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Abstract The author summarized recent diverse applications and advancements for proton‐conducting polymers since 2018, emphasizing their importance in various technological areas. These polymers are integral to fuel cells, water electrolysis, energy storage systems, actuators, and sensors, offering high proton conductivity, chemical stability, and adaptability. The review elucidated aspects of specific applications, highlighting their roles in optimizing fuel cell efficiency and enhancing water electrolysis for hydrogen production, improving energy storage in supercapacitors and batteries, and explaining their emerging use in smart materials and robotics. Additionally, the paper presented discussion of the latest research trends, particularly from environmental and cost perspectives, specifically addressing the chemical modification of these polymers to enhance their functionality and to broaden their scope of application.

Redox flow batteries (RFBs) are a promising option for long‐duration energy storage (LDES) due to their stability, scalability, and potential reversibility. However, solid‐state and non‐aqueous flow batteries have low safety and low conductivity, while aqueous systems using vanadium and zinc are expensive and have low power and energy densities, limiting their industrial application. An approach to lower capital cost and improve scalability is to utilize cheap Earth‐abundant metals such as iron (Fe). Nevertheless, all‐iron RFBs have many complications, involving voltage loss from ohmic resistance, side reactions such as hydrogen evolution, oxidation, and most significantly electrode plating, and dendrite growth. To address these issues, researchers have begun to examine the effects of various alterations to all‐iron RFBs, such as adding organic ligands to form Fe complexes and using a slurry electrode instead of common materials such as graphite or platinum rods. Overall, progress in improving aqueous all‐iron RFBs is at its infant stage, and new strategies must be introduced, such as the utilization of nanoparticles, which can limit dendrite growth while increasing storage capacity. This review provides an in‐depth overview of current research and offers perspectives on how to design the next generation of all‐iron aqueous RFBs. [ABSTRACT FROM AUTHOR]

Cerium, a unique rare earth element, possesses a relatively high abundance, low cost, and high redox voltage, making it an attractive candidate for redox flow batteries. However, the sluggish kinetics and corrosion nature of the Ce3+/Ce4+ electrolyte result in overpotential and degradation of carbon felt (CF) electrodes, which hinders the development of cerium‐based flow batteries. Therefore, it is essential to develop an electrode with high catalytic activity and corrosion resistance to the Ce3+/Ce4+ electrolyte. Herein, a TiC/TiO2 coated carbon felt (TiC/TiO2‐CF) electrode is proposed. Remarkably, the TiC/TiO2 coating effectively minimizes the exposure of the CF to the highly corrosive cerium electrolyte, consequently enhancing the electrode's corrosion resistance. Additionally, X‐ray photoelectron spectroscopy and high‐resolution transmission electron microscopy characterizations reveal the formation of a heterojunction between TiC and TiO2, which significantly enhances the redox reaction kinetics of the Ce3+/Ce4+ redox couple. Eventually, the practical application of TiC/TiO2‐CF catalytic electrode in a Ce–Fe flow battery is demonstrated. This study sheds light on the synthesis conditions of the TiC/TiO2‐CF electrode, elucidates its heterojunction structure, and presents a novel Ce–Fe flow battery system. [ABSTRACT FROM AUTHOR]

Background: There is a growing need for immunological assays to test toxic and modulatory effects of chemicals. The assays should be easy to use, reproducible and superior to cell line-based assays. We have therefore developed a comprehensive portfolio of assays based on primary human blood cells that are suitable for testing chemical effects. Methods: The flow cytometry-based assays were designed to target a wide range of human peripheral blood mononuclear cells and whole blood, including T cells, NK cells, B cells, basophils and innate-like T cells such as gdT, MAIT and NKT cells. We have selected a set of activation markers for each immune cell, e.g: CD154 (T cells), CD137, CD107a (NK cells), CD63 (basophils), CD69, CD83 (B cells), CD69, IFN-g (MAIT cells) and we selected cell specific stimuli: aCD3 antibodies (T cells); E. coli and cytokines IL-12/15/ 18 (MAIT cells); CpG ODN2006, R848 or aCD40 antibodies (B cells), fMLP or aFcϵR1 (basophils) or K562 cells (NK cells). Results: By selecting immune cell-specific markers and cell-specific stimuli, we were able to induce particular immune responses from the targeted immune cells. For example, the response to stimulation with anti-CD3 antibodies was in 36.8% of CD107a+CD8+ cells. Cytokine stimulation induced the production of IFN-g in 30% of MAIT cells. After stimulation with E. coli, around 50% of MAIT cells produced TNF. About 40% of basophils responded to aFcƐR1 stimulation. Similar activation ranges were achieved in K562-stimulated NK cells.Conclusion: Our test portfolio covers the most relevant immune cells present in human blood, providing a solid basis for in vitro toxicity and immunomodulatory testing of chemicals. By using human blood, the natural composition of cells found in the blood can be determined and the effects of chemicals can be detected at the cellular level. [ABSTRACT FROM AUTHOR]

The use of symmetrical cells is becoming popular for the search of new electroactive materials in redox flow batteries. Unfortunately, low‐cost battery cyclers, commonly used for electrochemical battery testing, are not compatible with symmetrical cells since they usually cannot apply negative bias voltages needed for symmetrical cells. The insertion of a Ni−Cd battery in the voltage sensing path is a simple and effective methodology to overcome this limitation for certain battery cyclers. Herein, the validity of this useful method is evaluated for other battery cyclers, realizing that the strategy is not universal. A modified methodology is developed for a battery cycler in which the previous method is not valid. The new strategy is based on inserting a Ni‐MH battery in the current path, and enables using a low‐cost Neware CT‐4008T‐5V6A‐S1 cycler for ferro‐ /ferricyanide symmetrical cells demonstrating proper operation for >19 days. This new method possesses advantages, e. g. direct reading of the cell voltage, and disadvantages, e. g. the Ni‐MH battery is charged/discharged during operation, which are discussed. The four battery cyclers evaluated show that, despite neither method is universal, both methods are complementary to each other. Thus, the decision of using either one method or the other must be reached on a case‐by‐case basis. [ABSTRACT FROM AUTHOR]

