Fade Characteristics Research Articles

Capacity fade prediction for vanadium redox flow batteries during long-term operations

In this paper, a dynamic prediction model for electrolyte capacity fade in vanadium redox flow batteries (VRFBs) is proposed. The capacity fade characteristics of VRFBs were analyzed quantitatively from both microscopic ions crossover and macroscopic electrolyte volumetric change perspectives. The dynamic behavior of vanadium ions (V2+, V3+, VO2+, and VO+ 2), protons, and water molecules in VRFB half-cells and electrolyte tanks has been thoroughly explored. The parameters related to the capacity fade were obtained from a self-discharge test and formation charge processes. The accuracy of the proposed model was experimentally validated using a unit cell (25 cm2) in a long-term operation. The results reveal that after 200 continuous charge/discharge cycles (duration of 739,257 s) with a current density of 80 mA cm2, the model can accurately predict changes in electrolyte volume and capacity fade with errors of 0.632 mL and 0.0295 Ah, respectively. The electrolyte capacity fade under various current densities for long-term operations has also been predicted by the model and experimentally validated. Under all current densities applied to the VRFB, the discrepancies between simulation and experimental results for electrolyte volume change and capacity fade were <8.46% and 4.99%, respectively. The proposed model significantly improves the accessibility and reliability of accurate capacity fade prediction for VRFBs, enhancing the competitiveness of VRFBs in energy storage applications.

Effect of graphitization percentage on fade and recovery performance of copper-free non-asbestos organic brake pads

PurposeThe purpose of this paper is to deal with the tribological study on the brake pads developed using various purity-based graphitized graphite.Design/methodology/approachThis paper deals with developing copper-free brake pads by using graphite as a key lubricant produced using a graphitization process with purity percentages (85, 90 and 95%). The brake pads were developed using traditional manufacturing processes and evaluated for their physical, chemical, thermal and mechanical properties as per industrial standards. Fade and recovery characteristics were analyzed using a full-scale inertia brake dynamometer as per JASO-C-406. The scanning electron microscope was used to analyze the worn surfaces of the brake pads.FindingsThe testing findings reveal that the brake pads with 95% graphitized graphite showed better shear strength with good adhesion levels and lesser density, hardness, acetone extract value, loss on ignition and higher porosity. Effectiveness studies of brake pads with graphite (95% graphitized) showed better results at higher pressure speed conditions than others because of better plateau formation and adequate lubrication.Originality/valueThis paper discusses graphitized graphite of different purity influences brake pad's tribological performance by modifying tribo-films and reducing friction undulations.

Synergistic performance of expanded graphite—mica amalgamation based non-asbestos copper-free brake friction composites

Recent advancements in brake pad applications emphasise various friction compositions that exclude toxic components such as asbestos, copper etc, in order to provide superior performance without hurting the environment, human life and aquarium species. In this work, brake friction materials were fabricated by the conventional manufacturing process as standard brake pads using expanded graphite with the synergetic effect of thermal resistant material mica flakes. Six standard brake pads were produced based on varying the expanded graphite by 16, 14, 12, 8, 6 & 4 weight percentage, which is compensated using the Mica flakes by 4, 6, 8, 12, 14 & 16 weight percentage, fixing the composition of other ingredients and designated as BM01, BM02, BM03, BM04, BM05 and BM06. Physical, chemical and mechanical, characterisations of the formed friction materials were carried out in accordance with IS 2742 and ISO 6312. A full-scale inertia brake dynamometer was used to determine the fade, recovery characterisations with the pressure and speed sensitivity as of JASO-C-406. From the experimental observations, BM03 friction composites reveal excellent low fade and high recovery characteristics because of the integrated effect of expanded graphite (superior lubricity) & mica (good thermal stability). Worn surface analysis was studied with the help of a scanning electron microscope. The inclusion of expanded graphite-mica as a hybrid ‘lubricant-filler’ combination in composite materials for friction braking application results in performance synergism.

