Ultrathin Foils Research Articles

Effect of additives on the microstructure and properties of pulsed electrodeposited copper foils

ABSTRACT A low-roughness ultra-thin copper foil was prepared by pulsed electrodeposition with a duty cycle 60%, pulse frequency of 600 Hz on titanium. The influence of sodium 3,3'-dithiodipropane sulphonate (SPS), hydroxyethyl cellulose (HEC), gelatin and collagen additives on the microstructure, mechanical properties and electrochemical behaviour of electrolytic copper foil was explored. Furthermore, the reaction mechanism of SPS and collagen additives on electrodeposited copper were discussed. The results showed that at 0.08 g L−1 collagen concentration, the lowest thickness, the highest microhardness and the optimal surface roughness were achieved (5.12 μm, 279.63 HV and 1.885 μm, respectively). X-ray diffraction results confirmed that electrolytic copper foils prepared when SPS was introduced into the blank solution had a preferred orientation of (220) texture, which benefitted from the synergistic effect of copper ions and additives. The intermediates formed by the additive and Cu+ occupied the active sites on the cathode surface that increased the nucleation sites for deposition. In addition, the formed complexes can act as a barrier to narrow ion deposition channels and inhibit the growth of Cu ions.

Comprehensive Understanding of Steric‐Hindrance Effect on the Trade‐Off Between Zinc Ions Transfer and Reduction Kinetics to Enable Highly Reversible and Stable Zn Anodes

AbstractThe electrode interface concentration polarization attributed to the contradiction between sluggish mass transfer process and rapid electrochemical reduction kinetics significantly restricts the practical application of Zn anode. Creating a moderate Zn ions transfer and reduction chemistry is essential for durable zinc‐ion batteries. In this work, this trade‐off effect is realized by selecting large‐size 4‐Aminomethyl cyclohexanecarboxylic acid (AMCA) molecule as the electrolyte additive. Intriguingly, AMCA molecules reorganize the Zn2+ solvation structure via the robust coordination with Zn2+ and reconstruct H‐bond networks, giving a pulled desolvation process. Meanwhile, AMCA enlarges the Zn2+ solvation size with a push force, confining the rapid electrochemical reduction kinetics. The balanced chemical environment is maintained via the moderate pull‐push interplay. Besides, AMCA can anchor on zinc surface to create a water‐poor microenvironment, fostering homogeneous Zn (002) deposition and effectively restricting water‐induced side‐reactions. Notably, the Zn||Zn symmetric cell with AMCA operates stably over 167 days at 20 mA cm−2. Moreover, the Zn||VOX full cell employed AMCA ensures outstanding capacity retention of 99.15% after 590 cycles at 2 A g−1, even with low N/P (4.3), lean electrolyte (50 µL mAh−1) and ultrathin Zn foil of 10 µm. This work reveals unique insights into the balanced interfacial chemistry design toward high‐performance zinc batteries.

Directed pulsed neutron source generation from inverse kinematic reactions driven by intense lasers

Neutron production driven by intense lasers utilizing inverse kinematic reactions is explored self-consistently by a combination of particle-in-cell simulations for laser-driven ion acceleration and Monte Carlo nuclear reaction simulations for neutron production. It is proposed that laser-driven light-sail acceleration from ultrathin lithium foils can provide an energetic lithium-ion beam as the projectile bombarding a light hydrocarbon target with sufficiently high flux for the inverse p(Li7,n) reaction to be efficiently achieved. Three-dimensional self-consistent simulations show that a forward-directed pulsed neutron source with ultrashort pulse duration 3 ns, small divergence angle 26°, and extremely high peak flux 3 × 1014n/(cm2⋅s) can be produced by petawatt lasers at intensities of 1021 W/cm2. These results indicate that a laser-driven neutron source based on inverse kinematics has promise as a novel compact pulsed neutron generator for practical applications, since the it can operate in a safe and repetitive way with almost no undesirable radiation.