Pseudo‐nanophase separation enabled by supramolecular‐interaction‐grafted sidechains proves a promising alternative for constructing high‐performance commercially viable membranes with quick ion transport, excellent chemical stability, and simplified membrane manufacturing. Nonetheless, the concept of pseudo‐nanophase separation is still in nuce, and determinants for controlling pseudo‐nanophase separation remain somewhat opaque. In this contribution, supramolecular sidechain topology is found critical to engineering pseudo‐nanophase separation. Three supramolecular sidechain topological (viz. linear, branched, and cyclic) structures are investigated using experimental and theoretical protocols, and the underlying mechanisms by which supramolecular sidechain topology alters the microstructure and ion‐conducting behaviors of the membranes are proposed. Consequently, the cyclic sidechain‐mediated membrane achieves the highest proton conductivity with an area resistance as low as 0.10 Ω cm2. The resulting membrane endows an acidic aqueous redox flow battery with an energy efficiency of up to 80.7% even at high current densities of 220 mA cm−2, breaking the record set by the pseudo‐nanophase separation strategy constructed membranes and ranking among the highest values ever documented. This study advances the understanding of supramolecular sidechain topology for the design and preparation of high‐performance membranes via pseudo‐nanophase separation engineering for flow batteries and beyond. [ABSTRACT FROM AUTHOR]

Non-aqueous redox flow batteries constitute a promising solution for grid-scale energy storage due to the ability to achieve larger cell voltages than can be readily accessed in water. However, their widespread application is limited by low solubility of the electroactive species in organic solvents. In this work, we demonstrate that organic functionalization of titanium-substituted polyoxovanadate-alkoxide clusters increases the solubility of these assemblies over that of their homoleptic congeners by a factor of >10 in acetonitrile. Cyclic voltammetry, chronoamperometry, and charge–discharge cycling experiments are reported, assessing the electrochemical properties of these clusters relevant to their ability to serve as multielectron charge carriers for energy storage. The kinetic implications of ligand variation are assessed, demonstrating the role of ligand structure on the diffusivity and heterogeneous rates of electron transfer in mixed-metal charge carriers. Our results offer new insights into the impact of structural modifications on the physicochemical properties of these assemblies. [ABSTRACT FROM AUTHOR]

The vanadium redox flow battery has been intensively examined since the 1970s. What is missing is a connection between the current‐overpotential Butler‐Volmer equation, which provides an extremely helpful starting point for analytical and numerical studies, and microscopic quantum mechanical behavior at the atomic level. Such a connection will allow further advancements beyond the macroscopic, though very useful and insightful, modeling already done in the literature. Here we show rigorously the connection between the Butler‐Volmer transfer coefficients, and the Marcus Gibbs free energy quantum mechanical parameters, and develop the equation directly in terms of the quantum mechanical parameters. [ABSTRACT FROM AUTHOR]

Redox flow batteries (RFBs) are a promising technology for long‐duration energy storage; but they suffer from inefficiencies in part due to the overvoltages at the electrode surface. In this work, more than 70 electrode treatments are reviewed that are previously shown to reduce the overvoltages and improve performance for vanadium RFBs (VRFBs), the most commercialized RFB technology. However, identifying treatments that improve performance the most and whether they are industrially implementable is challenging. This study attempts to address this challenge by comparing treatments under similar operating conditions and accounting for the treatment process complexity. The different treatments are compared at laboratory and industrial scale based on criteria for VRFB performance, treatment stability, economic feasibility, and ease of industrial implementation. Thermal, plasma, electrochemical oxidation, CO2 treatments, as well as Bi, Ag, and Cu catalysts loaded on electrodes are identified as the most promising for adoption in large scale VRFBs. The similarity in electrode treatments for aqueous‐organic RFBs (AORFBs) and VRFBs is also identified. The need of standardization in RFBs testing along with fundamental studies to understand charge transfer reactions in redox active species used in RFBs moving forward is emphasized. [ABSTRACT FROM AUTHOR]

[Display omitted] Vanadium redox flow batteries (VRFBs) are promising energy storage systems with the potential to bridge the gap between intermittent renewable electricity generation and continuous supply of reliable electricity. The electrodes found in VRFB cells affect their energy efficiency (EE) and power density. It is important to fabricate electrodes with intriguing properties to enable VRFBs to have high performance. Herein, the abundant and cost-effective lignin is employed as the precursor to produce amorphous carbon particles after undergoing thermal decomposition treatment. The carbon particles cover the surface of carbon felt (CF). The resulting CF modified by lignin-derived carbon particles (Lignin-CF) with increased active sites and improved hydrophilicity displays superior electrochemical activity towards the VO 2 +/VO2+ pair than both the pristine CF and the heated bare CF. Remarkably, the VRFB consisting of Lignin-CF which acts as the positive electrode shows high performance in terms of the average EE (83.3 %) and average voltage efficiency (VE) (85.0 %) over 1000 cycles (long cycling life) for more than 16 days at 100 mA cm−2, and high power density of 1053.2 mW cm−2. It is noted that the EE and VE are comparable to the highest reported value of CF modified by carbon-based materials, aside having evidently longer cycling life. This study provides a feasible strategy for fabricating an affordable electrode for high-performance VRFBs. [ABSTRACT FROM AUTHOR]

Bromine‐based flow batteries (Br‐FBs) are highly competitive for stationary energy storage due to their high energy density and cost‐effectiveness. However, adding bromine complexing agents (BCAs) to electrolytes slows down Br2/Br− reaction kinetics, causing higher polarization and lower power density of Br‐FBs. Herein, in situ vertically aligned MoS2 nanosheet arrays on traditional carbon felt substrates as electrodes to construct high power–density BCA‐free Br‐FBs are proposed. MoS2 arrays exhibit strong adsorption capacity to bromine, which helps the electrodes capture and retain bromine species. Even without BCAs, the battery self‐discharge caused by bromine diffusion is also inhibited. Moreover, the rate‐determining step of Br2/Br− reactions is boosted and the vertically aligned array structure provides sufficient sites, motivating Br2/Br− reaction kinetics and decreasing the battery polarization. The capacity retention rate of the BCA‐free Br‐FB based on MoS2 arrays‐based electrodes reaches 46.34% after the 24‐h standing test at 80 mA cm−2, meeting the requirements of practical applications. Most importantly, this BCA‐free Br‐FB exhibits a high Coulombic efficiency of 97.00% and an ultralong cycle life of 1000 cycles at a high current density of 200 mA cm−2. This work provides an available approach to developing advanced electrode materials for high power–density and long‐lifespan Br‐FBs. [ABSTRACT FROM AUTHOR]