Characteristics of rain fade slopes on microwave communication in Mowe, Nigeria

In this paper, the rain fade characteristics at Ka-band (30 GHz) in Mowe (Lat 6.80° N, Lon 3.40° E) Nigeria have been presented. The analysis includes both the first- and second-order statistics of rain rate and rain attenuation, and fade duration and fade slope, respectively. Both parameters are useful for planning the point-to-point microwave link for various communication feeder networks. The estimated fade duration and the fade slope were compared with the ITU-R P.837-5 model. The results of this study would be valuable for improving rain fade mitigation techniques in Nigeria.

Design, characterization, and performance analysis of Miscanthus fiber reinforced composite for brake application

This study deals with the development of new friction materials by incorporating Miscanthus fiber (5, 10, and 15 weight %, noted Mat1, Mat2, and Mat3, respectively). The friction materials were tested for their physical, mechanical, and microstructural properties as per international standard. The performance analysis was carried out using Chase friction test rig. Results revealed that the biomass is beneficial with good fade, wear resistance, and recovery characteristics, with the same trend of other natural fibers. Therefore, this natural ingredient proved to be useful in the development of brake friction material.

Synthesis and Photochromic Properties of Naphthopyran Dimers

We realized the synthesis of 2H-naphtho[1,2-b]pyran derivatives with substituents of halo, methyl at 6-position and/or, methyl, cyclopropyl, aryl at the 2-position in addition to three different spironaphtho[1,2-b]pyran derivatives with terpene substituents at the 2-spiro position of the pyran ring. The prepared naphtho[1,2-b]pyran derivatives 1a-c,2a-c,3a-c were subjected to dimerization in acetic acid with a few drops of concentrated sulfuric acid affording the corresponding dimers 4a-i. The structures of the dimers were confirmed based on the spectral tools (especially nuclear magnetic resonance). On exposure of the produced dimers to unfiltered light, a change from colorless to color state was observed. The effect of the substituent nature at the 2- or 6-positions of dimers on the photochromic properties and thermal fade characteristics was investigated

Verification Methodology of Fade Characteristics in a DAB+ SFN in Wroclaw

Verification Methodology of Fade Characteristics in a DAB+ SFN in Wroclaw

Capacity fade characteristics of nickel-based lithium-ion secondary battery after calendar deterioration at 80 °C

In this study, we evaluated the calendar deterioration behavior of nickel-based lithium-ion secondary batteries by storing them at 80 °C for different durations. The results indicate that the battery capacity decreased with the increasing number of storage days in a high-temperature environment. From the differential capacity curves, we found that the change in the overvoltage, which was caused by the electrode reaction, that appeared at approximately 4.2 V was most significant. To analyze this phenomenon, electrochemical impedance spectroscopy of the deteriorated battery was measured at 4.2 V, and it was confirmed that the cathode-based resistance of the battery increased significantly at this potential. Furthermore, post-mortem analysis revealed that the cathode active material of the tested batteries clearly deteriorated; however, no significant change in the active material in the anode was observed. Therefore, it is considered that the cathode materials of nickel-based lithium-ion secondary batteries deteriorate by storing at 80 °C, thereby resulting in reduced battery capacity and increased cathode component resistance after storing at high temperatures.

Analysis of rain fade characteristics from experimental satellite measurements at Ka/Q bands for a temperate location Vigo, Spain

Rain is one of the most dominant factors for satellite communication systems link performance at frequencies above 10 GHz, increasing rapidly at higher frequencies. The prediction of time dynamics of the rain attenuation is required to improve the efficiency of various fade mitigation techniques (FMTs) to reduce signal fading. Fade duration and fade slope statistics are used to describe the dynamic behavior of attenuation experienced by radio communication links. The present study is based on experimental measurements from a Ka band (KaSAT) and Q band (AlphaSAT) beacon receiver at the frequencies 19. 7 GHz and 39. 4 GHz respectively. In this paper, annual and monthly variation of rain attenuation statistics for a temperate location Vigo, Spain is presented. Monthly variation of rain attenuation statistics is much larger than the yearly variation for the present location. This paper also analyzes the fade duration and fade slope statistics for both the bands. The conditional probability density function (PDF) of fade slope shows general symmetry between positive and negative slope values for both Ka and Q bands. All the measured statistics (1st order and 2nd order) are compared with the existing ITU-R and COST-205 models. Predictions of rain attenuation by both the models are close to the measured data. For fade duration statistics, as attenuation threshold increases, performance of both ITU-R and COST-205 models improves for Ka band. For Q band, COST model performs better compared to ITU-R model. Measured probability density function of fade slope fits with the ITU-R model more closely for Q band compared to Ka band.

