Search

Vanadium flow battery (VFB) is one of the most reliable stationary electrochemical energy‐storage technologies, and a membrane with high vanadium resistance and proton conductivity is essential for manufacturing high‐performance VFBs. In this study, a two‐dimensional (2D) MFI‐type zeolite membrane was fabricated from zeolite nanosheet modules, which displayed excellent vanadium resistance (0.07 mmol L−1 h−1) and proton conductivity (0.16 S cm−1), yielding a coulombic efficiency of 93.9 %, a voltage efficiency of 87.6 %, and an energy efficiency of 82.3 % at 40 mA cm−2. The self‐discharge period of a VFB equipped with 2D MFI‐type zeolite membrane increased up to 116.2 h, which was significantly longer than that of the commercial perfluorinated sulfonate membrane (45.9 h). Furthermore, the corresponding battery performance remained stable over 1000 cycles (>1500 h) at 80 mA cm−2. These findings demonstrate that 2D MFI‐type membranes are promising ion‐conductive membranes applicable for stationary electrochemical energy‐storage devices. [ABSTRACT FROM AUTHOR]

Despite the excellent electrochemical properties of non‐functionalized 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO), its use in aqueous organic redox flow battery (AORFB) is hindered to date due to its insolubility in water. However, in this study, an unprecedented solubility of 5.6 m is demonstrated in an aqueous solution of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), which is 80 times higher than in water (0.07 m). A computational study reveals that the unique interaction between TEMPO and TFSI is essential to achieve this record solubility. TEMPO catholytes are tested in symmetric flow cells, demonstrating high capacity (23.85 Ah L−1), high material utilization (89%), and robust reversible performance with long‐term stability (low capacity fading of 0.082%/day). When paired with sulfonated viologen anolyte ((SPr2)V), an AORFB with low capacity fading over cycling (0.60%/day, 0.048%/cycle) is achieved, constituting the first example of a non‐functionalized TEMPO catholyte for AORFB. Notably, this solubilization strategy could be applied to other unexplored chemistries in aqueous electrolytes, leading to the development of new AORFBs. [ABSTRACT FROM AUTHOR]

Flow batteries are one option for future, low-cost stationary energy storage. We present a perspective overview of the potential cost of organic active materials for aqueous flow batteries based on a comprehensive mathematical model. The battery capital costs for 38 different organic active materials, as well as the state-of-the-art vanadium system are elucidated. We reveal that only a small number of organic molecules would result in costs close to the vanadium reference system. We identify the most promising candidate as the phenazine 3,3′-(phenazine-1,6-diylbis(azanediyl))dipropionic acid) [1,6-DPAP], suggesting costs even below that of the vanadium reference. Additional cost-saving potential can be expected by mass production of these active materials; major benefits lie in the reduced electrolyte costs as well as power costs, although plant maintenance is a major challenge when applying organic materials. Moreover, this work is designed to be expandable. The developed calculation tool (ReFlowLab) accompanying this publication is open for updates with new data. To guide research and implementation of aqueous organic redox flow batteries it is essential to estimate their potential costs. In this perspective, the authors present an overview of the potential cost of organic active materials for aqueous flow batteries and identify cost reduction routes. [ABSTRACT FROM AUTHOR]

Aluminum (Al) is an ideal anode material in low‐cost battery system for energy storage, with high theoretical capacities. However, the sluggish Al3+‐involved kinetics challenges the selection of common cathode materials (Al3+ intercalation or conversion). Herein, a redox‐active Fe–Cl complex serves as the liquid‐state cathode to couple with a low‐cost Al anode, which synergizes the advantages of redox flow batteries and Al rechargeable batteries. The interplay of Fe‐Cl coordinated formula and electrochemical properties are revealed for the first time. It is found that [Fe2Cl7]− molecule has a high voltage versus Al anode (1.3 V), and the novel Fe‐Al hybrid battery fulfills a capacity of 1.6 mAh cm−2 (20 Ah L−1) record high in a coin cell among Al‐based batteries. Furthermore, the energy efficiency, which is a vital parameter to evaluate the energy cost of the energy storage technology, reaches 85% (superior to most Al‐based batteries) and an average of 70% over ≈900 h cycling. Particularly, the unique air‐stable character enables normal operation of the battery assembled in ambient air. This work establishes a new application scenario for Al anode toward low‐cost large‐scale energy storage. [ABSTRACT FROM AUTHOR]

The service life of soluble lead flow batteries can be extended by periodic addition of H2O2, especially when it failed. However in first few cycles after H2O2 treatment, its coulombic efficiency is very low. To clarify it, the properties of electrode and electrolyte, and cycle performance have been systematically analyzed. It has been found that the negative/positive electrode reactions have serious overpotentials during early charging due to oxygen, which are produced and dissolved into the electrolyte during H2O2 treatment. With increasing the cycle number, the polarization degree decreases to the normal level of the battery. To solve it, oxygen is removed using argon after H2O2 treatment. The flow cell is normally recovered in the cycling performance. The average coulomb efficiency is 94.5±5.8 % for 500 times. After H2O2 treatment and oxygen removal, it exhibits a good cycling performance at the average coulomb efficiency of 93.9±4.2 % for another 500 times. [ABSTRACT FROM AUTHOR]

Neutral aqueous flow batteries with common traits of the redox flow batteries, such as the independence of energy and power, scalability and operational flexibility, and additional merits of outstanding safety and low corrosivity show great promise for storing massive electrical energy from solar and wind energy. Particularly, the ferricyanide/ferrocyanide ([Fe(CN)6]3−/4−) couple has been intensively employed as redox mediator to store energy in the catholyte ascribed to its abundance, low corrosivity, remarkable redox reversibility and stability. However, the low energy density arising from poor solubility of [Fe(CN)6]3−/4− restricts their commercial applications for energy storage systems. In this study, the practical energy density of a [Fe(CN)6]3−/4−‐based catholyte is significantly boosted from 10.5 to 92.8 Wh L−1 by combining the counter‐ion effect and the single‐molecule redox‐targeting (SMRT) reactions between [Fe(CN)6]3−/4− and Prussian blue (Fe4[Fe(CN)6]3, PB)/Prussian white (PW). Paired with concentrated K2S anolyte, we demonstrate a neutral aqueous SMRT‐based PB−Fe/S flow battery with ultra‐long lifespan over 7000 cycles (4500 h) and ultra‐low chemical cost of electrolytes in the cell as 19.26 $ kWh−1. Remarkably, under the influences of SMRT reactions in the presence of PB granules in the catholyte, the capacity after 7000 cycles of the PB−Fe/S flow battery is 181.8 % of the initial capacity without PB. [ABSTRACT FROM AUTHOR]

