown that femtosecond pulsed laser ablation can achieve high-rate material removal with minor material damage locally at the interface of the impacted zones. The capacity achieved during a 6C (10 min) constant-current constant-voltage charge to 4.2 V improved from 1 mAh cm−2 for the non-ablated electrodes to almost 2 mAh cm−2 for the ablated electrodes. This benefit is attributed to a synergistic effect of enhanced wetting and decreased electrode tortuosity. The benefit was maintained for over 120 cycles, and upon disassembly decreased Li-plating on the graphite anode was observed. Finally, multi-physics modeling in conjunction with wetting analyses showed that laser ablating either one of the electrodes led to substantial improvements in wetting and rate capability, indicating that substantial performance benefits can be achieved by ablating only the graphite anode as apposed to both electrodes. 

Nayna Khosla a, Jagdish Narayan a, Roger Narayan a b, Xiao-Guang Sun c, Mariappan Parans Paranthaman c 

a Department of Materials Science and Engineering, Centennial Campus, North Carolina State University, Raleigh, NC, 27695-7907, United States

b Joint Department of Biomedical Engineering, Centennial Campus, North Carolina State University and UNC Chapel Hill, Raleigh, NC, 27695, United States 

c Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6100, United States 

Nanosecond pulsed laser annealing significantly improves cyclability and current carrying capacity of lithium-ion batteries (LIBs). This improvement is achieved by engineering of microstructure and defect contents present in graphite in a controlled way by using pulsed laser annealing (PLA) to increase the number density of Li+ ion trapping sites. The PLA treatment causes the following changes: (1) creates surface steps and grooves between the grains to improve Li+ ion charging and intercalation rates; (2) removes inactive polyvinylidene difluoride (PVDF) binder from the top of graphite grains and between the grains which otherwise tends to block the Li+ migration; and (3) produces carbon vacancies in (0001) planes which can provide Li+ charging sites. From X-ray diffraction data, we find upshift in diffraction peak or reduction in planar spacing, from which vacancy concentration was estimated to be about 1.0%, which is higher than the thermodynamic equilibrium concentration of vacancies. The laser treatment creates single and multiple C vacancies which provide sites for Li+ ions, and it also produces steps and grooves for Li+ ions to enter the intercalating sites. It is envisaged that the formation of these sites enhances Li+ ion absorption during charge and discharge cycles. The current capacity increases from an average 360 mAh/g to 430 mAh/g, and C–V shows significant reduction in SEI layer formation after the laser treatment. If the vacancy concentration is too high and charge-discharge cycles are long, then trapping of electrons by Li+ may occur, which can lead to Li0 formation and Li plating causing reduction in current capacity. 

Quansheng Li a b, Xuesong Mei a b c, Xiaofei Sun a b c, Yanbin Han a b, Bin Liu a b c, Zikang Wang a b, Anastase Ndahimana a b, Jianlei Cui a b c, Wenjun Wang a b c 

a State key laboratory for manufacturing system engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China 

b School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China 

c Shaanxi Key Laboratory of Intelligent Robots, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China 

Owing to their excellent structural superiorities of large storage space, high specific surface area and reduced volume expansion during battery charge and discharge cycles, 3D porous current collectors have received much concern in the anode of lithium-ion batteries. However, reasonable designing and efficient manufacturing of 3D porous copper foils as current collectors (PCFCCs) remain a great challenge due to the small thickness, soft texture, and variability of copper foils. These material characteristics make it hard to manufacture 3D micro-structure on copper foils and impede the practical application of lithium-ion batteries in more fields. Herein, an efficient and effective strategy is reported to enhance the electrochemical performance of Li4Ti5O12 (LTO) electrodes via rationally designing and manufacturing 3D porous copper foils as current collectors. As a result, the 3D PCFCCs based LTO electrode displays low electrode polarization, excellent-cycle performance and ultra-high rate capacity. Moreover, the structures of various 3D PCFCCs are systematically studied for the first time, the design of 3D PCFCCs is optimized, and the mechanism of improving battery performance is explored. In addition, the proper micro-nano-pore-structures can facilitate electrolyte penetration and the solvated Li+ transport, and the excellent Li+ transmission ability of 3D PCFCCs is verified by simulation. 

