Influence Of Electrode Thickness Research Articles

Thickness effect on the mechanical performance of cathodes in lithium-ion batteries

As battery capacity and energy density increase, the safety of batteries deteriorates with a more severe capacity fade. Increasing the electrode thickness is an effective approach to enhance battery capacity and energy density. Currently, research on the influence of electrode thickness on batteries has primarily focused on electrochemical aspects, while there is limited study on the impact of thickness on the mechanical properties of electrodes. In this work, we thoroughly investigated the mechanical behavior of NCA (LiNiaCobAlcO2, a + b + c = 1) cathodes with varying thicknesses through uniaxial tensile tests. Experimental measurements show that as the cathode thickness increases, tensile strength and elastic modulus of the cathode decrease. Cathodes with thin coating exhibit brittle fracture, while cathodes with thick coating display relatively higher toughness prior to fracture. The distribution of cracks and the structure of cathodes varying with thicknesses were studied by scanning electron microscopy. Results show that cathodes with thick coating have wider and deeper cracks. Thinner cathode coatings can withstand larger tensile and shear stresses compared to thicker cathode coatings, thus thicker cathode coatings experience more severe damage. By combining microstructural observation and stress analysis, the mechanism for the degradation of mechanical properties and rapid capacity fade in thick electrodes were revealed. This study provides a reference for the optimal design and safe operation of lithium-ion batteries.

A Versatile Strategy for Manufacturing Separator-Free Li-Ion Battery Cells: Combination of Dry Process for Electrodes and Solvent-Based Impregnation of Polymer Electrolytes

A Separator for conventional Lithium-Ion Batteries (LiBs) typically consists of functionalized Polypropylene or Polyethylene to avoid short circuiting and host the liquid electrolyte[1]. The successful removal of the separator would not only facilitate the cell assembly process, but would also reduce the process cost related to z-stacking machines, which corresponds to around 12 % of total process cost[2]. Therefore, a different strategy needs to be applied in this case to prevent short circuits while maintaining sufficient ionic conduction.An often-mentioned strategy to achieve the separator-free architecture is to impregnate and overcoat the electrodes with a polymer electrolyte dissolved in a solvent. However, a meticulous investigation of a compatible combination of binder-polymer electrolyte, conductive salt and solvent is usually necessary to avoid negative impacts of this strategy, with the delamination of the electrodes, the insufficient impregnation of the electrodes or the emergence of high interfacial resistances being only some examples of potential problems which can occur during this process.Here, we present a novel approach to overcome the above-mentioned barriers, by combining different manufacturing techniques. Firstly, in order to avoid the delamination of the electrodes, electrodes with adjustable porosity are prepared by a fully dry process using fibrillated polytetrafluorethylene (PTFE) as a binder. Due to the non-solubility of PTFE in a plethora of different solvents, the choice of solvent is much less limited and a wider range of solvents can be used to tune the viscosity during the impregnation process. Into the porous electrodes, a , dissolved in a solvent, is impregnated via a standard doctor blade-coating method. Furthermore, using dry process electrodes mitigates the impact of inhomogeneous vertical distribution, avoiding self-aggregation in electrodes and forming non-uniform pores[3]. The mentioned flexibility in the choice of solvent type and amount ensures a complete impregnation into the pores of the electrode for different mass loadings and various types of active material. A sufficient thickness of the polymer electrolyte layer during the coating step leads to an overcoating of both electrodes of around 8-10 µm, which is close to the range of commercial separators, enabling practically required high energy densities for battery applications.In our proof-of-concept study, we fabricated and tested LiB cells composed of polymer-impregnated LFP and Graphite electrodes without any separators based on the above mentioned concept. The resulting cells showed promising cyclability and high coulombic efficiencies for more than 100 cycles at intermediate C-rates. The flexibility of the concept is presented by varying the solvent, used during the impregnation step and tailoring the properties of the specialized fluoropolymer electrolyte via addition of ceramic fillers. In addition to the electrochemical performance, an efficient impregnation process of the polymer electrolyte into the porous cathodes, which can be confirmed by SEM, was successfully implemented.In summary, this study provides not only a strategy for the rational design of separator-free architecture, but also creates a novel possibility for solid-state battery applications.[1] Huang, Xiaosong “Separator technologies for lithium-ion batteries”, J Solid State Electrochem 15, 649–662 (2011).[2] Orangi, Stina, et al. “A Techno-Economic Model for Benchmarking the Production Cost of Lithium-Ion Battery Cells”, Batteries, 8, 83, (2022).[3] Kumberg, Jana, et al. "Drying of lithium‐ion battery anodes for use in high‐energy cells: influence of electrode thickness on drying time, adhesion, and crack formation." Energy Technology 7.11 (2019). Figure 1

