Electrochemical Energy Sources Research Articles

Development of Binder–free Ni3S2/CoS2 nano–composite as electrode material for Energy Storage Application

Global energy crisis imposes immense obstacles leading towards development of innovative devices, and supercapacitors (SCs) are thought to be a viable energy storage technology. The engineering of nanostructured materials with a distinct and consistent morphological design is seen as a better option for various range of electrochemical energy sources. This study reports novel binder-free Ni3S2/CoS2 electrode material that acquires higher energy, higher energy density, as well as its simple preparation method, low cost, and earth–abundant resources. The morphological, structural, and textural characteristics resulted in surface area of 46 m2 g–1 of Ni3S2/CoS2 that will increase active sites also. The synthesized nanocomposite has particle size of 41.1 nm that leads to enhanced active sites and greater surface area as confirmed through BET analysis. Ni3S2/CoS2 nanocomposite has high specific capacity around 828.14 F g–1 at 5 mV s–1 sweep rate using 2 M KOH, a high energy density around 115.01 Wh kg–1, and power density of 1000 Wh kg–1. Ni3S2/CoS2 acquires higher ionic conductivity of 5 S m-1, this will enhance the inter-layer transference of electrons, and these results perfectly correlates with EIS, resulting in charge transfer resistance value of 0.9 Ω for nano-composite. These enhanced electrochemical capabilities of Ni3S2/CoS2 hold significant potential in practical viability.

Assessing the Possibility of Implementing Distributed Diagnostic Systems for Hydrogen Fuel Cells Using Local and Global Telecommunication Networks

The development of effective methods and means for diagnosing hydrogen fuel cells during their operation is an urgent task, since their implementation will improve the energy characteristics and stability of operation by detecting incorrect operating modes and malfunctions at the early stages of development. This problem can be solved by using various approaches based on the analysis of impedance, relaxation or fluctuation-noise characteristics. All of these methods require the implementation of rather complex computational procedures and the accumulation of fairly large amount of statistical data, which makes it difficult to implement diagnostic devices on inexpensive embedded microprocessor tools. To overcome this drawback, this work proposes the use of distributed diagnostic systems with high-performance server devices connected to local modules via global or local telecommunication networks. Such an implementation will significantly simplify the requirements for local diagnostic modules and reduce their cost, but this raises the question of the efficiency of making diagnostic decisions by such systems.The work carried out, is a study of delays in making diagnostic and control decisions when using remote server devices for signal processing. It has been shown that the use of such systems makes it possible to achieve delays of less than one second even when using intercontinental communication lines. It should be noted that in applications critical to time delays, the distance between the client and server systems should be reduced. The advantages of the proposed implementation of a diagnostic system for electrochemical energy sources are the possibility of simplifying local measurement systems installed on individual sources, the possibility of accelerating signal processing through the use of more productive computing tools and the accumulation of statistical data.

Rare Earth metal oxide nanoparticle-infused polymer nanocomposites for enhanced supercapacitor electrodes

