Collector Contact Research Articles

Wetting characteristics of Li-ion battery electrodes: Impact of calendaring and current collector contact angle - A Lattice Boltzmann Method investigation

Calendaring is a common process for enhancing the power density of Li-ion battery electrodes. In this study, the Shan-Chen-based Lattice Boltzmann Method is used to investigate the effects of different calendaring levels (0%, 10%, 20%, and 25%) on the wetting behavior of a Li-ion battery electrode. The actual contact angles between the electrolyte and battery components are incorporated, and the GPU-accelerated in-house code is developed to facilitate adequate meshing. An increased calendaring degree leads to a longer saturation time and increases gas entrapment within the cathode structure. The findings provide valuable insights into the dynamics of the electrolyte wetting process within the porous structure as calendaring levels change. The positioning of the pores and electrode particles strongly affects the electrolyte imbibition rate. In addition, this study examines the influence of the contact angle between the electrolyte and current collectors as a function of calendaring degrees. A 15° contact angle results in marginally lower gas entrapment at 25% calendaring while consistently showing lower imbibition rates across all calendaring levels. At lower calendaring cases, 35° and 60° contact angle cases perform nearly the same, while at higher calendaring, the 60° case outperforms the 35° case but at the expense of higher gas entrapment.

Tuning wettability of gallium-based liquid metal anode for lithium-ion battery via a metal mixing strategy

Exploring highly stable alloy-type anodes for rechargeable lithium batteries is urgent with the ever-increasing demands for high energy density batteries. The liquid metal (LM)-based anodes demonstrate great potential in advanced lithium-ion batteries due to their high energy densities and self-healing performance. However, its high surface tension leads to poor wettability towards the current collector and higher interfacial contact resistance. In this study, we developed a new free-standing LM-based anode LM-W10/Cu foil with good wettability and machinability by mixing high-melting-point tungsten (W) nanoparticles. It greatly improves the inherent defects of poor interfacial contact and lithium diffusion kinetics between the LM and current collectors, reduces the tedious and costly electrode manufacturing process, and regulates lithium deposition behaviors. And this metal mixing strategy has a negligible effect on the self-healing nature of LM. Symmetric cells of LM-W10/Cu foil anodes displayed a low overpotential (~13 mV) and cycled stably for more than 8,000 h (4,000 cycles) at 0.5 or 1 mA/cm2; full cells coupled with LiFePO4 cathode showed a high capacity retention of 95.15% after 150 cycles.

Exploring particle-current collector contact damage in Li-ion battery using DEM-FEM scheme

Calendering is an essential step in the manufacturing process of lithium-ion batteries. However, the intrusion of active particles into metal foil can damage the current collector during calendering. Here, we investigate the changes in surface morphology and the tensile properties of current collector after calendering. The damage mechanisms of tensile strength reduction for current collector due to compressive pressure are revealed by combining the calendering tests, tensile experiments, and simulations. Specifically, the DEM-FEM scheme is proposed, which combines the discrete element method (DEM) with the finite element method (FEM) to characterize the mechanical behavior of current collectors after the intrusion of active particles. The results show that the current collectors become more brittle and vulnerable with the increase of compressive pressure. Finally, the failure phase diagrams are presented during the winding and electrochemical processes. This study can reveal the failure behavior of current collectors and guides the electrode manufacturing optimization.

Interfacial effect on the polarization resistance of SrM0.1Mo0.9O3-δ (M = Mg2+, Fe3+)/GDC-based composite electrodes

