Electrode Layer Thickness Research Articles

Quantifying Lithium-Ion Battery Rate Capacity, Electrode Structuring, and Transport Phenomena Using E-I Measurements

The specific energy of lithium-ion batteries (LIBs) can be enhanced through various approaches, one of which is increasing the proportion of active materials by thickening the electrodes. However, this typically leads to the battery having lower performance at a high cycling rate, a phenomenon commonly known as rate capacity retention. One solution to this is perforating the electrode, by creating channels or corrugations in the active electrode material, either as holes or as channels. This is known to reduce the rate capacity retention effect, but in order to engineer this better, a simplified transport process analysis needs to be established. In this paper, we propose a classic electrochemical analysis based on voltage–charge cycling measurements in order to obtain a classical mass transport coefficient, hm, that is further used as a main indicator for electrode design quality assessment. We also demonstrate theoretically and experimentally how the mass transfer coefficient, hm, can be determined and how it changes as the electrode layer thickness increases, with and without electrode corrugations.

Upscaling of the Laser Structuring of Lithium-Ion Battery Electrodes - Process Development and Electrochemical Properties As a Function of Design Patterns

Structuring of electrodes for lithium-ion batteries by using ultrashort pulsed laser ablation is a quite promising approach to significantly increase the electrochemical performance of lithium-ion batteries. The main impact of such 3D electrodes is due to shortening of lithium-ion diffusion pathways and improving the electrolyte wetting of composite electrodes The latter is reducing the electrolyte filling process time and saving the need for warm aging in the manufacturing process. The 3D electrode concept, in combination with an increase in electrode layer thickness, facilitates an increase in energy and power density of batteries at the same time. To implement the laser structuring process in industrial cell manufacturing, an adaptation of the ultrafast laser technology to the coating speed has to be established.In the presented study, the use of an ultrashort pulsed laser system of high power up to 300 W and high repetition rate in the MHz regime was evaluated regarding processing speed for patterning of graphite and silicon/graphite anodes. For composite graphite anodes (film thickness > 76 µm) with an areal capacity of about 2.5 – 4.0 mAh/cm2 and a thick-film silicon/graphite anode with 5 wt.% silicon content (film thickness 80 µm, areal capacity 4.3 mAh/cm2) the laser and process parameters and processing speed were evaluated and optimized. Furthermore, different structure patterns including hole, grid and line pattern, were studied regarding upscaling in roll-to-roll processing. The different types of patterns were evaluated with respect to accessible electrochemical properties. Prior to cell assembly and during post-mortem studies, the quality of structured electrodes was examined by profilometry and scanning electron microscopy. Debris formation and a thermal impact to active material and current collector could be avoided. To evaluate the electrochemical properties such as high rate capability, cell impedance, and cell lifetime, coin cells and pouch cells were manufactured. For this purpose, NMC 622 cathodes were prepared as the respective counter-electrodes and a cell balancing in the range of 1.1-1.2 was ensured.

Active layer and electrode thickness dependent performances of bottom contact photosensitive organic field-effect transistors

Abstract Optimizing the thicknesses of the organic active layer and source/drain electrode layer of photosensitive organic field-effect transistors (PhOFET) for high device performance is of great importance. With the increase of organic active layer thicknesses, both the photocurrent and photoresponsivity display the same variation trend of increasing sharply at first and then tending to saturate at large values. The Au source/drain electrode-layer thickness shows great impact on the performance of PhOFET. With the increase of Au source/drain electrode-layer thicknesses, both the dark current and photoresponsivity increase sharply at first and then tend to saturate at large thicknesses. For pentacene PhOFETs with bottom-gate bottom-contact geometry, the Au source/drain electrode-layer thickness should be larger than 150 nm for optimized device performance. This research may supply a theoretical basis for the development of PhOFET.