Graphite felt is commonly used in redox flow batteries, but the low specific surface area and poor catalytic activity cause unsatisfactory mass transfer and reaction kinetics. Here, nitrogen‐doped vertical graphene is in‐situ grown on graphite felt via a metal‐free chemical vapor deposition method, which exhibits a high specific surface area and remarkable catalytic activity due to abundant exposed high‐density sharp graphene edges and nitrogen doping. Multiphysical simulations reveal that the vertical‐standing nanostructure promotes the accessibility of vanadium ions to electrode/electrolyte interfaces, effectively decreasing the mass transport resistance of active species. Density functional theory calculation evidence shows that nitrogen doping aids in the improvement of catalytic activity via boosting vanadium ions' adsorption and redox. Consequently, the nitrogen‐doped vertical graphene/graphite felt electrode shows an energy efficiency of 87.1% at 200 mA cm−2, significantly higher than that of pristine (65.9%) and air‐oxidize (73.1%) electrodes, an energy efficiency over 80.2% at 300 mA cm−2 during 1500 cycles, and a high‐peak power density of 1308.56 mW cm−2, which are superior to previously reported carbon nanomaterial decorated electrodes for flow batteries. Significantly, the synthesis process only involves gas‐phase reactions without metal catalysts to avoid hydrogen evolution reactions. This work provides an exciting pathway for developing high‐performance electrodes for flow batteries. [ABSTRACT FROM AUTHOR]

Redox flow batteries (RFBs) are perceived to lead the large-scale energy storage technology by integrating with intermittent renewable energy resources such as wind and solar to overcome current challenges in conventional energy storage devices. Recently, several modifications have been employed in the development of RFBs to achieve efficient energy storage at an economically acceptable cost of the system. For large-scale deployment, further improvement in energy efficiency, longevity of the system, and reduction in cost are required. Most of the recent research activities are focused on the discovery of new materials to increase RFBs' energy storage-release performance with long-term stable operations suitable for implementation in mobile devices. Considering the growth in research interest, and the volume of literature generated over the past decade on the topic, a review article highlighting the key development and status of research is essential. Herein, we intend to provide the basics of the RFB system including their cell components, various types, and the current trends highlighting the study gaps that require extra effort. Moreover, we conducted an analysis of the cost of the RFBs, associated challenges, and mitigation strategies. The review also includes electrode/electrolyte materials in a table format for quick access for comparison purposes. [ABSTRACT FROM AUTHOR]

In recent years, aqueous organic redox flow batteries (AORFBs) have attracted considerable attention due to advancements in grid‐level energy storage capacity research. These batteries offer remarkable benefits, including outstanding capacity retention, excellent cell performance, high energy density, and cost‐effectiveness. The organic electrolytes in AORFBs exhibit adjustable redox potentials and tunable solubilities in water. Previously, various types of organic electrolytes, such as quinones, organometallic complexes, viologens, redox‐active polymers, and organic salts, were extensively investigated for their electrochemical performance and stability. This study presents an overview of recently published novel organic electrolytes for AORFBs in acidic, alkaline, and neutral environments. Furthermore, it delves into the current status, challenges, and prospects of AORFBs, highlighting different strategies to overcome these challenges, with special emphasis placed on their design, composition, functionalities, and cost. A brief techno‐economic analysis of various aqueous RFBs is also outlined, considering their potential scalability and integration with renewable energy systems. [ABSTRACT FROM AUTHOR]

The ever‐increasing threat of climate change and the depletion of fossil fuel resources necessitate the use of solar‐ and wind‐based renewable energy sources. Large‐scale energy storage technologies, such as redox flow batteries (RFBs), offer a continuous supply of energy. Depending on the nature of the electrolytes used, RFBs are broadly categorized into aqueous redox flow batteries (ARFBs) and non‐aqueous redox flow batteries (NARFBs). ARFBs suffer from various problems, including low conductivity of electrolytes, inferior charge/discharge current densities, high‐capacity fading, and lower energy densities. NARFBs offer a wider potential window and range of operating temperatures, faster electron transfer kinetics, and higher energy densities. In this review article, a critical analysis is provided on the design of organic electroactive molecules, their physiochemical/electrochemical properties, and various organic solvents used in NARFBs. Furthermore, various redox‐active organic materials, such as metal‐based coordination complexes, quinones, radicals, polymers, and miscellaneous electroactive species, explored for NARFBs during 2012–2023 are discussed. Finally, the current challenges and prospects of NARFBs are summarized. [ABSTRACT FROM AUTHOR]

The global rapid transition from fossil fuels to renewable energy resources necessitates the implementation of long‐duration energy storage technologies owing to the intermittent nature of renewable energy sources. Therefore, the deployment of grid‐scale energy storage systems is inevitable. Sulfur‐based batteries can be exploited as excellent energy storage devices owing to their intrinsic safety, low cost of raw materials, low risk of environmental hazards, and highest theoretical capacities (gravimetric: 2600 Wh/kg and volumetric: 2800 Wh/L). However, sulfur‐based batteries exhibit certain scientific limitations, such as polysulfide crossover, which causes rapid capacity decay and low Coulombic efficiency, thereby hindering their implementation at a commercial scale. In this review article, we focus on the latest research developments between 2012–2023 to improve the separators/membranes and overcome the shuttle effect associated with them. Various categories of ion exchange membranes (IEMs) used in redox batteries, particularly polysulfide redox flow batteries and lithium‐sulfur batteries, are discussed in detail. Furthermore, advances in IEM constituents are summarized to gain insights into different fundamental strategies for attaining targeted characteristics, and a critical analysis is proposed to highlight their efficiency in mitigating sulfur cross‐shuttling issues. Finally, future prospects and recommendations are suggested for future research toward the fabrication of more effective membranes with desired properties. [ABSTRACT FROM AUTHOR]

The use of graphene oxide (GO) has shown potential in improving the performance of redox flow lithium‐ion batteries (RFLIBs). These types of batteries use a liquid electrolyte containing redox‐active species to store and release energy. Despite being scalable, RFLIBs face limitations, namely, low energy density of the electrolyte and reduced cycling stability of the electrodes. However, GO's unique properties, such as its high conductivity as well as large surface area, create an attractive option for enhancing the electrochemical properties of both the electrolyte and electrodes in RFLIBs. When used as an electrode, GO improves the kinetic reversibility reactions, leading to increased electrochemical activity towards redox couples. Charge transfer resistances of positive and negative reactions are reduced, leading to increased voltage energy and efficiency of lithium batteries in terms of energy usage. As redox flow batteries made of lithium ions are an established subsystem and a growing research and development field, there is potential to enhance their performance and reduce costs through the use of GO. The objective of this review is to provide an overview of the chemistry of GO as it pertains to RFLIBs use, covering topics such as its surface chemistry, functionalization, and interactions with redox‐active species, as well as its potential for enhancing high‐density storage of electricity in batteries. Specifically, it will discuss the impact of GO on redox reactions in the electrolyte, including its ability to raise the redox‐active species concentration as well as enhance their stability. The review will also examine how GO impacts the electrodes, including its potential to increase their surface area and conductivity and promote cycling stability. Additionally, the review will address the importance of optimizing the quantity and distribution of GO in both the electrolyte and electrodes of RFLIBs. [ABSTRACT FROM AUTHOR]

