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Introduction: Mild cognitive impairment (MCI) is a prodromal stage to dementia, affecting up to 20% of the aging population worldwide. Patients with MCI have an annual conversion rate to dementia of 15–20%. Thus, conditions that increase the conversion from MCI to dementia are of the utmost public health concern. The COVID-19 pandemic poses a significant impact on our aging population with cognitive decline as one of the leading complications following recovery from acute infection. Recent findings suggest that COVID-19 increases the conversion rate from MCI to dementia in older adults. Hence, we aim to uncover a mechanism for COVID-19 induced cognitive impairment and progression to dementia to pave the way for future therapeutic targets that may mitigate COVID-19 induced cognitive decline. Methodology: A prospective longitudinal study is conducted at the University of Oklahoma Health Sciences Center. Patients are screened in the Department of Neurology and must have a formal diagnosis of MCI, and MRI imaging prior to study enrollment. Patients who meet the inclusion criteria are enrolled and followed-up at 18-months after their first visit. Visit one and 18-month follow-up will include an integrated and cohesive battery of vascular and cognitive measurements, including peripheral endothelial function (flow-mediated dilation, laser speckle contrast imaging), retinal and cerebrovascular hemodynamics (dynamic vessel retinal analysis, functional near-infrared spectroscopy), and fluid and crystalized intelligence (NIH-Toolbox, n-back). Multiple logistic regression will be used for primary longitudinal data analysis to determine whether COVID-19 related impairment in neurovascular coupling and increases in white matter hyperintensity burden contribute to progression to dementia. [ABSTRACT FROM AUTHOR]

The development of a rechargeable battery that can produce valuable chemicals in both electricity storage and generation processes holds great promise for increasing the electron economy and economic value. However, this battery has yet to be explored. Herein, we report a biomass flow battery that generates electricity while producing furoic acid, and store electricity while yielding furfuryl alcohol. The battery is composed of a rhodium‐copper (Rh1Cu) single‐atom alloy as anode, a cobalt‐doped nickel hydroxide (Co0.2Ni0.8(OH)2) as cathode, and furfural‐containing anolyte. In a full battery evaluation, this battery displays an open circuit voltage (OCV) of 1.29 V and a peak power density up to 107 mW cm−2, surpassing most catalysis‐battery hybrid systems. As a proof‐of‐concept, we demonstrate that this battery produces 1 kg furoic acid with 0.78 kWh electricity output, and yields 0.62 kg furfuryl alcohol when 1 kWh electricity is stored. This work may shed light on the design of rechargeable batteries with value‐added functionality such as chemicals production. [ABSTRACT FROM AUTHOR]

In this article, a graphite felt electrode was modified by NS double‐element and NB double‐element codoping. The surface morphology, crystal structure, element content, and surface chemical state of the modified electrode were characterized by scanning electron microscopy, X‐ray powder diffraction (XRD), Raman spectroscopy, and X‐ray photoelectron spectroscopy. The electrochemical performance of the modified electrode was evaluated by cyclic voltammetry, electrochemical impedance spectra, and a single cell. The results show that nitrogen (N) and boron (B) double‐element codoping can enhance the catalytic activity of graphite felt and create abundant defect sites, which increases the electrocatalytic activity by approximately a factor of 2. The reason why the doped graphite felt can obtain higher electrocatalytic activity may be related to the synergy between N and B atoms, especially the synergy between pyridine‐N and BC3, and the resistance of the first charge transfer reaction of 1,8‐dihydroxyanthraquinone on the doped graphite felt electrode is then reduced. [ABSTRACT FROM AUTHOR]

This paper presents a study on flow hydrodynamics for single-channel serpentine flow field (SCSFF) and cross-split serpentine flow field configurations (CSSFF) for different geometric dimensions of channel and rib width ratios with electrode intrusion over varying compression ratios (CRs) in an all-iron redox flow battery. Pressure drops (Δ p) measured experimentally across a cell active area of 131 cm2 for different electrolyte flow rates were numerically validated. A computational fluid dynamics study was conducted for detailed flow analyses, velocity magnitude contours, flow distribution, and uniformity index for the intrusion effect of a graphite felt electrode bearing a thickness of 6 mm with a channel compressed to varying percentages of 50%, 60%, and 70%. Experimental pressure drops (Δ p) over the numerical value resulted in the maximum error approximated to 4%, showing good agreement. It was also reported that the modified version of the cross-split serpentine flow field, model D, had the lowest pressure drop, Δ p , of 2223.4 pa, with a maximum uniformity index at the electrode midplane of 0.827 for CR 50%, across the active cell area. The pressure drop (Δ p) was predominantly higher for increased compression ratios, wherein intrusion phenomena led to changes in electrochemical activity; it was found that the velocity distribution was quite uniform for a volumetric uniformity index greater than 80% in the felt. [ABSTRACT FROM AUTHOR]

Composite of dextrose-derived oxygen-rich carbon spheres and graphene oxide, synthesised using a cost-effective and easy hydrothermal process, was used as an active material in two of the trending and promising energy storage devices. The surface morphology and properties of the composite were studied using scanning electron microscope, X-ray diffractometer, energy dispersive X-ray analysis, elemental mapping and Raman spectra. To analyse the electrochemical behaviour of the material, several electrochemical techniques such as cyclic voltammetry (CV), chronopotentiometry, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation study were used. The reversibility of Fe2+/Fe3+ redox species and resistance offered by electrolyte towards the modified electrode were studied using CV, EIS and Tafel studies. Further evaluation of efficacy of the active material towards the iron redox flow battery (IRFB) of 132 cm2 area was analysed by performing charge discharge studies at varied current densities. Substantial increase in the electrochemical performance of the IRFB with a coulombic efficiency (CE) 93% along with the good life cycle stability up to 25 cycles was observed. The composite was also used as a superior electrode material for supercapacitor application resulting in significant enhancement in the electrochemical performance with specific capacitance of 610 F g−1 and CE of 83% with 93% retention up to 1600 cycles. [ABSTRACT FROM AUTHOR]