A Fast-Charging Study on the Lifetime of Power-Optimized Lithium Titanite Batteries By Electrochemical Impedance Spectroscopy

In order to meet the growing demand of extended lifetime and fast charging capability, Li-ion batteries (LiBs) have been optimized and further developed since the beginning. From a wide choice of LiB technologies, Li4Ti5O12 (LTO) anode are known for its fast charging characteristics which is a key requirement of present electrical vehicles (EVs). The longer lifetime is a crucial criterion too to make it a popular choice for EVs and hybrid electric vehicles (HEVs). Since, the aging of Li-ion batteries depend on several degradation factors related mostly to used active materials, electrolyte etc., two types of LTO battery cells are selected for cycle life aging investigation in this research. Fast charging is selected as the key variation in the cycling conditions to understand the battery aging under accelerated lithiation process. Electrochemical impedance spectroscopy (EIS) is used along with typical capacity check during tests to characterize the batteries during lifetime.In this study, two types of LTO batteries were cycled under a long cycling campaign. Both the cells are power optimized and commercially available. The pouch shaped EIG 5Ah cell has a LiNixCoyAl1-x-yO2 (NCA) cathode material and a specific power of more than 2000 W/kg. On the other hand, TOSHIBA manufactured LTO is a prismatic cell, which operates at a nominal voltage of 2.3V, has a specific power of more than 1200 W/kg and it has a cathode material possibly of LiNixCoyMn1-x-yO2 (NMC). These batteries were cycled with four fast charging conditions at room temperature and with 90% and 80% depth-of-discharge (DoD), respectively. LTO 5Ah cell was cycled with 0.5C to 5C charging currents against 1C discharge current, where C-rate refers to the cell’s nominal capacity. Whereas, LTO 23Ah was tested in the range of 1C to 8C charging current versus 2C discharge rate. The ongoing lifetime test campaign is already more than 2-yr long, however, aging characteristics is quite different. The lifetime tests and the capacity measurement are done with PEC ACT0550 battery cycler and the EIS is performed with the Biologic’s MPG-205 equipment. The performance tests were done in the frequency based on full equivalent cycles (FEC) of which, FEC is taken as the nominal charge Ah throughput from a single charge-discharge cycle. All the tests were performed inside controlled environment temperature chambers (CTS).The capacity fade characteristics during aging, is found to be insignificant for the EIG cell as it has a negative degradation which basically means an improved state of health (SoH). A SoH can be defined as the percentile of actual or latest capacity divided by the beginning of life (BoL) value. All the aging conditions have experienced capacity gain for the EIG cell and even after 4000 FEC, no degradation is found. This proves both the fast charging suitability of this cell and longer lifetime as well. On the contrary, TOSHIBA LTO 23Ah cell has shown charging C-rate dependency on the capacity fade. Cells cycled with 2C rate aged faster (6%) than the other conditions. This is little unusual thus further investigation is necessary. While other conditions with different charging speed have moderate degradation with the maximum of 2.5% fade for 4C charge-cycling after 4800 FEC. The ongoing cycling investigation of LTO 23 Ah cell will have better illustration of the degradation characteristics in future.The impedance growth is analyzed after obtaining the parameters through an equivalent circuit model (ECM). The quantitative black box type modeling was done by EC-lab software by choosing a one-RQ circuit where the Nyquist plot is fitted by ohmic resistance (R0), charge transfer resistance (Rct) and constant phase elements (CPEs, Q). The results show that LTO 5Ah has a maximum ohmic resistance increase of 26% for 1C charge condition while the charge transfer resistance growth is gradually higher for the higher C-rate cycling eventually reaching 84% growth for this cell. To the opposite, the TOSHIBA cells have insignificant R0 increase and have decreasing Rct growth by C-rate.In general, the lower impedance growth in both the cells indicate their long lifetime and good performance under fast charging conditions. The characterization parameters in terms of capacity and power fade investigated in this study, can be used as model input parameters to do prognosis and/or diagnosis of LTO-anode based cells as state of charge/health/power/energy prediction. Figure 1

