High Current Load Research Articles

(Digital Presentation) Impact of the Cathode Catalyst Ink Solvent Composition on the Polymer Electrolyte Membrane Fuel Cell (PEMFC) Performance at High Current Densities

Polymer electrolyte membrane fuel cells (PEMFC) are promising candidates for the replacement of internal combustion engines. Still, alongside the necessary enhancement of the mass activity of cathode catalyst material, the performances of the PEMFC cathode must be improved in the high current densities range where the O2 reactant mass transport towards the catalytic site is limiting for the reaction rate [1]. High current density performance of the PEMFC strongly depends on the ionomer distribution in the catalytic layer constituting the electrode, which depends on the solvent used for the catalyst ink preparation [2]. From different studies, it has been observed that the nature of the solvent composition modifies the resulting structure and size of the dispersed ionomer agglomerates in the catalyst ink [3–5]. The main objective of our investigation is to resolve in more detail the influence of the ink solvent composition on the PEMFC performances. For this purpose, the agglomerate size distribution of the 1100 EW Nafion® ionomer dispersed into various solvents was determined at first by dynamic light scattering (DLS) in a systematic fashion and found to be strongly influenced by the kind of alcohol (isopropanol, ethanol and methanol) and its concentration in water. Then, in order to attempt a correlation between the agglomerate size of the ionomer and the MEA performances, cathode catalyst layers were prepared from inks with these alcohols at different concentrations, while keeping all the other parameters in the CCM preparation unchanged. Electrochemical impedance spectroscopy (EIS) and O2 mass transport resistance measurements (O2-MRT) were performed in addition to the recording of single cell polarization curves. The latter were modeled following the equation suggested by Larminie et al. [6] to discriminate the kinetic, ohmic and mass transport overvoltages (losses).The ink-solvent compositional characteristics significantly influence the O2 reactant mass transport overvoltages. An analog equivalent circuit including a Nernst impedance element to account for the finite O2 diffusional limitations at the cathode catalyst layer was fitted to the experimental EIS data. The Warburg parameter scales very well with the O2 transport resistance through the catalytic layer derived from O2-MRT measurements, this strengthening the robustness of the overall set of experimental data. As the fraction of ionomer agglomerates in the range 50-500nm progressively increases in the catalyst ink up to ca. 37-45%, the losses attributed to the limited O2 mass transport to the catalytic sites are lowered by down to ca. 70% at 1.76 A∙cm-2 current load under the given cell testing conditions, independently of the nature of the alcohol and its relative content. For the higher fraction of ionomer agglomerates in this size range, no further change is observed in the O2 transport loss parameter. These results highlight quantitatively the significant influence of the size distribution of ionomer agglomerates on the cell performances under high current loads and suggest a convolution with other parameters, such as, e.g., the porous structure of the catalyst layer, that has yet to be quantitatively asserted.

Parametric Sensitivity Analysis and Performance Evaluation of High-Temperature Anion-Exchange Membrane Fuel Cell

In this paper, a three-dimensional model of a high-temperature anion-exchange membrane fuel cell (HT-AEMFC) operating at 110 °C is presented. All major transport phenomena along with the electrochemical reactions that occur in the cell are modeled. Since the water is exclusively in the form of steam and there is no phase transition to deal with in the cell, the water management is greatly simplified. The cell performance under various current loads is evaluated, and the results are validated against the experimental data. The cell performance is examined across a range of operating conditions, including cell temperature, inlet flow rate, and inlet relative humidity (RH). The critical link between the local distributions of species and local current densities along the channels is identified. The distribution of reactants continuously drops in the gas flow direction along the flow channels, causing a non-uniform local current distribution that becomes more pronounced at high current loads, where the rate of water generation increases. The findings show that while a higher inlet flow rate enhances the cell performance, a lower flow rate causes it to drop because of reactant depletion in the anode. The sensitivity analysis reveals that the performance of an AEMFC is highly dependent on the humidity of the gas entering the cell. While high inlet RH on the cathode side enhances the cell performance, high inlet RH on the anode side deteriorates it.