Quan Li a b, Baogang Quan a, Wenjun Li a, Jiaze Lu a b, Jieyun Zheng a, Xiqian Yu a, Junjie Li a, Hong Li a 

a Institute of Physics, Chinese Academy of Science, Beijing 100190, China 

b University of Chinese Academy of Sciences, Beijing 100049, China 

The growth of lithium dendrite is one of the major problems that need to be solved before the application of metallic lithium anode to commercial rechargeable lithium batteries. The three-dimensional host framework with well-defined architecture acting as current collector has been proved to be able to regulate the lithium plating/stripping behavior and thus to suppress the dendrite growth. In this work, a surface-patterned lithium electrode (spLi) with hexagonal arrays of micro-sized holes has been successfully fabricated by micro-fabrication methods. By employing scanning electron microscope (SEM) and optical microscope, the lithium plating/stripping behavior on spLi was directly visualized. The electrochemical performances of the spLi electrode were evaluated in Li symmetric cell and Li|LiCoO2 half-cell using carbonate ester and ether based electrolyte. It is found that the geometry of the hole has a strong influence on the lithium plating/stripping behavior, and the deposited lithium perfers to fill in the micro-sized holes due to the favorable kinetics. The hole structure preserves throughout battery cycling with no obvious dendrite growth and surface roughness after multiple plating/stripping cycles. These phenomena can well explain the excellent electrochemical performances of the surface-patterned lithium electrode (spLi) compared with bare lithium electrode. This research also demonstrates that lithium metal can serve as stable framework to host lithium plating/stripping, nevertheless, efforts are still needed to further optimize the architecture to achieve more evenly lithium plating/stripping. 

Johannes Kriegler, Tran Manh Duy Nguyen, Lazar Tomcic, Lucas Hille, Sophie Grabmann, Elena Irene Jaimez-Farnham, Michael F. Zaeh 

Technical University of Munich (TUM); TUM School of Engineering and Design; Department of Mechanical Engineering, Institute for Machine Tools and Industrial Management (iwb); Boltzmannstrasse 15, 85748 Garching, Germany 

Lithium metal is a favored anode material in various post-lithium-ion battery types. Developing processing routines for lithium anodes is necessary to pave the way for large-format lithium metal batteries. Laser cutting is a feasible production process to create the required electrode contours. In the scope of this work, model calculations were used to derive implications of the cell design on the relevant range of lithium layer thicknesses. Furthermore, nanosecond-pulsed laser cutting was evaluated for separating 50 μm-thick lithium foils. Cause-effect relationships between process parameters and quality criteria were analyzed through empirical investigations. The ablation thresholds for various pulse durations were determined experimentally. Different process regimes were identified using scanning electron microscopy with explosive boiling at high fluences as the most efficient ablation mechanism enabling cutting speeds of up to 6.6 m s−1. The influence of the peak pulse fluence, the pulse frequency, the pulse duration, and the pulse overlap on the formation of melt superelevations at the cut edge was studied using laser scanning microscopy. The presented results contribute to a better understanding of the nanosecond-pulsed laser process and provide a basis for developing tailored process strategies for laser cutting of lithium metal within industrial-scale battery production. 

Zechuan Huang a, Haoyang Li b, Zhen Yang b, Haozhi Wang a, Jingnan Ding a, Luyao Xu c, Yanling Tian d, David Mitlin e, Jia Ding a, Wenbin Hu a 

a Key Laboratory of Advanced Ceramics and Machining Technology (Ministry of Education), School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China 

b School of Mechanical Engineering, Tianjin University, Tianjin 300072, China 

c Shenzhen Zhongwu Technology Co., Ltd., Shenzhen 518052, China 

d School of Engineering, University of Warwick, Coventry CV4 7AL, UK 

e Materials Science Program & Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712-1591, USA 