This article utilizes the research method of the Life Cycle Assessment (LCA) to scrutinize Lithium Iron Phosphate (LFP) batteries and Ternary Lithium (NCM) batteries. It develops life cycle models representing the material, energy, and emission flows for power batteries, exploring the environmental impact and energy efficiency throughout the life cycles of these batteries. The life cycle assessment results of different power battery recycling process scenarios are compared and analyzed. This study focuses on retired LFP batteries to assess the environmental and energy efficiency during the cascade utilization stage, based on a 50% Single-Cell Conversion Rate (CCR). The findings of the research reveal that, in terms of resource depletion and environmental emission potential, LFP batteries exhibit lower impacts compared to NCM batteries. The use of hydrometallurgy in recovering LFP power batteries leads to minimal life cycle resource consumption and environmental emission potential. During the cascade utilization stage of LFP batteries, significant benefits are noted, including a 76% reduction in mineral resource depletion (ADP e) and an 83% reduction in fossil energy depletion (ADP f), alongside notable reductions in various environmental impact factors. Simultaneously, considering the sensitivity of life cycle assessment indicators and their benefit percentages to different CCRs, it is observed that ODP exhibits the highest sensitivity to CCR changes, while evaluation indicators such as HTP, AP, and GWP show relatively lower sensitivity. This study can provide an effective reference for the establishment of an energy saving and emission reduction evaluation system of power batteries. [ABSTRACT FROM AUTHOR]

The micro-grid (μ-grid) has picked up momentum worldwide with the ability to supply cost-effective, clean, and reliable electrical power to the present-day demand. The practical μ-grids are comprised of non-conventional and conventional sources such as wind turbine generators (WTG) and diesel generators (DG). Due to the encouragement of wind power which is exceedingly sporadic in nature and thus the frequency of the μ-grid is exceedingly vulnerable due to the erratic nature of wind speed. Variations in the load demand have also added to the vulnerability of the μ-grid at distinctive moments of time. Consequently, this paper appears to be a novel plan that utilizes artificial neuro-fuzzy inference system (ANFIS) within the built frequency regulation of the μ-grid. The proposed research has been employed within the μ-grid, and the application outcomes have taken all possibilities, such as load variety at the distinctive moment of time, modification of the load demand on the μ-grid, and step alteration of the wind input. The achieved results are coordinated with a few of the most recent results, which presents the ANFIS ahead over other strategies. Although there is a probable scope for improvement which subsequently involves the fuel cell (FC) with a hydrogen aqua electrolyzer (HAE) unit, as well as a redox flow battery (RFB), that is introduced one at a time in the μ-grid and the results of μ-grid are calculated for various working conditions to show the impact that the ANFIS technology has upon storage devices with regards to the μ-grid architecture. [ABSTRACT FROM AUTHOR]

In regard to the present-day electrical power scenario, this article reports a power generation control of restructured hybrid power system with a multi-source combination of solar-thermal, geothermal, electric vehicle (EV), and conventional thermal system. Involvements of renewables and EVs in an electrical grid system with appropriate system non-linearities make the power system complex and a practical one. Such a system needs a robust controller to function optimally. In view of this, several controllers are examined for system dynamics. Performance comparison reveals the novel disturbance rejection-based fractional-order–proportional–integral–derivative (DR-foPID) as an optimal controller. Furthermore, the impact of energy storage devices (ESD) such as redox flow battery (RFB) for system dynamics enhancement are explored. To obtain the optimal performance of the linked restructured power system, the secondary controller gains and other parameters are optimized using a powerful biogeography-based krill herd (BBKH) optimization technique. The results indicate that with the proposed controller, a 38% reduction in response undershoot, a 13% reduction in overshoot, and a 8.3% reduction in settling time are exhibited. Moreover, the objective function (error) values for the proposed controller reduce to 95% with respect to other controllers. The effect of renewables and EVs on system stability is also studied. Moreover, the proposed secondary DR-foPID controller is also examined on a three-area hybrid regulated power system. Sensibility evaluation related to different alterations in nominal system parameters verifies the strength of the DR-foPID controller. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel method to classify battery slurries using echo state network (ESN) model with real-time pressure and flow rate signals during circulating channel flows. To collect the signal, a closed circuit flow system with a pump, pressure sensors, and flow rate sensors is installed. The slurries with different states are prepared by two methods: long-term circulation and dispersant content control. Sensor signals are collected while the slurries are flowing through the pipe system. The collected signals show distinctive chaotic fluctuating patterns for different slurries, which are assumed to reflect the states of the slurries. The hidden state of the ESN is generated from these collected data, which are then split into training and test data. Consequently, the ESN can effectively distinguish the slurries by the output (label). We also analyze the accuracy of the network, based on training time and output averaging time. This study demonstrates that the states of the slurries can be detected from the fluctuating flow signals. We argue that the manufacturing process of any complex fluid can be optimized with this approach. [ABSTRACT FROM AUTHOR]

Due to its adaptability in scaling up, a redox flow battery (RFB) is seen to be one of the finest options for large-scale electrical backup systems. As a result, it is feasible to create RFB systems that are both cost and performance effective. Recently, a zinc-manganese RFB that relies on Zn(s)/Zn2+(aq) and Mn2+(aq)/MnO2 redox couples has gained attention since both zinc and manganese are cheap, abundant, and eco-friendly. However, the reversibility of Mn2+(aq)/MnO2 at the positive electrode is limited by the formation of Mn3+ species upon charge/discharge (CD) cycling, resulting in severe capacity fading. Herein, this study examines the use of reducing agents as electrolyte additives to enhance the reversibility of the Mn2+(aq)/MnO2 reaction. Experimental results indicate that sulfuric acid and oxalic acid as additives can significantly improve the reversibility of the Mn2+(aq)/MnO2 reaction and the cycling stability of zinc-manganese RFBs. The acetate-based system demonstrates better reversible reaction than the sulfate-based system having more than 100 CD cycles at a current density of 10 mA/cm2. Coulombic efficiency (CE) is also seen to be higher than 90%. Overall, results lead to increased efficiency and cycling stability for zinc-manganese RFBs. [ABSTRACT FROM AUTHOR]