Intimate triple phase interfaces confined in two-dimensional ordered mesoporous carbon towards high-performance all-solid-state lithium-sulfur batteries

All-solid-state lithium-sulfur battery (ASSLSB) is one of the most promising next-generation energy storage devices while confronting great challenges for practical applications, in particular the sluggish reaction kinetics of the insulating active materials, less solid-solid contact, and insufficient electronic/ionic conduction networks within cathode layer. Herein, a two-dimensional (2D) ordered mesoporous carbon (OMC) framework is developed and serves as an advanced host for active material Li2S and solid electrolyte Li6PS5Cl (LPSC), forming a mixed conductive nanocomposite with 5 orders and 12 orders of magnitude increase in ionic and electronic conductivities compared with Li2S, respectively. The ordered mesoporous in OMC provide confined space for the intimate contact between nanosized Li2S and LPSC, which are favorable for continuous lithium-ion transport and increasing Li2S utilization. Benefiting from these merits, the ASSLSBs employing Li2S/OMC/LPSC nanocomposite achieve high reversible capacity and excellent cyclic performance at both high current density and high cathode loading.

Carbon coated electric arc furnace dust prepared by one-pot pyrolysis: An efficient, low carbon footprint electrode material for lithium-ion batteries

This work offers useful insights into the evaluation of the electric arc furnace dust in green energy applications by surface engineering. To produce low-carbon-footprint electrodes, for the first time in the open literature, the practical pyrolysis (of sucrose) method is applied to create a nanometer-thick carbon layer over the dust. Advanced techniques are used to characterize the carbon-coated electric arc furnace flue dust morphologically, structurally, and chemically. Galvanostatic tests reveal that the carbon-coated dust exhibits 600 mAh g−1 discharge capacity after 250 cycles. The rate test proves that the carbon-coated dust can withstand a high current load (2A g−1) and delivers 540 mAh g−1 after 250 cycles when the current load is decreased to 0.1A g−1. This obtained capacity shows that with the correct material selection and process design, it is possible to produce low-carbon footprint electrodes at a low cost. Electrochemical characterizations indicate that the lithiation reaction of the carbon-coated dust takes place similarly to that of the anode materials which are made of synthetically fabricated carbon-coated transition metal oxides and/or ferrites. It is anticipated that this study sets an example for the valorization of the various industrial wastes in energy applications in the future.

Design and Demonstration of a 540 V/28 V SiC-Based Resonant DC–DC Converter for Auxiliary Power Supply in More Electric Aircraft

Efficient and robust power electronic converters are vital to the success of the electrification of aircraft. Especially, low voltage auxiliary converters, which usually supply high current and low voltage loads, are not readily available industrially and need special attention. In terms of energy density and efficiency, LLC converters are among the most commonly used and efficient topologies for automotive and aerospace applications. In the case of aerospace applications, a fault-tolerant topology is highly desirable to reduce the need for redundant components and weight by removing backup systems. To solve this issue, this study introduces a new 2.0 kW LLC-based converter with a reconfigurable fault-tolerant architecture. With the help of a specially designed secondary side, the proposed converter can reconfigure itself so that even if one of the semiconductor switches fails permanently, the converter can still maintain power at nominal voltage levels, ensuring that the aircraft’s vital functionality is preserved. This paper also describes the basic operation principle, component-design aspects, conduction loss reduction techniques, and control system algorithm. Finally, a 2.0 kW experimental prototype is built to verify and demonstrate the operation of the proposed reconfigurable LLC converter.

Multiple Adaptive Current Feedback Technique for Small-Gain Stages in Adaptively Biased Low-Dropout Regulator

Adaptive bias scheme, which can be used to provide a current proportional to the current flowing through the power transistor under high current load, avoiding the need for providing additional large fixed bias current to the circuit, has been adopted in many low-dropout regulators (LDO). When an adaptive bias scheme is applied to an LDO with a current mirror buffer, although a low chip area consumption and a better transient response can be achieved, the loop gain of LDO at high-load current and loop bandwidth at low load are still low. In previous works, multiple small-gain stages can effectively improve the gain and bandwidth but may lead to stability problems or even need to consume large currents to ensure stability, thus affecting current efficiency. This article proposes the multiple adaptive current feedbacks technique for small-gain stages in adaptively biased low dropout regulator (AB-LDO) with a current mirror buffer, improving the loop gain and bandwidth and eliminating the need for frequency compensation to meet stability requirements. Moreover, in the case that multiple adaptive bias loops can be introduced after the proposed technique is applied to this design, an intuitive and simple method is adopted to analyze the whole circuit. The designed AB-LDO was fabricated in Semiconductor Manufacturing International Corp (SMIC) 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m process. The measured results show that the designed LDO realizes 30.75-mV transient performances with a step of 10 ns.