Variable frequency selective structure (CFRP/Cu/CFRP) micro blind hole laser high-quality drilling method guided by acoustic emission technology

The laminated structure of carbon fiber reinforced plastic (CFRP)-Cu-CFRP is an important structure for aerospace radome. The blind holes manufacturing is core process, but there are technological challenges in achieving the exposure of a 10 μm thick copper foil at the bottom of the blind hole. The exact position of the 10 μm thick copper foil within the material’s internal space is unknown, and the uneven heat accumulation and conduction can easily cause burning and damage to the ultra-thin copper foil. To date, there is no publicly accessible literature that documents the execution of this specific process. In this paper, novel variable inner diameter spiral scanning guided by Cu-CFRP interface accurately extracted using cosine similarity (CS) algorithm is proposed to obtain a blind hole with near-zero ablation damage. The similarity of acoustic emission signals generated by laser interaction with Cu and CFRP, as well as thermal accumulation and conduction behavior under different scanning radius, are described. The high-quality blind holes have been successfully drilled, with a large area copper foil exposed at the bottom, while the surface of the copper foil remaining intact without any damage or heat affected zone. Compared with traditional drilling method, the average exposed copper foil area at the bottom of the blind holes is increased by 238.4 % (from 0.464 mm2 to 1.570 mm2). And the average taper of blind hole is reduced by 41.7 % (from 0.470 to 0.274). This method can effectively increase the area of exposed copper foil and reduces the taper of blind holes, improve the welding strength and conductivity of wires in aerospace radomes, thereby enhancing the stealth performance and operational reliability of fighter jets.

Development of Lightweight and Flexible Perovskite Solar Cells on Ultrathin Colorless Polyimide Foils.

The development of Perovskite Solar Cells (PSCs) on flexible substrates marks a significant advancement in thin-film photovoltaic technology. However, current state-of-the-art research predominantly utilizes Poly(ethylene terephthalate) (PET) substrate, which limits the deployment to less challenging environments. To address this limitation, we explore the fabrication of inverted PSCs on colorless polyimide (CPI) substrates that can withstand harsh environmental conditions. We employed a sequential sputtering technique to deposit indium tin oxide (bottom electrode) and nickel oxide (hole transport layer) as a base stack for the perovskite. This base layer was further enhanced by incorporating MeO-2PACz into the hole transport bilayer, significantly improving the NiOx interface, and thereby enhancing the efficiency of the devices. The PSCs fabricated on CPI demonstrated a power conversion efficiency (PCE) of 15.52% and a remarkable power-to-weight ratio (PWR) of 4.39 W/g, which is five times higher than that of devices on PET (0.87 W/g). Moreover, the active stack developed in this study can be used on any transparent substrate, showing its broader application potential.

Investigating laser and ultrasonic welding of pouch cell multi-foil current collectors for electric vehicle battery fabrication

The escalating necessity for more efficient and defect-free joining of ‘ultra-thin foil collectors-to-tabs’ in electric vehicle (EV) Li-ion pouch cells motivates this study. The prevalent ultrasonic welding (USW) method for these joint types, faces limitations such as design constraints and access requirements, laser welding (LW) emerges as a promising alternative offering flexibility, one-side access and faster speeds with efficient heat input. This study aims to investigate the feasibility of LW as a viable alternative to USW for joining current collectors-to-tab joints. It compares the mechanical, metallurgical, electrical and thermal analysis of the joints to evaluate both welding techniques for joint defects. The comparison of solid-state material mixing during USW and the intermixing of aluminium (Al) and copper (Cu) during fusion LW using EDX analysis presents interesting observations in the study. The USW generates a thin transition layer with intermetallic compounds (IMCs) attributed to the diffusion of Cu into the Al matrix during joining, which is comparatively lower as in the case of LW with higher material mixing with brittle IMCs like Al2Cu and Al4Cu9. However, the joint strength of LW is comparatively lower than the USW joint attributed to the reduced fusion zone area. Furthermore, from the electrical contact resistance and the joint temperature analysis, it was found that the resistance and temperature vary by as much as 13% and 6%, respectively, for the 50 A and 75 A passing currents when the USW is replaced with the LW process.