Laser processing is employed to fabricated zinc-ion battery (ZIB) anodes with state-of-the-art electrochemical performance from commercial zinc foils. Lasers are widely utilized for industrial surface finishing but have received minimal attention for zinc surface modification. Laser lithography patterned zinc foils “LLP@ZF” are hydrophilic, with an electrolyte contact angle of 0°. This is due to the concave-convex surface geometry that enhances wetting (periodic crests, ridges and valleys, roughness 16.5 times planar). During electrodeposition LLP@ZF's surface geometry generates a periodic electric field and associated current density distribution that suppresses tip growth (per continuum simulations). Per Density Functional Theory (DFT) its surface oxide is zincophilic, resulting in low nucleation barriers during plating (e.g. 3.8 mV at 1 mA cm−2). A combination of these attributes leads to stable dendrite-free plating/stripping behavior and low overpotentials at fast charge (e.g. 48.2 mV at 8 mA cm−2 in symmetric cell). Cycling is possible at an unprecedented areal capacity of 50 mA h cm−2, with 400 h stability at 1 mA cm−2. Moreover, exceptional aqueous zinc battery (AZB) performance is achieved, with MnO2-based cathode loading 10 mg cm−2 and corresponding anode capacity 7.6 mA h cm−2. A broad comparison with literature indicates that LLP@ZF symmetric cell and full battery performance are among most favorable. 

Yijing Zheng 1,*,Lisa Pfäffl 1,Hans Jürgen Seifert 1 andWilhelm Pfleging 1,2 

1 Institute for Applied Materials—Applied Materials Physics (IAM—AWP), Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany 

2 Karlsruhe Nano Micro Facility (KNMF), H.-von-Helmholtz-Pl. 1, 76344 Eggenstein-Leopoldshafen, Germany 

* Author to whom correspondence should be addressed. 

For the development of thick film graphite electrodes, a 3D battery concept is applied, which significantly improves lithium-ion diffusion kinetics, high-rate capability, and cell lifetime and reduces mechanical tensions. Our current research indicates that 3D architectures of anode materials can prevent cells from capacity fading at high C-rates and improve cell lifespan. For the further research and development of 3D battery concepts, it is important to scientifically understand the influence of laser-generated 3D anode architectures on lithium distribution during charging and discharging at elevated C-rates. Laser-induced breakdown spectroscopy (LIBS) is applied post-mortem for quantitatively studying the lithium concentration profiles within the entire structured and unstructured graphite electrodes. Space-resolved LIBS measurements revealed that less lithium-ion content could be detected in structured electrodes at delithiated state in comparison to unstructured electrodes. This result indicates that 3D architectures established on anode electrodes can accelerate the lithium-ion extraction process and reduce the formation of inactive materials during electrochemical cycling. Furthermore, LIBS measurements showed that at high C-rates, lithium-ion concentration is increased along the contour of laser-generated structures indicating enhanced lithium-ion diffusion kinetics for 3D anode materials. This result is correlated with significantly increased capacity retention. Moreover, the lithium-ion distribution profiles provide meaningful information about optimizing the electrode architecture with respect to film thickness, pitch distance, and battery usage scenario. 

Peichao Zou, Yang Wang, Sum-Wai Chiang, Xuanyu Wang, Feiyu Kang & Cheng Yang 

Peichao Zou, Yang Wang, Sum-Wai Chiang, Xuanyu Wang, Feiyu Kang & Cheng Yang Division of Energy and Environment, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, China 

Feiyu Kang School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China 

Uncontrolled growth of lithium dendrites during cycling has remained a challenging issue for lithium metal batteries. Thus far, various approaches have been proposed to delay or suppress dendrite growth, yet little attention has been paid to the solutions that can make batteries keep working when lithium dendrites are already extensively present. Here we develop an industry-adoptable technology to laterally direct the growth of lithium dendrites, where all dendrites are retained inside the compartmented copper current collector in a given limited cycling capacity. This featured electrode layout renders superior cycling stability (e.g., smoothly running for over 150 cycles at 0.5 mA cm−2). Numerical simulations indicate that reduced dendritic stress and damage to the separator are achieved when the battery is abusively running over the ceiling capacity to generate protrusions. This study may contribute to a deeper comprehension of metal dendrites and provide a significant step towards ultimate safe batteries. 