Design, Analysis and Finite Element Modeling of Solidly Mounted Film Bulk Acoustic Resonator for Gas Sensing Applications

This paper reports the effect of the design parameters of a solidly mounted film bulk acoustic resonator (SMFBAR) for better gas sensing performance. The electrical equivalent circuit of the proposed device has been developed with the help of a Butterworth Van-Dyke (BVD) circuit. The electro-mechanical response of the SMFBAR has been obtained with the help of 3-D finite element method (FEM) analysis. The analytical modeling and FEM simulation results are compared. The physical parameters of the proposed design such as piezoelectric layer material, its thickness, active area of the device and sensing layer thickness affecting the characteristics of the SMFBAR have been investigated in detail. To achieve enhanced sensitivity, the variation of square active area has been analysed with one side dimension ranging from 700 μm to 300 μm. Gas sensing performance of the proposed sensor is tested by exposing toluene gas concentration ranging from 0 ppm to 500 ppm and enhanced sensitivity of 20 kHz/ppm has been achieved and reported. Also, it is reported that the variation in ratio of electrode layer thickness to piezoelectric layer thickness results in improvement of coupling coefficient (keff2) up to 7.46%.

The effect of electrode calendering on the performance of fully printed Zn∣MnO2 batteries

Primary zinc–carbon batteries with a coplanar battery architecture were prepared by screen printing. Prior to battery activation by printing of an acidic zinc chloride electrolyte, printed zinc and manganese dioxide electrodes were compacted by calendering. Material densification of the electodes resulted in electrode layer thickness reduction on both sides, modified micropore surface area and volume on the cathode side. Galvanostatic impedance measurements and chronopotentiometry were used to characterise fabricated batteries with the individually prepared electrode configurations. While calendering of both electrodes of the batteries showed adverse effects by an increase of internal resistances and a reduction of discharge capacities, exclusive calendering of the zinc anode increased the active material utilisation by electrochemical cell reaction and thus the discharge efficiency of the battery.

Simulation of Lithium-Ion Battery with Effect of Volume Expansion of Active Materials

In order to improve the performance of Lithium ion secondary batteries (LiBs) for electric vehicles and hybrid electric vehicles, it is very important to understanding the internal transport phenomena under high rate condition to increase power density. In our previous studies, we focused on the actual porous electrode structure, and the Li ion and electron conductivity was evaluated by the effective conductive path with the actual reconstruction electrode structure [1]. In addition, the charge-discharge performance was simulated with the model of reaction and mass transfer in heterogeneous porous electrode structure [2]. This model was developed with the multi-block method which is the method of coarse graining to keep the information of heterogeneous structure [3]. Furthermore, in order to design high capacity anodes based on volumetrically expanding active materials for lithium-ion batteries, we investigated the effects of the expansion ratio of active materials on the charge capacity by carrying out numerical simulations based on the porous electrode theory [4]. In this simulation, as assumptions, Li concentration and potential distribution in active material (AM) and electrolyte (EL) were calculated with Butler-Volmer equation as the boundary condition of the interface between AM and EL. it was assumed that temperature is constant, the formation of SEI is ignored, binder phase inhibit ionic transfer. From these calculation results, the effect of heterogeneous porous structure, which consist of active material, conductive material and binder, on the cell performance could be evaluated. Especially, we focused on the dynamic effective parameter which means the ratio of the effective ionic conductivity in porous electrode between the local time and the initial condition. In the case of expansion ratios of 0.5, which means the 50 % enlargement of active material at the SOC=100%, this value becomes approximately 0.24. Thus, the effective ionic conductivity decrease about 0.2 times than that at initial condition. However, in order to examine then in detail, there are some subjects. In this study, the effect of various expansion ratio and the aggregate structure of active materials was examined. And also, the validity of this simulation was evaluated with some experimental charge-discharge curve and direct observation of volume expansion. Figure 2 shows the cross section view of cell under charge condition and the change of electrode layer thickness. In our presentation, we will discuss the effect of the micro-scale structure on cell performance with volume expansion and the validity of this simulation. Figure 1

Development and Experimental Validation of a Non-Linear, All-Elastomer In-Plane Capacitive Pressure Sensor Model

A large deformation mechanics model is applied to predict capacitance changes in an all-elastomer capacitive tactile sensor, and the predictive model is experimentally validated. The compressive model predicts a non-linear relationship between the contact normal force and resulting capacitance change due to changes in electrode gap and electrode layer thickness. Broad parametric studies demonstrate that higher sensitivities can be achieved with lower modulus materials and smaller electrode gaps. Sensors are fabricated using a reusable silicon mold and experimental results are compared to predictions from the capacitance model. Capacitance-force model predictions yielded by the calibrated capacitance analytical model are shown to be in remarkable agreement with experimental measurements. A fringe effects term included in the capacitance model highlights the limitations of the parallel plate model especially for sensors with large electrode layer gaps.