Effect of rolling schedules on ridging resistance of ultra-thin ferritic stainless steel foil

Effect of rolling schedules on ridging resistance of ultra-thin ferritic stainless steel foil

Strategies for Printing Ultra-Thin and Variable Width Lithium Foil

The commercial success of rechargeable lithium-related batteries in electronic devices since the 1990s has been remarkable. Technologies in the field continue to develop to make batteries safer, longer lasting, and more powerful. Emerging lithium-ion battery technologies such as solid-state batteries or high-silicon anode materials utilize, for example, ultra-thin lithium metal foil due to lithium metal high specific capacity (3860 mA h g-1), however; traditional thin lithium foil manufacturing methods have proven challenging at scale due to metal reactivity, poor foil tensile strength, and safety concerns. Additionally, lithium metal foil is needed in a variety of thicknesses, widths, and surface characteristics, which are all crucial for advancing lithium metal based batteries. Fortunately, it can be done via industry standard technologies when using LIOVIX®, Printable Lithium Technology.LIOVIX formulation has been coated using direct slot die technology at the benchtop scale and tension web slot die technology at the Roll-to-Roll (R2R) scale. Slot die technology facilitates two major elements of this process; particles larger than the theoretical wet film thickness can be deposited, and also the material can be shipped, delivered, and mixed without exposing lithium to air until it leaves the slot die head. This approach allowed us to achieve a uniform coating with heights ranging from 7 µm to 30 µm at a variety of coating widths. This has been done at the benchtop level at speeds up to 200 mm s-1 while maintaining a uniform coating on a copper substrate. R2R coating has done via a tension web coater, with similar theoretical wet film thickness. Specifically, the application of LIOVIX as a coating is particularly noteworthy for offering a strategic advantage in large scale manufacturing while maximizing the electrochemical performance.LIOVIX formulation enables the R2R production of lithium foil materials, and using a pre-metering system, the coating can be reliably produced at a variety of areal capacity targets.

Study on fracture toughness of ultra-thin stainless steel foils

Abstract Ultra-thin stainless steel foils have garnered significant attention due to their exceptional mechanical properties, including light weight, high strength, toughness, corrosion resistance, oxidation resistance, high temperature resistance, and superior shielding properties. In this study, we conducted experimental tests to evaluate the mechanical properties of ultra-thin stainless steel foils, focusing on the determination of Young’s modulus and yield stress for two distinct thicknesses of steel foils. Furthermore, employing both experimental and numerical simulation methodologies, we investigated the impact of wrinkles on the fracture toughness of steel foils containing central cracks subjected to tensile loading. The findings presented in this paper not only contribute to a comprehensive understanding of the mechanical behavior of ultra-thin stainless steel foils but also serve as a fundamental basis for subsequent numerical simulations and fracture toughness estimations. This research lays the groundwork for advancing the development and utilization of ultra-thin stainless steel foils across various industrial applications.

Efficient laser-driven proton acceleration from a petawatt contrast-enhanced second harmonic mixed-glass laser system

Efficient laser-driven plasma acceleration of ion beams requires precision control of the target–plasma profile, which is crucial to optimize the laser energy transfer. Along the laser propagation direction, this can be achieved by tailoring the temporal structure of the laser pulse. We show for the first time that frequency-doubling of a short pulse (hundreds-femtosecond range) petawatt-class mixed-glass laser system, which results in temporal intensity contrast enhancement, enables surface and volumetric laser–energy coupling, and the acceleration of proton beams from few-nanometer-thick foil targets. Experimentally, maximum ion energies and laser-to-proton energy conversion efficiencies were found to be both maximized at optimum laser and target conditions manifested when the normalized target density nearly equalizes the normalized laser vector potential, which is in agreement with theory and simulations. These signatures are recognized as a unique indication of the interaction between ultra-intense laser pulses with high temporal intensity contrast and ultra-thin nanometer-scale targets. Transverse modulations of accelerated proton beams in the form of bubble- and ring-like structures measured in the thinnest targets provide additional evidence of volumetric laser-driven particle acceleration regimes and transitional features in ultra-thin foil targets specific to laser–plasma interactions characterized by a high temporal intensity contrast. These results open avenues in the generation of high contrast laser pulses from short-pulse-femtosecond petawatt mixed-glass laser systems and demonstrate the feasibility of this technique for applications requiring high laser intensity contrast with high efficiency.