Flow batteries (FBs) are characterized by relatively high round trip efficiencies and benefit from high scalability. The storable energy and the power of charging and discharging the battery can be increased by increasing the size of the electrolyte storage tanks and the electrodes. Charge and discharge cycles covering many hours may be designed with flow batteries. This makes flow batteries a better choice than lithium‐ion batteries for large‐scale energy storage systems, particularly for non‐dispatchable renewable energy systems such as wind and solar, where the energy generated is highly variable and requires effective energy storage solutions. However, flow batteries also have some disadvantages, including a higher cost per unit of energy stored compared with other batteries, as well as the use of materials that in some cases are toxic, expensive, or scarce. Additionally, flow batteries cannot solve the energy storage issues over long times of a grid only supplied by non‐dispatchable electricity such as wind or solar, namely intermittency and summer to winter variability of solar, or low wind days of wind. Despite these limitations, the potential benefits of flow batteries in terms of their scalability and long cycle life, and cost‐effectiveness in case their design could be improved, making them one of the key contributors progressing towards net zero. Specifically in New Zealand, in the progress toward net‐zero the total energy supply (TES) cannot be covered by only expanding wind energy production and pumped hydro energy storage (PHES). Solar photovoltaic and likely nuclear energy supply will have to be introduced. Not all of the TES will be electrified, part of the TES will need coverage by green hydrogen fuel. Hydrogen energy storage (HES) will have to grow much more than PHES, energy storage by FBs as well as lithium‐ion batteries (LIBs) will also have to be included, given their complementarity to the other energy storage systems. [ABSTRACT FROM AUTHOR]

The current task explores automatic generation control knowledge under old-style circumstances for a triple-arena scheme. Sources in area-1 are thermal-solar thermal (ST); thermalgeothermal power plant (GPP) in area-2 and thermal-hydro in area-3. An original endeavour has been set out to execute a new performance index named hybrid peak area integral squared error (HPA-ISE) and two-stage controller with amalgamation of proportional-integral and fractional order proportional-derivative, hence named as PI(FOPD). The performance of PI(FOPD) has been compared with varied controllers like proportional-integral (PI), proportional-integralderivative (PID). Various investigation express excellency of PI(FOPD) controller over other controller from outlook regarding lessened level of peak anomalies and time duration for settling. Thus, PI(FOPD) controller's excellent performance is stated when comparison is undergone for a three-area basic thermal system. The above said controller's gains and related parameters are developed by the aid of Artificial Rabbit Optimization (ARO). Also, studies with HPA-ISE enhances system dynamics over ISE. Moreover, a study on various area capacity ratios (ACR) suggests that high ACR shows better dynamics. The basic thermal system is united with renewable sources ST in area-1 also GPP in area-2. Also, hydro unit is installed in area-3. The performance of this new combination of system is compared with the basic thermal system using PI(FOPD) controller. It is detected that dynamic presentation of new system is improved. Action in existence of redox flow battery is also examined which provides with noteworthy outcome. PI(FOPD) parameters values at nominal condition are appropriate for higher value of disturbance without need for optimization. [ABSTRACT FROM AUTHOR]

Renewable energy has significant output fluctuation. In areas with a small thermal power generation capacity, some wind power plants need to install storage batteries. Additionally, fluctuations in wind power generation output on remote islands are putting pressure on the control capacity of thermal power generation. This paper proposes a new wind speed prediction method using a wind generation power system with redox flow batteries. A fixed order of the autoregressive (AR) coefficient predicts the wind speed 60 minutes ahead, the AR model's predicted wind speed is added to the average value of the difference between the actual wind speed and the AR model's predicted wind speed, and the prediction wind speed curve is passed through a low-pass filter. As a result, the predicted power output of the power system was determined with high prediction accuracy by using the measured wind speed data, and frequency fluctuations were suppressed within an acceptable range. [ABSTRACT FROM AUTHOR]

State‐of‐the‐art applications of computational fluid dynamics (CFD) in the analysis and optimization of electrochemical reactors and redox flow batteries are reviewed. Various factors are covered which affect the efficiency of electrochemical reactors and redox flow batteries created using CFD simulation approaches, including physical and chemical factors, such as pH, treatment time, temperature, and the conductivity of the solution, as well as design elements like inter‐electrode distance and electrode materials. Different hydrodynamic variables are discussed that impact the efficiency of these systems, such as pressure distribution, velocity, tracer mass fraction, geometry, flow‐based electrochemical energy storage, and residence time distribution. Although CFD methods are reliable, more straightforward, and cost‐effective, also the limitations of CFD and the challenges are considered that remain in its development and application in electrochemical engineering. The significant progress made in the use of CFD to study electrochemical reactors and redox flow batteries and the technology's potential to improve the efficiency and sustainability of these technologies are emphasized. [ABSTRACT FROM AUTHOR]

Herein, a new semi‐organic aqueous flow battery based on a hydroxylated tetracationic viologen, 1,1′‐bis(3‐((2‐hydroxyethyl)dimethylammonio)propyl)‐[4,4′‐bipyridine]‐1,1′‐diium tetrachloride ([(DMAE‐Pr)2‐Vi]Cl4), and the ferrocene derivative, (ferrocenylmethyl)trimethylammonium chloride (FcNCl), is demonstrated. Efficiency, accessible capacity, and capacity retention of the battery are investigated at two concentrations of the active redox species: 0.1 and 0.5 mol dm−3 in 1 mol dm−3 KCl near‐neutral electrolytes. The implementation of the ferrocene‐derivative posolyte decreases the capacity fade rate by a factor of ≈4 with respect to previous work using 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPOL) as posolyte. Capacity loss is driven by crossover of the positive redox couple into the negolyte, in particular at high concentrations, indicating the need for more selective membranes and less permeable ferrocene derivatives. Discussions are supported by conductivity measurements, cell resistance, and postmortem analysis of the electrolytes using cyclic voltammetry and nuclear magnetic resonance (NMR) spectroscopy. The characterization of [(DMAE‐Pr)2‐Vi]Cl4 is expanded as a high‐energy negolyte and future scaleup requirements for aqueous organic flow batteries are informed. [ABSTRACT FROM AUTHOR]

Redox flow batteries (RFBs) have attracted significant attention as a promising electrochemical energy storage technology, offering various advantages such as grid-scale electricity production with variable intermittent electricity delivery, enhanced safety compared to metal-ion batteries, decoupled energy and power density, and simplified manufacturing processes. For this review, we exclusively focus on organic, non-aqueous redox flow batteries. Specifically, we address the most recent progress and the major challenges related to the design and synthesis of robust redox-active organic compounds. An extensive examination of the synthesis and characterization of a wide spectrum of redox-active molecules, focusing particularly on derivatives of posolytes such as quinone, nitroxyl radicals, dialkoxybenzenes, and phenothiazine and negolytes such as viologen and pyridiniums, is provided. We explore the incorporation of various functional groups as documented in the references, aiming to enhance the chemical and electrochemical stability, as well as the solubility, of both the neutral and radical states of redox-active molecules. Additionally, we offer a comprehensive assessment of the cell-cycling performance exhibited by these redox-active molecules. [ABSTRACT FROM AUTHOR]

