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•Demonstrating Control of 2D MoSe2 Growth and Orientation on laser-structured substrates (dielectric, semiconductor, and metals).•Out-of-plane Orientation on Active Edge Sites Leading ...to Enhanced Raman Signals.•Laser-induced periodic surface structures offer a versatile and Scalable Strategy for Tailoring Properties of 2D Materials.
In this study, we explore the morphology and orientation of molybdenum diselenide, a Van der Waals 2D material, through isothermal closed space vapor deposition on both pristine and laser-structured substrates. Laser structuring is conducted on dielectric (sapphire), semiconductor (silicon), and conductive (titanium nitride) substrates using ultrashort laser pulses, resulting in smooth topographic changes such as laser-induced periodic surface structures (LIPSS) or selective ablation. Scanning electron microscopy (SEM) reveals the pivotal role of surface structuring in the growth of out-of-plane MoSe2 nanosheets. This effect is particularly pronounced on monocrystalline substrates like sapphire and silicon, exhibiting in-plane growth on pristine substrates. Additionally, Raman spectroscopy confirms the vertical orientation of flakes on structured substrates and highlights the presence of active edge sites by demonstrating an increased abundance of deposited material. Overall, our findings emphasize the controllability of directing the growth of MoSe2 flakes through appropriate pre-treatment of the substrate, with potential applications in various fields, including Surface-Enhanced Raman Scattering (SERS). Furthermore, the scalability, reproducibility, and applicability to any substrate make ultrashort laser structuration a promising general strategy for orienting 2D materials.
Lithium ion battery with ultra-thick electrode is hardly manufactured in practice due to its poor rate capability and large unusable capacity caused by high internal resistances in spite of the ...potential benefits of a high capacity and cost reduction by less inactive material usage in the same volume. In this work, we report the effectiveness of laser structuring of ultra-thick electrodes for high-energy battery. Lithium cobalt-oxide cathode (700 μm) and graphite anode (650 μm) are prepared with the areal discharge capacity, 25 mAh cm−2. After laser structuring, electrode surface morphology and chemistry are investigated. Internal resistances and diffusion characteristics are analyzed by electrochemical impedance spectroscopy using symmetric cells with non-intercalating salt. Geometric changes of ultra-thick electrode by laser structuring contributes to decrease of tortuosity, decrease of electronic and ionic resistances, and enhancement of diffusion characteristics in both laser-structured cathode and anode without chemically negative reaction, thermal damage or a failure of electrode structure. The rate capability and areal discharge capacity of laser-structured cells increases by 5 times than that of unstructured one at 0.1 C condition. Therefore, laser structuring of ultra-thick electrodes is a viable approach for the high-energy battery with practical use of space.
•Effects on laser structuring of ultra-thick LCO and graphite full cell are reported.•Laser structuring improves rate capability of electrode by 5 times at 0.1C.•Arial discharge capacity of laser-structured electrode increases by 5 times at 0.1C.•These results are due to improvement of tortuosity and chemical characteristics.•It contributes to the faster mass transport and reduction of internal resistance.
•Production of large-format lithium-ion batteries with laser-structured anodes.•Laser-structuring of anodes improves discharge and charge rate capability.•Extension of cyclic lifetime under ...fast-charging operation.•Incremental capacity analyses reveal a reduction of lithium-plating.•Post-mortem analyses of anode surface revealing a reduced surface layer formation.
Improving the performance characteristics of lithium-ion batteries is a central research objective for the widespread introduction of electric vehicles. Laser-induced structures in graphite anodes have been reported to improve various performance characteristics of lithium-ion batteries. Nevertheless, electrode structuring has been studied mostly with single-layer coin cells on a laboratory scale to date. In addition to electrochemical tests on multi-layer NMC111/graphite pouch cells with a nominal capacity of ≈ 2.9 Ah, this paper presents the transfer of the technology from the laboratory to an industry-oriented battery production scale. A significant improvement of the discharge rate capability of lithium-ion batteries with laser-structured anodes was observed at temperatures of -10 °C, 0 °C, and 25 °C at discharge rates of up to 8C. Moreover, an enhanced fast-charging capability at charge rates as high as 6C was determined. In an aging study with 500 charge and discharge cycles, a significantly higher capacity retention of cells containing structured anodes was demonstrated. The effects of aging were investigated by incremental capacity analyses. Additionally, the results are supported by post-mortem analyses of the anode material using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The investigations revealed a distinctly reduced surface layer formation on structured anodes in comparison to their non-structured counterparts, which is attributed to a decrease in lithium-plating during cycling.