Theory of battery ageing in a lithium-ion battery: Capacity fade, nonlinear ageing and lifetime prediction

Forecasting the lifetime of Li-ion batteries is a critical challenge that limits the integration of battery electric vehicles (BEVs) into the automotive market. Cycle-life performance of Li-ion batteries is intrinsically linked to the fundamental understanding of ageing mechanisms. In contrast to most previous studies which utilise empirical trends (low real-time information) or rough simplifications on mathematical models to predict the lifetime of a Li-ion battery, we deployed a novel ageing formulation that includes heterogeneous dual-layer solid electrolyte interphase (SEI) and lithium-plating ageing mechanisms with porosity evaluation. The proposed model is parameterized and optimized for mass transport and ageing parameters based on fresh and an aged cell and validated against our experimental results. We show that our advanced ageing mechanisms can accurately calculate experimentally observed cell voltage and capacity fade with respect to cycling number and can predict future fade for new operating scenarios based on constant-current and a dynamic power profile cycling experimental data consisting of high discharge C-rates and fast-charging periods. Our model is able to capture the linear and nonlinear (knee-point) capacity fade characteristics with a high accuracy of 98% goodness-of-fit-error and we compared our model performance with well-accepted existing model in literature.

Experimental studies of Ka Band Rain Fade Slope at a Tropical Location of India

Dynamic characteristics of Ka band rain fade (or rain attenuation) over tropical region are relatively less studied, though they are essential for implementation of suitable fade mitigation techniques. In this paper, dynamic characteristics of rain fade at 20 GHz and 30 GHz from GSAT-14 satellite are reported with experimental measurements at Ahmedabad, India. ITU-R model for fade slope probability distribution has been analyzed in this paper and Ka band rain fade has been investigated based on this fade-slope analysis. The ITU-R model is found to closely match 20 GHz measurements, though differences increase at 30 GHz. Fade slopes are found to be within ±0.5 dB/s at both 20 and 30 GHz. Both positive and negative slopes of the fade slope distributions are quasi-similar. ITU-R model’s s parameter, relating fade slope to filter characteristics, is found to be very close to the measured value for this region. Distributions of fade slopes are also found to be dependent on the standard deviation values similar to ITU-R recommendation at 20 GHz, but significant deviation is observed at 30 GHz. This observed frequency dependency might be due to increase in cloud attenuation at high frequencies or may be due to limited data set. Results indicate needs of further experimental data at high frequencies from other tropical regions to gain further insight into the fade slope characteristics. This will ultimately help in designing a better prediction model in future.

Capacity fade characteristics of lithium iron phosphate cell during dynamic cycle

Abstract As a key issue of electric vehicles, the capacity fade of lithium iron phosphate battery is closely related to solid electrolyte interphase growth and maximum temperature. In this study, a numerical method combining the electrochemical, capacity fading and heat transfer models is developed. The electrolyte interphase film growth, relative capacity and temperature change of lithium iron phosphate battery are obtained under various operating conditions during the charge-discharge cycles. The results show that the electrolyte interphase film thickness increases as the C rate rises and relative capacity decreases. The capacity loss is almost 19.7% when the C-rate rises from 0.5C to 2C after 2000 cycles. The thickness of electrolyte interphase film increases and relative capacity decreases when the ambient temperature goes up. A thicker negative electrode is adverse to the electrolyte interphase film growth, and leads to the increased relative capacity, while the influence of separator thickness can be negligible. The battery maximum temperature rises with increasing the C rate and initial temperature, which exceeds the safe upper limit when the ambient temperature increases to 318.15 K at 3C. By increasing the convective heat transfer coefficient, the maximum temperature can be reduced to the security value.