Porous electrodes govern the electrochemical performance and pumping requirements in redox flow batteries, yet conventional carbon‐fiber‐based porous electrodes have not been tailored to sustain the requirements of liquid‐phase electrochemistry. 3D printing is an effective approach to manufacturing deterministic architectures, enabling the tuning of electrochemical performance and pressure drop. In this work, model grid structures are manufactured with stereolithography 3D printing followed by carbonization and tested as flow battery electrode materials. Microscopy, tomography, spectroscopy, fluid dynamics, and electrochemical diagnostics are employed to investigate the resulting electrode properties, mass transport, and pressure drop of ordered lattice structures. The influence of the printing direction, pillar geometry, and flow field type on the cell performance is investigated and mass transfer vs. electrode structure correlations are elucidated. It is found that the printing direction impacts the electrode performance through a change in morphology, resulting in enhanced performance for diagonally printed electrodes. Furthermore, mass transfer rates within the electrode are improved by helical or triangular pillar shapes or by using interdigitated flow field designs. This study shows the potential of stereolithography 3D printing to manufacture customized electrode scaffolds, which could enable multiscale structures with superior electrochemical performance and low pumping losses. [ABSTRACT FROM AUTHOR]

Transition metal complexes are a promising class of redox mediators for targeting redox flow batteries due to the tunability of their electrochemical potentials. However, reliable time‐efficient tools for the prediction of their reduction potentials are needed. In this work, we establish a suitable density functional theory protocol for their prediction using an initial experimental data set of aqueous iron complexes with bidentate ligands. The approach is then cross‐validated using different complexes found in the redox‐flow literature. We find that the solvation model affects the prediction accuracy more than the functional or basis set. The smallest errors are obtained using the COSMO‐RS solvation model (mean average error (MAE)=0.24 V). With implicit solvation models, a general deviation from experimental results is observed. For a set of similar ligands, they can be corrected using simple linear regression (MAE=0.051 V for the initial set of iron complexes). [ABSTRACT FROM AUTHOR]

There are a number of critical requirements for electrolytes in aqueous redox flow batteries. This paper reviews organic molecules that have been used as the redox‐active electrolyte for the positive cell reaction in aqueous redox flow batteries. These organic compounds are centred around different organic redox‐active moieties such as the aminoxyl radical (TEMPO and N‐hydroxyphthalimide), carbonyl (quinones and biphenols), amine (e. g., indigo carmine), ether and thioether (e. g., thianthrene) groups. We consider the key metrics that can be used to assess their performance: redox potential, operating pH, solubility, redox kinetics, diffusivity, stability, and cost. We develop a new figure of merit – the theoretical intrinsic power density – which combines the first four of the aforementioned metrics to allow ranking of different redox couples on just one side of the battery. The organic electrolytes show theoretical intrinsic power densities which are 2–100 times larger than that of the VO2+/VO2+ couple, with TEMPO‐derivatives showing the highest performance. Finally, we survey organic positive electrolytes in the literature on the basis of their redox‐active moieties and the aforementioned figure of merit. [ABSTRACT FROM AUTHOR]

A comprehensive study of the impact of electrode design and iron deposition mechanism on the enhancement of the capacity of an all-iron redox flow battery (AIFB) has been conducted. The research is focused on revealing the complex interaction between electrode architecture, iron deposition behaviour, and battery capacity. Using a developed experimental setup, five different electrode designs are investigated. These designs include variations in the arrangement of carbon felt (CF) and non-woven fabric (NWF) layers and critical factors affecting iron deposition. Battery charge and discharge experiments were carried out under controlled conditions, simulating practical operating regimes with a current density of 50 mA/cm² and a compression ratio of 80 %. The results demonstrate the influence of electrode design on iron deposition and, consequently, on battery capacity. The electrode configuration with two layers of CF and two layers of NWF exhibits a specific capacity exceeding 700 mA•h/cm². Analysis using scanning electron microscopy (SEM) complements the capacity determination results by providing valuable information about the spatial distribution of iron on the electrode surfaces. Furthermore, quantitative analysis using ZAF correction reveals uniform models of iron deposition on the surface of electrode E, indicating its potential for optimizing AIFB performance. This study provides a comprehensive understanding of the relationship between electrode design, iron deposition behaviour, and AIFB capacity. The results offer insights for improving electrode configurations, ultimately contributing to the development of efficient energy storage solutions. [ABSTRACT FROM AUTHOR]

The electrochemical performance of iron chromium flow batteries was improved by optimizing the electrolyte with high-entropy oxides. The influence of high-entropy oxide content in the electrolyte on the electrochemical performance of iron chromium flow batteries was studied and analyzed. Due to the synergistic effect of conductivity and electrochemical activity, the flow batteries exhibit better electrochemical performance when the electrolyte doping amount is 1 wt%. When the current density is 160 mAcm-2, the capacity of the assembled flow battery after optimizing the electrolyte is 210 mAhL-1, and the capacity after 100 cycles is 187 mAhL-1. From the calculation of adsorption energy and Gibbs free energy, it can be seen that the adsorption free energy of CuMn 2 O 4 for iron ions is -151.256 J/mol, which greatly promotes the rate of redox reaction in the iron chromium flow batteries. This work effectively improves the electrochemical performance of iron chromium flow batteries, and further provides theoretical guidance and data support for the application of high-entropy oxides in flow batteries. [ABSTRACT FROM AUTHOR]

Due to climate change and the increasing scarcity of resources, the sustainability performance of companies is increasingly becoming the focus of science and practice. Consequently, bicriteria energy-efficient production planning under price-dynamic electricity tariffs—e.g., real-time-pricing (RTP) or time-of-use (TOU)—is meanwhile well established, often fathoming the tradeoffs between electricity costs of production and another criterion such as makespan. However, tradeoffs between electricity costs and electricity consumption in general are rarely the focus of such analyses. So-called green power purchase agreements (PPAs), which are becoming increasingly popular in the European business community as a means of improving corporate sustainability performance, are also largely ignored. Thus, for the first time in the scientific literature, we put this type of electricity tariff to the test by analyzing the tradeoffs between electricity costs and electricity consumption in a lot-sizing and scheduling context. Here, we additionally consider a real-world redox flow battery storage system that may be the system of the future, which is also new to the literature on lot-sizing and scheduling. Even more: due to the complex nature of our bicriteria mixed-integer problem, we develop and present suitable heuristics. These include an energy-efficient allocation heuristic in the case of PPA and, among others, a fix-relax-and-optimize heuristic combined with a decomposition approach in the case of RTP and TOU. Ultimately, a scenario analysis demonstrates the performance of these heuristics. [ABSTRACT FROM AUTHOR]