Experimental investigation of reverse voltage phenomenon during galvanostatic start-up of a proton exchange membrane fuel cell

The reverse voltage is critical for the performance and durability of a proton exchange membrane fuel cell (PEMFC). The reverse process will cause a complex kinetic transformation from normal to abnormal, leading to degradation of catalyst. There are few experimental studies and some numerical simulations reported on this issue, however, the process of reverse voltage under dehydration conditions is still unclear. This article explores the voltage reversal process and dehydration phenomenon of a PEM fuel cell during the start-up process. The effects of operating parameters on the occurrence of the reverse voltage are examined, including the startup current density, the inlet gas relative humidity (RH) and the gas stoichiometric ratio. To understand the reverse process, the voltage, high frequency resistance (HFR) and the outlet gas relative humidity during startup are monitored online in real time. Results show that the reverse voltage occurs when the fuel cell starts up at the condition of low relative humidity, high current density load and high hydrogen stoichiometry at low humidity. From the beginning of the startup process, the humidity of the anode outlet gas decreased significantly, which is correlated with the increase of HFR and the drop of voltage. By time constant analyzing of the process, it was observed that the dehydration on the anode side of the membrane electrode during the startup period led to an instantaneous increase of HFR, which reveals the process mechanism of voltage reversal. Finally, we suggest a startup strategy to reduce or even avoid the reverse voltage.

A High-Efficiency Dynamic Inverter Dead-Time Adjustment Method Based on an Improved GaN HEMTs Switching Model

Benefited from the fast switching speed, Gallium nitride (GaN) high electron mobility transistors (HEMTs) have been widely used in high switching frequency converters. However, due to the significant correlation between the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> time and operating conditions (more than 20 times difference of the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> time between the high load current and small load current for GaN HEMTs), using a fixed dead time will introduce extra dead-time (DT) losses in inverters where the output voltage and current are constantly varying. Therefore, this article proposes a high-efficiency adaptive method to dynamically adjust the GaN-inverter DT with operating conditions. An improved transient model including the parasitic inductance and output voltage with bidirectional solution flow has been proposed for GaN HEMTs to increase the accuracy of DT adjustment. Based on this model, the dynamic DT adjustment can be realized without extra sensors for GaN-inverters. Using the dynamic DT adjustment, the experimental results show a peak efficiency of 98.25% in a 1200 W inverter with triangular current mode modulation. Compared with using the fixed DT, the dynamic DT method can reduce the power loss by 26.7% under full load and 49.14% under light load.

Tailored 3D Foams Decorated with Nanostructured Manganese Oxide for Asymmetric Electrochemical Capacitors

Tailored 3D (Ni and NiCo) metallic foam architectures were produced by electrodeposition and decorated via electrochemical routes with manganese oxide (MnOx) to serve as positive electrodes for supercapacitors. For comparative purposes, an electrode made of commercial Ni foam was also prepared. The foam-based electrodes were paired with a carbon cloth electrode and used to assemble asymmetric electrochemical cells. The electrochemical response of these cells was studied by applying different electrochemical techniques. In addition, two different protocols (cycling and floating) were applied to assess cells durability and fade. Despite the significant differences in the decorated foams morphology and structure their electrochemical responses revealed similar trends. The electrodes made of tailored foams showed higher specific capacitance, better capacitance retention at high current load and enhanced cycling stability compared to the electrodes made of commercial foam. The asymmetric cells made with the tailored foams revealed higher (maximum) specific energy (11–14 Wh kg−1) and specific power (1.3–1.4 × 104 W kg−1) compared to cells assembled with commercial foams (8.4 Wh kg−1 and 6.3 × 103 W kg−1). The durability tests evidenced that corrosion of the NiCo electrodeposited foams and electrochemical dissolution of MnOx are possible causes of cells degradation.

