Types Of Current Collectors Research Articles

Comparison of Electronic Resistance Measurement Methods and Influencing Parameters for LMFP and High-Nickel NCM Cathodes

The automotive industry aims for the highest possible driving range (highest energy density) in combination with a fast charge ability (highest power density) of electric vehicles. With both targets being intrinsically contradictory, it is important to understand and optimize resistances within lithium-ion battery (LIB) electrodes. In this study, the properties and magnitude of electronic resistance contributions in LiMn0.7Fe0.3PO4 (LMFP)- and LiNixCoyMnzO2 (NCM, x = 0.88~0.90, x + y + z = 1)-based electrodes are comprehensively investigated through the use of different measurement methods. Contact resistance properties are characterized via electrochemical impedance spectroscopy (EIS) on the example of LMFP cathodes. The EIS results are compared to a two-point probe as well as to the results obtained using a novel commercial 46-point probe system. The magnitude and ratio of contact resistance and compound electronic resistance for LMFP- and NCM-based cathodes are discussed on the basis of the 46-point probe measurement results. The results show that the 46-point probe yields significantly lower resistance values than those in EIS studies. Further results show that electronic resistance values in cathodes can vary over several orders of magnitude. Various influence parameters such as electrode porosity, type of current collector and the impact of solvent soaking on electronic resistance are investigated.

Current collectors’ effects on the electrochemical performance of LiNi0.6Co0.2Mn0.2O2 suspension electrodes for lithium slurry battery

Take after the advantages of lithium-ion battery (LIB) and redox flow battery (RFB), semi-solid flow battery (SSFB) is a promising electrochemical energy storage device in renewable energy utilization. The flowable slurry electrode realizes decouple of energy and power density, while it also brings about new challenge to SSFBs, electron transport between active material and the out circuit. In this consideration, three types of current collectors (CCs) are applied to study the resistance and electrochemical performances of slurry cathodes within pouch cells for the first time. It proves that the electronic resistance (Re) between slurry electrode and the CC plays a decisive role in SSFB operation, and it is so large when Al foil is adopted that the cell cannot even work. Contact angle between Ketjen black (KB) slurry without active material (AM) and the CC is a preliminarily sign for the Re, the smaller the angle, the lower the resistance, and the better electrochemical performance of the cell.

Damage Caused by Material Defects of Carbon Composites Used on Various Types of Railway Pantographs.

Mainstream materials of the railway pantograph strips are carbon composites. They are subject to wear during use, as well as various types of damage. It is important that their operation time is as long as possible and that they are not damaged, as it may damage the remaining elements of the pantograph and the overhead contact line. As part of the article, three types of pantographs were tested: AKP-4E, 5ZL, and 150 DSA. They had carbon sliding strips made of MY7A2 material. By testing the same material on different types of current collectors, it was possible to check what impact the wear and damage of the sliding strips has on (among others) the method of their installation, i.e., whether the damage to the strips depends on the type of current collector and what is the participation of damage caused by material defects. As a result of the research, it was found that the type of pantograph on which it is used has an undoubted influence on the damage characteristics of the carbon sliding strips, whereas the damage caused by material defects can be classified as a more general group-the group of damage of a sliding strip, which also includes overburning of a carbon sliding strip.

Recent advances and challenges of current collectors for supercapacitors

Global energy and environmental issues are driving the development of modern advances in efficient and environmentally friendly energy storage systems. Such systems must meet a range of requirements, which include high energy and power density, long service life, flexibility, industrial scalability, security and reliability. Progressive achievements in the field of energy storage are associated with the development of various kinds of batteries and supercapacitors. Supercapacitors are state-of-the-art energy storage devices with high power density, long lifespan, and the ability to bridge the power/energy gap between conventional capacitors and batteries/fuel cells. However, supercapacitors have limitations associated with low energy density, which can be solved by using various types of current collectors, since current collectors are one of the main massive components of supercapacitors. This review gives a complete understanding of the effect of current collectors on the actual performance and properties of supercapacitors. We reviewed current collectors based on carbon and metal-containing materials, and supercapacitor configurations to identify possible improvements in electrochemical performance in terms of specific capacitance, energy density, power density, service life and variability in their application.