The present study examines the interfacial effect on the area-specific resistance (ASR) offered by SrM0.1Mo0.9O3-δ (M = Mg2+, Fe3+)/Gd0.1Ce0.9O2-δ (GDC) composite electrodes. The symmetrical cells having 8YSZ electrolyte and SrFe0.1Mo0.9O3-δ/Gd0.1Ce0.9O2-δ composite electrodes are fabricated with and without the GDC buffer layer. The electrode ASR in cells with and without GDC-buffer layer is 0.09 Ω.cm2 and 0.68 Ω.cm2 at 850 °C in 3% H2O/H2, respectively. More than a 50% rise in the magnitude of electrode ASR is seen in cells with no GDC buffer layer after 10 redox cycles. Phase analysis of these cells reveals a dense layer of an insulating SrZrO3-based phase formed at the electrode/electrolyte interface due to the chemical reaction between SrFe0.1Mo0.9O3-δ and 8YSZ. In contrast, the cells possessing a GDC buffer layer show a small ASR increase from 0.09 Ω.cm2 to 0.14 Ω.cm2 after the same number of redox cycles without the presence of any secondary phase. The effect of the current collector contact area on the ASR of the SrMg0.1Mo0.9O3-δ/Gd0.1Ce0.9O2-δ composite electrode is also evaluated. Symmetrical cells with a dense GDC buffer layer and composite electrodes are prepared. The Pt current collector area on the electrode layer is varied from 0.13 cm2 to 0.5 cm2, and the electrode specific resistance is measured at 850 °C in a 3% H2O/H2 environment. The electrode resistance declines with increasing current collector area. The cell with the electrode surface entirely covered by the current collector exhibits a very low ASR of ∼ 0.07 Ω.cm2. The sensitivity of the interfacial polarization resistance towards a slight change in the strength of the current field is the possible reason for observing such ASR variation.

Modeling Contact Behavior of Multiparticles and Particle–Current Collector Contact in Porous Electrode

Modeling Contact Behavior of Multiparticles and Particle–Current Collector Contact in Porous Electrode

Impact of Ring-Shaped Collector Contact on Total Ionizing Dose Susceptibility of Vertical n-p-n Bipolar Transistors

The impact of ring-shaped collector contact (RCC) on total ionizing dose (TID) susceptibility of 40-V vertical n-p-n bipolar transistors is investigated. The 60Co <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> -ray irradiation experiment shows that the devices with RCC suffer less current gain degradation than their counterparts with conventional collector contact structure, which is independent of the emitter area and bias condition during irradiation. Technology computer-aided design (TCAD) simulation results indicate that the enhancement in radiation tolerance of the RCC devices should be attributed to the mitigation of trap-assisted carrier recombination at the Si/SiO2 interfaces near emitter–base (EB) junction rather than the concentration or distribution variations of radiation-induced traps. Moreover, the mitigation of carrier recombination in RCC devices could result from the creation of new current flow paths that suppress the diffusion of injected electrons toward the trap-enriched Si/SiO2 interfaces.

Modeling Contact Behavior of Multiparticles and Particle–Current Collector Contact in Porous Electrode

There are various component contacts in porous electrodes, such as the direct contact between the active particles and the particle–current collector, during electrode manufacturing and lithium‐ion battery electrochemical cycles. Herein, an electrochemical–mechanical representative volume element model is developed to study the contact behavior of porous electrodes. For the direct contact behavior of multiple particles, stronger battery constraints and larger size differences enhance the reduction in Li‐ion concentration in the contact area of the active particles in the porous electrode and the contact stress in the porous electrode particles. For the contact between the active particles and current collector, the decrease in the elastic modulus of the current collector slightly increases the contact radius and significantly reduces the contact stress. By comparing the contact area and contact stress of the smooth and rough current collectors, the latter has a smaller contact area and larger contact stress when in contact with active particles. These findings provide insights into designing Li‐ion batteries from the perspective of contact stress to minimize the mechanical failure of porous electrodes.