The contemporary energy shortage has spurred scientists to explore other options. In this regard, there's significant interest in utilizing electrochemical energy sources for converting and storing energy. Here, a fresh endeavor involves utilizing a set of semiconducting rare earth Gd2O3/conducting polymers (CP) (CP= polypyrrole, polyindole) for energy storage purposes. The synthesis method involves the straightforward oxidative polymerization of either indole or pyrrole to produce Gd2O3/PIn or Gd2O3/PPy, respectively. The integrity of the garnets synthesized was verified through XRD, Raman, XPS, FESEM, and TEM analysis, ensuring their phase purity and morphology. The scanning electron microscopy (SEM) analysis reveals the particle morphology, with sizes ranging from 100 to 800 nanometers. FTIR and Raman spectroscopy further validate the integration of Gd2O3 into the conducting polymer matrix. XRD shows broad peaks for amorphous structures in Gd2O3/PPy and Gd2O3/PIn nanocomposites. To evaluate its performance in supercapacitors, cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and impedance spectroscopy (EIS) were employed using a three-electrode configuration. The rectangular CV curves indicate the pseudo-capacitance mechanism of the Gd2O3/CP nanocomposite-coated carbon fiber electrode in an H2SO4 electrolyte. Specific capacitance (SC) values for Gd2O3/PPy and Gd2O3/PIn binary nanocomposite electrodes are determined as 341.61 F/g and 305.56 F/g, respectively, from GCD curves. In hybrid energy systems, especially electric automobiles, the Gd2O3/PPy and Gd2O3/PIn nanocomposite-coated carbon fiber electrode has a potential of up to 1.8 V and short charging and discharging durations, implying fast-charging and extended lifespan. The easy oxidative polymerization process utilized to produce gadolinium oxide/conducting polymer nanocomposites for supercapacitors is the main breakthrough of this research.

Molecular dynamics modelling of the structural, dynamic, and dielectric properties of the {LiF - ethylene carbonate} energy storage system at various temperatures

Lithium-ion batteries (LIBs) play a vital role in advancing the hybrid industry, especially in electric vehicles, as clean and sustainable electrochemical energy sources. However, the prevalent use of organic solvents in the liquid electrolytes of these energy storage systems raises environmental concerns. In this study, we investigated the impact of a polar aprotic solvent, Ethylene Carbonate (EC), on the structural, dynamic, and dielectric properties of the LiF electrolyte using molecular dynamics simulations. By employing the CHARMM 36 force field, our goal was to comprehend the various physicochemical phenomena occurring in this electrolytic system across different temperatures within the saturation region. The structural properties were analyzed through the computation of the radial distribution function (RDF) for various pairs, while the dynamic and dielectric behaviors were elucidated by simulating the self-diffusion coefficient (D) and the dielectric constant (?).

Insights into the Complex Oxidation Behaviour of Aqueous H3PO3 through in Situ P K- Edge XANES

High-temperature electrolyte membrane fuel cells (HT-PEMFCs) using H3PO4-doped membranes are an enticing choice for electrochemical energy sources at elevated temperatures [1]. Yet, one of the challenges concerning these systems is the reduction of H3PO4 to lower valency phosphorus compounds, such as H3PO3, during operation [2,3,4]. H3PO3 can strongly adsorb on the Pt catalysts, hence poisoning it and thereby lowering the fuel cell performance [5,6]. Interestingly, the presence of Pt may, under certain conditions, catalyze the chemical (re-)oxidation of aqueous H3PO3 back to H3PO4, illustrating the complexity of the H3POx – Pt interaction. Therefore, to optimize the performance of HT-PEMFCs by rational design of the catalyst/electrolyte interface, further insight into H3PO3 oxidation behaviour and Pt/H3PO3 interaction under conditions relevant to HT-PEMFCs operation is required.In this study, in situ P K- edge XANES (x-ray absorption near edge structure) spectroscopy was conducted to shed light on the oxidation behaviour of aqueous H3PO3 by investigating the impact of (i) different temperatures (25°C vs 75°C), (ii) varying electrode roughness (flat planar Pt vs rough Pt black), (iii) different electrode potentials (open circuit potentials vs more positive potentials [+0.8, +0.9, and +1.0 VRHE]), and (iv) varying molar concentrations of H3PO3 (0.1 , 1 , and 5 mol dm-3). Initially, XANES coupled with electrochemical characterization (e.g. OCP, cyclic voltammetry) of the system was performed under different radiation doses (i.e.: photon fluxes, exposure time) to determine the effect of radiolysis and/or radiation damage during experiments that may lead to misinterpretations of XANES results. Under high radiation dose, we find evidence of H2 presence in the vicinity of the Pt electrode, likely generated by water radiolysis. We have developed experimental procedures to suppress these undesirable effects during the collection of the XANES data, enabling an accurate determination of H3PO3 oxidation behaviour and minimizing the radiolysis contribution to the process. It was found that higher temperature facilitates the oxidation of aqueous H3PO3 to H3PO4, presumably because H3PO3 exists in the thermodynamically preferred “active” pyramidal form at elevated temperatures, which is more prone to react with H2O, forming H3PO4 and H2. In aqueous H3PO3 solutions with higher H2O contents, also more pronounced oxidation of H3PO3 is observed, indicating that oxidation of H3PO3 to H3PO4 in aqueous solutions proceeds via the presence of H2O. The experiments using rough Pt black electrodes additionally hint at the observation of electrochemical oxidation of H3PO3 to H3PO4 during the application of positive potentials. This work provides insights into the underlying chemical processes that occur at conditions relevant for HT-PEMFCs operation and thus it paves the way for possible strategies to mitigate H3PO3 poisoning of the Pt electrode during operation.