Three-dimensional crystalline-Ni5P4@amorphous-NiOx core–shell nanosheets as bifunctional electrode for urea electro-oxidation and hydrogen evolution

The electrochemical urea oxidation (UOR) involves the generation of gases bubbles, which often cause the blockage of the electrode surface leading to decline activity. Herein, we report the growth of Ni5P4 nanosheets on nickel foam as bifunctional electrode (CA-Ni5P4@NiOx/NF) for urea electrolysis. The results indicated that a thin layer of amorphous NiOx formed on the surface of Ni5P4 nanosheets to yield a unique crystalline@amorphous core–shell structure, which can be maintained during long time urea electrolysis. The outstanding UOR performance of CA-Ni5P4@NiOx/NF was attributed to the unique structure, which not only combine the good conductivity and abundant active sites, but also rendered the CA-Ni5P4@NiOx/NF superhydrophilic and aerophobic that significantly facilities the release of gases bubbles formed during UOR to avoid the blockage of the active sites. As a result, the CA-Ni5P4@NiOx/NF electrode exhibited excellent performance for UOR, which only needs 1.45 V (vs. RHE) to deliver a current of 100 mA/cm2. When used as anode for direct urea fuel cell (DUFC), it could reach a maximal power density as high as 3.4 mW/cm2with an OCV of 0.76 V. The CA-Ni5P4@NiOx/NF also exhibited excellent activity for hydrogen evolution reaction (HER), with -0.089 V (vs. RHE) to deliver a current of 10 mA/cm2. The electrolyzer constructed with CA-Ni5P4@NiOx as both anode and cathode could run for more than 10 h at a high current load about 100 mA/cm2 without appreciable potential change, indicating the superb stability of the CA-Ni5P4@NiOx electrode. Our work provides new insights for understanding as well as the development of advanced electrode for DUFC and urea electrolysis.

Mechanism Characterization and Nondestructive Inspection Method of Thermal Degradation Faults in EPDM Cable Termination

There is a significant positive proportional correlation between the condition of ethylene propylene diene monomer (EPDM) insulation and partial discharge(PD) characteristics in electric multiple units (EMU) cable termination. Especially for the cable terminations with long service life, the aging effect of EPDM insulation material is significant due to long-term high-current load. In this paper, electrical deterioration and PD development of EPDM insulation under long-term thermal degradation is conducted. During the test process, the phase-resolved partial discharge (PRPD) analysis, partial discharge inception voltage (PDIV), physicochemical properties, and flashover voltage of EPDM samples with different thermal degradation are measured. The relationship between the thermal degradation extent of EPDM insulation and PD characteristics is also proposed. The results show that electrical deterioration of the aged sample can be divided into four gradations by PD amplitude and pulse repetition rate. In the four gradations, the shape of the PRPD spectrum in every gradation changes significantly with different thermal degradations. Surface morphologies of EPDM insulation show different features such as gully areas and white particles. The results of the Fourier transform infrared spectroscopy(FTIR) test indicate that the increase of oxygen-containing groups and free radicals are the key reasons for the rapid PD development process of cable insulation under different electrical gradations and thermal-oxygen degradations.

EFFECT OF WATER-SOLUBLE POLYMER NV-1A ON ELECTROCHEMICAL PARAMETERS OF SULFUR ELECTRODE

Studies have shown the possibility of a long cycle of sulfur electrode with a high content of active material. The use of water-soluble binder material NV-1A leads to the realization of high current loads in the Li-S battery. Impedance spectroscopy has shown that the low coulombic efficiency in the cycling of the sulfur electrode is primarily due to the spontaneous dissolution of sulfur in the electrolyte, which requires high energy consumption when charging the Li-S battery. The reduction of the specific capacity during cycling is associated with the formation and accumulation of non-conductive films of short-chain polysulfides. On the basis of the conducted researches and the review of the literature sources ways of overcoming of this problem are offered. The ability of cycling the sulfur electrodes at the high current loads has been shown. The discharge capacity values of the sulfur electrodes at the current load 790 mA∙cm-2 are 500 і 420 mAh∙g-1 on the 5-th and 100-th cycles, accordingly. Using the method of impedance spectroscopy, it has been supposed that the formation and accumulation of unconductive Li2S2 / Li2S phases is the main process, which induce the quick capacity reduction of Li - S batteries upon cycling.