Thermal additive centrifugal abrasive flow machining (TACAFM) is the latest hybrid of abrasive flow machining, which involves a combination of centrifugal action of rotating electrode and the spark to manage the limitation of low material removal (MR). The present investigation involves the study of the morphology of internal surface hollow cylindrical brass surface finished by TACAFM process. The researchers proposed a novel spline-shaped centrifugal force-generating electrode with a curved blade instead of straight blade for improving the process efficiency. The computation of MR and percentage improvement in surface finish (%ΔRa) is done using the proposed electrode with curved blade, and the results are compared with the primitive electrode with straight blade against the process parameters (supply current, duty cycle, abrasive concentration, rotational speed of centrifugal force generating electrode and the extrusion pressure). The surface roughness plot using Taylor-Hobson tallysurf, micrographs taken by optical microscope and SEM images were used for analysis of the finished workpiece surface. The proposed electrode resulted in an 8.5% increase in MR and 27.38%ΔRa compared to initial straight spline-shaped electrode used for TACAFM process. Also, XRD and EDAX analysis was done to predict the morphological change on the finished workpiece surface. [ABSTRACT FROM AUTHOR]

Battery storage systems are an important key element for a successful energy transition. Increasingly, the focus is also on the sustainability analysis of the various energy storage technologies. In particular, the vanadium flow battery (VFB) is mentioned as a promising day storage technology. Nevertheless, its high cost and environmental impacts are attributed to its electrolyte. It is assumed that this issue can be addressed through reprocessing and reuse. The aim of this study is to provide, for the first time in the literature, information on the process design and the potential emissions of the treatment of end‐of‐life (EoL) vanadium electrolyte with various critical impurities, in order to be able to validly estimate the total emissions of VFB with recycled electrolyte. Four different scenarios are considered, combining treatment steps for electrolyte with different critical contaminations, revealing detailed mass and energy balances. The life cycle assessment provides valuable results for the sustainability assessment of the EoL vanadium electrolyte and the entire VFB system. The treatment of the electrolyte leads to significantly lower CO2 emissions (−79.2% to −99.8%) compared to the primary electrolyte and must be taken into account in future when assessing the sustainability of the VFB. [ABSTRACT FROM AUTHOR]

Commercial electrolyte for vanadium flow batteries is modified by dilution with sulfuric and phosphoric acid so that series of electrolytes with total vanadium, total sulfate, and phosphate concentrations in the range from 1.4 to 1.7 m, 3.8 to 4.7 m, and 0.05 to 0.1 m, respectively, are prepared. The electrolyte samples of the series for positive and negative half‐cells at various state‐of‐charges are produced by electrolysis and are investigated for stability in the range of temperatures from −20 to +65 °C. It is attempted to reveal a correlation between initial electrolyte formulation in terms of total vanadium and total sulfate concentrations, which are measurable parameters in practice, and electrolyte thermal stability properties. The study of negative electrolyte samples by headspace online mass spectrometry enables to detect hydrogen gas, which evolves by chemical reaction of vanadium(II) species with protons during thermally induced aging. The battery with vanadium electrolyte at 1.4 m total vanadium, 4.7 m total sulfate, and 0.1 m phosphate concentrations displays more stable operation in terms of capacity decay during galvanostatic charge–discharge cycles than the battery with electrolyte at 1.7 m vanadium, 3.8 m sulfate, and 0.05 m phosphate concentrations under the same conditions. [ABSTRACT FROM AUTHOR]

Non-aqueous redox flow batteries (NARFBs) have been attracting much attention because they can significantly increase power and energy density compared to conventional RFBs. In this study, novel pore-filled anion-exchange membranes (PFAEMs) for application to a NAPFB employing metal polypyridyl complexes (i.e., Fe(bpy)32+/Fe(bpy)33+ and Co(bpy)32+/Co(bpy)33+) as the redox species are successfully developed. A porous polyethylene support with excellent solvent resistance and mechanical strength is used for membrane fabrication. The PFAEMs are prepared by filling an ionic liquid monomer containing an imidazolium group and a crosslinking agent into the pores of the support film and then performing in situ photopolymerization. As a result, the prepared membranes exhibit excellent mechanical strength and stability in a non-aqueous medium as well as high ion conductivity. In addition, a low crossover rate for redox ion species is observed for the prepared membranes because they have relatively low swelling characteristics in non-aqueous electrolyte solutions and low affinity for the metal-complex redox species compared to a commercial membrane. Consequently, the PFAEM is revealed to possess superior battery performance than a commercial membrane in the NARFB tests, showing high energy efficiency of about 85% and stable operation for 100 cycles. [ABSTRACT FROM AUTHOR]

Polyaniline boronic acid, a conducting polymer with unique properties, has gained attention for its potential applications in flow batteries, sensors, drug delivery systems, and electrochemical devices. Understanding the redox behavior of this polymer in the presence of sugars is of particular interest due to the potential implications for its functionality in various applications. Cyclic voltammetry is employed to analyze the redox behavior of the polymer in aqueous solutions with glucose and table sugar. Preliminary results suggest that the presence of glucose increase and table sugar decrease the peak values. The diffusion coefficient of the polymer is found as 2.6x10-9 cm² /s. The choice of supporting electrolyte, exemplified by potassium carbonate and potassium chloride, also exhibited an influence on redox behavior of polyaniline boronic acid, and peak potential and peak values are higher in potassium chloride solutions. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the power-system stability and the mitigation of fluctuations in a hybrid wind/wave power-generation system (HWWPGS) under different operating and disturbance conditions. This evaluation is performed by employing a vanadium redox flow battery-based energy storage system (VRFB-ESS) as proposed. The measurement results obtained from a laboratory-scale HWWPGS platform integrated with the VRFB-ESS, operating under specific conditions, are used to develop the laboratory-scale simulation model. The capacity rating of this laboratory-scale simulation model is then enlarged to develop an MW-scale power-system model of the HWWPGS. Both operating characteristics and power-system stability of the MW-scale HWWPGS power system model are evaluated through frequency-domain analysis (based on eigenvalue) and time-domain analysis (based on nonlinear-model simulations) under various operating conditions and disturbance conditions. The simulation results demonstrate that the fluctuations and stability of the studied HWWPGS under different operating and disturbance conditions can be effectively smoothed and stabilized by the proposed VRFB-ESS. [ABSTRACT FROM AUTHOR]