Investigating the Suitability of Printed Circuit Components for Fuel Cells

Flexible electrochemical energy sources using non-traditional cell materials and topologies have attracted growing attention because they offer unique design opportunities that are still being explored. They also offer potential advantages such as conformability, high power density, high specific power, and low cost through the adoption of electronics manufacturing techniques. This study examines the feasibility of using flexible printed circuits boards (PCBs) as the anode and cathode current collectors (CCs) of single cell Proton Exchange Membrane Fuel Cell (PEMFCs). In this work, we determine the best anode and cathode interfaces at which to embed flexible CCs to obtain the highest power, as illustrated in Figure 1. The flexible anode and cathode CCs are embedded A) inside the PEM|Catalyst Layer (CL) interface, B) between the CL|Micro Porous Layer (MPL) interface and C) between the Gas Diffusion Layer (GDL)| Flow field (FF) interface. The performance of the single cell PEMFC with the embedded flexible anode and cathode CCs at the different interfaces described in Figure 1 is investigated by using I-V polarization curves, electrochemical impedance spectroscopy (EIS), and thermal imaging. The performance of the cells tested with the embedded flexible CCs is compared to the performance of a standard cell. This study also investigates the effect of varying the anode and cathode CC geometry (square shape vs. circular) and opening ratio (20%, 30%, 40%, 50% and 60%) on the cell performance. Figure 1

Unconventional frequency response analysis of PEM fuel cell based on high-order frequency response function and total harmonic distortion

Electrochemical impedance spectroscopy (EIS) is a commonly used technique for studying internal dynamics of the proton exchange membrane (PEM) fuel cell. However, due to its linear frequency response nature and reliance on the linear target hypothesis, EIS has limitations in analyzing the nonlinear behavior of the PEM fuel cell, which is the inherently nonlinear system. To overcome this issue, this paper employs an unconventional frequency analysis technique that utilizes the high-order frequency response function (FRF) and total harmonic distortion (THD) in a broad frequency range, to conduct the nonlinear frequency response analysis (NFRA) of the PEM fuel cell. In addition to the traditional electrochemical impedance based on the first-order harmonic response, the high-order harmonic response is also included. Based on this, the appropriate excitation amplitude is determined through a comprehensive examination of the impact of varying excitation amplitudes on the impedance, second-order FRF, and THD. Then, the impacts of operating conditions, such as reactant stoichiometry, humidity, temperature, and pressure, on the FRF and THD were investigated incorporating the dynamics losses computed using EIS and equivalent circuit model. Furthermore, the nonlinear frequency response is investigated under various fault conditions, such as flooding, membrane drying, and air starvation. The results demonstrate the heightened sensitivity of the NFRA method towards detecting changes in internal processes of the PEM fuel cell, which offers a multidimensional frequency-domain perspective, facilitating the study of the advanced diagnosis, system control, material optimization, and even other electrochemical energy sources.