One essential element of redox flow batteries (RFBs) is the flow field. Certain dead zones that cause local overpotentials and side effects are present in all conventional designs. To lessen the detrimental effects, a dead-zone-compensated design of flow field optimization is proposed. The proposed architecture allows for the detection of dead zones and their compensation on existing flow fields. Higher reactant concentrations and uniformity factors can be revealed in the 3D multiphysical simulation. The experiments also demonstrate that at an energy efficiency (EE) of 80%, the maximum current density of the novel flow field is 205 mA cm-2, which is much higher than the values for the previous ones (165 mA cm-2) and typical serpentine flow field (153 mA cm-2). Extensions of the design have successfully increased system EE (2.7 to 4.3%) for a variety of flow patterns. As a result, the proposed design is demonstrated to be a general method to support the functionality and application of RFBs. [ABSTRACT FROM AUTHOR]

Realizing decarbonization and sustainable energy supply by the integration of variable renewable energies has become an important direction for energy development. Flow batteries (FBs) are currently one of the most promising technologies for large-scale energy storage. This review aims to provide a comprehensive analysis of the state-of-the-art progress in FBs from the new perspectives of technological and environmental sustainability, thus guiding the future development of FB technologies. More importantly, we evaluate the current situation and future development of key materials with key aspects of green economy and decarbonization to promote sustainable development and improve the novel energy framework. Finally, we present an analysis of the current challenges and prospects on how to effectively construct low-carbon and sustainable FB materials in the future. [ABSTRACT FROM AUTHOR]

Aqueous organic redox flow batteries (AORFBs) are an emerging technology for fire safe grid energy storage systems with sustainable material feedstocks. Yet, designing organic redox molecules with the desired solubility, viscosity, permeability, formal potential, kinetics, and stability while remaining synthetically scalable is challenging. Herein, the adaptability is demonstrated of a single‐step, high‐yield hydrothermal reaction for nine viologen chloride salts. New empirical insights are gleaned into fundamental structure–property relationships for multiobjective optimization. A new asymmetric Dex‐DiOH‐Vi derivative showcases an enhanced solubility of 2.7 m with minimal tradeoff in membrane permeability. With a record viologen cycling volumetric capacity (67 Ah L−1 anolyte theoretical), Dex‐DiOH‐Vi exhibits 14‐d of stable cycling performance in anolyte‐limiting AORFB with no crossover or chemical degradation. This work highlights the importance of designing efficient synthetic approaches of organic redox species for molecular engineering high‐performance flow battery electrolytes. [ABSTRACT FROM AUTHOR]

Aqueous flow batteries are considered very suitable for large‐scale energy storage due to their high safety, long cycle life, and independent design of power and capacity. Especially, zinc‐iron flow batteries have significant advantages such as low price, non‐toxicity, and stability compared with other aqueous flow batteries. Significant technological progress has been made in zinc‐iron flow batteries in recent years. Numerous energy storage power stations have been built worldwide using zinc‐iron flow battery technology. This review first introduces the developing history. Then, we summarize the critical problems and the recent development of zinc‐iron flow batteries from electrode materials and structures, membranes manufacture, electrolyte modification, and stack and system application. Finally, we forecast the development direction of the zinc‐iron flow battery technology for large‐scale energy storage. [ABSTRACT FROM AUTHOR]

Fossil fuels greenhouse gases emissions for remote and island electrification and transport application have led to the study of hybrid renewable energy systems. These comprise renewable energy generation units (Solar Photovoltaics, Wind Turbines, etc.), storage units (Battery, Hydrogen Storage Tanks), and other components (compressors, inverters, pressure regulators, etc.). Component selection is key for reducing the negative effects on the system's cost, reliability, environmental, and social impacts, and reaching its full potential. The aim of this study is to review recent advancements in the architecture sizing and energy management strategies of hybrid renewable energy systems, considering various locations and applications, and based on technical, reliability, environmental, and social factors. The employed optimization formulation frameworks based on various linear and non-linear objective functions, equality and non-equality constraints, and decision variables are also investigated. Optimization methods including tools and solvers used to solve complex hybrid renewable energy system optimization problems are also explored. The study's important results include identifying various components that could help optimize the performance of hybrid renewable energy systems. Additionally, the study highlights the potential of optimization-based energy management strategies to enhance the reliability and efficiency of these systems. Trends in the studies of the implementation of grid-integrated or off-grid hybrid renewable energy systems in remote, island, or urban locations are highlighted. It could also aid in the development of methodologies for designing sustainable energy infrastructure that is resilient and environmentally friendly. Furthermore, the study could inspire future research that addresses the identified research challenges and areas of interest. [ABSTRACT FROM AUTHOR]

The production of renewable energy from solar panels and windmills is rapidly increasing these years. However, one of the biggest hurdles that need to be overcome in the green transition is cost‐efficient energy storage to reach the full exploitation of their potential. A promising energy storage technology is redox flow batteries (RFBs), particularly using quinones as electron carriers. The prototypes of quinone batteries have been derived from crude oil, which unfortunately falls short of the ambition of sustainable energy production purely from renewable sources. It is well‐known that filamentous fungi have a great capacity for quinone production. and the first RFB with a fungal‐produced quinone was recently generated as a proof‐of‐concept. Here, we give our opinion and perspectives on which challenges need to be solved before an RFB with fungal‐produced quinones can be applied in the green transition. [ABSTRACT FROM AUTHOR]

Non‐fluorinated ion exchange membranes with high proton selectivity and conductivity are sought as separators for vanadium redox flow batteries (VRFB) to substitute the typically used perfluorosulfonic acid (PFSA) polymer membranes. Polybenzimidazole based membranes offer a promising non‐fluorinated alternative due to their excellent thermomechanical properties, low vanadium crossover, and ionic conductivity in acidic media. In this work, a series of polybenzimidazole‐polyvinylchloride polymer blends were cast and decorated with different quaternary ammonium functionalities. The polymer blends were systematically studied with respect to the blend composition and chemical structure of the quaternary ammonium groups. Assessment of relevant membrane properties for use in an aqueous acidic flow battery was conducted through a combination of VRFB single cell testing, permeability measurements, water/electrolyte uptake, and infrared spectroscopy. The blend with a polybenzimidazole content of 90 % decorated with DABCO (1,4‐diazabicyclo[2.2.2]octane) was found to combine low polarization resistance with low swelling and high stability. The performance was found to be similar to that of a benchmark polybenzimidazole membrane despite being three times thicker. This led to the conclusion that quaternary ammonium functionalized polybenzimidazole‐polyvinylbenzylchloride systems is an excellent candidate for further modification or fabrication of thinner membranes to further reduce the membrane resistance without compromising on vanadium blocking properties. [ABSTRACT FROM AUTHOR]