The Influence of Electrode Thickness on the Structure and Water Splitting Performance of Iridium Oxide Nanostructured Films.

For a safe environment, humanity should be oriented towards renewable energy technology. Water splitting (WS), utilizing a photoelectrode with suitable thickness, morphology, and conductivity, is essential for efficient hydrogen production. In this report, iridium oxide (IrOx) films of high conductivity were spin-cast on glass substrates. FE-SEM showed that the films are of nanorod morphology and different thicknesses. UV-Vis spectra indicated that the absorption and reflectance of the films depend on their thickness. The optical band gap (Eg) was increased from 2.925 eV to 3.07 eV by varying the spin speed (SS) of the substrates in a range of 1.5 × 103–4.5 × 103 rpm. It was clear from the micro-Raman spectra that the films were amorphous. The Eg vibrational mode of Ir–O stretching was red-shifted from 563 cm−1 (for the rutile IrO2 single crystal) to 553 cm−1. The IrOx films were used to develop photoelectrochemical (PEC) hydrogen production catalysts in 0.5M of sodium sulfite heptahydrate Na2SO3·7H2O (2-electrode system), which exhibits higher hydrogen evaluation (HE) reaction activity, which is proportional to the thickness and absorbance of the used IrOx photocathode, as it showed an incident photon-to-current efficiency (IPCE%) of 7.069% at 390 nm and −1 V. Photocurrent density (Jph = 2.38 mA/cm2 at −1 V vs. platinum) and PEC hydrogen generation rate (83.68 mmol/ h cm2 at 1 V) are the best characteristics of the best electrode (the thickest and most absorbent IrOx photocathode). At −1 V and 500 nm, the absorbed photon-to-current conversion efficiency (APCE%) was 7.84%. Electrode stability, thermodynamic factors, solar-to-hydrogen conversion efficiency (STH), and electrochemical impedance spectroscopies (EISs) were also studied.

Design and Characterization of Novel Barium Strontium Titanate Thick Films for Sub-6 GHz RF Applications

In this article, a novel study of the design and characterization of barium strontium titanate (BST) thick films produced by electrophoretic deposition (EPD) on flexible platinum foils is reported. Intended for sub-6 GHz radio frequency (RF) applications, a study on film and electrode thickness is conducted. First, a comparison of tunability and quality factor between different film thicknesses regarding frequency is performed. The Ba <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> varactors demonstrate variable capacitance between 49% and 55% for frequencies from 500 MHz to 5 GHz. Afterward, the influence of electrode thickness on the capacitance and quality factor of the films are studied. The variable capacitance and the quality factor present a tradeoff regarding the parametric studies of film and electrode thicknesses. Lastly, a microstrip line is deposited over the BST thick film to simulate and measure the phase-shifting capabilities of the device. Using a one-tone measurement setup, the small-signal S-parameter measurements of the phase shifter are also presented, and the linearity is analyzed considering two different bias voltages, 0 and 10 V. For the first time, the BST thick films fabricated by EPD process are implemented and measured in the RF regime as a metal–insulator–metal capacitor and as a phase shifter circuit.