A panel of novel vanadium(IV)–betaine complexes has been synthesized according to new and efficient methodologies and characterized through both spectroscopic techniques and thermal analyses. Vanadium(IV)–betaine solutions have been electrochemically oxidized and the effect of betaine ligands on the thermal and pH stability of vanadium(V) solutions has been evaluated under different temperature and acidity conditions. The obtained results displayed a remarkable effect for both of the examined parameters, achieving the preparation of aqueous vanadium(V) solutions displaying long term stability at more than 55 °C under mild acidic conditions. The species formed in the betaine rich vanadium(V) solutions have been sprectroscopically identified in relationship with the acidity of the solution, and the obtained results were confirmed through computational techniques. Vanadium–betaine based solutions have been finally tested in a lab-scale redox flow battery setup, providing preliminary insight into the possible use of this type of electrolyte in VRFBs. [ABSTRACT FROM AUTHOR]

Ion‐selective membranes are widely used in various energy storage applications. However, conventional polymer‐based ion‐selective membranes, such as Nafion, are not perfectly ion‐selective, leading to a significant permeation of undesirable ionic species. As the imperfect ion‐selectivity of membranes leads to the failure of energy storage devices, much effort is devoted to improving membrane ion‐selectivity. Herein, an immiscible liquid‐state membrane is introduced for aqueous redox flow batteries. As hydrophobic ionic liquids are immiscible with aqueous catholyte and anolyte solutions, they separate the two without crossover. This property renders them suitable for use as a membrane for aqueous redox flow batteries. In addition, ionic liquids with long side alkyl chains, such as 1‐hexyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIM‐TFSI), are miscible with sulfuric acid, whereas transition metal sulfates remain insoluble in HMIM‐TFSI. For this reason, HMIM‐TFSI is selectively permeable to protons and remains impermeable to transition metal cations. As a result, the HMIM‐TFSI membrane is almost perfectly proton‐selective, leading to negligible permeability of unfavorable ionic species, such as transition metal cations. Eventually, the HMIM‐TFSI membrane shows the excellent electrochemical performance of vanadium redox flow batteries, such as negligible self‐discharge over 2800 h, high Coulombic efficiency (≈99%), and stable capacity retention over 100 cycles. [ABSTRACT FROM AUTHOR]

Viologen‐derivatives are the most widely used redox organic molecules for neutral pH negative electrolyte of redox flow batteries. However, the long‐established toxicity of the herbicide methyl‐viologen raises concern for deployment of viologen‐derivatives at large scale in flow batteries. Herein, we demonstrate the radically different cytotoxicity and toxicology of a series of viologen‐derivatives in in vitro assays using model organisms representative of human and environmental exposure, namely human lung carcinoma epithelial cell line (A549) and the yeast Saccharomyces cerevisiae. The results show that safe viologen derivatives can be molecularly engineered, representing a promising family of negolyte materials for neutral redox flow batteries. [ABSTRACT FROM AUTHOR]

Vanadium redox flow batteries are recognized as well-developed flow batteries. The flow rate and current density of the electrolyte are important control mechanisms in the operation of this type of battery, which affect its energy power. The thermal behavior and performance of this battery during charging and discharging modes are also important. As a consequence, the aim of this investigation is to deeply study the impact of different working parameters on the temperature distribution and state of charge of these batteries. To achieve these goals, a single battery thermal model is established. The effects of various operating parameters, including working temperature, molar concentration, flow rate, and current density of the electrolyte, on the thermal behavior, state of charge, and performance of this type of battery are investigated. It is observed that the temperature distribution of high flow rate (90 mL min−1) is more uniform than that of other flow rates (30 and 60 mL min−1). In the end of the discharging mode, the battery voltage performance increases with the increase in the electrolyte flow rate. The temperature distribution of high current density (80 mA cm−2) is relatively uneven, and the local heating is produced at the battery outlet. The end time in the charging and discharging modes for the case of the high current density (80 mA cm−2) is faster than other current densities (20 and 40 mA cm−2). [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) display great potential to be assembled into proton conductive membranes for their uniform and controllable pore structure, yet constructing self‐standing COF membrane with high crystallinity to fully exploit their ordered crystalline channels for efficient ionic conduction remains a great challenge. Here, a macromolecular‐mediated crystallization strategy is designed to manipulate the crystallization of self‐standing COF membrane, where the −SO3H groups in introduced sulfonated macromolecule chains function as the sites to interact with the precursors of COF and thus offer long‐range ordered template for membrane crystallization. The optimized self‐standing COF membrane composed of highly‐ordered nanopores exhibits high proton conductivity (75 mS cm−1 at 100 % relative humidity and 20 °C) and excellent flow battery performance, outperforming Nafion 212 and reported membranes. Meanwhile, the long‐term run of membrane is achieved with the help of the anchoring effect of flexible macromolecule chains. Our work provides inspiration to design self‐standing COF membranes with ordered channels for permselective application. [ABSTRACT FROM AUTHOR]

Recent advances in synthetic methodologies for selective, oxidative transformations using Bobbitt's salt (4-acetamido-2,2,6,6-tetramethyl-1-oxopiperidinium tetrafluoroborate, 1) and its stable organic nitroxide counterpart ACT (4-acetamidoTEMPO, 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxyl, 2) have led to increased applications across a broad array of disciplines. Current applications and mechanistic understanding of these metal-free, environmentally benign, and easily accessible organic oxidants now span well-beyond the seminal use of 1 and 2 in selective alcohol oxidations. New synthetic methodologies for the oxidation of alcohols, ethers, amines, thiols, C–H bonds and other functional groups with 1 and 2 along with the field's current mechanistic understandings of these processes are presented alongside our contributions in this area. Exciting new areas harnessing the unique properties of these oxidants include: applications to drug discovery and natural product total synthesis, the development of new electrocatalytic methods for depolymerization of lignin and modification of other biopolymers, in vitro and in vivo nucleoside modifications, applications in supramolecular catalysis, the synthesis of new polymers and materials, enhancements in the design of organic redox flow batteries, uses in organic fuel cells, applications and advancements in energy storage, the development of electrochemical sensors, and the production of renewable fuels. [ABSTRACT FROM AUTHOR]