Intelligent seam tracking in foils joining based on spatial–temporal deep learning from molten pool serial images

Vision-based weld seam tracking has become one of the key technologies to realize intelligent robotic welding, and weld deviation detection is an essential step. However, accurate and robust detection of weld deviations during the microwelding of ultrathin metal foils remains a significant challenge. This challenge can be attributed to the fusion zone at the mesoscopic scale and the complex time-varying interference (pulsed arcs and reflected light from the workpiece surface). In this paper, an intelligent seam tracking approach for foils joining based on spatial–temporal deep learning from molten pool serial images is proposed. More specifically, a microscopic passive vision sensor is designed to capture molten pool and seam trajectory images under pulsed arc lights. A 3D convolutional neural network (3DCNN) and long short-term memory (LSTM)-based welding torch offset prediction network (WTOP-net) is established to implement highly accurate deviation prediction by capturing long-term dependence of spatial–temporal features. Then, expert knowledge is further incorporated into the spatio-temporal features to improve the robustness of the model. In addition, the slime mould algorithm (SMA) is used to prevent local optima and improve accuracy, efficiency of WTOP-net. The experimental results indicate that the maximum error detected by our method fluctuates within ± 0.08 mm and the average error is within ± 0.011 mm when joining two 0.12 mm thickness stainless steel diaphragms. The proposed approach provides a basis for automated robotic seam tracking and intelligent precision manufacturing of ultrathin sheets welded components in aerospace and other fields.

Developing novel ultra-thin refractory medium-entropy foils with excellent strength-ductility synergy

Developing novel ultra-thin refractory medium-entropy foils with excellent strength-ductility synergy

Accumulated laser-photoneutron generation

We present repeated generation of photoneutrons by double-pulse irradiation of ultrathin foils. A ~ mJ prepulse turns a foil into a 100-μm scale plasma plume from which a beam of MeV electrons is generated by the main pulse. Neutrons are generated in a secondary metal target placed downstream to the electron beam. We utilize an automated target system capable of delivering ultrathin foils to the laser focus at an average rate of 0.1 Hz. With 153 consecutive laser shots taken over the course of 24 min, we generated a total 2.6 × 107 neutrons. We present a method for evaluating how the number of photoneutrons scales with the laser intensity in this experimental scenario, which we validate against the measured yields.

Formability and mechanism of ultra-thin titanium foil under the elevated temperature and high strain rate in electromagnetic forming

Electromagnetic forming (EMF) is a high-speed forming process with significant potential for manufacturing bipolar plates. However, titanium's low conductivity requires the use of a driver sheet in traditional EMF, limiting its formability improvement. This study proposed a novel electromagnetic forming method with independent loading of the magnetic field and current (EMF-ILMFC), enabling separate application of electromagnetic force and Joule heating. The dynamic deformation behavior of ultra-thin titanium was investigated using three different loading methods: quasi-static (QS), electromagnetic bulging with driver sheets (EMB-DS), and electromagnetic bulging with the new method (EMB-ILMFC). The study revealed that the forming limit under EMB-ILMFC was significantly higher than under EMB-DS and QS, with a maximum improvement of 139.1%. Numerical simulations and experimental analyses were conducted to elucidate the thermal effects on formability during dynamic deformation. The results indicate that thermal effects reduce flow stress, extend the duration of inertia and high strain rates, and thereby improve the formability of titanium.

Battery electronification: intracell actuation and thermal management

Electrochemical batteries – essential to vehicle electrification and renewable energy storage – have ever-present reaction interfaces that require compromise among power, energy, lifetime, and safety. Here we report a chip-in-cell battery by integrating an ultrathin foil heater and a microswitch into the layer-by-layer architecture of a battery cell to harness intracell actuation and mutual thermal management between the heat-generating switch and heat-absorbing battery materials. The result is a two-terminal, drop-in ready battery with no bulky heat sinks or heavy wiring needed for an external high-power switch. We demonstrate rapid self-heating (∼ 60 °C min−1), low energy consumption (0.138% °C−1 of battery energy), and excellent durability (> 2000 cycles) of the greatly simplified chip-in-cell structure. The battery electronification platform unveiled here opens doors to include integrated-circuit chips inside energy storage cells for sensing, control, actuating, and wireless communications such that performance, lifetime, and safety of electrochemical energy storage devices can be internally regulated.

Generation of attosecond gigawatt soft x-ray pulses through coherent Thomson backscattering.