Drying of Lithium‐Ion Battery Anodes for Use in High‐Energy Cells: Influence of Electrode Thickness on Drying Time, Adhesion, and Crack Formation

When fabricating battery electrodes, their properties are strongly determined by the adjusted drying parameters. This does not only affect their microstructure in terms of adhesion, but also influences cell performance. The reason is found to be the binder transported to the surface during drying. Herein, it is shown that when thicker electrodes are processed, new challenges arise. On the one hand, loss of adhesion associated with certain drying conditions becomes a more serious problem; on the other hand, cracking occurs at a certain drying rate and with increasing electrode thickness.

Experimental Measurements of Constriction Resistance for Electrical Contacts Simulated Using Microfabrication

Contact resistance in electrical connectors is a consequence of both film resistance and constriction resistance. Film resistance is caused by a material’s high resistivity (e.g., oxidized metals) or contamination of the material. Constriction resistance results from the narrowing of the current as it passes through the electrical connector. In this paper, we propose a method for evaluating how contact structure affects constriction resistance using physically simulated samples processed using microfabrication. The samples’ physical structure was designed and fabricated arbitrarily with an electron-beam lithography system so that the complicated contact structure could be simulated physically. Several samples representing the contact-simulated structure with various distributions of “A-spots” were fabricated, and their electrical resistances were measured precisely. The influence of electrode thickness on constriction resistance was estimated based on these precise measurements. To compare the experimental result eliminating the influences with an expression for constriction resistance, the validity of our method with physically simulated samples was confirmed. By comparing the electrical resistances of various samples with different A-spot distributions, we were able to establish a relationship between contact structure and constriction resistance.

Effect of electrode thickness for reducing ozone generation in electrostatic precipitator

AbstractThe influence of electrode thickness on ozone generation in an electrostatic precipitator (ESP) was experimentally investigated. The experimental ESP was a two‐stage‐type consisting of a precharger followed by the collecting section. The precharger consisted of high‐voltage electrodes and grounded electrodes. The thickness of the high‐voltage electrodes was selected as 0.1, 0.2, 0.5, and 0.8 mm and that of the grounded electrodes was 1.0 mm. The collecting electrode section had a parallel‐plate configuration. The gases emitted from the diesel engine were diluted with air and introduced into the ESP in order to measure the particle counts. In the present study, the electric field distribution was calculated using the “Ansys” software. The relationship between ozone generation and collection efficiency was investigated. The ozone concentration was found to decrease with decreasing electrode thickness, while the same collection efficiency was maintained. This result was attributed to a decrease in the dissociation area of O2 in the vicinity of the electrodes. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(7): 24–31, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10291

Influence of electrode thickness on the performance of composite electrodes for SOFC

Measurements on half-cells consisting of yttria-stabilized zirconia (YSZ) electrolyte pellets and slurry-coated cathodes of different thickness were performed in order to determine the active area for oxygen reduction in composite cathodes of lanthanum strontium manganite (LSM) and YSZ. Electrochemical impedance spectroscopy was used to evaluate the main electrochemical parameters of the cathodic process. The temperature range was between 500 and 900 °C. The experimental results show a remarkable effect of the electrode thickness on the overall reaction rate in all the temperature range. At 750 °C a change in the controlling regime of the oxygen reduction is detectable and has been ascribed to the transition of the rate-determining step from a charge transfer to a mass transfer of the ionic species. A simplified theoretical model of the cathode that accounts for charge transfer and ionic conduction was developed to give insight into the experimental results. The model simulations compared satisfactorily with the experimental data confirming that the behaviour experimentally observed could be approached with the proposed model.