Performance Characteristics of PTC Elements for an Electric Vehicle Heating System

A high-voltage positive temperature coefficient (PTC) heater has a simple structure and a swift response. Therefore, for cabin heating in electric vehicles (EVs), such heaters are used either on their own or with a heat pump system. In this study, the sintering process in the manufacturing of PTC elements for an EV heating system was improved to enhance surface uniformity. The electrode production process entailing thin-film sputtering deposition was applied to ensure the high heating performance of PTC elements and reduce the electrode thickness. The allowable voltage and surface heat temperature of the high-voltage PTC elements with thin-film electrodes were 800 V and 172 °C, respectively. The electrode layer thickness was uniform at approximately 3.8 μm or less, approximately 69% less electrode materials were required compared to that before process improvement. Furthermore, a heater for the EV heating system was manufactured using the developed high-voltage PTC elements to verify performance and reliability.

Silicon-containing anodes with high capacity loading for lithium-ion batteries

Comparative analysis of cycling performance of hybrid electrodes based on the MAG synthetic graphite mechanic mixtures with silicon nanopowder and “nano-Si/SiO2/hard carbon” ceramic frame-ordered composite in 1 M LiPF6 solution in a monofluoroethylene carbonate-ethyl methyl carbonate mixture (30: 70, v/v), added with 3 wt % vinylene carbonate and 2 wt % ethylene sulfite, is performed. The high capacity loading (up to 6.8 mA h cm−2 at the electrode layer thickness of 37 μm) and acceptable accumulated irreversible capacity of the composite-containing electrodes are achieved, due to the electrodes’ high density and stable silicon-containing electrode/electrolyte interface formation.

고분자연료전지 내 촉매 이동 및 노화메커니즘에 관한 연구

We studied the degradation phenomenon of Pt catalyst in PEMFC. We used the electron microscope analysis technique including the ultra-microtome pretreatment method, FEG-SEM and TEM analysis methods for analysis of Pt nanoparticles. The Pt catalyst degradation is observed not only in electrode site but also in membrane site. We investigated these various degradation phenomena. The cathode electrode layer thickness is reduced. The size of the catalyst is increased much larger than initial size in membrane site. The catalyst moved from electrode layer to the electrolyte membrane. The rounded shape of catalyst was changed to the polygon. As a result, we found that the catalyst degradation processes of migration and coarsening occurred by the followings mechanisms; (1) dissolution of Pt ; (2) diffusion of Pt ion ; (3) Pt ion chemical reduction in membrane; (4) Coarsening of Pt particles (Ostwald ripening) ; (5) polygon shape change of Pt by {111} plane growth.

Effects of electrode layer composition/thickness and electrolyte concentration on both specific capacitance and energy density of supercapacitor

In this paper, the effects of several experimental conditions, such as electrode layer binder content, conducting carbon content, electrode layer thickness, as well as electrolyte concentration, on both the specific capacitance and energy density of a BP2000 carbon-based supercapacitor are investigated using both cyclic voltammetry and a galvanic charging–discharging curve. The electrode layer studied contains Super C45 carbon as the conducting additive, PTFE as the binder, and Na 2SO 4 as the aqueous electrolyte, respectively. With the purpose of optimizing the electrode layer structure, 15 wt% of Super C45 and 5 wt% of PTFE in the electrode layer with a thickness of 100 μm, are found to be the best composition in terms of improving both specific capacitance and energy density. Regarding the effect of electrolyte concentration in the range of 0.1–1.0 M, 0.5 M of Na 2SO 4 gives the best performance.