Influence of aerodynamic parameters of current collector on current collection at movement speeds up to 160 km/h

Introduction. This article investigates the influence of the aerodynamic parameters of the current collector on the contact force. For this purpose, the influence in the speed range up to 160 km/h on the quality of the current collection, in particular on the increased wear of the current collector contact strips, was determined.Materials and methods. A method for calculating aerodynamic forces was developed using mathematical modelling by the method of computational fluid dynamics. The current collector can be conditionally divided into three parts: the base, the current collector lifting mechanism and the current collector head. The main characteristic of this interaction is the force with which the head is pressed against the contact wire and the stability of this force in dynamically changing external conditions.Results. The simulation performed showed that at a speed of about 140 km/h, head vibrations occur that change the contact force. This made it possible to explain the increased wear of the inserts during testing and commissioning of electric trains of the ES2G and ET4A types, which use the same type of current collectors. The presence of the current collector holder near its head, which is a pipe located along the entire length of the head at a slight distance, fundamentally changes the flow pattern. Based on the performed mathematical modelling, changes were made to the design of the current collector head in order to improve its aerodynamic properties. Other current-collecting elements were used to ensure stable aerodynamic properties of the head in a given speed range.Discussion and conclusion. The introduced changes made it possible to solve the problem with increased wear of the contact strips at a speed of up to 160 km/h. The conducted studies and the introduction of changes in GOST 32204–2013 based on these studies will improve the reliability and durability of the current collection devices.

Cover Picture: Fast Charge and High Stability of Solid‐State Graphite Organic Ionic Plastic Crystal Composite Anodes (Batteries &amp; Supercaps 7/2022)

The Front Cover shows a solid-state graphite composite anode containing an organic ionic plastic crystal electrolyte as a multifunctional lithium-ion conductor by which the electrolyte/electrode and electrode/current collector contacts are improved, enabling fast lithiation and stable cycling. More information can be found in the Research Article by H. Ueda, P. C. Howlett and co-workers.

Fast Charge and High Stability of Solid‐State Graphite Organic Ionic Plastic Crystal Composite Anodes

AbstractAll‐solid‐state batteries (ASSBs) using organic ionic plastic crystals (OIPCs) are promising candidates to overcome the inherent safety issues of lithium‐ion batteries (LIBs). Although OIPCs have excellent process applicability in the roll‐to‐roll electrode fabrication process, their application as solid electrolytes incorporated in composite electrodes has yet to be demonstrated in detail. Herein, we denote the positive effect of the N‐ethyl‐N‐methylpyrrolidinium bis(fluorosulfonyl)imide ([C2mpyr][FSI]) incorporated within a composite graphite anode on the charge rate capability and cycle life. The highest charge capacity ratio (the charge capacity at 2C vs. that measured at 0.1C) was measured for the composite anode with an OIPC composite ratio of 50 wt % (89.5 %, 295.7 mAh/g at 2C charge), almost the same as that of the graphite anode with a liquid electrolyte (85.7 %, 295.9 mAh/g at 2C charge). More favorable lithium‐ion conduction pathways were resolved for the anode with a higher OIPC composite ratio, whereas an excessive amount of OIPC reduced the long‐term cyclability. The most stable discharge capacity retention was obtained for 30 wt % OIPC composite (257.4 mAh/g at the 100th discharge), which showed no signs of discharge capacity fading within 100 cycles. The lithiation/delithiation process of the solid‐state graphite‐[C2mpyr][FSI] composite anode was evaluated to be stable and reversible. In addition, the incorporated OIPC composite enhanced the electrolyte/electrode and electrode/current collector contacts. This work highlights multiple advantageous functions of the OIPC in a composite graphite anode, which will broaden our horizons for the use of OIPC composites in ASSBs.

Prediction of collector contact efficiency for colloid transport in porous media using Pore-Network and Neural-Network models