Effect of Electrode Thickness for Reducing Ozone Generation in Electrostatic Precipitator

The influence of electrode thickness on ozone generation in the electrostatic precipitator(ESP) was experimentally investigated. The experimental ESP was two-stage-type which composed of a prechager, followed by the collecting section. The precharger consists of high voltage electrodes and grounded electrodes. The thickness of high voltage electrode was selected as 0.1, 0.2, 0.5 and 0.8 mm and the grounded electrodes was 1.0mm. The collecting electrode section had parallel-plates configuration. The gases emitted from the diesel engine were diluted with air and introduced into ESP in order to measure the particle counts were attributed to saw type electrode. In the present study, the electric field distribution was caluculated using the commercial coad called “Ansys”. The relationship between the ozone generation and collection efficiency was investigated. As a result, the ozone concentration decreased with decreasing the electrode thickness maintaining the same collection efficiency. This result is attributed to decreasing the dissociation area of O2 in the vicinity of the electrodes.

HERMETIC PACKAGING OF MEMS WITH THICK ELECTRODES BY SILICON-GLASS ANODIC BONDING

Thick electrodes, which are widely used in micro-electro-mechanical system (MEMS) devices, create serious surface imperfection and would result in a low-quality bond or even debonding. In this work, the influence of electrode thickness on hermetic sealing was investigated. Two approaches to realise hermetic sealing via anodic bonding of silicon to glass with thick electrodes are presented. Embedded electrode is one method in which metal was deposited on shallow trench etched on the surface of wafers and planarisation of bonding surface was performed with a Chemical Mechanical Polishing (CMP) process. Another approach, called vertical via electrode method, is to form vertical electrodes through vias by deposition and patterning of metal film.

Influence of MH electrode thickness and packing density on the electrochemical performance of air–MH batteries

Thin and thick metal hydride (MH) electrodes used in air–MH batteries were evaluated with respect to electrochemical performances. The influence of electrode thickness on the discharge capacity, rate capability, charge and discharge voltages was investigated as well as the effect of MH packing density within electrodes on the electrode performances was also examined. The mass transport within the porous electrode was found to be the rate limiting step with increasing electrode thickness. The power output could be increased by either using thin electrodes or decreasing electrode density. This was, however, done at the expense of the energy density of the cell.

Review of SrBi2Ta2O9 thin films capacitor processing

Ferroelectric memories (FeRAMs) are new types of memories especially suitable for mobile applications due to their unique properties like non-volatility, small DRAM-like cell size, fast read and write as well as low voltage/low power behavior. Although standard CMOS processes can be used for frontend and backend processes, FeRAM technology development has to overcome major challenges due to new materials used for capacitor formation. This work gives an overview of SrBi2Ta2O9 (SBT) thin films capacitor processing using Pt as electrode material. The study describes in detail SBT formation using metal organic deposition (MOD) as well as influence of electrode thickness and capacitor patterning on SBT electrical properties. Also, results for integration of the capacitor process into a 0.5μm CMOS process with 2-layer tungsten/aluminum metallization as well as stacked capacitor results are given.

The kinetics of porous insertion electrodes

The kinetics of porous electrodes with an insertion compound as active material is a compound function of the kinetics of the insertion material and transport of inserted ions in the electrolyte-filled pores. The insertion compound and the electrolyte transport are first treated separately and then combined in the treatment of the porous electrode. The overvoltage and the materials utilization for the insertion compound are treated in terms of simple, solid state diffusion and a potential/composition dependence based on an idealized model with first order interactions. Transport in the electrolyte is treated using transport equations which take into consideration cross diffusion terms using the molar conductance. From this treatment an estimate of the conditions necessary to avoid depletion of electrolyte salt in the pores is derived. The concepts of load factors for the insertion compound and for the electrolyte part of the electrode are introduced to express the severity of the discharge in relation to the transport rates in the systems. The couplings between the insertion reaction and the transport in the pores are defined. Based on these the potentials and concentrations in the porous electrode during discharge can be found. As an example, results from such calculations on a typical porous TiS 2 electrode with liquid electrolyte are presented. The influence of electrode thickness and porosity is demonstrated and a contour representation of the influence of the load factors on the materials utilization is shown. It is demonstrated that a low mobility for the anion in the electrolyte is an advantage. In consequence, a theory for composite electrodes using solid electrolytes is developed. It is shown that this electrode behaves as a non-porous insertion electrode with a much enhanced transport rate.