For this article, we propose a power management controller for a hybrid system; the study of the model proposed includes a fuel cell, a PV, a lithium-ion battery, and a catalyst to produce Hydrogen. Furthermore, the control system of the active power uses the Stateflow approach. This study gives an easy scheme of the power management controller and a practical code to implement the target hardware. The state flow controller is used to equalize the energy flow inter the system's elements. At first, to simulate these elements, MATLAB Simulink software is used, then all modes of operation of this controller using Stateflow are detailed. This paper showed that the management of the power source flow could use the Stateflow approach as an efficient alternative means. [ABSTRACT FROM AUTHOR]

Copyright of Kirkuk Journal of Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work demonstrates an improved cell design of a zinc–silver/air hybrid flow battery with a two‐electrode configuration intended to extend the cycling lifetime with high specific capacities up to 66.7 mAh cm−2 at a technically relevant current density of 50 mA cm−2. A hybrid approach combines the advantages of both zinc–air and zinc–silver batteries enabling enhanced energy efficiency while maintaining high battery capacity. A pulsed charging protocol is applied to maintain compact zinc deposits on a porous copper foam, which extends capacity compared to a planar surface. The single‐cell battery is successfully operated for 216 cycles (t = 756.10 h) after an interruption after 47 cycles (t = 163.20 h), which reveals that the gas‐diffusion electrode aging is the first cycling lifetime limitation. At the end of operation, an accumulation of zinc in the inlet zone of the cell sets a second‐lifetime limitation driven by progressively shorter discharge associated again with the aging of the gas‐diffusion electrode. Despite zincate ion depletion and the final irregular deposition, postmortem analysis shows no dendrites, only the compact zinc structure, confirming the benefits of a pulsed current. Developments within this path can further raise the technological prospects of the zinc–silver/air battery. [ABSTRACT FROM AUTHOR]

Vanadium redox flow batteries are gaining great popularity in the world due to their long service life, simple (from a technological point of view) capacity increase and overload resistance, which hardly affects the service life. However, these batteries have technical problems, namely in balancing stacks with each other in terms of volumetric flow rate of electrolyte. Stack power depends on the speed of the electrolyte flow through the stack. Stacks are connected in parallel by electrolytes to increase battery power. If one of the stacks has a lower hydrodynamic resistance, the volume of electrolytes passing through it increases, which leads to a decrease in the efficiency of the remaining stacks in the system. This experimental study was conducted on a 10 kW uninterruptible power supply system based on two 5 kW stacks of all-vanadium redox flow batteries. It was demonstrated that forced flow attenuation in a circuit with low hydrodynamic resistance leads to an overall improvement in the system operation. [ABSTRACT FROM AUTHOR]

A thermal management system for lithium-ion batteries is an essential requirement for electric vehicle operation due to the large amount of heat generated by these cylindrical batteries during fast charging/discharging. Previously, researchers have focused mostly on pouch and prismatic cells with heat pipes arranged in the horizontal direction. The current study introduces a novel vertically-oriented heat-pipe-based hybrid cooling battery thermal management system (BTMS) that numerically evaluates the thermal performance of the cylindrical batteries and the flow pattern within the cooling channel at C rates as high as 8C. The model was experimentally validated using five round heat pipes in a vertical orientation utilizing the effect of gravity to assist condensate flow through the heat pipe. The heat pipes were arranged in a staggered pattern to improve the overall heat transfer performance by means of forced convective cooling. This design allowed for maximizing the heat transfer process despite the lack of contact between the cylindrical-shaped batteries and round-shaped heat pipes. During this study, the temperatures of the evaporator end and the condenser end of the heat pipes and battery surfaces were monitored, and the thermal performances of the system were determined at varying inlet cooling liquid temperatures (15, 20, 25 °C) and high rates of 4C and 8C. Representatively, the proposed hybrid BTMS could maintain a maximum battery surface temperature of around 64 °C and a temperature difference between cells under 2.5 °C when the inlet velocity was 0.33 L/min and the cooling liquid temperature was 25 °C. The high temperatures reached the fourth and fifth heat pipes because they are part of the backflow design and are affected by backflow temperature. Nevertheless, the current design shows that the proposed system can maintain battery surface temperatures well within 5 °C. [ABSTRACT FROM AUTHOR]

TiO2 photoelectrode has become an attractive platform due to its excellent photoelectric performance and has been widely used in battery, photocatalysis, and other photoelectric fields. However, when the TiO2 photoelectrode is used in solar flow batteries, the small photo-charging current is a potential problem, which will extend the charging process and lower the battery utilization efficiency. To address this issue, Cu2O is introduced to the surface of the TiO2 photoelectrode, and Cu2O-TiO2 forms a heterojunction to improve battery performance in this work. The formation mechanism of Cu2O-TiO2 is revealed and utilized to deposit Cu2O on pre-treated FTO glass covered with TiO2 films using electrochemical deposition (ECD). The photoelectrochemical properties of Cu2O-TiO2 photoelectrodes are characterized using XRD, UV-vis diffuse reflectance spectroscopy, XPS, and electrochemical characterizations. The successful deposition of Cu2O on the surface of TiO2 photoelectrode is confirmed, and the UV-vis spectroscopic test results show that the incorporation of Cu2O enhances and broadens the absorption and utilization of sunlight in the UV range by the TiO2 photoelectrode. Furthermore, the electrochemical test results manifest that the Cu2O-TiO2 photoelectrode possesses a higher carrier concentration under illumination conditions due to the formation of a heterojunction. Finally, a 30 min unbiased photocharging test demonstrates that the Cu2O-TiO2 photoelectrode charges in a current density of 425.03 μA·cm−2, indicating an increased photogenerated carrier concentration and a decreased photogenerated carrier recombination rate, which results from the enlarged doping concentration and improved charge transfer process at the electrolyte/semiconductor interface due to the incorporation of Cu2O. Compared with the current density of 116.21 μA·cm−2 for the bare TiO2 photoelectrode, the performance can be improved by over 365%. [ABSTRACT FROM AUTHOR]