Ryan J. Tancin, Dana B. Sulas-Kern, François L.E. Usseglio-Viretta, Donal P. Finegan, Bertrand J. Tremolet de Villers

National Renewable Energy Laboratory (NREL), 15013 Denver West Parkway, Golden, CO 80401, United States of America

Characterization of the rate and quality of ultrafast-laser ablation of Li-ion battery (LIB) electrode materials is presented for a collection of common and next-generation electrodes. Laser ablated micro-structures on the surface of LIB electrodes have been shown to provide dramatic enhancement of high-rate capability and electrode wetting. However, industrial adoption is hampered by a lack of data enabling informed choice of laser parameters and predicting process throughput. This work bridges this gap by providing characterization of the ablation process at more laser parameters (laser fluence and number of pulses used) than are currently available in the literature. Further, we expand on previous graphite and lithium iron phosphate (LFP) ablation work by extending ablation characterization to new LIB materials, providing high data resolution and adopting new characterization metrics which are relevant for industrial application of this technology. Ablated pores are characterized by their ablated depth, volume, and how the depth and volume ablation rate changes as a function of pore depth. Finally, we provide a detailed characterization of the morphology of laser ablated micro-structures which informs how material and laser parameters affect the quality of laser-processed electrodes. 

L.A. Dobrzan´ski a,  A. Drygała a, K. Gołombek a, P. Panek b, E. Bielan´ ska b, P. Zie˛ba b

a Division of Materials Processing Technology, Management and Computer Techniques in Materials Science, Institute of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego Street 18a, 44-100 Gliwice, Poland

b Institute of Metallurgy and Materials Science, Polish Academy of Sciences, Reymonta Street 25, 30-059 Cracow, Poland

To minimise reflection from the flat surface, the multicrystalline silicon wafers were textured. This means creating a roughened surface so that incident light may have a larger probability of being absorbed into the solar cell. Due to grains of random crystallographic orientation, most of the texturing methods used for monocrystalline silicon are ineffective in case of multicrystalline silicon. Therefore, in the present paper a new approach to surface texturisation was developed. Texturisation of multicrystalline silicon wafers was carried out by means of laser surface treatment. Then, a special etching procedure was applied to remove laser-damaged layer. The reflectance of produced textures was measured by PerkinElmer Lambda spectrophotometer with an integrating sphere. The topography of laser-textured surface was investigated using ZEISS SUPRA 25 and PHILIPS XL 30 scanning electron microscopes. The laser treatment and etching in alkaline solution ensured obtaining texture of regular structure that was insensitive to random crystallographic orientation of different grains. The laser processing parameters were adjusted by performing a number of experiments for different values of processing parameters. It is a new approach to texturisation problem of multicrystalline silicon. 

M. Domke a,*,  V. Matylitsky b, S. Stroj a

a Josef Ressel Center for Material Processing with Ultrashort Pulsed Lasers, Research, Center for Microtechnology, Vorarlberg University of Applied Sciences, Hochschulstr. 1, Dornbirn 6850, Austria 

b Spectra-Physics, Feldgut 9, Rankweil 6830, Austria 

In recent years, the burst-mode caught a lot of attention in the field of ultrashort-pulse laser micro machining. One of the major issues is the influence of the burst pulse number and frequency on ablation efficiency and quality. A recent publication reported of a significant increase in ablation efficiency when processing with ≥25 burst pulses at ≥100 MHz burst frequencies. This raises the question of whether processing with such high pulse densities can be attributed to non-thermal ablation, or whether a quasi-nanosecond laser ablation behavior is achieved. To answer this question, we determined ablation efficiencies as function of fluence for silicon, stainless steel, and copper and compared the ablation quality at the optimal fluence using the following laser systems: femtosecond laser operated in single-pulse mode, fs laser operated in 28-pulse-burst mode with a burst pulse frequency of 148 MHz, and a nanosecond laser with a pulse duration of 175 ns, which is identical with the temporal length of the burst pulse train. The comparison showed that the burst mode used produces similar surface morphologies and melt burrs as the nanosecond laser, but at about 2/3 of its efficiency.

