The ultrafast laser ablation of Li(Ni0.6_{0.6}Mn0.2_{0.2}Co0.2_{0.2})O2_{2} electrodes with high mass loading

Lithium-ion batteries have become the most promising energy storage devices in recent years. However, the simultaneous increase of energy density and power density is still a huge challenge. Ultrafast laser structuring of electrodes is feasible to increase power density of lithium-ion batteries by improving the lithium-ion diffusion kinetics. The influences of laser processing pattern and film thickness on the rate capability and energy density were investigated using Li(Ni0.6Mn0.2Co0.2)O2 (NMC 622) as cathode material. NMC 622 electrodes with thicknesses from 91 µm to 250 µm were prepared, while line patterns with pitch distances varying from 200 µm to 600 µm were applied. The NMC 622 cathodes were assembled opposing lithium using coin cell design. Cells with structured, 91 µm thick film cathodes showed lesser capacity losses with C-rates 3C compared to cells with unstructured cathode. Cells with 250 µm thick film cathode showed higher discharge capacity with low C-rates of up to C/5, and the structured cathodes showed higher discharge capacity, with C-rates of up to 1C. However, the discharge capacity deteriorated with higher C-rate. An appropriate choice of laser generated patterns and electrode thickness depends on the requested battery application scenario; i.e., charge/discharge rate and specific/volumetric energy density

Lithium distribution in structured graphite anodes investigated by laser-induced breakdown spectroscopy

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 scenari

Improved Capacity Retention of SiO2_{2}-Coated LiNi0.6_{0.6}Mn0.2_{0.2}Co0.2_{0.2}O2_{2} Cathode Material for Lithium-Ion Batteries

Surface degradation of Ni-enriched layered cathode material Li[Ni0.6Mn0.2Co0.2]O2 (NMC622) is the main reason that leads to large capacity decay during long-term cycling. In the frame of this research, an amorphous SiO2 coating was applied onto the surface of the commercially available NMC622 powder by a wet coating process, through the condensation reaction of tetraethylorthosilicate. The chemical composition of the coating layer was analyzed by inductively-coupled plasma. The morphology was studied by scanning electron microscopy and transmission electron microscopy. Electrochemical properties, including cyclic voltammetry, galvanostatic cycling, and rate capability measurements in a half-cell configuration, were tested to compare the electrochemical behavior of the non-coated and coated NMC622 materials. It is shown that the rate performance of the NMC622 materials is not aected by the coating layer. After 700 cycles in the range of 3.0–4.3 V at 2 C discharge, the cells with SiO2-coated NMC622 materials retained 80% of their initial capacity, which is higher than the uncoated ones (74%). Physicochemical characterizations, e.g., XRD and SEM, were performed post-mortem to reveal the stabilizing mechanism of the SiO2-coated NMC622 electrodes after long-term cycling. Based on these results, this is due to the shielding effect of the coating between the NMC622 particle surface and the liquid electrolyte, along with its scavenging effect on HF. SiO2 coating is therefore a facile surface modification method that results in potentially significant enhancement of the cyclic stability of Ni-rich NMC materials

Laser-induced breakdown spectroscopy for studying the electrochemical impact of porosity variations in composite electrode materials

The porosity in composite electrode materials can vary on micro-and nanometer scale and has a great impact on electrochemical performance in lithium-ion cells. Liquid electrolyte has to penetrate into the entire porous electrodes in order to enable lithium-ion diffusion. For studying the electrochemical impact of porosity variations in composite lithium-nickel-manganese-cobalt-oxide thick films (Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 , NMC), laser-induced breakdown spectroscopy (LIBS) was applied. A rapid chemical screening of the complete electrode after electrochemical cycling and cell degradation was performed. This rather new technological approach was used to obtain post-mortem critical information about surface and bulk phenomena that define and control the performance of lithium-ion batteries. The influence of porosity variations along NMC electrode surfaces was studied regarding capacity retention, life-time, and lithium distribution. For this purpose, different geometrical arrangements of porosity distribution were generated by embossing. Using LIBS, elemental mapping of lithium was obtained with a lateral resolution of 100 μm. A correlation between porosity distribution, cell degradation and local lithium plating could be identified

Multiobjective Optimization of Laser Polishing of Additively Manufactured Ti-6Al-4V Parts for Minimum Surface Roughness and Heat-Affected Zone

Metal parts produced by additive manufacturing often require postprocessing to meet the specifications of the final product, which can make the process chain long and complex. Laser post-processes can be a valuable addition to conventional finishing methods. Laser polishing, specifically, is proving to be a great asset in improving the surface quality of parts in a relatively short time. For process development, experimental analysis can be extensive and expensive regarding the time requirement and laboratory facilities, while computational simulations demand the development of numerical models that, once validated, provide valuable tools for parameter optimization. In this work, experiments and simulations are performed based on the design of experiments to assess the effects of the parametric inputs on the resulting surface roughness and heat-affected zone depths. The data obtained are used to create both linear regression and artificial neural network models for each variable. The models with the best performance are then used in a multiobjective genetic algorithm optimization to establish combinations of parameters. The proposed approach successfully identifies an acceptable range of values for the given input parameters (laser power, focal offset, axial feed rate, number of repetitions, and scanning speed) to produce satisfactory values of Ra and HAZ simultaneously