Due to the high solubility, high reversibility, and low cost of iodide, iodine-based redox flow batteries (RFBs) are considered to have great potential for upscaling energy storage. However, their further development has been limited by the low capacity of I- as one-third of the I- is used to form I3- (I2I-) during the charging process. Herein, we have demonstrated that the pseudohalide ion, thiocyanate (SCN-), is a promising complexing agent for catholyte of iodinebased RFBs to free up the I- by forming iodine-thiocyanate ions ([I2SCN]-) instead of I3-, unlocking the capacity of iodide. Applying this strategy, we have demonstrated iodine-based RFBs with full utilization of iodide to achieve high capacity and high energy density. Both the zinc/iodine RFB and polysulfide/iodine RFB with SCN- complex agent achieve their theoretical capacity of around 160 A h Lposolyte-1 (6.0MI- in catholyte). Therefore, the zinc/iodine RFB delivers a high energy density of 221.34Wh Lposolyte-1, and the polysulfide/iodine RFB achieves a highenergy density of 165.62Wh Lposolyte-1. It is believed that this effective catholyte engineering can be further generalized to other iodine-based RFBs, offering new opportunities to unlock the capacity of iodide and achieve high energy density for energy storage. [ABSTRACT FROM AUTHOR]

Redox flow batteries (RFBs) are hindered by complex failure modes, particularly crossover through the membrane, resulting in capacity fade and reduced cycling efficiencies. Redox‐active oligomers (RAOs) have recently been proposed for mitigating this phenomenon while maintaining sufficient transport properties; however, to date, few studies have quantified how the chemical and electrochemical properties of RAOs influence their performance in redox flow cells. Here, we demonstrate that oligomeric derivatives of 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO) exhibit lower diffusivities than the monomeric species but retain facile charge transfer characteristics. The size‐dependent variations in mass transport rates directly translate to differences in flow cell polarization and symmetric cycling performance. Post‐mortem analyses reveal that oligomerization does not meaningfully alter decay processes as evinced by similar capacity fade across all species. Broadly, these findings corroborate and extend upon previously developed relationships between molecular size, electrochemical properties, and flow cell performance. [ABSTRACT FROM AUTHOR]

Redox flow batteries (RFBs) are a promising electrochemical platform for efficiently and reliably delivering electricity to the grid. Within the RFB, porous carbonaceous electrodes facilitate electrochemical reactions and distribute the flowing electrolyte. Tailoring electrode microstructure and surface area can improve RFB performance, lowering costs. Electrodes with spatially varying porosity may increase electrode utilization and provide surface area in reaction‐limited zones; however, the efficacy of such designs remains an open area of research. Herein, a non‐solvent‐induced phase‐separation (NIPS) technique that enables the reproducible synthesis of macrovoid‐free electrodes with well‐defined across‐thickness porosity gradients is described. The monotonically varying porosity profile is quantified and the physical properties and surface chemistries of porosity‐gradient electrodes are compared with macrovoid‐containing electrode, also synthesized by NIPS. Then, the electrochemical and fluid dynamic performance of the porosity‐gradient electrodes is evaluated, exploring the effect of changing the direction of the porosity gradient and benchmarking against the macrovoid‐containing electrode. Lastly, the performance is examined in a vanadium RFB, finding that the porosity‐gradient electrode outperforms the macrovoid electrode, is independent of gradient direction, and performs favorably compared to advanced electrodes in the contemporary literature. It is anticipated that the approach motivates further exploration of microstructurally tailored electrodes in electrochemical systems. [ABSTRACT FROM AUTHOR]

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Renewable energy systems are essential for carbon neutrality and energy savings in industrial facilities. Factories use a lot of electrical and thermal energy to manufacture products, but only a small percentage is recycled. Utilizing energy storage systems in industrial facilities is being applied as a way to cut energy costs and reduce carbon emissions. However, lithium-based batteries, which are predominantly used in traditional industries, face challenges in terms of affordability and reliability. Redox flow batteries, on the other hand, offer high power output and reliability, and are economical to manufacture for installations with high capacity. Although redox flow batteries are difficult to use in general electrical systems due to their small volume-to-capacity ratio, they can be easily utilized as energy storage devices in industrial parks or renewable energy parks with relatively little space constraints. In addition, since factories use a lot of heat energy in addition to electricity, utilizing combined heat and power can further reduce heat energy. In this study, we analyzed the cost estimation and economic feasibility of utilizing photovoltaics, redox flow cells, and combined heat and power to save energy in a factory's energy management system. [ABSTRACT FROM AUTHOR]

Redox flow batteries represent a captivating class of electrochemical energy systems that are gaining prominence in large-scale storage applications. These batteries offer remarkable scalability, flexible operation, extended cycling life, and moderate maintenance costs. The fundamental operation and structure of these batteries revolve around the flow of an electrolyte, which facilitates energy conversion and storage. Notably, the power and energy capacities can be independently designed, allowing for the conversion of chemical energy from input fuel into electricity at working electrodes, resembling the functioning of fuel cells. This work provides a comprehensive overview of the components, advantages, disadvantages, and challenges of redox flow batteries (RFBs). Moreover, it explores various diagnostic techniques employed in analyzing flow batteries. The discussion encompasses the utilization of RFBs for large-scale energy storage applications and summarizes the engineering design aspects related to these batteries. Additionally, this study delves into emerging technologies, applications, and challenges in the realm of redox flow batteries. [ABSTRACT FROM AUTHOR]