Specific capacitance behavior of Co‐Co 3 O 4 nanocomposite thin films synthesized via different electrodeposition modes

High capacitance Co-Co3O4 nanocomposite thin films have been synthesized on nickel foam (NF) using cyclic voltammetry (CV), combination of cyclic voltammetry and potentiostatic (CV PS −1.4 V and CV PS +1 V), and combination of cyclic voltammetry and pulse reverse potential (CV PRP) modes of electrodeposition. X-ray diffraction (XRD) studies reveal the presence of Co and Co3O4 phases for the four electrodeposition modes. The scanning electron microscope (SEM) revealed an interesting morphology correlating the electrochemical and capacitance behavior, while the energy-dispersive X-ray spectroscopy (EDX) spectra confirmed the varying quantities of Co and O in the Co-Co3O4 nanocomposite thin films. The presence of Co-O bonds were also confirmed by the attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra obtained on these films. The capacitance values of Co-Co3O4 composite thin films obtained by CV, CV PS −1.4 V, CV PS +1 V, and CV PRP, respectively, were found to be 1661, 1400, 1866, and 2580 F g−1 at an applied current load of 1 A g−1, while the capacitance retentions after 500 cycles under a high current load of 20 A g−1 for the same were 85.8%, 77.8%, 87.1%, and 90.5%, respectively. The high capacitance and their retention of the electrodeposited Co-Co3O4 nanocomposite thin films show potentials as high-performance supercapacitor electrode.

Comparative Analytical Modeling and Performance Investigation of Graphene-Based Super Capacitor with Four Traditional Batteries

Graphene, a magical development of 2004, has revolutionized today's energy storage technologies. It is nothing but a graphite two-dimensional (2D) allotropic pure carbon layer which is derived from a three-dimensional (3D) shape. Since batteries have been the most common storage device from the invention of the first electrical battery by an Italian physicist Alessandro Volta in 1799 A.D but batteries offer many drawbacks, such as length, weight, poor transient response, low power density, and high internal resistance. In this contrast, the impressive and unique properties of graphene supercapacitor such as high peak current, high surface area, high electrical conductivity, low internal resistance, high load current, long life cycle, high power density, low-temperature charging, and discharging make graphene supercapacitor a replacement of traditional energy storage devices and sets trend for the future. This analytical comparative analysis presents an overview between four traditional batteries and graphene-based supercapacitor. For this regard, dynamic models, modeling equations, and an integrated simulation model for batteries and graphene-supercapacitors under MATLAB/Simulink® 2020a environment is developed. In addition, the effect of temperature on battery output and graphene-supercapacitor is also addressed.

Combined effect of nitrogen-doped functional groups and porosity of porous carbons on electrochemical performance of supercapacitors

In this work, nitrogen-doped porous carbons obtained from chitosan, gelatine, and green algae were investigated in their role as supercapacitor electrodes. The effects of three factors on electrochemical performance have been studied—of the specific surface area, functional groups, and a porous structure. Varying nitrogen contents (from 5.46 to 10.08 wt.%) and specific surface areas (from 532 to 1095 m2 g−1) were obtained by modifying the carbon precursor and the carbonization temperature. Doping nitrogen into carbon at a level of 5.74–7.09 wt.% appears to be the optimum for obtaining high electrochemical capacitance. The obtained carbons exhibited high capacitance (231 F g−1 at 0.1 A g−1) and cycle durability in a 0.2 mol L−1 K2SO4 electrolyte. Capacitance retention was equal to 91% at 5 A g−1 after 10,000 chronopotentiometry cycles. An analysis of electrochemical behaviour reveals the influence that nitrogen functional groups have on pseudocapacitance. While quaternary-N and pyrrolic-N nitrogen groups have an enhancing effect, due to the presence of a positive charge and thus improved electron transfer at high current loads, the most important functional group affecting energy storage performance is graphite-N/quaternary-N. The study points out that the search for the most favourable organic precursors is as important as the process of converting precursors to carbon-based electrode materials.