Wettability and osteoblast cell response modulation through UV laser processing of nylon 6,6

With an ageing population the demand for cheap, efficient implants is ever increasing. Laser surface treatment offers a unique means of varying biomimetic properties to determine generic parameters to predict cell responses. This paper details how a KrF excimer laser can be employed for both laser-induced patterning and whole area irradiative processing to modulate the wettability characteristics and osteoblast cell response following 24 hour and 4 day incubation. Through white light interferometry (WLI) it was found that the surface roughness had considerably increased by up to 1.5 µm for the laser-induced patterned samples and remained somewhat constant at around 0.1 µm for the whole area irradiative processed samples. A sessile drop device determined that the wettability characteristics differed between the surface treatments. For the patterned samples the contact angle, θ, increased by up to 25° which can be attributed to a mixed-state wetting regime. For the whole area irradiative processed samples θ decreased owed to an increase in polar component, γP. For all samples θ was a decreasing function of the surface energy. The laser whole area irradiative processed samples gave rise to a distinct correlative trend between the cell response, θ and γP. However, no strong relationship was determined for the laser-induced patterned samples due to the mixed-state wetting regime. As a result, owed to the relationships and evidence of cell differentiation one can deduce that laser whole area irradiative processing is an attractive technology for employment within regenerative medicine to meet the demands of an ageing population

On the effects of using CO2 and F2 lasers to modify the wettability of a polymeric biomaterial.

Enhancement of the surface properties of a material by means of laser radiation has been amply demonstrated previously. In this work a comparative study for the surface modification of nylon 6,6 has been conducted in order to vary the wettability characteristics using CO2 and excimer lasers. This was done by producing 50 μm spaced (with depths between 1 and 10 μm) trench-like patterns using various laser parameters such as varying the laser power for the CO2 laser and number of pulses for the excimer laser. Topographical changes were analysed using optical microscopy and white light interferometry which indicated that both laser systems can be implemented for modifying the topography of nylon 6,6. Variations in the surface chemistry were evaluated using energy-dispersive X-ray spectroscopy and x-ray photoelectron spectroscopy analysis and showed that the O2 increased by up to 1.5% At. and decreased by up to 1.6% At. for the CO2 and F2 laser patterned samples, respectively. Modification of the wettability characteristics was quantified by measuring the advancing contact angle, which was found to increase in all instances for both laser systems. Emery paper roughened samples were also analysed in the same manner to determine that the topographical pattern played a major role in the wettability characteristics of nylon 6,6. From this, it is proposed that the increase in contact angle for the laser processed samples is due to a mixed intermediate state wetting regime owed to the periodic surface roughness brought about by the laser induced trench-like topographical patterns

Laser micro structuring of composite Li (Ni0.6Mn0.2Co0.2) O2cathode layersfor lithium-ion batteries

Lithium-ion batteries (LIB) using lithium nickel manganese cobalt oxide Li(Ni1/3Mn1/3Co1/3)O2, NMC-111) as cathode material have already become one of the most important types of mobile power sources due to their high gravimetric and volumetric capacity. Nevertheless, the automotive industry needs batteries with a further improved energy density to develop electric vehicles (EV) with comparable or even higher range than automobiles with ICE (Internal combustion engine). One approach to enhance the energy density is to increase the nickel content of the NMC cathode material. Therefore, NMC-622 cathodes were produced via tape casting containing 80 wt% of active material with a film thickness of 54 μm. The specific capacities were measured using galvanostatic measurements at different charging/discharging currents for cells with structured and unstructured electrodes. Laser-assisted generation of threedimensional architectures provides an increased active surface area to enhance interfacial kinetics with short lithium-ion diffusion paths. Ultrafast laser ablation was used in order to avoid a thermal-induced damage of the active material. It could be shown that laser structuring of electrode material leads to a significant improvement of the electrochemical performance, especially at high charging and discharging currents

Controlled experiments in lithic technology and function

From the earliest manifestations of tool production, technologies have played a fundamental role in the acquisition of different resources and are representative of daily activities in the lives of ancient humans, such as hunting (stone-tipped spears) and meat processing (chipped stone tools) (Lombard 2005; McPherron et al. 2010; Lombard and Phillipson 2010; Brown et al. 2012; Wilkins et al. 2012; Sahle et al. 2013; Joordens et al. 2015; Ambrose 2001; Stout 2001). Yet many questions remain, such as how and why technological changes took place in earlier populations, and how technological traditions, innovations, and novelties enabled hominins to survive and disperse across the globe (Klein 2000; McBrearty and Brooks 2000; Henshilwood et al. 2001; Marean et al. 2007; Brown et al. 2012; Režek et al. 2018).Projekt DEALinfo:eu-repo/semantics/publishedVersio