Highlights: A comprehensive discussion of the recent advances in zinc–bromine rechargeable batteries with flow or non-flow electrolytes is presented. The fundamental electrochemical aspects including the key challenges and promising solutions in both zinc and bromine half-cells are reviewed. The key performance metrics of ZBRBs and assessment methods using various ex situ and in situ/operando techniques are also discussed. Zinc–bromine rechargeable batteries (ZBRBs) are one of the most powerful candidates for next-generation energy storage due to their potentially lower material cost, deep discharge capability, non-flammable electrolytes, relatively long lifetime and good reversibility. However, many opportunities remain to improve the efficiency and stability of these batteries for long-life operation. Here, we discuss the device configurations, working mechanisms and performance evaluation of ZBRBs. Both non-flow (static) and flow-type cells are highlighted in detail in this review. The fundamental electrochemical aspects, including the key challenges and promising solutions, are discussed, with particular attention paid to zinc and bromine half-cells, as their performance plays a critical role in determining the electrochemical performance of the battery system. The following sections examine the key performance metrics of ZBRBs and assessment methods using various ex situ and in situ/operando techniques. The review concludes with insights into future developments and prospects for high-performance ZBRBs. [ABSTRACT FROM AUTHOR]

Aqueous redox flow batteries (RFBs) have attracted significant attention as energy storage systems by virtue of their inexpensive nature and long‐lasting features. Although all‐vanadium RFBs exhibit long lifetimes, the cost of vanadium resources fluctuates considerably, and is generally expensive. Iron–chromium RFBs take advantage of utilizing a low‐cost and large abundance of iron and chromite ore; however, the redox chemistry of CrII/III generally involves strong Jahn–Teller effects. Herein, this work introduces a new Cr‐based negolyte coordinated with strong‐field ligands capable of mitigating strong Jahn–Teller effects, thereby facilitating low redox potential, high stability, and rapid kinetics. The balanced full‐cell configuration features a stable lifetime of 500 cycles with energy density of 14 Wh L−1. With an excessive posolyte, the full‐cell can attain a high energy density of 38.6 Wh L−1 as a single electron redox process. Consequently, the proposed system opens new avenues for the development of high‐performance RFBs. [ABSTRACT FROM AUTHOR]

In recent years, there has been considerable interest in the potential of quinones as a promising category of electroactive species for use in aqueous organic redox flow batteries. These materials offer tunable properties and the ability to function as both positive and negative electrolytes, making them highly versatile and suitable for a range of applications. Ongoing research has focused on improving the stability, solubility, and performance of quinones, with a particular emphasis on the creation of stable negolytes. The pairing of these advancements with alternate chemistries has created new prospects for commercial applications. However, challenges persist regarding the stability of quinones in high‐potential electrolytes and the limited number of viable quinones available. Despite these obstacles, significant strides have been made, and the potential for quinones to revolutionize energy storage technology is vast. This review article provides a comprehensive overview of recent progress in this area, with a specific focus on redox potential, solubility, and stability, and offers valuable insights into the future of quinone‐based aqueous organic redox flow batteries. [ABSTRACT FROM AUTHOR]

While aqueous organic redox flow batteries (RFBs) represent potential solutions to large-scale grid storage, their electrolytes suffer from short lifetimes due to rapid degradation. We show how an understanding of these degradation processes can be used to dramatically improve performance, as illustrated here via a detailed study of the redox-active biomolecule, flavin mononucleotide (FMN), a molecule readily derived from vitamin B2. Via in-situ nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) we identify FMN hydrolysis products and show that these give rise to the additional plateau seen during charging of an FMN-cyanoferrate battery. The redox reactions of the hydrolysis product are not reversible, but we demonstrate that capacity is still retained even after substantial hydrolysis, albeit with reduced voltaic efficiency, FMN acting as a redox mediator. Critically, we demonstrate that degradation is mitigated and battery efficiency is substantially improved by lowering the pH to 11. Furthermore, the addition of cheap electrolyte salts to tune the pH results in a dramatic increase in solubility (above 1 M), this systematic improvement of the flavin-based system bringing RFBs one step closer to commercial viability. Aqueous organic redox-flow batteries are known to suffer capacity loss via degradation of the redox-active species. Here, the authors use in situ methods to study the electrolyte flavin mononucleotide, identifying a redox mediator mechanism that mitigates capacity loss and a route to prevent its degradation. [ABSTRACT FROM AUTHOR]

The development of water‐soluble redox‐active molecules with high potentials is one of the effective ways to enhance the energy density of aqueous organic flow batteries (AOFBs). Herein, a series of promising N‐substituted benzidine analogues as water‐soluble catholyte candidates with controllable redox potentials (0.78–1.01 V vs. standard hydrogen electrode (SHE)) were obtained by the molecular engineering of aqueous irreversible benzidines. Theoretical calculations reveal that the redox potentials of these benzidine derivatives in acidic solution are determined by their electronic structure and alkalinity. Among these benzidine derivatives, N,N,N′,N′‐tetraethylbenzidine(TEB) shows both high redox potential (0.82 V vs. SHE) and good solubility (1.1 M). Pairing with H4[Si(W3O10)4] anolyte, the cell displayed discharge capacity retention of 99.4 % per cycle and a high coulombic efficiency (CE) of ∼100 % over 1200 cycles. The stable discharge capacity of 41.8 Ah L−1 was achieved at the 1.0 M TEB catholyte with a CE of 97.2 % and energy efficiency (EE) of 91.2 %, demonstrating that N‐substituted benzidines could be promising for AOFBs. [ABSTRACT FROM AUTHOR]

Zinc‐based flow batteries are promising for distributed energy storage due to their low‐cost and high‐energy density advantages. One of the most critical issues for their practical application is the reliability that results from the heterogeneous zinc deposition and dead zinc from falling off the electrode. Herein, nitrogen‐doped carbon nanotubes (N‐CNTs)‐based composite membrane through a facilely partially embedded method is reported to enable a dendrite‐free alkaline zinc‐based flow battery. The results indicate that the electrically conductive N‐CNTs functional layer can enhance the transport dynamics of charge carriers and homogenize electric field distribution in membrane–electrode interface, which induces the initial nucleation of metallic zinc from the carbon felt electrode to N‐CNTs functional layer and further achieve a uniform and dense plating of metallic zinc in alkaline media. Thus, the engineered membrane enables a stable alkaline zinc–iron flow battery performance for more than 350 h at a current density of 80 mA cm−2. Moreover, an energy efficiency of over 80% can be afforded at a current density of 200 mA cm−2. The scientific finding of this study provides a new strategy on composite membranes design and their capability to adjust the plating of metallic zinc in alkaline media. [ABSTRACT FROM AUTHOR]