Conventional colloid filtration theory (CFT) uses the single collector contact efficiency (η) to describe the mass transfer of colloids to a collector surface. However, this approach neglects the full complexity of the pore structure and flow field of real porous media. In this study, the porous medium geometry, flow field, and colloid mass transfer are quantified using a pore-network model (PNM). A database of pore scale η is established by finite-element method to train a Neural-network model (NNM). The reasonable prediction of η indicates the potential of using the developed NNMs as an alternative to correlation equations, which can free the users from repeated numerical simulation. In contrast to the prediction by conventional CFT, the value of η in the PNM occurs as a distribution, which is dependent upon the geometry parameters of the PNM. The mean value of η increases with the standard deviation of pore radius and decreases with the curvature number, but the dependency on coordination number is more complex. Upscaled values of the deposition rate coefficient (kd) corresponding to the distribution of η are calculated by the breakthrough curves by PNMs. The prediction of kd by PNM is then compared with that by CFT. Results show that kd predicted by PNM shows more significant response to velocity change, and less remarkable response to colloid density change than kd predicted by CFT. The comparison between the flow velocity distribution between PNM and CFT shows that the high-velocity region of the flow field in the porous media has been neglected in CFT, which can lead to insufficient consideration of convection. The results of this work imply that it is necessary to consider the influence of the complex pore structure of porous media on the collection of colloids.

An evaluation method of preventive renewal strategies of railway vehicles selected parts

The aim of the work was to develop a method of verification of the preventive renewal strategies, which enables a simulation evaluation of the effects of the application of a specific schedule of inspections of parts that are important in the operation of complex renewable technical objects. Using it requires having an already established schedule of inspections, and the result of applying the method is determined by indicators that assess the usefulness of the strategy, even before implementation. The developed computational tool was used to evaluate the renewal strategy of the current collector contact plates. Based on the real operational data, several renewal intervals were considered, determining the frequency of events involving the plate covering a specific mileage, from exceeding the wear control limit value to the next inspection (replacement). The proposed verification method is an important tool for testing and planning technical inspections for systems and elements with planned wear, and parts are periodically replaced.

An Investigation of the Adsorption of Xanthate on Bornite in Aqueous Solutions Using an Atomic Force Microscope

An atomic force microscope (AFM) was applied to study of the adsorption of xanthate on bornite surfaces in situ in aqueous solutions. AFM images showed that xanthate, i.e., potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX), adsorbed strongly on bornite, and the adsorbate bound strongly with the mineral surface without being removed by flushing with ethanol alcohol. The AFM images also showed that the adsorption increased with the increased collector concentration and contact time. Xanthate adsorbed on bornite in a similar manner when the solution pH changed to pH 10. The AFM force measurement results showed that the probe–substrate adhesion increased due to the adsorption of xanthate on bornite. The sharp “jump-in” and “jump-off” points on force curve suggest that the adsorbate is not “soft” in nature, ruling out the existence of dixanthogen, an oily substance. Finally, the ATR-FTIR (attenuated total reflection-Fourier-transform infrared) result confirms that the adsorbate on bornite in xanthate solutions is mainly in the form of insoluble cuprous xanthate (CuX) instead of dixanthogen. This xanthate/bornite adsorption mechanism is very similar to what is obtained with the xanthate/chalcocite system, while it is different from the xanthate/chalcopyrite system, for which oily dixanthogen is the main adsorption product on the chalcopyrite surface. The present study helps clarify the flotation mechanism of bornite in industry practice using xanthate as a collector.

Collision dynamics analysis of lifting the pantograph

An extended pantograph-catenary (PAC) contact collision model is presented in this paper. The catenary is described by a finite element model while the pantograph is described by a multi-body model. The normal collision model is established by using the Hertzian contact theory. A 1:1 PAC collision contact test rig is built to validate the pantograph-lifting model. The dynamic responses of the PAC system during lifting the pantograph with different velocities and positions are studied. The research results show that the velocity and position of lifting the pantograph will affect the pantograph-lifting time, acceleration of collector piece, vertical displacement and contact force in the process of lifting pantograph. When the velocity of lifting the pantograph exceeds 0.5 m/s, the contact force between the pantograph and the contact wire will exceed 250 N, which is the allowed value set in the provisions of EN50367. It is essential to control the velocity of lifting the pantograph below 0.4 m/s to prevent the catenary or contact piece from being damaged due to the excessive impact force. The distribution of the droppers also affects the collision force between the PAC system.