Redox flow batteries (RFBs) are promising electrochemical energy storage systems, offering vast potential for large-scale applications. Their unique configuration allows energy and power to be decoupled, making them highly scalable and flexible in design. Aqueous RFBs stand out as the most promising technologies, primarily due to their inexpensive supporting electrolytes and high safety. For aqueous RFBs, there has been a skyrocketing increase in studies focusing on the development of advanced functional materials that offer exceptional merits. They include redox-active materials with high solubility and stability, electrodes with excellent mechanical and chemical stability, and membranes with high ion selectivity and conductivity. This review summarizes the types of aqueous RFBs currently studied, providing an outline of the merits needed for functional materials from a practical perspective. We discuss design principles for redox-active candidates that can exhibit excellent performance, ranging from inorganic to organic active materials, and summarize the development of and need for electrode and membrane materials. Additionally, we analyze the mechanisms that cause battery performance decay from intrinsic features to external influences. We also describe current research priorities and development trends, concluding with a summary of future development directions for functional materials with valuable insights for practical applications. [ABSTRACT FROM AUTHOR]

The development of energy storage systems (ESS) has become an important area of research due to the need to replace the use of fossil fuels with clean energy. Redox flow batteries (RFBs) provide interesting features, such as the ability to separate the power and battery capacity. This is because the electrolyte tank is located outside the electrochemical cell. Consequently, it is possible to design each battery according to different needs. In this context, zinc–bromine flow batteries (ZBFBs) have shown suitable properties such as raw material availability and low battery cost. To avoid the corrosion and toxicity caused by the free bromine (Br2) generated during the charging process, it is necessary to use bromine complexing agents (BCAs) capable of creating complexes. As an overview, the different BCAs used have been listed to compare their behavior when used in electrolytes in ZBFBs. In addition, the coulombic and energy efficiencies obtained have been compared. [ABSTRACT FROM AUTHOR]

Iron-chromium redox flow battery (ICRFB) is an energy storage battery with commercial application prospects. Compared to the most mature vanadium redox flow battery (VRFB) at present, ICRFB is more low-cost and environmentally friendly, which makes it more suitable for large-scale energy storage. However, the traditional electrode material carbon felt (CF) has poor electrochemical activity and hydrogen evolution side reactions, which hinders the application of ICRFB. In this paper, the surface of graphite felt (GF) was modified with pomelo peel powder to prepare biomass-modified graphite felt (Bio-GF). The optimal mass of pomelo peel powder and concentration of sucrose solution and pyrolysis temperature were determined. The surface morphology, elemental composition, hydrophilicity and electrochemical performance of the optimal biomass-modified GF(Bio-GF-O) were characterized. In addition, high performance can be achieved by employing ICRFB assembled with the Bio-GF-O electrode. At a low current density of 40 mA cm−2, the Coulombic efficiency(CE) was 92.34%, the voltage efficiency (VE) was 91.81%, and the energy efficiency (EE) was 84.78%. At the high current density of 120 mA cm−2, the CE increased and up to 96.87%, the VE and EE still have excellent cycle stability. It can be concluded that the use of waste biomass materials to modify GF to improve its electrochemical performance is conducive to the application of ICRFB. [ABSTRACT FROM AUTHOR]

The previous stochastic hosting capacity prediction method using the Monte Carlo method for high photovoltaic (PV) penetration with a battery energy storage system (BESS) required a large number of computations to achieve the expected accuracy. The problem of high computational load must be addressed so that the electrical distribution planner can practically use the PV hosting capacity prediction in actual situations. Therefore, this study developed a Markov-chain-based PV hosting capacity prediction method for high PV penetration using BESS. The proposed method is described in detail, followed by case and validation studies. The obtained hosting capacity was 123.58 kW, which increased to 3676.4 kW after the utility-scale BESS implementation. The results demonstrate that the proposed Markov-chain-based PV hosting capacity prediction method outperforms the Monte Carlo method, which is the most popular stochastic hosting capacity method, in terms of accuracy and computational cost. [ABSTRACT FROM AUTHOR]

By analysing the flow field of the bipolar plate, considering the inlet and outlet direction, increasing the inclined baffle and the number of channels, an improved multi-channel serpentine flow channel on the opposite side of double baffles is obtained based on the traditional serpentine flow channel. And the hydrodynamic model, electrochemical model and equivalent circuit model are coupled into a hybrid model to obtain the relationship between pump loss current changes during charging and discharging. The experimental results show that the reaction time of the change curve is 52 s earlier and the charging cut-off voltage is 0.3 V higher in the charging and discharging state. [ABSTRACT FROM AUTHOR]

The paper discusses the coordinated effect of redox flow battery (RFB) and accurate high voltage dc (AHVDC) link on the combined voltage and frequency control of two-area systems under deregulated environment. Each area has three generating companies (GENCOs) and three distribution companies. GENCOs in Area-1 are thermal, realistic dish-Stirling solar thermal system (RDSTS) and solar thermal power plants, and in Area-2 GENCOs are hydro, RDSTS, and geothermal power plants. Appropriate nonlinearity constraints are equipped with both hydro and thermal units. A maiden attempt has been made to employ a cascaded fractional-order PD with filter and PID with filter (CFOPDN-PIDN) as a secondary controller for the considered system. Artificial flora algorithm is used to optimize the controller parameters under various system conditions. The proposed CFOPDN-PIDN controller yields better system dynamic responses than the PIDN controller for the Poolco, bilateral, and contract violation power transactions. The investigations reveal that the parallel operation of the AC/AHVDC links deteriorates the system dynamics having more oscillations and peak deviations compared to individual AC and AHVDC links. The dynamic effect of Phase-Lock-Loop (PLL) is important for the realistic operation of AHVDC link. A novel approach for analyzing the dynamic effect of the AHVDC links considering PLL effects during the coordination with the AC system is presented. By adding the dynamic model of PLL to the parallel AC/AHVDC link, the system's performance is improved. The analysis reflects that the RFB-AHVDC links with PLL dynamics provided better system damping than the RFB-AC tie-line and AC tie-line alone. [ABSTRACT FROM AUTHOR]

Zinc‐bromine flow batteries (ZBFBs) are promising candidates for the large‐scale stationary energy storage application due to their inherent scalability and flexibility, low cost, green, and environmentally friendly characteristics. ZBFBs have been commercially available for several years in both grid scale and residential energy storage applications. Nevertheless, their continued development still presents challenges associated with electrodes, separators, electrolyte, as well as their operational chemistry. Therefore, rational design of these components in ZBFBs is of utmost importance to further improve the overall device performance. In this review, the focus is on the scientific understanding of the fundamental electrochemistry and functional components of ZBFBs, with an emphasis on the technical challenges of reaction chemistry, development of functional materials, and their application in ZBFBs. Current limitations of ZBFBs with future research directions in the development of high performance ZBFBs are suggested. [ABSTRACT FROM AUTHOR]