The increasing popularity of electric vehicles presents both opportunities and challenges for the advancement of lithium battery technology. A new longitudinal-flow heat dissipation theory for cylindrical batteries is proposed in order to increase the energy density and uniform temperature performance of cylindrical lithium-ion battery packs while also shrinking their size by roughly 10%. First, a genetic algorithm is used to identify a single cell's thermal properties. Based on this, modeling and simulation are used to examine the thermal properties of the longitudinal-flow-cooled battery pack. It is found that the best coolant flow scheme has one inlet and one outlet from the end face, taking into account the cooling effect of the battery pack and engineering viability. Lastly, thermal dummy cells (TDCs) are used to conduct a validation test of the liquid cooling strategy. Additionally, the simulation and test results demonstrate that the liquid cooling solution can restrict the battery pack's maximum temperature rise under the static conditions of a continuous, high-current discharge at a rate of 3C to 20 °C and under the dynamic conditions of the New European Driving Cycle (NEDC) to 2 °C. In applications where the space requirements for the battery pack are quite strict, the longitudinal-flow cooling method has some advantages. [ABSTRACT FROM AUTHOR]

Aqueous redox flow batteries, by using redox‐active molecules dissolved in nonflammable water solutions as electrolytes, are a promising technology for grid‐scale energy storage. Organic redox‐active materials offer a new opportunity for the construction of advanced flow batteries due to their advantages of potentially low cost, extensive structural diversity, tunable electrochemical properties, and high natural abundance. In this review, we present the emergence and development of organic redox‐active materials for aqueous organic redox flow batteries (AORFBs), in particular, molecular engineering concepts and strategies of organic redox‐active molecules. The typical design strategies based on organic redox species for high‐capacity, high‐stability, and high‐voltage AORFBs are outlined and discussed. Molecular engineering of organic redox‐active molecules for high aqueous solubility, high chemical/electrochemical stability, and multiple electron numbers as well as satisfactory redox potential gap between the redox pair is essential to realizing high‐performance AORFBs. Beyond molecular engineering, the redox‐targeting strategy is an effective way to obtain high‐capacity AORFBs. We further discuss and analyze the redox reaction mechanisms of organic redox species based on a series of electrochemical and spectroscopic approaches, and succinctly summarize the capacity degradation mechanisms of AORFBs. Furthermore, the current challenges, opportunities, and future directions of organic redox‐active materials for AORFBs are presented in detail. [ABSTRACT FROM AUTHOR]

Triclinic vanadium dioxide VO2 (T) films were produced using cathodic arc deposition. Under certain conditions, the film growth on sapphire substrates Al2O3 (001) is associated with the formation of triclinic monocrystals with lateral sizes of several tens of micrometers. Borders between different crystallites can be determined by Raman mapping analysis. X-ray diffraction measurements revealed that the micrometer-sized monocrystals had two different orientations—epitaxial (002) and non-epitaxial (201). The film was studied by polarized micro-Raman spectroscopy, which can be used to determine the orientation of any single crystallite. The Raman tensor elements of the VO2 (T) phase were determined, and it was shown that though crystallographically triclinic VO2 cell could be fitted by monoclinic one with a high degree of precision, such monoclinic approximation was not valid in terms of Raman spectroscopy. Contrary to the two types of phonons expected for the monoclinic crystal [having five nonzero (four independent) or four nonzero (two independent) Raman tensor elements], all phonons in VO2 (T) have nine (six independent) generally nonzero tensor components. [ABSTRACT FROM AUTHOR]

MoOX is commonly considered to be a high work-function semiconductor. From x-ray photoelectron spectroscopy and photo-electrochemical analysis, it is shown that MoOX can be considered as an effective hole transfer layer for the GaP-based device. Specifically, in the absence of carbon contamination using an ion beam cleaning step, the oxygen vacancy derived defect band located inside the bandgap becomes the main charge transfer mechanism. We demonstrate, for the first time, a device with a MoOX/GaP junction that functions as an unbiased photo-charging cell for the redox flow battery system with AQS/AQSH2∥I−/I3− redox couples. This work has important implications toward enabling MoOX applications beyond the conventional solar cells, including electrochemical energy storage and chemical conversion systems. [ABSTRACT FROM AUTHOR]

A benzoquinone derivative annelated by two imidazole rings was investigated as an organic anolyte of aqueous redox flow batteries. The anolyte showed a high solubility of 0.18 M in 1 M KOH aqueous solution and exhibited a one-step two-electron reversible redox wave with a half-wave potential of −0.59 V VS. SHE. An aqueous redox flow cell comprising the benzoquinone–imidazole hybrid as the anolyte and potassium ferrocyanide as the catholyte showed an operating voltage of ∼1.1 V and minimum capacity fading of over 220 cycles. [ABSTRACT FROM AUTHOR]

Redox flow batteries have been discussed as scalable and simple stationary energy storage devices. However, currently developed systems encounter less competitive energy density and high costs, restricting their wider application. There is a lack of appropriate redox chemistry, preferably based on active materials that are abundant in nature and show high solubility in aqueous electrolytes. A nitrogen‐centered redox cycle operating between the limiting species ammonia and nitrate via an eight‐electron redox reaction stayed practically unnoticed, albeit its ubiquity in biological processes. Ammonia or nitrate are world‐scale chemicals with high aqueous solubility, and are then comparably safe. We demonstrate here the successful implementation of such a nitrogen‐based redox cycle between ammonia and nitrate with eight‐electron transfer as a catholyte for Zn‐based flow batteries, which continuously worked for 12.9 days with 930 charging‐discharging cycles. A very competitive energy density of 577 Wh L−1 can be reached, which is well above most reported flow batteries (e.g. 8 times the standard Zn‐bromide battery), demonstrating that the nitrogen cycle with eight‐electron transfer can offer promising cathodic redox chemistry for safe, affordable, and scalable high‐energy‐density storage devices. [ABSTRACT FROM AUTHOR]