We investigate the short and long term wettability of laser textured stainless steel samples in order to better understand the interplay between surface topography and chemistry. Very different 1D ...and 2D periodic as well as non-periodic surface patterns were produced by exploiting the extreme flexibility of a setup consisting of five rotating birefringent crystals, which allows generating bursts of up to 32 femtosecond laser pulses with fixed intra-burst delay of 1.5 ps. The change of the surface morphology as a function of the pulse splitting, the burst polarization state and the fluence was systematically studied. The surface topography was characterized by SEM and AFM microscopy. The laser textured samples exhibited, initially, superhydrophilic behaviour which, during exposure to ambient air, turned into superhydrophobic with an exponential growth of the static contact angle. The dynamic contact angle measurements revealed a water adhesive character which was explained by XPS analyses of the surfaces that showed an increase of hydrocarbons and more oxidized metal species with the aging. The characteristic water adhesiveness and superhydrophobicity of laser textured surfaces can be exploited for no loss droplet reversible transportation or harvesting.
Time dependence of the contact angle for the 1D-LIPSS obtained with bursts of n = 16, linearly polarized pulses (black open square) and for the 2D-LIPSS obtained with bursts of n = 4, crossed polarized pulses (red open circle). The time delay in both cases is 1.5 ps. Display omitted
•1D-LIPSS with variable period were obtained with bursts of linearly polarized pulses with ps intraburst delay.•2D-LIPSS (triangles arranged over hexagons) were produced with bursts of crossed and circular polarization.•Changing the number of pulses within the bursts allowed varying the morphology of surface structuring among several patterns.•The contact angle of the laser treated surfaces varied over the time, settling at values close to 160° at long term.•Over the exposure time the laser treated steel surfaces become richer in hydrocarbons and present more oxidized metals.
The demand for improved performance and higher energy density of LIBs is growing due to their wide range of applications and advancement in the energy storage market for electric vehicles. ...Three-dimensional (3D) structured electrodes have recently been considered the best and most promising approach to improve battery performance as they exhibit high areal and specific capacity. In the work described here, a nanosecond pulsed fiber laser was used to generate four types of surface patterns named: line, grid, triangular end, and rectangular end patterns with an equal amount of ablated active material volume. A study on wettability was performed using the spread area, wetting time, wetting balance, and capillary rise measurements. Moreover, the Lucas Washburn and extended wettability models were used to quantitatively express the wetting behavior using the term wetting rate. In all approaches, line-patterned electrodes show better wettability along with a higher wetting rate, while poor behavior is seen with an unstructured electrode. Galvanostatic tests were used to examine how these electrode surface patterns influence the electrochemical performance of the battery. The capacity retentions, discharge capacity efficiencies, and cyclic stabilities were improved on cells with line, triangular end, and rectangular end patterned electrodes.
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•Laser structuring of Li-ion battery electrodes was performed using line, rectangular, triangular, and grid patterns.•Laser structuring increases the active surface area for enhanced Li-ion diffusion.•Gravity is negligible in the initial period of wicking during electrolyte wetting.•Capacity retentions, discharge capacity efficiencies, and cyclic stabilities were improved for the structured electrodes.
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•Effects on laser structuring of thick and dense NMC cathode are investigated.•Laser structuring enhanced the rate capability of the electrode at high current rate.•Specific energy ...also increased, while improving or retaining the power density.•Diffusion homogeneity and wettability were discussed for the performances.•Diffusivity and polarization in the cell were analyzed in details.
Increasing energy and power densities is one of the important required improvements in lithium ion batteries. However, there exist limitations in increasing both energy and power densities simultaneously because of the increase in internal resistance. In this work, we report the simultaneous improvement of these properties of lithium ion battery by adopting a laser structured LiNi0.5Mn0.3Co0.2O2 cathode. The electrode was processed to make uniformly spaced micro-grooves by using a femtosecond laser. The performance of laser structured electrodes with varying thickness (100∼210μm) and porosity (26% and 50%) were compared with that of unstructured conventional electrodes used in industry. It is demonstrated that the specific energy of thick and dense laser structured electrode (thickness=175μm, porosity=26%) at 0.5C is about twice higher than that of thin and sparse unstructured electrode (thickness=100μm, porosity=50%) while rate capability is almost the same. Also, although laser-structured electrodes are much thicker than unstructured electrodes, the rate performance (discharge capacity=93%) of the laser-structured electrode is better than that of unstructured electrode at 1C. The simultaneous enhancement of the power and energy densities of the laser-structured electrodes results from the improvement of lithium ion diffusivity and cell polarization.