Thickness-controlled porous hexagonal NiO nanodiscs electrodes for use in supercapacitors: How nanodiscs thickness influences electrochemical performance

Two-dimensional (2D) nickel oxide (NiO) hexagonal nanodiscs were synthesized via a hydrothermal route, followed by successive calcination. The decisive roles of the [OH−]/[Ni2+] molar ratios, as well as the calcination temperatures, were found in controlling the nanodiscs morphology of the NiO nanostructures. The increase in the concentration of OH− ions in the precursor solution influenced the crystal growth that directed to the formation of the hexagonal nanodisc morphology with increased edge thickness and beyond certain limits transformation from the nanodiscs to complete 3D morphology. The nanodiscs grew with increasing exposed surface size with a high BET area and varied thicknesses from 4 to 20 nm. The increase in calcination temperature improved crystallinity by eliminating crystal defects and voids, while crystals grew along the (200) plane. However, a reduction in the BET area and pore volume occurred at higher calcination temperature because of the collapse in micro-mesopores. The electrochemical performances of NiO electrodes show dependence on the thickness of the nanodiscs, the calcination temperature, and the type of current collector used. A distinct electrochemical feature was observed for NiO nanodiscs over planar conductive carbon fiber paper and 3D porous Ni foam substrates. The hydrothermal approach reported here to produce thickness-controlled NiO nanodiscs with high intrinsic surface area has great potential for developing next-generation battery-type faradic electrodes in conjunction with carbon allotropes and other metal oxide materials for high power and energy density throughput.

Electrochemical deposition of leaf stalk-shaped polyaniline doped with sodium dodecyl sulfate on aluminum and its use as a novel type of current collector in lithium ion batteries

A cyclic voltammetry (CV) method employing a solution containing H2SO4, aniline and sodium dodecyl sulfate (SDS) as the electrolyte solution was utilized to prepare a SDS-doped polyaniline (PANI) film onto the surface of the commercial aluminum (Al) foil at room temperature generating a novel current collector of SDS-PANI coated Al (denoted as SP/Al). The SDS-doped PANI films prepared in the presence of 2 mM, 5 mM and 10 mM SDS were, respectively, nominated as film SP-2, SP-5 and SP-10. As shown by the SEM images, many irregular particles covered with numerous protuberances were prepared in the absence of SDS, and very interestingly, in the presence of SDS, leaf stalk-shaped particles were fabricated on the surface of the commercial Al foil. As indicated by XRD and FTIR results, the main component of the leaf stalk-shaped particles was PANI. Most important of all, the initial discharge capacities of the commercial LiFePO4 (abbreviated as LFP) on the novel current collectors of SP/Al at 0.2 C were all remarkably higher than that of LFP on the commercial Al foil. Particularly, even at 5 C after 10 cycles, the average discharge capacity of LFP on SP-5/Al (65 mA h g−1) was still about 30% larger than that on the traditional Al foil (50 mA h g−1). Presenting the fact, that using the SDS-doped PANI film coated Al foil to replace the conventional Al foil was a feasible way to promote the electrochemical performance of LFP, is the main dedication of this preliminary work.

Effect of electrode loading on the electrochemical performance of LiAl0.1Mn1.9O4 cathode for lithium-ion batteries

LiAl0.1Mn1.9O4 spinel oxide was synthesized by combustion method and investigated as cathode material for Li-ion batteries, taking into account the effect of (i) the type of current collector and (ii) the electrode mass loading. Two different substrates were employed as current collectors: Al foil and carbon paper. The materials with higher loading showed an outstanding capacity retention in rate capability test. Although the samples with lower loading started with higher capacities, they showed poor capacity retention. From a practical point of view, the electrode with 4 mg loading per cm2 presented attractive properties with respect to elevated specific capacity and high retention in long-term stability tests.

Multi-scale impedance model for supercapacitor porous electrodes: Theoretical prediction and experimental validation

In this paper, a multi-scale impedance model is developed for evaluating the charge storage capacity and ion-transfer rate of supercapacitor porous electrodes. This model can be used to theoretically understand the contributions of the intra-particle pore at nano-scale, the inter-particle pore at micron-scale, and the porous electrode at millimeter-scale to the performance of supercapacitor. Then, impedance spectrum characteristics of porous electrodes are screened via numerical simulation based on the developed multi-scale impedance model, especially for different electrode thicknesses and various faradaic processes with different time constants. Subsequently, seven supercapacitor samples, four of them with electrode thicknesses of 60, 100, 180, and 370 μm respectively, and three of them with different types of current collectors (nickel, carbon-coated stainless-steel, and stainless-steel), are fabricated and characterized to validate the developed model. The fitting results and residuals of the measured impedance data validate the linear relationship of the scaled equivalent resistance of electrolyte v. s. electrode thickness and the scaled characteristic time constant v. s. the square of electrode thickness. The validated multi-scale impedance model might offer an effective method to rationally balance or optimize charge storage and charge transfer via morphology design for porous electrodes.