Application of High-Temperature Raman Spectroscopy (RS) for Studies of Electrochemical Processes in Solid Oxide Fuel Cells (SOFCs) and Functional Properties of their Components

SOFC efficiency is directly determined by the electrodes, optimization of which is related to the study of the mechanisms of electrochemical current-generating reactions taking place. Such studies are tricky due to the high operating temperature of SOFCs, high current loads, and corrosive gas media. A promising research method is Raman spectroscopy (RS) under operating conditions of SOFC. At ISSP RAS, a combined experimental technique and setup have been created that combines the capabilities of traditional electrochemical methods, as well as high-temperature Raman spectroscopy [1]. In order to study the processes in the electrochemically active zone, a special geometry of samples was developed on basis of optically transparent single crystal membranes of an anionic conductor with a counter-electrode of a toroidal shape. With the use of this combined technique and special geometry of samples in previous works, studies of the kinetics of reduction and morphological changes of nickel in composite SOFC anodes were carried out. It was shown that the first reduction cycle differs significantly from the subsequent ones both in the initial delay and in the total time of the process. SEM studies have shown that these changes are associated with a morphological rearrangement that occurs during the first reduction cycle: the grain size of NiO is significantly reduced compared to the initial one. For model SOFCs investigated in the OCV mode [2] after the initial microstructural rearrangement in the redox cycle, the behavior of standard cermet anodes in a H2–N2 flowing atmosphere can be described using Avrami model. The influence of the composition of fuel on Raman spectra obtained from the internal interface in the current load mode was also investigated [3], and the correlations of obtained data with the cell voltage were studied. It was shown that the corresponding mechanisms that determine the reaction kinetics can be associated with the transfer of ions through the GDC|YSZ. Subsequent rate limiting steps such as electrochemical oxidation of hydrogen in the Ni-GDC layer are undetectable for the geometry under test due to the limited penetration depth of the laser beam. Comparative studies of model SOFCs with a supporting anode substrate (ASC) and a supporting solid electrolyte (ESC) were carried out using the in-situ RS technique [4]. It was shown that the addition of the GDC indicator layer makes it possible to carry out an in-situ study of the chemical potential of oxygen at the internal interface of the anode|electrolyte depending on current load or fuel mixture, but the GDC/YSZ two-layer thin-film electrolyte exhibits electronic or gas leakage due to poor stability in a reducing atmosphere. Despite the significantly lower internal resistance compared to the ESC, the quality of the ASC thin film membrane severely limits research depending on the operating temperature, current load and fuel composition. In this case, the use of thin-film membranes significantly reduces the effect of 8YSZ on the Raman spectra of the internal interface. After post-processing and normalization, the obtained Raman spectra show a similar effect of the current load or the hydrogen content in the fuel gas mixture on the GDC peak area (460 cm-1). The linear dependence of the OCV on the peak area of ~460 cm-1 makes it possible to assess the relationship between changes in the peak area and the evolution of the chemical potential of oxygen at the anode under a current load. Comparative analysis of the anodic impedance for different fuel mixtures suggests that spectroscopic measurements of the internal interfaces provide direct information on the contribution of the fuel oxidation reaction to the total losses in SOFC. In addition to studies of complete fuel cells, high-temperature Raman spectroscopy is used to study the structure of single-crystal samples of anionic conductors [5], including at the operating temperature of SOFCs. High-temperature RS allows one to obtain additional information on the microstructure of samples both at room temperature and at working temperature, where most other research methods do not allow research. New combined technique was used to study other components of high-temperature electrochemical devices: sealing glasses [6] for SOFCs and optical glasses [7]. This work was supported by Russian Scientific Foundation, grant no. 17-79-30071.[1] D.A.Agarkov et al. ECS Trans., vol.68, iss.1, pp.2093-2103 (2015).[2] D.A.Agarkov et al. Solid State Ionics, vol.302, pp.133-137 (2017).[3] D.A.Agarkov et al. Solid State Ionics, vol.319C, pp.125-129 (2018).[4] D.A.Agarkov et al. Solid State Ionics, vol.344, p.115091 (2020).[5] D.A.Agarkov et al. Solid State Ionics, vol.346, p.115218 (2020).[6] A.Allu et al. ACS Omega, vol.2, pp.6233-6243 (2017).[7] M.K.Kokila et al. Solid State Sciences, vol.107, p.106360 (2020). Figure 1