Role of metal composite alloys in non-asbestos brake friction materials-A solution for copper replacement

Copper plays a vital role in the performance of brake friction materials due to its better thermal conductivity and fade resistance. But owing to the negative impact towards to the aquatic life, the usage of copper in brake material formulations is reduced considerably in developed nations. Research is being carried out globally to reduce the copper with single ingredient or combination in brake materials. Thus the present study dealt with the development of brake pads using a commercially available alloy of aluminum and iron (Mechanomade) in the formulation with other ingredients. To compare the performance, three other brake pads were also developed by replacing mechanomade with copper, aluminum, and iron in the formulation. The developed brake pads were analysed for the physical, chemical, mechanical and thermal properties as per standard industrial practice. The tribological characteristics were analysed using Chase test following SAE J661. It was evident from the test results that Iron aluminum alloy based brake pads showed good fade and recovery characteristics. To study in detail regarding the worn surface characteristics, Scanning Electron Microscope with Elemental mapping was used.

Fade and recovery characteristics of commercial disc brake friction materials: a case study

Friction materials are usually evaluated according to their friction performance at high temperatures, i.e. fade performance. In the present study, the vehicle under consideration is a sport utility vehicle. An experimental investigation is carried out to find out fade and recovery characteristics of four commercial disc brake friction materials using a four-wheeler inertia brake dynamometer. For these four grades naming is given i.e. FC1, FC2, FC3, and FC4. The Grade FC1 is without steel content. FC2 is with low steel content, FC3 is low steel content with organic brake friction material, and FC4 is non-asbestos organic friction material. SEM-EDX analysis is carried out for finding different elements and microstructural characterisation of brake friction material. Grade FC2 attained the highest temperature, and FC4 attained the lowest temperature during the fade test. Grades FC1 and FC4 show better recovery characteristics as compared to other grades.

Blue Channel and Fusion for Sandstorm Image Enhancement

Due to the scattering and absorption of light by sandstorm particles, images taken in sandstorm environments have low contrast, color distortion and other degradation problems, which seriously affect outdoor computer vision systems. In this paper, we propose a novel method to enhance images captured in sandstorm weather conditions. First, the method builds on the blending of two images that are directly derived from the original degraded image. Second, we use multilayer decomposition technology to enhance image details and use a blue channel and white balancing technology to restore image contrast and chromaticity. Third, we associate weight maps to improve image edge contrast. Finally, the Laplacian pyramid fusion method is used to obtain the fusion results of the sandstorm-free color correction image. The experimental results demonstrate that the proposed method can effectively restore the fade characteristics of sandstorm-degraded images and improve the clarity of the images. Experimental results via subjective and objective evaluations demonstrate that the proposed method can significantly improve images captured during sandstorm weather conditions, and the results are better than other methods.

Chemo-economic analysis of battery aging and capacity fade in lithium-ion battery

Abstract Degradation due to capacity fade is a major cause of concern involved in the design and implementation of lithium-ion battery. In particular, the formation and growth of Solid Electrolyte Interface (SEI) have been considered as one of the primary degradation mechanisms affecting the cycle life of the battery. Over the past decade, several models have been reported towards simulation of SEI growth-induced degradation and prediction of cycle life. In this work, an efficient reduced-order electrochemical model was developed for a lithium cobalt oxide/graphite battery. A reaction–diffusion based SEI model was integrated with the electrochemical model to predict the cyclic capacity loss due to electrolyte deposition on the anode. The algorithm developed for this battery module was designed to reduce the computational time for capacity fade calculation with any (dis)charging protocol. The model was also applied for a lithium ferrous phosphate/graphite cell and in both cases, the fade predictions were within ±1% deviation from the experimental results. A comparison of two charging protocols was undertaken to identify approaches that improve capacity fade characteristics of battery. The electrochemical benefit of a reduced fading rate for aged (or used) lithium battery was investigated. A concept of “aged-battery” was proposed to be used as an advantage for better cycle-life in battery for biomedical devices and recycling of electric vehicle battery for solar panels applications. An economic analysis was performed to justify the benefits from lower fade that was weighed against the additional cost involved in aging the battery.