Research and simulation of electrochemical processes in vanadium batteries

Formulation of the problem: In the modern world, the development of efficient energy sources is becoming an increasingly important issue. One of the promising areas in the field of electrochemical energy sources is vanadium batteries. These batteries are based on electrochemical processes involving vanadium in various oxidative states. Research and modeling of electrochemical processes in vanadium batteries are important to optimize their performance and improve energy efficiency. Research and modeling of electrochemical processes in vanadium batteries play a key role in the development of efficient energy sources. Understanding the basic principles of operation of vanadium batteries, as well as the development of accurate mathematical models and their numerical simulation, allows optimizing the processes associated with storing and releasing energy. Further research and development in this area could lead to the creation of more efficient and sustainable energy sources that can meet the sustainable energy needs of modern society. Objective of the project: modeling the processes of vanadium redox flow batteries (VRFB) by varying the electrolyte flow to optimize electrochemical processes occurring under membrane-electrode boundary conditions. Results: this study simulates in the COMSOL Multiphysics software package the electrochemical characteristics of HFSC as a function of electrolyte flow. Tests were carried out in which the flow velocity parameters were examined to evaluate their effect on the potential distribution and current density. Practical significance: the energy in an HFSC is stored in a liquid electrolyte that is pumped through the cell. The electrolyte is stored in external reservoirs rather than in porous electrodes as in conventional batteries. The results contribute to improved efficient energy storage, load balancing, and peak power smoothing of the GRPB. The construction of models allows us to predict the effect on the efficiency of mixing electrolytes, taking into account the hydrodynamic conditions inside the battery to determine how they affect the transport of vanadium ions, taking into account the electrolyte flow rate.

Polyampholyte saturated with simulated-body-fluid as a flexible, stretchable and self-healing gel electrolyte for biocompatible energy storages and capacitive circuit elements

As implantable electronic medical devices (IEMDs) develop, biocompatible polymer materials with body-friendly non-toxic nature are receiving great amount of attention. Polyampholyte hydrogels have mechanical flexibility and self-healing properties, as well as biocompatibility; thus, it can be applied in various implantable medical devices and wearable devices. In this study, the possibility of using a polyampholyte hydrogel saturated with simulated body fluid (PA-SBF) as the gel polymer electrolytes for energy storage devices and capacitive circuit elements of IEMDs is investigated. At the normal body temperature (35 °C), the PA-SBF exhibited high ionic conductivity of 17.6 mS cm−1 with negligible electron leakage. The supercapacitor fabricated with the PA-SBF gel electrolyte sandwiched between carbon-based electrodes showed an excellent areal capacitance of 219.6 mF cm−2 with a maximum potential window of 1.6 V. The self-healing properties and cytotoxicity of the PA-SBF gel electrolytes were examined as well. With high performance, flexibility, and self-healing property, the biocompatible PA-SBF gel electrolyte can be considered as a promising candidate for the electrolyte of electrochemical devices, energy sources and capacitive circuit elements of future IEMDs.

Aqueous electrolytes at the charged graphene Surface: Electrode-Electrolyte coupling

Electrochemical energy sources support the growth in performance and portability of consumer electronics. Further sustainable development assumes an atomistically precise understanding of how the electrolyte binds to the electrode in the charged and uncharged states of the supercapacitors and Li-ion batteries. The present work investigates electrode–electrolyte interactions at the cathode using ab initio molecular dynamics simulations and representative energy-minimized ion-molecular configurations. Graphene is chosen as a material for the cathode, whereas the aqueous solutions of LiCl, NaCl, and KCl are model electrolytes. The study reveals a few fundamentally new physical insights regarding the performance of a supercapacitor. First, the graphene-ions coordination regularities are qualitatively different at charged and uncharged cathode. It is, therefore, essential to account for the effect of charging when studying the physical chemistry of supercapacitors. Second, the energy capacity offered by the aqueous Na-ion electrolyte is worse than those of the aqueous Li-ion and K-ion electrolytes. This observation is a result of an interplay between the dehydration energies and adsorption energies at the cathode energies. Third, the role of cation-solvent binding represents a cornerstone contribution to the capacity of an energy storage device in addition to the well-recognized cation-cathode binding thermodynamics. The reported results are fundamentally important to thoughtfully designing electrolyte compositions and electrode materials for supercapacitors and alkali-ion batteries.