Electrolytes containing multiple redox couples are promising for improving the energy density of flow batteries. Here, two chelated chromium complexes that are structural isomers are characterized and combined to generate electrolytes containing up to 2 M of active species, corresponding to 53.6 Ah L−1. The mixed isomer approach enables a significantly higher active material content than the individual materials would allow, affording energy dense cells with Coulombic efficiencies of ≥99.6% at 100 mA cm−2 and an open circuit voltage of 1.65 V at 50% state-of-charge. This high concentration, however, comes with a caveat; at a given concentration, an equimolar mixed electrolyte leads to lower voltage efficiency compared to using the individual isomers, while Coulombic efficiency remains constant. Our work demonstrates that exploiting structural isomerism is an efficient approach to improve capacity, but active materials must be selected carefully in mixed systems as differences in operating potentials negatively affect energy efficiency. [ABSTRACT FROM AUTHOR]

For the application of CO2 as an energy storage material, a H2 storage system has been proposed based on the interconversion of CO2 and formic acid (or formate). However, energy losses are inevitable in the conversion of electrical energy to H2 as chemical energy (≈70 % electrical efficiency) and H2 to electrical energy (≈40 % electrical efficiency). To overcome these significant energy losses, we developed a system based on the interconversion of CO2 and formate for the direct storage and generation of electricity. In this paper, we report an aqueous redox flow battery system using homogeneous Ir catalysts with CO2‐formate redox pair. The system exhibited a maximum discharge capacity of 10.5 mAh (1.5 Ah L−1), capacity decay of 0.2 % per cycle, and total turnover number of 2550 after 50 cycles. During charging‐discharging, in situ fluorescence X‐ray absorption fine structure spectroscopy based on an online setup indicated that the active species was in a high valence state of IrIV. [ABSTRACT FROM AUTHOR]

Battery energy storage (BES) can provide many grid services, such as power flow management to reduce distribution grid overloading. It is desirable to minimise BES storage capacities to reduce investment costs. However, it is not always clear how battery sizing is affected by battery siting and power flow simultaneity (PFS). This paper describes a method to compare the battery capacity required to provide grid services for different battery siting configurations and variable PFSs. The method was implemented by modelling a standard test grid with artificial power flow patterns and different battery siting configurations. The storage capacity of each configuration was minimised to determine how these variables affect the minimum storage capacity required to maintain power flows below a given threshold. In this case, a battery located at the transformer required 10–20% more capacity than a battery located centrally on the grid, or several batteries distributed throughout the grid, depending on PFS. The differences in capacity requirements were largely attributed to the ability of a BES configuration to mitigate network losses. The method presented in this paper can be used to compare BES capacity requirements for different battery siting configurations, power flow patterns, grid services, and grid characteristics. [ABSTRACT FROM AUTHOR]

Transition metal single atoms anchored on nitrogen‐doped carbon (M‐N‐C) matrix with M‐N‐C active sites have shown to be promising catalysts for both hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Herein, a hybrid catalyst with low‐level loading of atomic Pt and Co species encapsulated in nitrogen‐doped graphene (Pt@CoN4‐G) is developed. The Pt@CoN4‐G shows low overpotential for HER in wide‐pH electrolyte and manifests improved mass activity with almost eight times greater than that of Pt/C at an overpotential of 50 mV. The Pt@CoN4‐G also exhibits a top‐level ORR activity (half‐wave potential, E1/2 = 0.893 V) and robust stability (>200 h) in alkaline medium. Using theoretical calculations and comprehensive characterizations , the strong metal–support interactions between Pt species and CoN4‐G support and synergistical cooperation of multiple active sites are clarified. A flow alkali‐Al/acid hybrid fuel cell using Pt@CoN4‐G as cathode catalyst delivers a large power density of 222 mW cm−2 with excellent stability to achieve simultaneously hydrogen evolution and electricity generation. In addition, Pt@CoN4‐G endows a flow Zn‐air battery with high power density (316 mW cm−2), good stability under large current density (>100 h at 100 mA cm−2), and long cycle life (over 600 h at 5 mA cm−2). [ABSTRACT FROM AUTHOR]

High solubility of active materials is crucial for achieving a high‐energy‐density catholyte/anolyte in redox flow batteries. However, solubility largely depends on the compatibility with electrolyte, limiting the types of redox‐active materials that can be used in aqueous electrolytes. Herein, a universal strategy is introduced to attain a high solubility of active materials regardless of the compatibility with aqueous electrolytes while preserving their intrinsic redox activity via micellar solubilization. Leveraging the amphiphilic nature of surfactant molecules, insoluble redox‐active materials are encapsulated by surfactants to be dissolvable with significant solubility. As a demonstration, it is showed that an order‐of‐magnitude solubility enhancement can be achieved for (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) in aqueous catholyte (≈0.8 m). Consequently, the catholyte performance of TEMPO is fully harnessed, leading to an energy density enhancement of more than ten times compared to that in bare electrolyte. It is also observed that micellar solubilization unexpectedly improves the cycle stability, attributed to the mitigation of intermolecular side reactions and reduced crossover. Finally, the fundamental electrochemical reaction mechanism of micelle‐encapsulated TEMPO is discussed. This strategy offers a new insight regarding the solubility and stability of the catholyte/anolyte, and is expected to be applicable to other redox‐active molecules, opening up an unexplored micellar chemistry in redox flow batteries. [ABSTRACT FROM AUTHOR]

This paper presents an electrochemical–thermal–hydraulic–mechanical (ETHM) coupling model by introducing the electrolyte flow field into the model of lithium-ion batteries (LIBs). First, the ETHM coupling model is established on the basis of the electrochemical–thermal–mechanical (ETM) coupling model and poroelasticity model. Then, the ETHM coupling model for the discharge of LIBs is numerically resolved and verified against the ETM coupling model using the commercial 11.5 Ah LiMn2O4 battery as an example. Subsequently, the flow and deformation characteristics (such as the Darcy's velocity, the pore pressure, the Péclet number, and the volumetric strain) are analyzed. The results suggest that the electrolyte does flow during the operation of LIBs. Furthermore, the electrolyte flow is governed by the internal pore pressure gradient induced by the poroelastic effect. The electrolyte flow behavior is also influenced by the boundary conditions. The findings in this study are of benefit to obtain in-depth understanding of the coupling mechanisms among the electrolyte flow field and the stress (strain) field, the temperature field, and the electrochemical field. [ABSTRACT FROM AUTHOR]