Solar‐to‐electrochemical energy storage in solar batteries is an important solar utilization technology comparable to solar‐to‐electricity (solar cells) and solar‐to‐fuel (photocatalytic cells) conversion. Unlike the indirect approach of integrated solar flow batteries combining photoelectrodes with redox‐electrodes, coupled solar batteries enable direct solar energy storage, but are hampered by low efficiency due to rapid charge recombination of materials and misaligned energy levels between electrodes. Herein, we propose a design for a coupled solar battery that intercouples two photo‐coupled ion transfer (PCIT) reactions through electron‐ion transfer upon co‐photo‐pumping of photoelectrochemical storage cathode and anode. We used a representative covalent organic framework (COF) to achieve efficient charge separation and directional charge transfer between two band‐matched photoelectrochemical storage electrodes, with a photovoltage sufficient for COF dual‐redox reactions. By pumping these electrodes, the coupled solar battery stores solar energy via two synergistic PCIT reactions of electron‐proton‐relayed COF oxidation and reduction, and the stored solar energy is released as electrochemical energy during COF regeneration in discharge while interlocking the loops. A breakthrough in efficiency (6.9 %) was achieved, adaptive to a large‐area (56 cm2) tandem device. The presented photo‐intercoupled electron‐ion transfer (PIEIT) mechanism provides expandable paths toward practical solar‐to‐electrochemical energy storage. [ABSTRACT FROM AUTHOR]

The hydrophilic poly(2,2,6,6‐tetramethylpiperdinyloxy‐4‐yl‐methacrylamide) (PTMAm) was utilized as redox target material in an aqueous organic redox targeting flow battery (RTFB). This polymer is processed into granules, which contain a conductive agent and an alginate binder. By this, a hydrophilic, yet water‐insoluble redox target can be obtained. The target was combined with the redox mediator molecule N,N,N‐trimethyl‐2‐oxo‐2‐[(2,2,6,6‐tetramethylpiperidin‐4‐yloxyl)amino]ethan‐1‐ammonium chloride (TEMPOAmide), that has been reported earlier as flow battery active material. This target/mediator combination has been characterized electrochemically and flow battery testing has been done. Furthermore, in‐operando characterization of the redox target via electrolyte state‐of‐charge (SOC) monitoring has been performed for the first time. The approach provides estimates for the redox target's SOC changes during cycling. In addition, a figure of merit – the "redox targetivity" – is proposed, which provides insights into the efficiency of the targeting reaction and supports the future optimization of materials, cell designs, and operational parameters for RTFBs. [ABSTRACT FROM AUTHOR]

Redoxmers are organic active molecules storing electrochemical energy in nonaqueous redox flow batteries (NRFBs). Increasing the solubility of redoxmers is an important approach for increasing energy density of NRFBs as effective redoxmer concentration determines how much electricity can be stored in a given volume. Molecular engineering redoxmers towards liquid forms is regarded as one promising strategy as liquid redoxmers represent an extreme scenario where fluidity is maintained at maximum concentration using a minimum amount of supporting solvents. In this Perspective, recent examples of liquid redoxmers as well as their development strategy will be discussed. [ABSTRACT FROM AUTHOR]

Redox flow batteries (RFBs) are promising for large‐scale long‐duration energy storage owing to their inherent safety, decoupled power and energy, high efficiency, and longevity. Membranes constitute an important component that affects mass transport processes in RFBs, including ion transport, redox‐species crossover, and the net volumetric transfer of supporting electrolytes. Hydrophilic microporous polymers, such as polymers of intrinsic microporosity (PIM), are demonstrated as next‐generation ion‐selective membranes in RFBs. However, the crossover of redox species and water migration through membranes are remaining challenges for battery longevity. Here, a facile strategy is reported for regulating mass transport and enhancing battery cycling stability by employing thin film composite (TFC) membranes prepared from a PIM polymer with optimized selective‐layer thickness. Integration of these PIM‐based TFC membranes with a variety of redox chemistries allows for the screening of suitable RFB systems that display high compatibility between membrane and redox couples, affording long‐life operation with minimal capacity fade. Thickness optimization of TFC membranes further improves cycling performance and significantly restricts water transfer in selected RFB systems. [ABSTRACT FROM AUTHOR]

Energy storage devices are imperative to damp out the oscillations caused by sudden magnified disturbances occurring in a power system. The presence of a small rating of storage device in each area can alleviate the system oscillations effectively. Therefore, in this work, redox flow batteries (RFBs) have been integrated in each area of a five-area interconnected system for effective load frequency control (LFC). The RFB pumps up the active power into the system quickly to meet the short-time overload; in turn, the efficacy of the LFC in the system is boosted. Despite the presence of the RFB in the power system, a secondary controller is necessary to quench the deviation of frequency and tie-line power caused by the power mismatch between demand and generation. In this perspective, a cascade controller incorporated with a fractional operator (FO) has been endorsed and designed through a nascent selfish herd optimizer technique to evaluate the transient response of the system. Besides this, the unprecedented performance of fractional-order cascade controllers has been compared with one-stage classical controllers with and without a fractional operator. Further, the robustness of the proposed controller has been inspected through subjecting it to a random load in the presence/absence of an RFB and parametric variation. Finally, the proposed model has been simulated in the OPAL-RT-4510 platform to validate the performance of the proposed controller that has produced in the MATLAB environment. [ABSTRACT FROM AUTHOR]

New energy storage materials are an object of study within the framework of the global energy transition. The development of renewable sources is being boosted thanks to stationary energy storage systems such as redox flow batteries (RFBs). This work reports the synthesis of the cobalt-containing Keggin-type polyoxometalates [CoW12O40]6− (CoW12) and [Co(H2O)SiW11O39]6− (CoSiW11), which have previously been shown to have applicability in RFBs. These procedures were reassessed to meet the strict requirements associated with the further implementation of RFBs, including fast and affordable synthetic procedures with high reaction yields. In contrast to the lengthy and complicated synthetic approaches published to date, the optimized synthesis reported in this work enables the isolation of the pure crystalline salt of the CoW12 anion with a 75% reduction of the time of the whole reaction procedure, eliminating tedious steps such as the recrystallization and including a 20% increased yield. The control of the stoichiometry, fine-tuning of reaction conditions, and the identification of intermediate species, as well as the acidic equilibria taking place during the process, were monitored via thermal, spectroscopic, and structural analyses. In the case of the CoSiW11 anion, its preparation was based on a simple and highly efficient procedure. Moreover, promising electrochemical properties were observed with the use of the one-pot synthetic approach, in which the stoichiometric amounts of the starting reagents are dissolved in the supporting electrolyte to be directly implemented as the electrolyte for a RFB. [ABSTRACT FROM AUTHOR]