Shorter-chained trialkylsulfonium cations are preferable as admixtures to lithium-ion and sodium-ion electrolytes in acetonitrile

The development and improvement of electrolytes is a persisting research agenda in the context of electrochemical energy sources. The sodium-ion is a possible and partial substitute for Li-ion in alkali ion batteries of the future. Many large-scale applications urge electrolytes featuring a competitive interplay of ionic conductivity, shear viscosity, and cohesion energy. The general applicability of sulfonium ionic liquids (ILs) reinforced with Li-ions to energy storage was experimentally exemplified in recent years. Herein, we employed potential energy surface exploration bundled with electronic-structure simulations to shed light on the ion-ionic and ion-molecular interactions in perspective electrolyte systems involving trialkylsulfonium cation, Li/Na salts, and acetonitrile (ACN). By analyzing a wealth of supramolecular conformations and characterizing them via thermodynamics, structure, charge density distributions, electrostatic potential surfaces, atom–atom couplings, and reactivity descriptors, we outline the most promising sulfonium-based electrolytes. We provide a critical discussion of the future of sodium-ion batteries and compare them to lithium-ion batteries directly. The oxygen atoms of bis(trifluoromethanesulfonyl)imide anion [TFSI] coordinate Li+ and Na+ to remarkably various extents. Surprisingly, the size of the chosen trialkylsulfonium-based cation impacts the ion-ionic interactions weakly, contrary to expectations. Whereas the difference between the behavior of the Li-ion and Na-ion is paramount irrespective of all other components and their stationary points. [TFSI] was confirmed to be a highly flexible chemical structure although its conformations (one cis and two trans) were unraveled to differ only within an amount of thermal energy at room conditions. The reported discussion drives ongoing trials of the alkali-ion electrolytes based on sulfonium ILs and ACN.

Advances of Biowaste-Derived Porous Carbon and Carbon–Manganese Dioxide Composite in Supercapacitors: A Review

One of the global problems is environmental pollution by different biowaste. To solve the problem, biowaste must be recycled. Waste-free technology is also a way of saving exhaustible raw materials. Research on electrochemical energy sources is currently the most dynamically developing area of off-grid energy. Electrochemical capacitors can operate for a long time without changing performance, they have smaller dimensions, high mechanical strength, and a wide operating temperature range. These properties are effective energy-saving devices. Therefore, supercapacitors are widely used in various industries. This review discussed the methods of obtaining and the characteristics of biowaste-derived activated carbon and carbon–manganese oxide (AC-MnO2)-based supercapacitor electrodes.

Nanocomposite Membranes Based on Fluoropolymers for Electrochemical Energy Sources.

The physicochemical and transport properties (ion-exchange capacity, water content, diffusion permeability, conductivity, and current-voltage characteristic) of a series of perfluorinated membranes with an inert fluoropolymer content from 0 to 40%, obtained by polymer solution casting, were studied. Based on the analysis of the parameters of the extended three-wire model, the effect of an inert component on the path of electric current flow in the membrane and its selectivity were estimated. The mechanical characteristics of the membranes, such as Young’s modulus, yield strength, tensile strength, and relative elongation, were determined from the dynamometric curves. The optimal amount of the inert polymer in the perfluorinated membrane was found to be 20%, which does not significantly affect its structure and electrotransport properties but increases the elasticity of the obtained samples. Therefore, the perfluorinated membrane with 20% of inert fluoropolymer is promising for its application in redox flow batteries and direct methanol fuel cells.

