Flow Battery Technology Research Articles

Optimal Planning of Standalone Rural Microgrid With Effective Dispatch Strategies and Battery Technology

ABSTRACTMicrogrids are a viable substitute for traditional power systems because they may deliver cleaner, more dependable, affordable power with fewer losses. However, the microgrid's performance is impacted by the variable nature of renewable energy sources. Battery storage is a crucial component of microgrid planning since it defines the system's techno‐economic feasibility. A standalone rural microgrid is designed in the current study, employing three distinct battery types: lithium‐ion, lead acid, and zinc‐bromine flow. The suggested microgrid's techno‐economic analysis employs three distinct dispatch mechanisms, that is, cycle charging, load flow, and complete dispatch. The case study of the suggested framework is carried out in Lucknow (India). The system comprises PV/battery/wind energy system/diesel and battery. The simulation results suggest that the optimal system with the least electrification cost is 0.113 $/kWh using complete dispatch strategies and a zinc‐bromine battery. It has 206 kWh zinc‐bromine flow batteries, a 10 kW converter, a 20 kW PV, a 13‐kW diesel generator, and a Combined dispatch strategy. The system's net present cost per unit cost of energy is $40 275 and 0.113 $/kWh for the chosen region, respectively. Compared to the other two battery technologies for hybrid systems, the zinc‐bromine flow battery technology is also shown to be the most environmentally friendly. Among the three battery technologies available, zinc‐bromine flow is best used in a particular location's hybridized operation.

Mapping the flow: Knowledge development and diffusion in the global innovation system of flow battery technology

Redox flow batteries (RFB) are receiving increasing attention as promising stationary energy storage systems. However, while first innovation activities in this technological field date back to the 1950s, the commercialization and diffusion rates of RFB technology have remained limited. Apart from technological challenges, the lack of a functioning innovation system is one of the main barriers to mainstream this technology. Here, we carried out a comprehensive bibliometric analysis of the RFB research field to shed systematic light on a core aspect of innovation systems - the production of knowledge. Based on the analysis of 4,872 papers published in the years 1981–2021, we reveal developments over time, describe the geographical distribution of research activities, and explore collaboration networks as well as emerging lines of research. Overall, our study allows for strengthening the RFB innovation system by providing the foundation for aligning a scattered research field, identifying needs for technology development, and fostering collaboration and synergy creation.

Degradation and Protection Mechanisms of Platinum-Based Catalysts in Hydrogen-Bromine Flow Batteries