Davi Neves a,b, Anselmo Eduardo Diniz a,∗, Milton Sérgio Fernandes Lima b 

a Faculty of Mechanical Engineering, University of Campinas, P.O. Box 6122, 13083-970 Campinas, SP, Brazil

b Institute for Advanced Studies (IEAv/DCTA), P.O. Box 6044, 12229-970 Sao Jose dos Campos, SP, Brazil 

Adhesion is one of the most important characteristics of coating on cutting tools. Poor coating adhesion on the tool favors fragmentation and release of hard abrasive particles between the tool and the workpiece. These particles interact with the surfaces of the tool, accelerating its wear and decreasing tool life. One possible solution is the use of laser texturing prior to coating in order to achieve a desired surface topography with enhanced adhesion properties. In the texturing, a high-frequency short-pulse laser changes surface characteristics, generating resolidified material and selective vaporization. This work evaluated the effectiveness of laser texturing in improving the substrate–coating adhesion of PVD coated cemented carbide tools. To this end, the substrates were textured with a Nd:YAG laser, in four different intensities, and then coated with a PVD TiAlN film. To ascertain the effectiveness of laser texturing, Rockwell C indentation and turning experiments were performed on both textured tools and conventional unlasered tools. The PVD coated laser-textured tool showed better performance in the indentation and turning tests than the standard tools. A comparative evaluation of tool wear mechanisms indicated that texturing did not change the wear mechanisms, but altered their importance to tool wear. The anchoring provided by the higher roughness of the textured surface increased the adhesion of the coating on the substrate, thus increasing tool life. Additionally, the chemical modification of the carbide grains due to the laser heating might be responsible for an enhanced adhesion between coating and substrate.

Hyunbin Nam a , Chulho Park a , Jongun Moon c , Youngsang Na b , Hyoungseop Kim c , Namhyun Kang a,⁎ 

a Department of Materials Science and Engineering, Pusan National University, Busan 46241, Republic of Korea

b Titanium Department, Korea Institute of Materials Science, Gyeongnam 51508, Republic of Korea 

c Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673, Republic of Korea 

To Laser similar welding of cast and rolled high-entropy alloys (HEAs) was performed using the cantor system (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2). As the welding velocity was increased from 6 to 10 m min−1, the shrinkage voids, primary dendrite arm spacing, and dendrite packet size decreased, thus improving the mechanical properties of the cast and rolled HEA welds. The cast HEA welds showed tensile properties comparable to those of the base metal (BM). In all the specimens fracture occurred near the heat-affected zone and BM at 298 K. However, the rolled HEA welds showed lower tensile strength than the BM, and fracture occurred in the weld metal (WM). This can be attributed to the larger dendrite packet size of the WM than the grain size of the BM. In addition, the tensile properties of the specimens at the cryogenic temperature were superior to those observed at 298 K, regardless of the cast and rolled HEA welds. This is because the formation of deformation twins and dislocations was predominant at 77 K. Therefore, the laser similar welds of cast and rolled HEAs are suitable for cryogenic applications. 

Bingfeng Wang a,b,* , Hao Peng a , Zhen Chen a

a School of Materials Science and Engineering, Central South University, Changsha, 410083, People’s Republic of China 

b State Key Laboratory for Powder Metallurgy, Central South University, Changsha, 410083, People’s Republic of China 

A high-power solid-state laser was used to weld the Ti–6Al–4V titanium alloy and the FeCoNiCrMn high-entropy alloy. By adding a pure Cu filler layer for the laser welding, a strong welded joint is obtained and the average tensile strength of the laser welded Ti–6Al–4V/FeCoNiCrMn joint exceeds 140 MPa. Composition and mechanical properties of phases in the laser welded Ti–6Al–4V/FeCoNiCrMn joint were investigated by the optical microscope, the electron probe microanalysis technique, the scanning electron microscope and the nanoindentation technique. The fusion zone is mainly composed of the Cu-rich and the FeCoNiCrMn-rich regions. The Cu-rich phases can disperse brittle intermetallic compounds such as Ti–Fe, to prevent the formation of a continuous brittle compound layer, thereby improving the plasticity of the welded joint and promoting the formation of the joint. The temperature distribution model in the fusion zone was established, and combined with the element distribution and phase composition analysis results in the fusion zone, microstructure mechanism for formation of the fusion zone was proposed.