Vanadium Flow Batteries (VFBs) are a stationary energy storage technology, that can play a pivotal role in the integration of renewable sources into the electrical grid, thanks to unique advantages like power and energy independent sizing, no risk of explosion or fire and extremely long operating life. The first part of this paper presents the main features and the basic performance parameters of VFB, which determine their electric, hydraulic, thermal, and aging feature. The latter part outlines the strengths and weaknesses of the technology, the services that it can provide to the grid, and a short economic analysis. After presenting the fundaments of the technology, prospects and trends of VFBs deployment are outlined. Most of the considerations highlighted in this paper are inspired to studies performed on an industrial-size VFB operated at the Electrochemical Energy Storage and Conversion Lab (EESCoLab) at the University of Padua (Italy). [ABSTRACT FROM AUTHOR]

A series of triarylamines was synthesised and screened for their suitability as catholytes in redox flow batteries using cyclic voltammetry (CV). Tris(4‐aminophenyl)amine was found to be the strongest candidate. Solubility and initial electrochemical performance were promising; however, polymerisation was observed during electrochemical cycling leading to rapid capacity fade prescribed to a loss of accessible active material and the limitation of ion transport processes within the cell. A mixed electrolyte system of H3PO4 and HCl was found to inhibit polymerisation producing oligomers that consumed less active material reducing rates of degradation in the redox flow battery. Under these conditions Coulombic efficiency improved by over 4 %, the maximum number of cycles more than quadrupled and an additional theoretical capacity of 20 % was accessed. This paper is, to our knowledge, the first example of triarylamines as catholytes in all‐aqueous redox flow batteries and emphasises the impact supporting electrolytes can have on electrochemical performance. [ABSTRACT FROM AUTHOR]

The objective of this work is to carry out a bibliographic review, leading to the evaluation and comparison of alternatives for internal components of a vanadium redox flow battery, which can improve efficient and economically viable energy storage. This review leads to the design of a theoretical BRFV on a laboratory scale (100 Wh and 12 V.), handling the following parameters: electrolyte 3.0 M in V2O5 and 6.0 M HCl and 3.0 M H2SO4, felt electrodes of graphite treated with polyacrylonitrile and NafionTM 117 membrane. In parallel, it is suggested to use 9 cells, 2 liters of electrolyte, flow rate of 373 mL/min and charging time of 13.69 hours. Finally, an Excel file is generated with the operating parameters for the proposed battery. [ABSTRACT FROM AUTHOR]

In this study, carbon blacks, containing nitrogen and boron, are used as cathode catalysts first time in a hydrogen-bromine redox flow cell. Nitrogen and boron doping has been applied to carbon blacks to improve the limited properties of the Vulcan XC72 (VXC). Here, we have examined the effect of nitrogen-/boron-doped Vulcan XC72 carbon black on hydrogen-bromine flow cell performance. Nitrogen gas and boric acid are used as nitrogen and boron sources in the post-doping process, respectively. XRD, SEM, XPS, Raman spectroscopy, and N2 adsorption analyses are used to characterize the structures of cathode catalysts. The electrochemical characterization of the catalysts has been carried out with the cyclic voltammetry technique using the conventional three-electrode system connected to a potentiostat. We have addressed the effect of nitrogen and boron doping into the carbon black onto the flow battery performance by comparing their polarization and power curves. The maximum power densities with the VXC, N-VXC, and B-VXC cathode catalysts have been measured at 0.75 V as 360, 390, and 430 mW cm−2, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] Bicontinuous microemulsions (BMEs) have attracted attention as unique heterogeneous mixture for electrochemistry. An interface between two immiscible electrolyte solutions (ITIES) is an electrochemical system that straddles the interface between a saline and an organic solvent with a lipophilic electrolyte. Although most BMEs have been reported with nonpolar oils, such as toluene and fatty acids, it should be possible to construct a sponge-like three-dimensionally expanded ITIES comprising a BME phase. Dichloromethane (DCM)–water microemulsions stabilized by a surfactant were investigated in terms of the concentrations of co-surfactants and hydrophilic/lipophilic salts. A Winsor III microemulsion three-layer system, consisting of an upper saline phase, a middle BME phase, and a lower DCM phase, was prepared, and electrochemistry was conducted in each phase. We found the conditions for ITIES-BME phases. Regardless of where the three electrodes were placed in the macroscopically heterogeneous three-layer system, electrochemistry was possible, as in a homogeneous electrolyte solution. This indicates that the anodic and cathodic reactions can be divided into two immiscible solution phases. A redox flow battery comprising a three-layer system with a BME as the middle phase was demonstrated, paving the way for applications such as electrolysis synthesis and secondary batteries. [ABSTRACT FROM AUTHOR]

In today's rapidly evolving interconnected electric power system network, ancillary service such as automatic generation control (AGC) plays a critical and important role in safeguarding the system's power supply quality by establishing an equilibrium between generation and load demanded plus losses. A power system with a robust and smart AGC strategy is obligatory for better power quality and system security. Cascade control schemes cope up better with nonlinearity by tuning the gain of controller of power system amid continuous load changing. Therefore, in this article, a supplementary control approach that is, cascade optimal controller‐proportional integral with derivative filter (COC‐PIDN) is suggested for AGC performance advancement of the power systems under deregulated environment. The OC designed consuming full state feedback control approach acts as master controller and PIDN plays the role of slave controller. The nature inspired salp swarm algorithm is employed to adjust the PIDN parameters. Initially, the efficacy of the COC‐PIDN control‐method is explored on a two‐area restructured reheat thermal system and then to validate its excellence and extensibility, the study is protracted to restructured two‐area thermal‐hydro system. Extensive analysis of the findings establishes that the dynamic performance of the COC‐PIDN controller is more valuable than the OC and COC‐PID approaches. The results of COC‐PIDN get further improved in presence of redox flow battery. Finally, the sensitivity analysis as well the acquired results with the COC‐PIDN controller with system nonlinearities demonstrate its robustness. [ABSTRACT FROM AUTHOR]