Active role of inactive current collector in aqueous aluminum-ion battery

The recent revival of research interest in rechargeable aluminum-ion batteries has opened up avenues to overcome its inherent challenges. While there are fierce attempts to find suitable electrode materials for aluminum-ion batteries, it is very important to carefully evaluate them. We show here that an essential criterion for correct electrochemical evaluation of aqueous aluminum-ion batteries is to appropriately select the current collector. Considering anatase TiO2 as a model electrode material, it is demonstrated that type of current collector could transform an inactive electrode material to an active one. TiO2 could exhibit initial Al3+ ion storage capacity of 256 mAhg−1 at a current density of 4 Ag−1 with graphite current collector, whereas it is only 82 mAhg−1 with titanium current collector at similar current density. Interestingly, no charge/discharge characteristics could be obtained with stainless steel and nickel current collectors at any current densities.

Improvement of the method of calculation of the parameters of the universal current collector with the increased motion speeds

The paper considers the main stages of development of a computer model of current collectors of an electric rolling stock. The original description of the kinematic scheme of a universal measuring current collector with the subsequent implementation of mathematical model in Matlab SimMechanics environment is offered. The model is based on the use of the method of homogeneous coordinates to represent the kinematic scheme of the current collector. It is shown that the computer model accurately and adequately describes the processes occurring with the current collector, is a universal instrument for simulating any types of current collectors, allows changing a wide range of parameters and characteristics incorporated in it.

Effects of Current Collector Materials on Performances of Micro-Tubular Solid Oxide Electrolysers for Splitting CO2

As renewable energy sources are inherently intermittent, their increasing contributions to electricity grids will necessitate large-scale energy storage to balance supply and demand. Storing electrical energy in chemical bonds by electrolysis of CO2 and / or H2O is one option to achieve this. We chose solid oxide reactors for this application, inter alia, because in principle they can be operated cyclically in electrolyser (SOE) and fuel cell (SOFC) modes. Results will be presented of measurements of ohmic and electrode polarization resistances and global performances for CO2 splitting to CO and O2 in micro-tubular solid oxide electrolysers (SOEs), with different types of current collectors; electrolysis of steam and (CO2 + steam) exhibited similar behaviour. Silver or nickel wire current collectors, with and without silver or nickel paste, were used to contact the 220 μm thick inner lumen Ni-YSZ electrode (SOE cathode) of micro-tubular solid oxide electrolysers [1] (SOEs: Ni-YSZ|YSZ|YSZ-LSM|LSM) incorporating 34 μm thick yttria-stabilized zirconia (YSZ) electrolyte, and 40 μm thick lanthanum strontium manganite (LSM, SOE anode), as described previously for CO2 reduction [2]. Silver wire and paste was used as the current collector for the LSM electrode. As shown in Fig. 1, the best performance (ca. 1 A cm-2 at 1.5 V (thermo-neutral potential difference) at 800 °C) was achieved for reactors with nickel wire current collectors alone, implying metallic pastes had no net beneficial effects on area-specific ohmic resistances. Furthermore, applying silver paste had a detrimental effect on the Ni cathode polarization resistance, for reasons that will be presented. Fig. 2 shows polarization and ohmic resistance data at open circuit; similar behaviour was exhibited with potential differences applied to reactors. Ohmic resistances were expected to decrease by using silver wire, due to its higher electronic conductivity compared to nickel, but no stable cell performance was achieved.

Micro-supercapacitors from carbide derived carbon (CDC) films on silicon chips

Interdigitated on-chip micro-supercapacitors based on Carbide Derived Carbon (CDC) films were fabricated and tested. A titanium carbide (TiC) film was patterned and treated with chlorine to obtain a TiC derived carbon (TiC–CDC) film, followed by the deposition of two types of current collectors (Ti/Au and Al) using standard micro-fabrication processes. CDC based micro-supercapacitors were electrochemically characterized by cyclic voltammetry and impedance spectroscopy using a 1 M tetraethylammonium tetrafluoroborate, NEt4BF4, in propylene carbonate (PC) electrolyte. A capacitance of 0.78 mF for the device and 1.5 mF cm−2 as the specific capacitance for the footprint of the device was measured for a 2 V potential range at 100 mV s−1. A specific energy of 3.0 mJ cm−2 and a specific power of 84 mW cm−2 were calculated for the devices. These devices provide a pathway for fabricating pure carbon-based micro-supercapacitors by micro-fabrication, and can be used for powering micro-electromechanical systems (MEMS) and electronic devices.