Redox-active organic/polymeric materials and carbon/small-sulfur composites are promising electrode materials for developing affordable, lightweight, and sustainable batteries because of their low cost, abundance, low carbon footprint, and flexible structural tunability. This feature article summarized the key aspects of the research related to organic batteries and Li–S batteries (LSBs) based on organic/polymeric/sulfur materials for next-generation sustainable energy storage. An in-depth discussion for organic electrode materials in alkali-ion, multivalent metal, all-solid-state, and redox flow batteries is provided. State-of-the-art LSBs under high mass loading and lean electrolyte conditions for practical applications is also covered. The challenges, reaction mechanisms, strategies, approaches, and developments of organic batteries and LSBs are discussed to offer guidance for rational structure design and performance optimization. This feature article will contribute to the development and commercialization of affordable, lightweight, and sustainable batteries. [ABSTRACT FROM AUTHOR]

Load frequency control (LFC) plays a crucial rule in matching the power generation with variable power demand, and hence, maintains the system frequency and tie-line power to its esteemed value. Further, most of the countries are dependent on thermal power plants to meet the electrical energy requirement, and hence, LFC strategies are available for these types of power plants only. As the world is moving to generate electrical energy via cleaner sources to reduce harmful environmental pollutants, and hence, hydro power are one of the well-developed and cleanest sources of electrical energy. Subsequently, this article shows up a novel LFC design for hydro-hydro system based on joint endeavors of fuzzy logic with PID viably optimized through particle swarm optimization (PSO) coming into a new and robust Fuzzy-PSO-PID for LFC. At to beginning with, the result of Fuzzy-PSO-PID is evaluated for step load alteration, and the outcomes of Fuzzy-PSO-PID are matched with recently published outcomes of LFC with regards to values of PID, error minimization, and graphical results. In any case, still, there may be a scope of LFC upgrade in Fuzzy-PSO-PID due to higher responding time of turbines used in hydro-hydro plants and subsequently, the combinations of storage devices such as ultra-capacitor (UC) in each zone and UC with redox flow battery combination are used to improve the LFC and the application outcomes are analyzed again and uncover considering the step load alteration, non-linearity, load pattern, and parametric modification to see the benefits of the proposed work for hydro-hydro LFC. [ABSTRACT FROM AUTHOR]

Lithium-based nonaqueous redox flow batteries (LRFBs) are alternative systems to conventional aqueous redox flow batteries because of their higher operating voltage and theoretical energy density. However, the use of ion-selective membranes limits the large-scale applicability of LRFBs. Here, we report high-voltage membrane-free LRFBs based on an all-organic biphasic system that uses Li metal anode and 2,4,6-tri-(1-cyclohexyloxy-4-imino-2,2,6,6-tetramethylpiperidine)-1,3,5-triazine (Tri-TEMPO), N-propyl phenothiazine (C3-PTZ), and tris(dialkylamino)cyclopropenium (CP) cathodes. Under static conditions, the Li||Tri-TEMPO, Li||C3-PTZ, and Li||CP batteries with 0.5 M redox-active material deliver capacity retentions of 98%, 98%, and 92%, respectively, for 100 cycles over ~55 days at the current density of 1 mA/cm2 and a temperature of 27 °C. Moreover, the Li||Tri-TEMPO (0.5 M) flow battery delivers an initial average cell discharge voltage of 3.45 V and an energy density of ~33 Wh/L. This flow battery also demonstrates 81% of capacity for 100 cycles over ~45 days with average Coulombic efficiency of 96% and energy efficiency of 82% at the current density of 1.5 mA/cm2 and at a temperature of 27 °C. Redox flow batteries are promising energy storage systems but are limited in part due to high cost and low availability of membrane separators. Here, authors develop a membrane-free, nonaqueous 3.5 V all-organic lithium-based battery and demonstrate its operation in both static and flow conditions. [ABSTRACT FROM AUTHOR]

The identity of active sites for redox reactions within vanadium redox flow batteries (VRFBs) isstill controversial despite decades of research into the matter. Here, we use density functional theory to examine the premise of selected surface functional groups as active sites and provide mechanistic insights into the reaction pathway for the positive electrode reaction. The adsorption of electroactive species on phenol and carbene‐like edge carbon sites was compared using model aromatic clusters. Phenol groups were not favorable sites for the chemisorption of VO2+ in either V‐down or O‐down approach In contrast, carbene‐like edge carbon sites readily adsorbed VO2+ via an oxygen‐down approach, mimicking gas‐phase CO2 adsorption mechanisms. Subsequent steps to complete the reaction pathway are a series of proton adsorptions and reaction products desorption. The rate‐determining step for a reaction pathway using an edge site is VO2+ desorption step with a Gibbs energy of activation of +84 kcal mol−1. [ABSTRACT FROM AUTHOR]

Flow batteries (FBs) are one of the most promising strategies for large‐scale energy storage, in which the flow rates of electrolytes are critical to the redox reaction efficiency. However, low‐power and energy‐efficient strategies to effectively monitor and adjust the flow rates of FBs are great challenges. Here, a liquid metal based thin‐film and self‐powered triboelectric sensor (LM‐TS) to monitor and adjust the real‐time electrolyte flow rates in FBs is developed. By integrating the LM‐TS with a peristaltic pump (flow rate control unit in FB), the flow rates of electrolytes can be converted into readable electrical output signals. Furthermore, a logical and a control module are adopted to adjust the flow rates of electrolytes automatically after receiving those electrical signals, which are available to guarantee the optimal working condition of FBs. Benefiting from the high conductivity and outstanding ductility of ultrathin LM film, the self‐powered LM‐TS is endowed with high sensitivity, short response time (9.1 ms), and remarkable cyclic stability (> 20000 cycles) without affecting the normal operation of FBs. This is the first prototype of self‐powered adjustment sensor for FBs, which is readily extended to scaled‐up FB equipment for intermediate trial and large‐scale energy‐storage demonstration. [ABSTRACT FROM AUTHOR]

N‐functionalized pyridinium frameworks derived from the three major vitamers of vitamin B6, pyridoxal, pyridoxamine and pyridoxine, have been screened computationally for consideration as negative electrode materials in aqueous organic flow batteries. A molecular database including the structure and the one‐electron standard reduction potential of related pyridinium derivatives has been generated using a computational protocol that combines semiempirical and DFT quantum chemical methods. The predicted reduction potentials span a broad range for the investigated pyridinium frameworks, but pyridoxal derivatives, particularly those involving electron withdrawing substituents, have potentials compatible with the electrochemical stability window of aqueous electrolytes. The stability of radicals formed upon one‐electron reduction has been analyzed by a new computational tool proposed recently for large‐scale computational screening. [ABSTRACT FROM AUTHOR]