A novel multiscale flow battery simulation approach is presented. Therefore, the mass transfer coefficient (MTC) is extracted from the 3D‐resolved microscale simulations, transferred to the homogenized cell scale and compared to empirical formulations from literature. The models are parameterized with an organic system and experimentally validated on the microscale. It resolves the real geometry of the electrode microstructure obtained by experimental image reconstruction from microtomography. It accounts for flow, mass, and coupled charge transport using Butler–Volmer kinetics. It is suitable to study power density as a function of concentration, velocity, and discharge rate. The MTC is extracted under transfer‐limiting operating conditions. Bulk and surface concentrations of active material and the reaction rate are used. The 2D homogenized cell‐scale model considers half‐cell single species transport and reduced order reaction. The extracted MTC is implemented as a function of state of charge (SOC) and velocity, distinctive for specific initial concentration and discharge rate. It is used to calculate the reaction rate for evolving species in the electrode and is investigated in a parameter study. The approach is compared to empirical formulations of the MTC based on velocity. It can be shown that the MTC is one order of magnitude higher and depends significantly on SOC. [ABSTRACT FROM AUTHOR]

Redox flow batteries (RFBs) hold great potential for large‐scale, extended‐duration stationary energy storage. Here, a novel computationally cost‐effective hydraulic‐electrical analogous model (HEAM) for fluid flow in RFBs is developed. The HEAM demonstrated that lowering the electrode compression and enhancing the channel area lowers the pump power loss independent of the flow fields and electrodes. Additionally, the HEAM helped elucidate the deficiencies of flow distribution in interdigitated flow fields (IFFs) and suggested designing wider manifolds and/or shorter channels improve the flow distribution. Moreover, the HEAM suggested shallower and/or wider channels, and more permeable electrodes enhance the flow penetration rate above the channels. Finally, the HEAM showed that the average penetration depth in the electrode above the ribs (hpen) was the critical parameter in the fluid‐flow modeling of IFFs and was inversely proportional to the permeability. Hence, there is a trade‐off between the pump power loss and hpen when configuring electrode permeability. [ABSTRACT FROM AUTHOR]

This paper defines terms such as "recycling rate" that enable the characterization of flows of battery materials and expands the terminology to accommodate the description of complex product recycling. It also estimates the maximum percentage of U.S. demand for critical elements that could be satisfied by recycling as demand continues to grow, and it defines and estimates the recycling rate for lithium-ion batteries. Finally, it clarifies the role of manufacturing scrap as the domestic U.S. supply chain is built up. It concludes that recycling will be important in the long term, but growth still requires that new material be extracted to supply additional material. [ABSTRACT FROM AUTHOR]

Redox flow batteries provide high flexibility and scalability for large-scale energy storage systems due to their safety, low cost and decoupling of energy and power. While typical flow frame designs usually assume all parts are standard, the industry can suffer from irregularity and manufacturing tolerances of cell components, such as the shape or dimensions of the flow frame and porous electrode. This paper evaluates the impact of side gaps and porosity differences of the graphite felt due to irregularity and manufacturing tolerances on the electrolyte flow in the active cell areas. A three-dimensional hydraulic model with parameterised multi-cell stack geometry has been developed in COMSOL to compare the cell velocity distributions and pressure losses of a vanadium redox flow battery with flow-through electrodes. The results indicate that the side gaps and porosity segments can result in preferential flow within low-resistance areas, leading to significantly lower flow rates for other cell areas compared with standard flow frames. Proposed countermeasures of adjusting channel locations and applying dimples protruding into the cell cavity from the flow frame show good potential to avoid stagnant zones and maintain theoretical flow rates for the active cell areas. [ABSTRACT FROM AUTHOR]

Zinc-based hybrid-flow batteries are considered as a promising alternative to conventional electrochemical energy-storage systems for medium- to large-scale applications due to their high energy densities, safety, and abundance. However, the performance of these batteries has been limited by issues such as dendritic growth and passivation of zinc anodes during charge–discharge cycling. To address this challenge, a variety of two- and three-dimensional zinc anodes have been investigated. While two-dimensional zinc anodes have been extensively studied, there has been limited investigation into three-dimensional zinc anodes for hybrid-flow batteries. This study highlights the potential of three-dimensional zinc anodes to mitigate overpotentials and improve the mass transport of active species to promote negative electrode reactions. The performance of a membraneless flow battery based on low-cost zinc and organic quinone was herein evaluated using experimental and numerical approaches. Specifically, the use of zinc fiber was shown to yield an average coulombic efficiency of approximately 90% and an average voltage efficiency of approximately 82% over the course of 100 cycles at a current density of 30 mA cm−2. These results indicate the viability of using zinc fiber anodes to improve the performance of existing hybrid-flow batteries. [ABSTRACT FROM AUTHOR]

This article presents an evaluation of the performance of a membrane-less organic-based flow battery using low-cost active materials, zinc and benzoquinone, which was scaled up to 1600 cm2, resulting in one of the largest of its type reported in the literature. The charge–discharge cycling of the battery was compared at different sizes and current densities, and its performance was evaluated under various mass transport and operating conditions. The results showed that the round-trip coulombic and voltage efficiencies were over 90% and 85%, respectively, for the laboratory-scale (1 cm2 electrode) cell, but these performances tended to deteriorate with the scaled-up (1600 cm2 electrode) cell due to inadequate mass transfer and sediment coverage of quinone, as well as the formation of a passivation film on the zinc anode. Despite this, the scaled-up batteries exhibited high coulombic and voltage efficiencies of up to 99% and 68.5%, respectively, at a current density of 10 mA cm−2. The capital cost of this system is also estimated to be several times lower than those of commercially available all-vanadium flow batteries and zinc bromide flow batteries for demand charge management applications. [ABSTRACT FROM AUTHOR]