The hydrogen‐iron (HyFe) flow cell has great potential for long‐duration energy storage by capitalizing on the advantages of both electrolyzers and flow batteries. However, its operation at high current density (high power) and over continuous cycling testing has yet to be demonstrated. In this paper, we discuss our design and demonstration of a water management strategy that supports high current and long cycling performance of a HyFe flow cell. Water molecules associated with the movement of protons from the iron electrode to the hydrogen electrode are sufficient to hydrate the membrane and electrode at a low current density of 100 mA cm−2 during the charge process. At higher charge current density, more aggressive measures must be taken to counter back‐diffusion driven by the acid concentration gradient between the iron and hydrogen electrodes. Our water management approach is based on water vapor feeding in the hydrogen electrode, and water evaporation in the iron electrode, thus enabling the high current density operation of 300 mA cm−2. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) are widely used as power sources for electric vehicles due to their various advantages, including high energy density and low self-discharge rate. However, the safety challenges associated with LIB thermal runaway (TR) still need to be addressed. In the present study, the effects of the battery SOC value and coolant flow rate on the TR behavior in a LIB pack are comprehensively investigated. The battery pack consists of 10 18650-type LIBs applied with the serpentine channel liquid-cooling thermal management system (TMS). The TR tests for various SOC values (50%, 75% and 100%) and coolant flow rates (0 L/h, 32 L/h, 64 L/h and 96 L/h) are analyzed. The retarding effect of the TMS on TR propagation is found to be correlated with both the coolant flow rate and the battery SOC value, and a larger coolant flow rate and lower SOC generally result in fewer TR batteries. Furthermore, the TR propagation rate, evaluated by the time interval of TR occurrence between the adjacent batteries, increases with the battery SOC. The battery pack with 100% SOC shows more rapid TR propagation, which can be completed in just a few seconds, in contrast to several minutes for 50% and 75% SOC cases. In addition, the impact of the battery SOC and coolant flow rate on the maximum temperature of the TR battery is also examined, and no determined association is observed between them. However, it is found that the upstream batteries (closer to the external heater) show a slightly higher maximum temperature than the downstream ones, indicating a weak association between the TR battery maximum temperature and the external heating duration or the battery temperature at which the TR starts to take place. [ABSTRACT FROM AUTHOR]

Ion-selective membranes based on non-ionic polymers are promising for redox flow batteries due to their superior chemical stability and low cost. In this work, a poly(vinylidene fluoride) (PVDF) ion-selective membrane is successfully prepared using a solvent-controlled swelling method, where Nafion is used as a channel-forming promoter. The influences of Nafion on the channel formation of the membranes are studied. The results indicate that the addition of Nafion resin can greatly promote the formation of ion-conducting channels in the PVDF matrix. The obtained membranes show well-controlled proton conductivity and proton/vanadium selectivity. A battery test on a vanadium redox flow single cell is successfully performed. The energy efficiency of the cell equipped with the PVDF-based ion-selective membrane reaches 81.7% at a current density of 60 mA cm−2 and possesses excellent cycling stability and suppressed self-discharge after modification with Nafion. [ABSTRACT FROM AUTHOR]

To achieve carbon neutrality, integrating intermittent renewable energy sources, such as solar and wind energy, necessitates the use of large-scale energy storage. Among various emerging energy storage technologies, redox flow batteries are particularly promising due to their good safety, scalability, and long cycle life. In order to meet the ever-growing market demand, it is essential to enhance the power density of battery stacks to lower the capital cost. One of the key components that impact the battery performance is the flow field, which is to distribute electrolytes onto electrodes. The design principle of flow fields is to maximize the distribution uniformity of electrolytes at a minimum pumping work. This review provides an overview of the progress and perspectives in flow field design and optimization, with an emphasis on the scale-up process. The methods used to evaluate the performance of flow fields, including both experimental and numerical techniques, are summarized, and the benefits of combining diverse methods are highlighted. The review then investigates the pattern design and structure optimization of serpentine- and interdigitated-based flow fields before discussing challenges and strategies for scaling up these flow fields. Finally, the remaining challenges and the prospects for designing highly efficient flow fields for battery stacks are outlined. [ABSTRACT FROM AUTHOR]

Flow battery has recently drawn great attention due to its unique characteristics, such as safety, long life cycle, independent energy capacity and power output. It is especially suitable for large-scale storage system and has a good application prospect. In this paper, the overall structure of the megawatt-level flow battery energy storage system is introduced, and the topology structure of the bidirectional DC converter and the energy storage converter is analyzed. Secondly, the influence of single battery on energy storage system is analyzed, and a simulation model of flow battery energy storage system suitable for large power grid simulation is summarized. The model of the whole system of flow battery is summarized from the grid-connected side and the energy storage system itself. The model of flow battery energy storage system should not only accurately reflect the operation characteristics of flow battery itself, but also meet the simulation requirements of large power grid in terms of simulation accuracy and speed. Finally, the control technology of the flow battery energy storage system is discussed and analyzed. The multi-DC/DC control strategy on the DC side and the parallel operation control strategy of the energy storage converter on the AC side are compared and analyzed. The advantages and disadvantages of each control method are analyzed accurately, which can provide reference for the modeling and control strategy of the megawatt flow battery energy storage system.

Abstract Redox flow batteries (RFBs) are a promising technology for long‐duration energy storage; but they suffer from inefficiencies in part due to the overvoltages at the electrode surface. In this work, more than 70 electrode treatments are reviewed that are previously shown to reduce the overvoltages and improve performance for vanadium RFBs (VRFBs), the most commercialized RFB technology. However, identifying treatments that improve performance the most and whether they are industrially implementable is challenging. This study attempts to address this challenge by comparing treatments under similar operating conditions and accounting for the treatment process complexity. The different treatments are compared at laboratory and industrial scale based on criteria for VRFB performance, treatment stability, economic feasibility, and ease of industrial implementation. Thermal, plasma, electrochemical oxidation, CO2 treatments, as well as Bi, Ag, and Cu catalysts loaded on electrodes are identified as the most promising for adoption in large scale VRFBs. The similarity in electrode treatments for aqueous‐organic RFBs (AORFBs) and VRFBs is also identified. The need of standardization in RFBs testing along with fundamental studies to understand charge transfer reactions in redox active species used in RFBs moving forward is emphasized.