How lasers can push silicon-graphite anodes towards next-generation battery

Graphite anode material is commonly used in lithium-ion batteries. Due to the demand for a significantly increased energy density for xEVs (electromotive vehicles), there is worldwide a strong effort to add nano-sized silicon particles to composite graphite electrodes. Silicon has the benefit to provide one order of magnitude higher gravimetrical energy density than graphite. However, a bottleneck of silicon is its huge volume expansion of about 300 % during electrochemical cycling which induces high compressive stress and subsequent film delamination, crack formation, and finally degradation of electrochemical cells. In this study, thick film graphite, silicon, and silicon–graphite composite electrodes were developed and subsequently ultrafast laser structured in order to reduce compressive stress during electrochemical cycling and diffusion overpotential. The latter one is a critical issue at elevated power densities and for high film thicknesses, i.e., mass loading. By laser ablation, grid structures were introduced into the electrodes and 3D elemental mapping could demonstrate that new lithium-ion diffusion pathways arise along the structure\u27s sidewalls and are activated with increasing power densities. It was successfully shown that laser structured electrodes benefit from a homogenous lithiation, reduced compressive stress, and an overall improved electrochemical performance in comparison to unstructured electrodes. A reduced mechanical and chemical cell degradation was achieved with structured electrodes in comparison to unstructured ones and design rules for silicon–graphite electrode architectures were derived. Laser structuring of electrodes offers a new manufacturing tool for next-generation battery production to overcome current limitations in electrode design and cell performance

Compact and Highly Efficient 2.5 MHz SiC Electronic Ballast for Inductively Coupled UV Lamps

Inductively coupled UV lamps require a high-frequency alternating current for ignition and efficient operation. In this work, we present a switch-mode half-bridge inverter, with SiC-MOSFETs, which achieves a conversion efficiency from the DC-Link to a 2.5 MHz alternating current of 95% at 750W lamp power, including auxiliary power for the gate drivers and the controller. Furthermore, the paper describes an algorithm for the active power measurement of a 2.5 MHz voltage and current signal with an oscilloscope, averaging in the frequency domain and spectral distinction of the active power at the switching frequency

How lasers can push silicon-graphite anodes towards next-generation battery

Graphite anode material is commonly used in lithium-ion batteries. Due to the demand for a significantly increased energy density for xEVs (electromotive vehicles), there is worldwide a strong effort to add nano-sized silicon particles to composite graphite electrodes. Silicon has the benefit to provide one order of magnitude higher gravimetrical energy density than graphite. However, a bottleneck of silicon is its huge volume expansion of about 300 % during electrochemical cycling which induces high compressive stress and subsequent film delamination, crack formation, and finally degradation of electrochemical cells. In this study, thick film graphite, silicon, and silicon–graphite composite electrodes were developed and subsequently ultrafast laser structured in order to reduce compressive stress during electrochemical cycling and diffusion overpotential. The latter one is a critical issue at elevated power densities and for high film thicknesses, i.e., mass loading. By laser ablation, grid structures were introduced into the electrodes and 3D elemental mapping could demonstrate that new lithium-ion diffusion pathways arise along the structure\u27s sidewalls and are activated with increasing power densities. It was successfully shown that laser structured electrodes benefit from a homogenous lithiation, reduced compressive stress, and an overall improved electrochemical performance in comparison to unstructured electrodes. A reduced mechanical and chemical cell degradation was achieved with structured electrodes in comparison to unstructured ones and design rules for silicon–graphite electrode architectures were derived. Laser structuring of electrodes offers a new manufacturing tool for next-generation battery production to overcome current limitations in electrode design and cell performance

Characterization of Argon/Hydrogen Inductively Coupled Plasma for Carbon Removal over Multilayer Thin Films

Inductively coupled plasma with an argon/hydrogen (Ar/H2) mixture is a potential solution to many surface treatment problems, especially when encountering carbon contamination in optical X-ray and extreme ultraviolet instruments. Removing carbon contamination on multilayer thin films with Ar/H2 plasma extends the lifetime of the above devices. To further investigate the reaction between plasma and carbon, both optical emission spectroscopy and finite element method with multiphysics fields were employed. The results demonstrated that the intensities of the Balmer lines were in good agreement with the densities of the radical hydrogen atoms from the simulation model, showing a dependence on the mixing ratio. At an electrical input power of 165 W and a total pressure of 5 Pa, an optimum mixing ratio of about 35 ± 5 % hydrogen produced the highest density of hydrogen radicals, coinciding with the highest carbon removal rate. This shows that the carbon removal with Ar/H2 plasma was mainly controlled by the density of hydrogen radicals, and the mixing ratio showed a significant impact on the removal rates

Ultrafast laser ablation of aqueous processed thick-film Li(Ni0.6_{0.6}Mn0.2_{0.2}Co0.2_{0.2})O2_{O2} cathodes with 3D architectures for lithium-ion batteries