Cost-effective and large-scale electrical energy storage is pivotal in facilitating the assimilation of renewable energy sources like wind and solar, as well as enhancing the resilience of the future electricity grid. Hydrogen-Bromine flow battery (HBFB) technology is a candidate for a low cost and flexible system. Bromine is abundantly available on Earth. In addition, the reaction between bromine and bromide is characterized by rapid kinetic properties, thus no platinum group metals (PGMs) are required on the bromine side of the cell as a catalyst to sustain a high current density of >500 mA/cm2. Moreover, hydrogen-based flow batteries can be coupled with hydrogen pipelines & electrolyzers to boost the integration of new energy systems.However, the selection of bromine brings technical challenges that can limit the commercial deployment of such HBFB systems. We have proven a lifetime of more than 8,000 hours of continuous cycling at the lab scale. During this proof-of-concept validation, we found that bromine species (liquid) crosses through a dense proton exchange membrane to the hydrogen side of the cell. On this side, a Platinum-based catalyst layer is present to promote hydrogen oxidation-evolution reactions (HOR/HER). The crossover liquid interacts first with the catalyst layer before it crosses through the gas diffusion layer and exits the membrane electrode assembly (MEA). Chemical interactions between the crossover liquid and the catalyst can lead to catalyst migration, Ostwald ripening, or even permanent catalyst dissolution. This is a concern and must be addressed. The root of this concern is that the Platinum-based catalyst is highly reactive (high surface-active area respective to the loading, m2/g), and also the crossover bromine species are likely corrosive (highly acidic, pH <0, and contain polybromides). Therefore, chemical interaction cannot be fully avoided. Nevertheless, the cathodic protection reduces this interaction, which prolongs the lifetime of the electrochemical system. The cathodic protection consists of an applied positive potential and the presence of hydrogen gas on the catalyst nanoparticles. The catalyst degradation together with cathodic protection needs to be better understood and quantified to gain the confidence that the HBFB system fundamentally can last for more than 10 years of continuous operation. This confidence is essential to deliver a minimum viable product (MVP) of HBFB, e.g. on a 100 kW – 1 MW scale, to the market.To address the aforementioned scientific challenges, this work studies the liquid crossover phenomena and the interaction between the crossover liquid and platinum-based catalyst in depth. Liquid crossover rate, concentration, and bromine speciation from working electrochemical cells are quantified at different states of charge (SoCs) and different modes (charge or discharge). This information is used to set up further ex-situ experiments to understand and determine the chemical interaction between crossover liquid and catalyst. Electrochemical ex-situ tests for Pt dissolution measurement such as determination of the electrochemically active surface area (ECSA), are performed before and after soaking hydrogen electrodes in different concentrations of hydrogen bromide solutions that mimic the crossover liquid. These results are then combined with in-situ tests, where the catalyst dissolution rate is quantified in actual crossover liquid and electrolyte by the inductively coupled plasma (ICP) method. Finally, post-mortem analyses on the catalyst layer based on scanning electron microscopy (SEM), transmission electron microscopy (TEM), etc. will give quantitative and qualitative insights into the impact of cycling and liquid crossover on the catalyst performance, morphology, crystal structure, and chemical state of the catalyst.The goal of this work is to quantify the extrapolated lifetime of HBFB systems within a high confidence level. Then conclude if this technology is fundamentally sound and can be scaled up to an MVP to be deployed to the market. As a low cost energy storage solution, the HBFB’s lifetime should be at least 5 years and preferably more than 10 years to attract commercial attention. Moreover, the collective knowledge gained in this work about the catalyst degradation mechanisms will spark further ideas and guide the next generation of the system and its operating conditions to reduce the degradation rate. These presented ideas may also shine a light on catalyst degradation and protection mechanisms in other electrochemical applications that operate in corrosive conditions.Figure 1 Membrane electrode assembly architecture, incl. electrochemical reactions and species transport phenomena in the charge and discharge modes. Figure 1

(Digital Presentation) Innovative Cylindrical Cell Design for Sustainable Static Zinc-Bromine Battery Technology

Zinc-bromine flow batteries (ZBFBs) are suitable for large-scale stationary energy storage applications due to their scalability, flexibility, safety, and sustainability [1, 2]. However, the ZBFBs' efficiency is compromised by the heavy accessories and pumps involved in flowing electrolytes on the electrode surface [3]. Because of their heavy weight and other accessories, ZBFBs can only be used for large energy storage systems. Further research is required to expand the application fields of the small-scale static zinc-bromine battery, including portable applications. Therefore, we proposed an innovative cylindrical cell design for a static zinc-bromine battery with a non-flowing liquid electrolyte that offers substantial improvements over existing zinc-bromine flow battery technology. This design aims to enhance coulombic efficiency and energy density, particularly targeting portable applications such as electric vehicles and E-bikes. Our battery configuration involves electrodes (carbon felt and carbon sponge) separated by a microporous separator for ionic migration. The liquid electrolyte, comprising zinc bromide, zinc chloride, potassium chloride, and 1-ethyl-1-methyl pyrrolidinium bromide, facilitates the electrochemical reaction. The battery's electrochemical process involves the plating of zinc ions at the anode and the formation of a bromine complex at the cathode during charging, with reverse reactions during discharge. The entire proposed static battery configuration is made of recyclable Polytetrafluoroethylene (PTFE) polymer, ensuring environmental sustainability. The anode comprises highly conductive graphene-coated carbon felt, while the cathode employs a graphene-coated high-surface-area carbon fiber sponge. Here, we aim to provide more details on the manufacturing methods for the assembly, emphasizing slurry preparation, electrode modification, and electrolyte concentration to achieve enhanced battery performance. With 96 % coulombic efficiency and stable cyclability, the present technology outperforms the existing commercial zinc-bromine battery. Comparative analyses with conventional zinc-bromine flow batteries highlight the advantages of this static battery, including its compactness, reduced weight, and potential for higher energy density. This research represents a significant step towards developing static zinc-bromine batteries suitable for widespread use in portable applications, surpassing the limitations of current zinc-bromine battery technologies.