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•Laser structuring of LiFePO4 electrode material.•Effect of the aspect ratio of structured electrodes on wettability and its comparison with unstructured electrodes.•Comparative study ...of wetting rate with the capillary rise and wetting balance test between structured and Unstructured electrodes.•Usage and comparison of Lucas Washburn model and Zhmud extended model for quantifying the wetting rate.•Electrochemical analysis for cyclic stability, rate capability, and charge–discharge profile.
Lithium-ion batteries are widely used for their high energy density, high power density, long lifetime, and safety which are crucial for the environmentally friendly future energy system. Electrodes are the key component of LIBs that determines battery performance. LiFePO4 is a common electrode used in battery technology due to its long cycle life and good safety. Laser structuring of electrodes has recently been considered a promising approach to increase energy density. In this work, LiFePO4 electrodes were structured into a grid-type pattern by varying the laser power, resulting in different aspect ratios. To evaluate the effects of the structuring, wettability and electrochemical performance were tested. The wetting property was investigated using spread area, wetting time, and contact angle measurements. Besides, the wetting rate was measured using the wetting balance test and capillary rise test. Lucas Washburn model and Zhmud extended model were used to quantitatively express the wetting rate. The influence of gravity on the wetting performance was also investigated by comparing those models. Furthermore, an electrochemical test was performed to see the cyclic stability, rate capability, and charge–discharge profile with a C rate up to 1C.
Achieving effective dropwise capture and ultrafast water transport is essential for fog harvesting. In nature, cactus uses the conical spine with microbarbs to effectively capture fog, while ...Sarracenia utilizes the trichome with hierarchical microchannels to quickly transport water. Herein, we combined their advantages to present a novel configuration, a spine with barbs and hierarchical channels (SBHC), for simultaneous ultrafast water transport and high-efficient fog harvesting. This bioinspired SBHC exhibited the fastest water transport ability and the highest fog harvesting efficiency in comparison with the spine with hierarchical channels (SHCs), the spine with barbs and grooves (SBG), and the spine with barbs (SB). Based on the fundamental SBHC unit, we further designed and fabricated a two-dimensional (2D) spider-web-like fog collector and a three-dimensional (3D) cactus-like fog collector using direct laser structuring and origami techniques. The 2D spider-web and 3D cactus-like fog collectors showed high-efficient fog collection capacity. We envision that this fundamental understanding and rational design strategy can be applied in fog harvesting, heat transfer, liquid manipulation, and microfluidics.
•Regular patterns of nanoripples produced by bursts of fs laser pulses with ps delay.•The spatial frequency and depth of the nanoripples depends on the burst features.•For bursts with two sub-pulses ...the spatial period increases with the delay.•The ripples depth decreases with the intraburst delay due to a plasma shielding.•Plasma shielding is compensated by incubation for higher number of sub-pulses.
Bursts of linearly polarised femtosecond laser pulses with variable intra-burst delays on the picosecond timescale and different number of sub-pulses were used to produce laser-induced periodic surface structures (LIPSS) on stainless steel surfaces. The influence on the LIPSS morphology of the number sub-pulses, from 2 to 32, and the time separation between them, from 1.5 ps to 24 ps, was systematically investigated and compared to the case of unsplit pulses. The spatial periods and depths of the LIPSS produced by different irradiation conditions were derived by scanning electron and atomic force microscopies revealing that, in case of bursts with only two sub-pulses, an increase of the intra-burst delay produces nanoripples with higher spatial separation but shallower depth which is ascribed to a shielding effect. Whereas, increasing the number of sub-pulses a slight increase of the LIPSS spatial period has been observed.
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Stretchable lithium-ion batteries (SLIBs) hold great potential as a power source for wearable electronics. A major challenge in the development of SLIBs is fabricating stable and ...reliable stretchable electrodes. Herein, we develop a novel laser-structured microarray electrodes based SLIBs. An active material film adhered to a planar stretchable current collector is ablated by ultrafast laser into an independent microscale square array, enabling electrodes stretchable. A one-dimensional elastic analytical model is developed to evaluate the stretchability of the microarray electrodes under tensile conditions. The microscale square array adheres to the current collector and keeps intact if the shear stress is less than the adhesion force as well as the tensile stress is less than the tensile strength of the active material. The demonstrated electrodes have a mass active material loading of 10 mg cm−2 and maintain robust electrochemical performance when stretched beyond 500 cycles at 100 % strains. The fabricated SLIBs show a stable capacity of 1.2 mAh cm−2, and over 70 % of initial capacity can be maintained at 100 % strain.