All vanadium flow batteries (VFBs) are considered one of the most promising large‐scale energy storage technology, but restricts by the high manufacturing cost of V3.5+ electrolytes using the current electrolysis method. Here, a bifunctional liquid fuel cell is designed and proposed to produce V3.5+ electrolytes and generate power energy by using formic acid as fuels and V4+ as oxidants. Compared with the traditional electrolysis method, this method not only does not consume additional electric energy, but also can output electric energy. Therefore, the process cost of producing V3.5+ electrolytes is reduced by 16.3%. This fuel cell has a maximum power of 0.276 mW cm−2 at an operating current of 1.75 mA cm−2. Ultraviolet–visible spectrum and potentiometric titration identify the oxidation state of prepared vanadium electrolytes is 3.48 ± 0.06, close to the ideal 3.5. VFBs with prepared V3.5+ electrolytes deliver similar energy conversion efficiency and superior capacity retention to that with commercial V3.5+ electrolytes. This work proposes a simple and practical strategy to prepare V3.5+ electrolytes. [ABSTRACT FROM AUTHOR]

A pH-neutral aqueous organic redox flow battery (AORFB) is one of the most attractive redox flow battery systems due to its non-corrosivity and low-cost as well as a wider electrochemical stability potential window than the acidic and alkaline electrolytes. Herein, by incorporating two quaternary ammonium groups into an anthraquinone nucleus, a water-soluble redox-active molecule, 2,2′-((9,10-dioxo-9,10-dihydroanthracene-1,4-diyl)bis(azanediyl))bis(N,N,N-trimethylethan-1-aminium)dichloride (BDEAQCl2), was achieved that could serve as an anolyte material in pH-neutral AORFBs. The BDEAQCl2 displays a highly negative redox-potential of −0.554 V (vs. SHE) in pH-neutral aqueous electrolytes, rapid electrochemical kinetics and high aqueous-solubility (∼1.2 M in H2O) as well as low permeability. The pH-neutral AORFB with BDEAQCl2 as the anolyte and potassium ferrocyanide as the catholyte yields open-circuit voltage approaching ∼1.04 V. Long-term charge–discharge cycling measurements were conducted to determine the efficiency, capacity, and chemical stability of BDEAQCl2. Post-analysis indicates that BDEAQCl2 undergoes a hydrolytic side reaction during charge–discharge cycling, which is mainly responsible for capacity degradation. [ABSTRACT FROM AUTHOR]

Aqueous redox flow batteries (ARFBs) are a promising technology for grid‐scale energy storage, however, their commercial success relies on redox‐active materials (RAM) with high electron storage capacity and cost competitiveness. Herein, a redox‐active material lithium ferrocyanide (Li4[Fe(CN)6]) is designed. Li+ ions not only greatly boost the solubility of [Fe(CN)6]4− to 2.32 M at room temperature due to weak intermolecular interactions, but also improves the electrochemical performance of [Fe(CN)6]4−/3−. By coupling with Zn, ZIRFBs were built, and the capacity of the batteries was as high as 61.64 Ah L−1 (pH‐neutral) and 56.28 Ah L−1 (alkaline) at a [Fe(CN)6]4− concentration of 2.30 M and 2.10 M. These represent unprecedentedly high [Fe(CN)6]4− concentrations and battery energy densities reported to date. Moreover, benefiting from the low cost of Li4[Fe(CN)6], the overall chemical cost of alkaline ZIRFB is as low as $11 per kWh, which is one‐twentieth that of the state‐of‐the‐art VFB ($211.54 per kWh). This work breaks through the limitations of traditional electrolyte composition optimization and will strongly promote the development of economical [Fe(CN)6]4−/3−‐based RFBs in the future. [ABSTRACT FROM AUTHOR]

Ion conductive membranes with rapid and selective ion transport are in high demand for high‐power energy storage devices. Surface periodic Turing microstructures are scientifically compelling for their high specific surface area which can promote ion transport of membranes. Here, high‐conductivity thin Turing membranes prepared by Co2+ coordination with polybenzimidazole (OPBI) are designed and their efficient ion transport in the alkaline zinc‐iron flow battery (AZIFB) is demonstrated. In this design, the Turing structure increases the effective contact area with the electrolyte, and the 7.9 µm thickness shortens the transmembrane pathway for ions. Molecular dynamics simulations further show that Co2+‐coordination enlarges the inner‐chain volume of membranes and forms continuous water channels for rapid ion transport. The boosting effect of membranes with high ion conductivity is proven by the peak power density and energy efficiency of the AZIFB, which shows an ultrahigh peak power density of 1147 mW cm−2 and demonstrates an energy efficiency of 80% even at a high current density of 200 mA cm−2. [ABSTRACT FROM AUTHOR]

This article gives an overview of historical and present uses of lead against the backdrop of gradual realization that lead is an environmental hazard. In this paper the lead in the lead-acid batteries is investigated from the view of its present use. This use continues because there does not exist economical and practical alternative to lead for this purpose. In fact the use is still steadily increasing. This may not be a concern as it has been demonstrated that in countries with strong economies, recycling of lead from the batteries can near 100%. Here, we take a look at reality, by comparing select countries on both sides of the economic spectrum. In poorer countries, recycling suffers more on the safe and clean side of the process. Historical uses of lead are also reviewed, as well as a new approach of using lead compounds in soluble lead flow batteries. [ABSTRACT FROM AUTHOR]