Ultra High-efficiency Integrated Mid Infrared to Visible Up-conversion System

In this paper, we have introduced and investigated an integrated optoelectronic chip for the up-conversion of mid-infrared to visible light. A thin layer of the nanocrystalline photoconductive PbSe is put on the Base of the NPN bipolar junction transistor and a doped phosphorescence organic light-emitting diode is placed on the Collector contacts. The incoming mid-infrared light is converted into an electric current by quantum dot photodetector, then amplified by the NPN bipolar junction transistor, and finally, the amplified current is driven through the Collector in the organic light-emitting diode. The organic light-emitting diode is designed to emit a green color. Our findings indicated that the proposed devices provide an up-conversion process from mid-infrared to visible light with a high-efficiency rate. The quantum dot photodetector is designed to detect 3 μm and also the organic light-emitting diode works at 523 nm. It is easy to tune the 3 ~ 5 μm incoming light by tuning the PbSe quantum dots, and the output light is tuned by tuning the organic light-emitting diode structure. Thus, the proposed structure is highly flexible regarding receiving mid-infrared and generating visible light. It is concluded that the external quantum efficiency for the proposed structure for 3 μm to 523 nm is 600. Also, the enhancement of the transistor current gain (β) can further increase the conversion efficiency of the proposed device. Moreover, different structures such as Darlington can be used instead of the bipolar junction transistor to enhance conversion efficiency.

The role of surface roughness in the wettability and floatability of quartz particles

Surface roughness affects both the adsorption capacity of collector and mineral flotation separation. To investigate the role of surface roughness in quartz flotation, in this study, quartz particles were ground by different mills to produce two quartz samples with different nano-sized roughness, which was quantified with atomic force microscopy (AFM). Flotation experiments were carried out using CaCl2 as an activator and sodium oleate (NaOL) as a collector. The results of flotation experiments showed an excellent performance with high recoveries for the rough quartz particles in contrast to the case with the smooth ones. Surface chemical aspects for the role of surface roughness in flotation were investigated through measurements of X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscope-Energy Dispersive Spectrometry (SEM-EDS), collector adsorption capacity and contact angle analysis. Both XPS and SEM-EDS results demonstrated larger adsorption capacity of Ca2+ for the rough quartz particles due to more adsorption sites provided by larger specific surface area. The NaOL adsorption capacity results also confirmed that larger surface roughness corresponded to higher adsorption capacity of NaOL. Subsequently, the contact angle results revealed that after interacting with NaOL the rough quartz particles presented more hydrophobic. Combined with flotation tests and surface chemical analysis, it might be arrived that surface roughness affected the adsorption capacity of both Ca2+ and NaOL, therefore impacting the wettability and floatability of quartz particles.

Modelling of Escherichia coli removal by a low-cost combined drinking water treatment system

AbstractThis work presents mathematical modelling of Escherichia coli (E.coli) removal by a multi-barrier point-of-use drinking water system. The modelled system is a combination of three treatment stages: filtration by geotextile fabric followed by filtration and disinfection by silver-coated ceramic granular media (SCCGM) then granular activated carbon (GAC) filtration. The presented models accounted for removal mechanisms by each treatment stage. E.coli was modelled as a microbial particle. E.coli inactivation by SCCGM was modelled using the Chick's, Chick-Watson, Collins-Selleck and complete mix system bacterial inactivation kinetic models, which were considered adequately representative for describing the removal. Geotextile removal was modelled using colloidal filtration theory (CFT) for hydrosol deposition in fibrous media. The filtration removal contributions by the SCCGM and GAC were modelled using CFT for removal of colloidal particles by granular media. The model results showed that inactivation by silver in the SCCGM was the main bacterial removal mechanism. Geotextile and GAC also depicted appreciable removals. The theoretical modelling approach used is important for design and optimization of the multi-barrier system and can support future research in terms of material combinations, system costs, etc. Collector diameter, particle size, filtration velocity and contact time were identified as critical parameters for E.coli removal efficiency.