Effects of current collectors on power performance of Li4Ti5O12 anode for Li-ion battery

The effects of current collector on the charge/discharge capacity and cycle stability of Li4Ti5O12 (LTO) electrode under high C-rates (up to 20C) have been investigated by applying five types of current collectors, including a Al foil, an anodization-etched Al (E-Al), the same etched Al with a conformal C coating (C-E-Al), a Cu foil (Cu) and the same Cu foil with a C coating (C-Cu). The C coatings on both metal current collectors are deposited by a chemical vapor deposition process using CH4 at 600°C. The capacities of the LTO electrodes above 1C rate are in the order of Al<E-Al<Cu∼C-E-Al<C-Cu, exhibiting remarkable enhancement in rate performance by the C-coating for both metals. Surface analyses indicate that the enhancement can be attributed to the combination of two factors, including removal of the native oxide layer and modification of surface hydrophobicity, which improves adhesion of active layer, on the current collector surface. Both contribute to the reduction of the resistance at the current-collector/active layer interface. All electrodes show good cycle stability.

Thin nanostructured LiMn 2O 4 films by flame spray deposition and in situ annealing method

A new approach has been developed to rapidly synthesize nanostructured LiMn 2O 4 thin films by flame spray deposition (FSD) and in situ annealing. A precursor solution of lithium acetylacetonate and manganese acetylacetonate in an organic solution was supplied through a flame spray pyrolysis (FSP) reactor. The liquid solution spray was ignited and stabilized by a premixed methane/oxygen flame ring surrounding the FSP nozzle. Thus, LiMn 2O 4 nanoparticles were formed by combustion and deposited onto a current collector followed by in situ annealing. Two different types of current collectors, i.e. stainless steel and aluminum coated with carbon-based primer were tested. The prepared thin films were characterized by X-ray diffraction and field-emission scanning electron microscopy. The electrochemical properties of the thin films were evaluated by cyclic voltammetry and galvanostatic cycling. The LiMn 2O 4 films exhibited good cyclability. Films that underwent sintering and crystal growth during in situ annealing developed more robust film structures on the current collector surface and exhibited better electrochemical performance than poorly adhered films.

Electrochemical Properties of High-Power Supercapacitors Using Single-Walled Carbon Nanotube Electrodes

We have investigated the key factors determining the performance of supercapacitors constructed using single-walled carbon nanotube (SWNT) electrodes. Several parameters, such as composition of the binder, annealing temperature, type of current collector, charging time, and discharging current density have been optimized for the best performance of the supercapacitor with respect to energy density and power density. We find a maximum specific capacitance of 180 F/g and a measured power density of 20 kW/kg at energy densities in the range from 7 to 6.5 Wh/kg at 0.9 V in a solution of 7.5 N KOH (the currently available supercapacitors have energy densities in the range 6‐7 Wh/kg and power density in the range 0.2‐5 kW/kg at 2.3 V in non-aqueous solvents).

Two‐Dimensional Simulation of Direct Methanol Fuel Cell. A New (Embedded) Type of Current Collector

A two‐dimensional numerical model of the direct methanol fuel cell with gas fuel is developed. Simulation of the cell with current collectors of conventional geometry reveal the formation of fuel‐depleted, “shaded” regions in the cathode and anode catalyst layers. These regions are positioned in front of current collectors, farther from the gas channel windows. Another disadvantage of the conventional geometry is the concentration of electron current at the edges of current collectors. Based on the simulation results, a new design of current collectors is suggested. It is beneficial to position current collectors inside the backing and catalyst layers, parallel to the flow of the fuel. These embedded collectors do not produce shaded regions in the catalyst layers. Two plausible geometries of such collectors are considered: of rectangular and circular shape. Simulations show that depending on the transport properties of the backing and catalyst layers the embedded current collectors may significantly improve the performance of the fuel cell. This conclusion is valid also for hydrogen‐oxygen fuel cells. © 2000 The Electrochemical Society. All rights reserved.