Effect of Cr additions on the microstructural stability of Ni electrodes in ultra-thin BaTiO3 multilayer capacitors

Microstructural control in thin-layer multilayer ceramic capacitors (MLCC) is one of the present day challenges to maintain an increase in capacitive volumetric efficiency. This present paper opens a series of investigations aimed to engineer the stability of ultra-thin Ni electrodes in BaTiO3-based multilayer capacitors using refractory metal additions to Ni. Here, pure Ni and Ni–1 wt.% Cr alloy powders are used to produce 0805-type BME MLCCs with 300 active layers and with dielectric and electrode layer thickness around 1 μm. To investigate the continuity of Ni electrodes, both MLCC chips with pure and doped electrodes were sintered at different temperatures for 5 h. It is found that the continuity of Ni electrodes is improved most likely due to the effect of Cr on the low-melting point (Ni,Ba,Ti) interfacial alloy layer formation. The interfacial alloy layer is not observed when Cr is segregated at Ni-BaTiO3 interface in the Cr-doped samples, while it is found in all undoped samples. The interfacial alloy layer is believed to increase mass-transfer along the Ni-BaTiO3 interfaces facilitating an acceleration of Ni electrodes discontinuities.

Electrochemical Properties of Electrode Materials of the Composition (Yb,Y)0.5Ca0.5MnO3

Electrochemical characteristics, such as the parameter of resistance (ρ/d) of an intermediate layer at the electrode material/electrolyte interface and the polarization resistance (Rη) of the three-phase boundary gas/solid-electrolyte/electrode under study, are studied as a function of the electrode layer thickness, temperature, and oxygen content in the gas phase for electrode materials of the composition (Yb, Y)0.5Ca0.5MnO3. Established is the similarity in the behavior of ρ/d and Rη from the above parameters. The determined effect on these characteristics is exerted by the composition of the electrode material. In the temperature range 300–1100 K, at \(P_{0_2 }\) = 102–105 Pa, the least values of the parameter of resistance and polarization resistance are intrinsic to samples with the thickness of the electrode layer 100 mg cm–2 of the composition Y0.5Ca0.5MnO3. For systems studied, the least temperature of establishment of electrochemical equilibrium at the three-phase boundary is 875 (±5) 5 K.

Doping effects on the physicochemical and electrochemical properties of lanthanum manganite

The structural, thermal, electrical, and electrochemical properties of La0.7Ca0.3Mn1-x(Co,Ni)xO3 and La0.6Sr0.4Mn1-x(Co,Ni)xO3 (x = 0, 0.02, 0.05, 0.1) electrode materials were studied. Doping of the cubic perovskites with Co or Ni increases the fraction of Mn4+ ions, up to 49% in La0.7Ca0.1O3 and 57% in La0.6Sr0.4Mn0.95Co0.05O3. The 300-K conductivity of La0.7Ca0.3Mn1-xNixO3 passes through a maximum atx = 0.05, while that of La0.6Sr0.4Mn1-xCoxO3 decreases steadily with increasingx. In the range 300–1100 K, the conductivity of the Ca-containing manganites exhibits semiconducting behavior, whereas that of the Sr-containing materials shows metallic behavior. No phase transformations were detected in this temperature range. In the four systems, the thermal-expansion coefficients are virtually independent ofx. In both undoped and doped electrode materials, the resistance parameterp/d of electrode layers on solid-electrolyte substrates shows semiconducting behavior at temperatures from 300 to 1100 K and oxygen partial pressures from 102 to 105 Pa. With increasing oxygen partial pressure or electrode-layer thickness (d = 15–100 mg/cm2),p/d decreases. The optimal electrode-layer thickness is found to be about 50 mg/cm2. The introduction of Co or Ni into the electrode materials decreases the polarization resistance of the electrode layer in gas/electrode/electrolyte systems. Compositions ensuring the lowest polarization resistance were found.

Influence of insulating electrode layers on the nonlinear dielectric properties of paraelectric-semiconductors

Calculations of the nonlinear properties in a d.c. biasing field of a flat paraelectric semiconducting capacitor possessing insulating electrode surface layers are presented. The thickness of electrode layers and the law of the change of resistivity near the electrode surfaces influence strongly the dependence upon C(E0), where C is the capacity of paraelectric condenser and E0 is the random d.c. field. The problem was solved completely analytically. Computer calculations were performed for frequencies much higher than the free charge relaxation frequency in semiconductors. BaTiO3 at temperatures of 5°, 15° and 25°C higher than the Curie point is chosen as a concrete paraelectric. The theoretical data obtained explain the discrepancy between the experimental relations, C(E0), and the theoretical ones, predicted by thermodynamic theory for the ferroelectrics with first-order phase transitions.