Fractal correction in advanced solar energy material’s current–voltage equation

The world energy crisis necessitated the cause of the research interest into new, renewable and alternative energy sources. From this point of view, there is research on phenomena and different synthetic methods and on structure and electronic property optimization expressed by important material and device advancement. Efficiency and electricity generation (batteries, fuel cells, hydrogen energy) are nowadays actual questions. Because of that research, innovations and applications require extended knowledge by fractal nature characterization. The electrochemical energy sources solutions, especially electrolytes, are in fractal nature science focus. Based on the research novelties, especially electronic materials, we presented an investigation on fractal structure influence in electrochemistry. We explore the activation energy and fundamental thermodynamic functions and values, also the electrode surface changed by complex fractal correction through fractal dimension of grains and pores, and Brownian motion of involved particles, as well. At the end, the electrochemical Arrhenius and Butler–Volmer equation fractalization is applied. All of these open new perspectives for electrochemical energy processes, within electrolyte bulk and related electrodes and more precise energy generation. This is important for semiconductor processing in solar cells and devices. So, we included the knowledge of fractal sciences advancement in this field for current–voltage equation.

Revealing the effects of conductive carbon materials on the cycling stability of rechargeable Zn‐air batteries

Rechargeable zinc-air batteries (RZABs) are considered to be one of the promising electrochemical energy sources, and considerable efforts are devoted to high-performance bifunctional catalysts. Since the conductivity of catalysts is usually unsatisfactory, conductive carbon materials are needed in electrodes to provide the electron pathway. However, the effects of conductive carbon materials on the cycling stability of RZABs are usually overlooked. Herein, this topic is comprehensively investigated combing the electrochemical testes, in-situ oxygen monitor during charging, and characterization of the electrodes and electrolytes. Three kinds of electrodes made of bi-functional catalysts without additional carbon (N/A) and with Vulcan carbon (VC) and carbon nanotubes (CNT) are taken as examples. The results show that the CNT-based electrode releases the most oxygen under the same charging current density, which is 1.43 times that of the VC-based electrode and exhibits high stability in terms of voltage profile, structure morphology, and surface state. In addition, carbon corrosion is a serious issue for RZABs, which not only decreases the oxygen releasing efficiency but also contaminates the electrolyte. This work demonstrates the significant roles of conductive carbon materials in cycling stability and indicates that the in-situ gas analysis is essential to more rigorously evaluate the charging performance of RZABs.

Digitalni merač kapaciteta i punjač akumulatora

In this paper, a digital battery capacity meter with an integrated battery charger is developed and built. Also, the software used to control and monitor the microcontroller of the device from the PC has been developed, so that the data obtained from measurement can be processed and compared further using one of the available spreadsheet software packages. Due to the widespread use of electrochemical energy sources, whether primary ones or of the battery type, it is extremely important to know and measure their actual capacity. Primary cell capacity measurement helps in selecting the most appropriate solution (with respect to the cost/ capacity ratio) for powering portable or mobile devices. By measuring the capacity of the used battery, its condition and capability of further exploitation can be determined. Measuring capacity can provide verification of the data in the manufacturer's specifications, for example, in order to compare measurements and confirm statements in technical documentation.

Graphdiyne interface: electrode optimization strategy from microscale to macroscale

<p indent="0mm">Graphdiyne is one of the emerging two-dimensional carbon allotropes, and its unique structure and properties have inspired many original concepts in the green energy, green chemistry, biomedical and intelligent electronic devices. In the field of electrochemical energy source, graphdiyne, as one of the key materials with great potential, shows many new ideas for solving the crucial issues in the electrochemical energy field. This review briefly summarizes recent progress in solving the bottleneck problems in electrochemical energy devices by the advantages of graphdiyne. It mainly contains the atomic-level suppression in the shuttle effect of active mass and the interfacial side reactions, stabilizing the primary and secondary structures in nanoscale, and avoiding the exfoliation of the active mass from substrate and the crack of the conductive network in macroscale. With the recent progress, the opportunities and challenges in using graphdiyne as the key materials for electrochemical energy sources are discussed.