Collision between relativistic electron sheets and counterpropagating laser pulses is recognized as a promising way to produce intense attosecond x rays through coherent Thomson backscattering (TBS). In a double-layer scheme, the electrons in an ultrathin solid foil are first pushed out by an intense laser driver and then interact with the laser reflected off a second foil to form a high-density relativistic electron sheet with vanishing transverse momentum. However, the repulsion between these concentrated electrons can increase the thickness of the layer, reducing both its density and subsequently the coherent TBS. Here, we present a systematic study on the evolution of the flying electron layer and find that its resulting thickness is determined by the interplay between the intrinsic space-charge expansion and the velocity compression induced by the drive laser. How the laser driver, the target areal density, the reflector, and the collision laser intensity affect the properties of the produced x rays is explored. Multidimensional particle-in-cell simulations indicate that employing this scheme in the nonlinear regime has the potential to stably produce soft x rays with several gigawatt peak power in hundreds of terawatt ultrafast laser facilities. The pulse duration can be tuned to tens of attoseconds. This compact and intense attosecond x-ray source may have broad applications in attosecond science.

Improving the beam quality of the low-energy muon beamline at Paul Scherrer Institute: Characterization of ultrathin carbon foils

The low-energy muon (LEM) beamline at the Paul Scherrer Institute currently stands as the world’s only facility providing a continuous beam of low-energy muons with keV energies for conducting muon spin rotation experiments on a nanometer depth scale in heterostructures and near a sample’s surface. As such, optimizing the beam quality to reach its full potential is of paramount importance. One of the ongoing efforts is dedicated to improving the already applied technique of single muon tagging through the detection of secondary electrons emerging from an ultrathin carbon foil. In this work, we present the results from installing a thinner foil with a nominal thickness of 0.5 μg cm−2 and compare its performance to that of the previously installed foil with a nominal thickness of 2.0 μg cm−2. Our findings indicate improved beam quality, characterized by smaller beam spots, reduced energy loss and straggling of the muons, and enhanced tagging efficiency. Additionally, we introduce a method utilizing blue laser irradiation for cleaning the carbon foil, further improving and maintaining its characteristics. Published by the American Physical Society 2024

Preparation of Ultra-thin Copper Foil with Low Profile and High Tensile Strength on Surface of 18-µm Carrier Copper Foil

Preparation of Ultra-thin Copper Foil with Low Profile and High Tensile Strength on Surface of 18-µm Carrier Copper Foil

High-efficiency and low-consumption preparation of ultra-thin and high-performance nanotwinned copper foils by high-gravity intensified direct current electrodeposition

In study, a novel strategy was adopted by the integration of microstructure control and electrodeposition process intensification for high-efficiency, low-consumption and convenient electrodeposition of high performance and ≤4.5 μm ultra-thin copper foils for lithium-ion battery (LIB) collectors. The microstructure and the electrodeposition process of copper foils were effectively controlled and enhanced by the synergy of optimized electrolyte and Multi-Concentric Cylindrical Electrodes-Rotating Bed (MCCE-RB) which was used to generate high-gravity fields. Equiaxed nanotwinned copper (nt-Cu) foils possessed ultra-thin thicknesses ranging from 3.70 to 4.08 μm. They exhibited tensile strength and elongation of 787 MPa and 21.2 %, respectively. In contrast to the conventional direct current electrodeposition, electrodeposition and current efficiency were increased by 15.1 % and 27.2 %, respectively, while the energy consumption was decreased by 23.7 % in the high-gravity field. This is beneficial to improve the weight and energy density of LIBs by applying the strategy and technique of high-gravity intensifying.

Properties and microstructure regulation of electrodeposited ultra-thin copper foil in a simple additive system

Hydroxyethyl cellulose (HEC) has been commonly used in a variety of complex formulations for acid copper plating. However, the roles of HEC acting in acid copper plating still lacks of systematic investigation. To explore the efficacy of HEC in the deposition of the ultra-thin electrodeposited copper foil (ED-Cu), we designed a simple formulation system, in which HEC was used as the single organic additive. Using electron backscatter diffraction (EBSD), microstructures of the prepared ED-Cu was comprehensively investigated. The results showed that the ED-Cu was characterized by a mixed distribution of columnar and equiaxed crystals. Grain morphology, dislocation density and crystal orientation of the ED-Cu could be regulated by HEC concentration. According to the cyclic voltammetry (CV) and chronoamperometry (CA) results, the introduction of HEC between 0–200 ppm led to a polarizing effect, which marginally increased with the HEC concentration. Meanwhile, the increase of HEC concentration enhanced the nucleation rates of copper and reduced the grain size during instantaneous nucleation. The introduction of the HEC also altered the preferred orientation of the ED-Cu foil. Mechanical results showed that the optimum concentration of HEC addition was 125 mg l−1.