Pulsed Reverse Potential Electrodeposition of Carbon-Free Ni/NiO Nanocomposite Thin Film Electrode for Energy Storage Supercapacitor Electrodes

A combined cyclic voltammetry and pulse reverse potential electrodeposition technique has been used to synthesize carbon-free Ni/NiO nanocomposite thin film supercapacitor electrode. The structural and morphological analyses have revealed the presence of crystalline phases of both Ni and NiO in the form of nanospheres of size ~50 nm. The electrochemical analysis of the Ni/NiOna nocomposite electrode has shown a remarkable performance by delivering a high specific capacitance of 2000 Fg−1 at an applied current load of 1 Ag−1 and a capacitance retention of 98.6%, after over 800 cycles under a high current load of 20 Ag−1.

N-Enriched Porous Carbon/SiO2 Composites Derived from Biomass Rice Husks for Boosting Li-Ion Storage: Insight into the Effect of N-Doping.

A N-enriched porous carbon/SiO2 (SiO2 /NC) composite from rice husks was prepared by ball milling and tested as a stable anode for lithium ion batteries (LIBs), in which the homogeneous dispersion of SiO2 nanoparticles and carbon matrix, and high level of N-doping can be realized simultaneously. The influence of N-doping on a series of SiO2 /NCs was systematically studied; this proved that the porosity, N-doping content, and electronic conductivity of SiO2 /NC can be controlled by adjusting common nitrogen sources (urea and melamine) and doping routes, including dry and wet milling, to reach a desirable balance of high capacity, long-term cyclability, and rate property. The optimized SiO2 /NC composite delivers a stably reversible capacity of 581 mA h g-1 at the high current load of 1.0 A g-1 at the 1000th cycle. The novel Li-storage mechanism of active silica in a composite was first proposed after observation of the N-doping effect that the redox reaction between SiO2 and Li+ is accelerated to transform into an alloying reaction of generated Si and Li+ , thus enhancing the reversible capacity. Moreover, kinetics analysis confirms that there is a combined Li-storage mechanism of battery-capacitive pattern in composite that contributes to fast charge transfer and ion diffusion during cycle.

Optimization of the Relative Humidity of Reactant Gases in Hydrogen Fuel Cells Using Dynamic Impedance Measurements

Water management is a key factor affecting the efficiency of proton exchange membrane fuel cells (PEMFCs). The currently used monitoring methods of PEMFCs provide limited information about which processes or components that humidity has a significant impact upon. Herein, we propose the use of a novel approach of impedance measurements using a multi-sinusoidal perturbation signal, which enables impedance measurements under dynamic operating conditions. The manuscript presents the effect of the relative humidity (RH) of the reactants on the instantaneous impedance of the middle cell in the PEMFC stack as a function of the current load. Analysis of changes in the values of equivalent circuit elements was carried out to determine which process determines the stack’s performance depending on the load range of the fuel cell during operation. Comprehensive impedance analysis showed that to ensure optimal cell operation, the humidity of the reactants should be adjusted depending on the load level. The results showed that at low-current loads, the humidity of gases should be at least 50%, while at high-current loads, the cell should operate optimally at a gas humidity of 30% or lower. The presented methodology provides an important tool for optimizing and monitoring the operation of fuel cells.

ELECTRONIC FUSE USING RESETTABLE POLY FUSE FOR OVER CURRENT PROTECTION

This paper presents a new technique to deal with the high load currents or fluctuating currents using poly fuse as its major component. Poly fuse is a resettable fuse which goes on increasing its resistance, blocking the excess current until the current is back to normal. Once the current is under normal conditions, the resistance stabilizes and the path between supply and load is reconnected. The proposed work also uses a reed relay which breaks the path exactly at the specified rating, allowing a fast switch. The combination of poly fuse and reed relay provides more efficient outputs as compared to traditional circuit breakers. The fast-switching action, accurate results and the smaller size makes poly fuse more suitable for most of the power devices.