In Ukrainian

The solution to the problem of negative impact on the ecology of fossil fuel consumption is the use of electrochemical energy sources. The special attractiveness has shown of lithium power sources is highlighted and the need to develop new cheap electrode materials and electrolytes with unique properties. The peculiarities of the behavior of lithium and the formation of a layer of reaction products on its surface upon contact with a liquid organic electrolyte have considered. The analysis of the main problems and ways of their solution at use of conversion electrodes of the II type for lithium-ion batteries has carried out. Emphasis is placed on the need to use in the development of new electrode materials of such parameters as capacity loading and accumulated irreversible capacity of the electrodes. The triad “electrode – solid electrolyte interphase – electrolyte” is considered as a basis of a systematic approach to the creation of new generations of lithium power sources. The optimal scenarios have proposed for the formation of an effective solid electrolyte interphase on the surface of the electrodes. The advantages of electrolytes based on fluoroethylene carbonate with synergistic acting additives of vinylene carbonate and ethylene sulfite are described. A new strategy for the use of “secondary” silicon nanomaterials to prevent direct contact of its surface with the electrolyte has considered. It has shown that the solid electrolyte interphase is a dynamic system that self-organizes from the unstable state into a stable one. The electrochemical behavior of electrodes with silicon nanocomposites with high capacity loading and low accumulated irreversible capacity has described.

Quantitative analysis of internal polarization dynamics for polymer electrolyte membrane fuel cell by distribution of relaxation times of impedance

Investigating and interpreting each internal polarization dynamics that occurs in the polymer electrolyte membrane fuel cell is significant. Traditional equivalent circuit model fitting by nonlinear least-squares relies on prior model assumptions and initial value selection of components. In this paper, the distribution of relaxation times methodology with powerful separating ability is applied to reveal a more precise analysis of polarization processes. First, the electrochemical impedance spectroscopy under a broad of operating conditions is carried out. Four polarization dynamics related to oxygen transfer, charge transfer of the oxygen reduction, proton transfer inside cathode ionomer, and interface contact process between catalyst layer and membrane (perhaps, including anode oxidation reaction) are effectively extracted. Then, a fourth-order equivalent circuit model established via distribution of relaxation times results is introduced to quantify the loss of each polarization process. Based on this, for the first time, the sensitivity of each polarization loss against operating conditions is analyzed by the multiple stepwise regression analysis, and its application on vehicular fuel cell system control is discussed. Afterward, the distribution of relaxation times is also first to explore the loss and variation trend of each polarization process under flooding, membrane drying, and air starvation fault, where each failure type contains at least eight test sequences. These efforts represent a comprehensive and systematic guideline for fuel cells using distribution of relaxation times, which can also guide the study of degradation mechanisms, optimization design of materials, and even other electrochemical energy sources.

Polynomial description of dynamic impedance spectrogram—Introduction to a new impedance analysis method

This paper presents a polynomial description of spectrograms obtained using Dynamic Electrochemical Impedance Spectroscopy. A method to fit the polynomial degree correctly is discussed. A simple electrical system of a diode connected in parallel with a capacitor was used for testing. Dynamic impedance measurements during potentiodynamic polarization were conducted. This paper presents an alternative analysis method that allows the determination of system electrochemical characteristics. This method was compared to classical analysis based on equivalent circuit fitting. An alternative method of analysis yielded many advantages in describing impedance results—the potential to obtain an infinite number of impedance spectra over a various range and the possibility to show the resistance and capacitance characteristics as a function of frequency and control of electrochemical energy sources. The polynomial description marks a step forward in analysis automation, facilitating easy and reliable automation and control of electrochemical energy sources.