Snapback‐free reverse conducting IGBT with p‐poly trench‐collectors

A reverse conducting (RC) insulated-gate bipolar transistor (IGBT) with p-poly trench-collectors is proposed. A narrow n-drift region between two p-poly trench-collectors is formed as a self-controlled electron path to the collector contact. Owing to the built-in potential between the p-poly and n-drift regions, the narrow n-drift region is depleted to offer a high-resistance electron path at forward bias, which helps to suppress snapback. At reverse bias, holes accumulate at the n-drift/trench-collector interface and then the potential difference between the p-poly and n-drift regions mainly drops at the thin oxide layer. Thus, the narrow n-drift becomes undepleted to offer a low-resistance electron path, and the RC diode can be turned on. Simulation results show that the proposed RC-IGBT is able to suppress snapback with a much smaller cell width and obtain a 21% lower turn-off loss compared to the conventional RC-IGBT.

Nanolayer in brush collector contact under Joule heating

There has been little research into the contact areas between electric brushes and collectors during sliding interactions due to the difficulty of observing them. A layer of nanosized wear particles forms on the brush contact due to stochastic interactions between the surfaces that give the layer a mottled/speckled structure. This causes the output signal current or voltage to fluctuate. Taking a new approach, we investigate different polyhedral nanoparticle shapes, considering each particle to be enclosed in a bounding cube. Here we focus on Joule’s first law and assume that the particles are flattened due to electric currents, leading to Joule heating and hence temperature changes. Our results show that the degree of wear particle dispersion has a significant effect on the wear rate and electrical contact durability.

Integrated and Interconnected Array of Light-Emitting Transistors and Transistor Lasers on Silicon for Photonic Logic

A scalable method of integrating III-V epitaxial structures onto silicon and producing a large-area array of interconnected three-terminal photonic devices in the integrated material is demonstrated. This work establishes CMOS-compatible techniques for GaAs-based active photonic material (n-InGaP/p-GaAs/n-GaAs) to be converted into a distribution of epitaxial islands with direct thermal and electrical connection to a silicon host wafer. A temporary epitaxial bonding process orients and etches modified heterojunction bipolar transistor (HBT) material into a gridded mesh of islands (collector-side up) on a silicon-based carrier wafer with device-level alignment. A subsequent epitaxial transfer creates a permanent metal-eutectic bond between the III-V islands and the silicon host wafer that serves as a uniform electrical interconnect between front-end-of-line processed CMOS and the collector terminals of a photonic chip layer. Thermal, electrical, and mechanical characterization of the integrated material is performed to ensure that the interconnect is suitable for fabrication of photonic devices into the larger-area transferred material. A separate epitaxial process for uniting passive waveguide materials to the same host wafer is then similarly performed. The result is a closely-aligned grid where each III-V island is surrounded by passive material islands. The integrated III-V islands (emitter-side up) are then patterned in unison into an array of light-emitting transistors (LET) and edge-emitting transistor lasers (TL) that are designed for efficient optical coupling into waveguides formed in the passive material, functioning together as active and passive devices in a single network. Device processing parameters are inspected and optimized to account for variations in processing on integrated (thin-film) III-V materials as compared to monolithic device processing, as well as to adhere to CMOS-compatible methods and metallization. The resulting array of three-terminal photonic devices are linked by means of a vertical electrical interconnect through the collector contact and a lateral optical interconnect aligned to the carrier-recombination quantum well (QW) in the base region. Optical and electrical testing (DC) is performed on the integrated devices both individually and as an integrated network for electrical and optical output characteristics, while a comparison to fabricated monolithic three-terminal photonic devices is utilized to relate performance of integrated active photonic devices. Initial work on high-speed testing is performed to benchmark the thermal and electrical improvements in integrated photonic devices. Simulation of the device characteristics is further employed to investigate methods to optimize optical output in relation to electrical gain and beta suppression. The techniques and processes established enable a scalable network of photonic devices for novel heterogeneously integrated electronic-photonic circuitry. This heterogeneous integration produces a platform for pairing a photonic chip layer with a CMOS host wafer such that the interconnects for electrical and optical signals allow for photonic logic designs. Figure 1