Water soluble biomimetic models of Riboflavin (B2 vitamin) and Folic acid (B8 vitamin) demonstrated to be good oxidant of formic acid at various pH. Their usage as anolyte mediators in a flow fuel cell to convert formic acid (or formate) into electricity is validated with measured power densities up to 16 mW.cm− 2. These preliminary optimum conditions demonstrated a volumetric energy density of 0.68 Wh.L− 1 when operating at 5 mA.cm− 2 and neutral pH. These new conditions inspired from redox flow batteries processes permit to remove noble metals at both sides of the formate flow fuel cell. [ABSTRACT FROM AUTHOR]

Polysulfides aqueous redox flow batteries (PS‐ARFBs) with large theoretical capacity and low cost are one of the most promising solutions for large‐scale energy storage technology. However, sluggish electrochemical redox kinetics and nonnegligible crossover of aqueous polysulfides restrict the battery performances. Herein, it is found that the Co, Zn dual‐doped N‐C complex have enhanced electrochemical adsorption behaviors for Na2S2. It exhibits significantly electrochemical redox activity compared to the bare glassy carbon electrode. And the redox reversibility is also improved from ΔV = 210 mV on Zn‐doped N‐C complex to ΔV = 164 mV on Co, Zn‐doped N‐C complex. Furthermore, membrane‐electrode assembly (MEA) based on Co, Zn‐doped N‐C complex is firstly proposed to enhance the redox performances and relieve the crossover in PS‐ARFBs. Thus, an impressively high and reversible capacity of 157.5 Ah L−1 for Na2S2 with a high capacity utilization of 97.9% could be achieved. Moreover, a full cell PS‐ARFB with Na2S2 anolyte and Na4[Fe(CN)6] catholyte exhibits high energy efficiency ≈88.4% at 10 mA cm−2. A very low capacity decay rate of 0.0025% per cycle is also achieved at 60 mA cm−2 over 200 cycles. [ABSTRACT FROM AUTHOR]

The voltage and current sensors are normally necessary to estimate parameters of batteries like redox flow batteries. The estimable internal battery parameters are normally the state of charge and the available capacity of the battery in charging and discharging modes. These sensors have inherent delay and error, which result in error and delay in estimations of the battery parameters. The cost of these sensors also increases the total cost of the battery system. Therefore, this research aims to propose algorithms with a reduced number of sensors to estimate the parameters of Vanadium redox flow batteries. An algorithm is introduced in the current study in discharging mode with only a voltage sensor and without current sensor, and further, the battery current is estimated. Another algorithm is proposed in charging mode without current and voltage sensors; further, the battery current and terminal voltage are estimated. The proposed algorithms are based on the electrochemical model of the battery. The algorithm is tested in discharging mode, and the results show the Root Mean Square (RMS) error of 0.39 for the estimated battery current. In charging mode, the proposed algorithm is verified via two CC‐CV charging datasets, and the results show the RMS errors of 0.29 and 0.61, respectively for the estimated battery current. The estimation errors in charging and discharging modes are considerably low, and further, the state‐of‐charge and the capacity of the battery are also estimated. [ABSTRACT FROM AUTHOR]

A series of proton exchange membranes (PEMs) of sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) with different sulfonated graphene oxide (SGO) (0, 0.25, 0.5, 0.75, 1.0, 1.5%) were prepared for possible application in Iron‐air/flow battery. The presence of SGO in the membrane improved the water uptake of all membranes prepared and decreased the swelling ratio. The SPPO/1% w/w SGO showed good properties with higher water uptake of 44.1%, water retention of 42.48% and swelling ratio of 21.4% at 25°C. However, the 0.75% SGO exhibited the highest proton conductivity of 0.98 S/cm and better dispersion, elemental distribution, and morphology. In addition, SGO improved the thermal stability of all composite membranes. The chemical stability of all membranes remained good after 7 days in a 1 M HCL solution. The SPPO/0.75%w/w SGO showed increased proton conductivity when degradation properties were evaluated. Compared to Nafion 117, all composites showed lower iron crossover. Nafion had a high permeability of 3.03 × 10−7 cm−2/s, which is 75% higher than the 7.6 × 10−8 cm−2/s of SPPO/SGO‐1.5% and 52% higher than the 1.46 × 10−7 cm−2/s of SPPO/SGO‐0.75%. The results indicate that SGO is a good inorganic filler for the composite proton exchange membrane and stable enough for possible application in an iron‐air/flow battery. [ABSTRACT FROM AUTHOR]

Non-aqueous organic redox flow batteries (NAORFBs) suffer from rapid capacity fading mainly due to the crossover of redox-active species across the membrane. Minimizing the crossover of redox-active species through ion exchange membranes remains a complex challenge in NAORFBs. To address the crossover issue, we approached the problem through a molecular size exclusion principle designing a dimer of viologen derivative as an anode material. Coupled with N-hexyl phenothiazine as a catholyte, a static cell was demonstrated, which exhibits an excellent cycling stability (100 cycles) with an average Coulombic efficiency of 90% at 10 mA cm−2 current density. [ABSTRACT FROM AUTHOR]

High energy density and cost‐effective zinc‐iodide flow battery (ZIFB) offers great promise for future grid‐scale energy storage. However, its practical performance is hindered by poor cyclability, because of irreversible zinc plating/stripping, slow kinetics of redox reactions, and solid I2 precipitation. Herein, we report NaCl‐supported electrolyte chemistry to address these issues simultaneously. The formation of soluble chloride anions by coordination interactions between Zn2+ and Cl−, are key factor for the improvement of Zn/Zn2+ redox reversibility. While formation of soluble I2Cl− complex stabilizes ZIFB from I2 precipitation, participation of Na+ and K+ as dominant migrating carriers passing through Nafion, restricts Zn2+ migration, thus, blocking electrolyte crossover. A ZIFB with this improved electrolyte stably cycled 100 times with excellent capacity retention and energy efficiency at 20 mA cm−2, while conventional ZIFB shows the trend of capacity fade from 10th cycle onwards. These encouraging results of NaCl‐added electrolyte chemistry enlighten great prospects for high‐performance ZIFB applications. [ABSTRACT FROM AUTHOR]