Influence of iron–aluminum alloy on the tribological performance of non-asbestos brake friction materials – a solution for copper replacement

PurposeThe purpose of this study is to investigate the influence of commercially available iron–aluminum alloy compared to copper, iron and aluminum powders on the tribological performances of friction composites. The main objective is to replace copper from the friction composite formulations.Design/methodology/approachIn this study, friction composites were fabricated as of standard brake pads using commercially available iron–aluminum alloy and compared to copper powder, iron powder and aluminum powder-based without varying the other ingredients. The brake pads were developed as per the industrial procedure. The physical, mechanical and thermal properties of the developed brake pads were analyzed as per industrial standards. Tribological properties were analyzed using the chase test. Initial speed and deceleration tests in a real-time braking scenario were performed using a full-scale inertia brake dynamometer. Worn surface analysis was done using a scanning electron microscope.FindingsThe results indicate that iron–aluminum alloy (mechanomade)-based friction composites possess good physical, chemical, thermal and mechanical properties with stable fade and recovery characteristics due to its composition and flake morphology. During initial speed and deceleration braking conditions, iron–aluminum alloy also showed good tribological behavior.Originality/valueThis paper explains the influence of commercially available iron–aluminum alloy in friction composites in enhancing tribological performance by its composition and flake morphology, which could potentially replace copper in friction composites by solving subsequent problems.

Development and Performance Evaluation of Eco-Friendly Crab Shell Powder Based Brake Pads for Automotive Applications

The present study deals with the effective usage of crab shell, which is a solid waste in the seafood industry. The crab shell was powdered and treated with chemicals to obtain the chemically treated crab shell powder. The crab shell was powdered and heated to the desired conditions to obtain thermally processed crab shell powder. These two powders so obtained were used with other ingredients in the development of brake pads. For comparison crab shell powder free brake pads were also developed. The developed brake pads were tested for various characteristics as per the industrial standards. Thermal stability was found using Thermogravimetric analysis. The fade and recovery behaviours were estimated for the developed brake pads using Chase test following IS2742 Part-4. The test results indicate that the thermally processed crab shell powder based brake pads showed better thermal stability with a char residue of 37%, while the chemically treated crab shell powder based brake pads had better fade and recovery characteristics with a fade rate of 1.71 % and recovery rate of 99.86 % due to its better heat dissipation and coarse structure. Scanning electron microscopy paved the way to study the worn characteristics of the Chase tested samples. An extensive evaluation method was used to rank the developed brake pads based on the Chase test performance; it also ranked chemically treated crab shell powder-based brake pads as the best performer.

The effects of rain fade on millimetre wave channel in tropical climate

The main objective of this paper to determine multipath and time-varying channel behaviour of short-terrestrial millimetre-wave point-to-point radio links. In an attempt to invigorate the impact of rain attenuation on mm-wave channel parameters such as the RMS delay spread, path loss received power strength and Rician distribution with a K factor. A brief analysis of rain fading was presented based on the simultaneous measurement of one-minute rain rate and its effects on a short experimental link of 38 GHz. Rain fade average is observed as high as 16 dB for 300 m path at about 125 mm/hr rain intensity. The statistical spatial channel mode (SSCM) simulation software was utilized for an operating frequency of 38 GHz. To generate of power delay profile (PDP). For both omnidirectional and directional antenna. The RMS delay spread and path loss has been estimated using the environmental parameters of Kuala Lumpur city which illustrates the theoretical performances of 5G in Malaysia. It is observed that RMS delay spread, path loss received power strength and K factor effected dramatically by rain fade. (SSCM) simulation software has to be modified to consider rain fade dynamic characteristics to achieve ultra-reliability requirements of outdoor applications in the tropical regions. This study is important for understanding signal propagation phenomena in short distance and enabling the utilization of the millimetre wave band for an urban micro-cellular environment for 5G communication system.