Lithium-ion batteries have dominated the field of electrochemical energy storage for years due to their high energy density. Recently, with the rapid development of E-mobility, the quest for high power and high energy batteries with reduced production costs has aroused great interest and is still a huge challenge. The energy density at battery level can be increased by using electrodes with thicknesses > 150 μm. However, capacity fade of thick-film electrodes at C-rates > C/2 is observed. To compensate the capacity loss, 3D architectures with a high aspect ratio are produced using ultrafast laser ablation. In addition, aqueous processing of cathodes using water-based binders can achieve environmentally friendly production and cost reduction by replacing the conventional organic PVDF binder and the toxic and volatile NMP solvent. However, the pH value of aqueous processed cathode slurries increases to 12 due to the reaction between active material and water, which decreases the specific capacity of the cells and on the other side results in chemical corrosion of the current collector during casting. In order to determine the optimal pH range and avoid the damage of the current collector, slurries with pH values ranging from 8 to 12 are manufactured. In this work, thick-film Li(Ni0.6Mn0.2Co0.2)O2 electrodes are manufactured with aqueous binders and acid adjustment, and are subsequently structured using ultrafast laser ablation. This combination is beneficial to achieve green production, low cost, high power, and high energy application of lithium-ion batteries

Laser-induced forward transfer as a versatile tool for developing silicon-based anode materials

Further efforts are needed to increase the power and energy density of lithium-ion batteries. This increase can be achieved by developing new electrode architectures and new active materials. As a new active material for anodes, silicon is in the focus of current research, as it has an order of magnitude higher specific energy density compared to the commonly used graphite. In terms of new architecture, printing anodes with the "laser induced forward transfer" (LIFT) process offers a variety of possibilities. For this work, printing with LIFT adapted anode paste was realized and corresponding laser parameters were optimized. The anodes were printed with graphite for subsequent analyses in a coin cell and compared with state-of-the-art coated electrodes made with the same paste. The conventional coated electrodes were either calendered or uncalendered. It was shown that the electrochemical behavior of the printed anodes is comparable to that of the conventional coated anodes. Finally, preliminary studies were made to print an anode with a multilayer architecture. Within the anode layer, which consists of three individual printed layers, silicon layers are incorporated in order to significantly increase the specific capacity

Inductive Medium Pressure UV-Source

Abstract: In this paper, an efficient inductively coupled medium pressure source for ultraviolet radiation (UV-source) is demonstrated. The lamp was operated with powers up to 3kW while the radiation and the coldest point temperature were measured. In addition, different coil geometries were investigated. Here a symmetrical and asymmetrical winding density were compared. Also the operation pressures and DC to radiation efficiencies are presented. In this work, an operation pressure of one atmosphere and an UV-efficiency (200–380 nm) of 15.5% was achieved. This is comparable to conventional medium pressure Hg-lamp technology. The main advantage of the presented inductive lamp is the electrodeless operation and therefore the longer service life, since an electrode failure is eliminated

Laser-induced forward transfer as a versatile tool for developing silicon-based anode materials

Further efforts are needed to increase the power and energy density of lithium-ion batteries. This increase can be achieved by developing new electrode architectures and new active materials. As a new active material for anodes, silicon is in the focus of current research, as it has an order of magnitude higher specific energy density compared to the commonly used graphite. In terms of new architecture, printing anodes with the "laser induced forward transfer" (LIFT) process offers a variety of possibilities. For this work, printing with LIFT adapted anode paste was realized and corresponding laser parameters were optimized. The anodes were printed with graphite for subsequent analyses in a coin cell and compared with state-of-the-art coated electrodes made with the same paste. The conventional coated electrodes were either calendered or uncalendered. It was shown that the electrochemical behavior of the printed anodes is comparable to that of the conventional coated anodes. Finally, preliminary studies were made to print an anode with a multilayer architecture. Within the anode layer, which consists of three individual printed layers, silicon layers are incorporated in order to significantly increase the specific capacity

Ultrafast laser ablation of aqueous processed thick-film Li(Ni0.6_{0.6}Mn0.2_{0.2}Co0.2_{0.2})O2_{O2} cathodes with 3D architectures for lithium-ion batteries

Lithium-ion batteries have dominated the field of electrochemical energy storage for years due to their high energy density. Recently, with the rapid development of E-mobility, the quest for high power and high energy batteries with reduced production costs has aroused great interest and is still a huge challenge. The energy density at battery level can be increased by using electrodes with thicknesses > 150 μm. However, capacity fade of thick-film electrodes at C-rates > C/2 is observed. To compensate the capacity loss, 3D architectures with a high aspect ratio are produced using ultrafast laser ablation. In addition, aqueous processing of cathodes using water-based binders can achieve environmentally friendly production and cost reduction by replacing the conventional organic PVDF binder and the toxic and volatile NMP solvent. However, the pH value of aqueous processed cathode slurries increases to 12 due to the reaction between active material and water, which decreases the specific capacity of the cells and on the other side results in chemical corrosion of the current collector during casting. In order to determine the optimal pH range and avoid the damage of the current collector, slurries with pH values ranging from 8 to 12 are manufactured. In this work, thick-film Li(Ni0.6Mn0.2Co0.2)O2 electrodes are manufactured with aqueous binders and acid adjustment, and are subsequently structured using ultrafast laser ablation. This combination is beneficial to achieve green production, low cost, high power, and high energy application of lithium-ion batteries