Energy Storage Capacity Utilization in Redox Flow Batteries

Redox flow batteries (RFBs) are predicted to be a major contributing technology in the need for four-to-ten-hour energy storage. Other energy storage technologies, such as lithium-ion batteries, provide well-documented performance indicators such as efficiency and especially energy storage capacity utilization. While redox flow batteries are compared similarly based on cost and round-trip efficiency, they often neglect a comparison of their operational energy storage capacity utilization. The breakdown of operational losses that represent the current state of operation for RFBs are pivotal to further compare the development of these technologies to the standard of other electrochemical storage devices. Quantifying the current state-of-the-art in relation to the theoretical potential of RFBs allows us to assess the extent of development required to enhance their effectiveness in contributing to future energy storage goals.In this work, we set out to depict the operational energy storage density (W-h L-1) of various redox flow battery technologies based on consideration from experimental parameters and results from literature as key inputs. After reviewing five RFBs including the all-vanadium RFB, Hydrogen-Bromine RFB, All-Iron RFB, Zinc-Bromine RFB, and the Iron-Chromium RFB, results indicate that the VRFB is the most developed technology attaining around 60% of its theoretical energy storage density. While the Zinc-Bromine RFB has approximately the largest theoretical energy storage density (due to its high electroactive species concentration and standard potential difference), it is currently only able to operate at about a lowly 15% of it, dependent on its operational current density. We also assess the volumetric footprint for each RFB electrolyte system by considering a 6 MWh (6 MW, 1 hr) system. This assessment considers how large the electrolyte component of the RFB would be for operation. The Hydrogen-Bromine RFB would require electrolyte tanks to be more than 1600 m3 based on operational parameters, but if it were able to operate at 100% of its capability, the electrolyte tanks would shrink to be about 400 m3.

Quantum-Chemistry Enabled AI for Materials Discovery for Energy Storage

A priori and reliable simulations can enable timely and cost-efficient design and discovery of materials for energy. Therefore, ‘Let’s Start from Computing’ is an optimal approach to initialize modern day R&D processes. In energy storage, beyond lithium-ion (BLI) research has the potential to revolutionize consumer electronics including portable and stationary power, transportation, and grid energy storage sectors. Multi-valent (Mg, Ca, Zn) energy storage or economically viable monovalent (Na, K) batteries, high-density metal-air, metal-sulfur batteries, or grid-storage systems are considered in the beyond lithium-ion research and development. All these R&D efforts require significant fundamental knowledge via a priori computations for materials discovery, property prediction, and optimization. Atomistic modeling when coupled with reliable Artificial Intelligence (AI) approaches can provide accurate insights to accelerate discovery of optimalelectrolytes, electrodes, and membranes for BLI systems to reduce the cost. Thus, coupled with AI and multi-scale simulations techniques, atomistic modeling can address prediction of molecular level properties of materials (redox potentials, solvation, spectroscopic, and reactivity) to down-select optimal materials or material combinations. In this presentation, I will describe some of our recent efforts in active learning coupled with large scale first principles simulations to down select/optimize desired molecules for flow battery technology. This concept can be utilized for design of experiments using autonomous experimentation. Additionally, I will describe some of our quantum chemistry-informed molecular property predictions redoxmers and liquid organic hydrogen carriers. In addition to molecules, I will present. A data driven approach to study longer time scale diffusion of ions for multivalent battery concepts. Figure 1

Comparison of Fluid Dynamics of Different Flow Geometries in an Iron Flow Battery Prototype

Introduction: Renewable energy sources demand is increasing in the world due to their less environmental effect. Solar and wind energy, which requires largescale electrical energy storage, are major contributors to this growth. The iron flow battery is one of the Redox flow battery technologies, which is encouraging for electrical energy storage because of their long lifetime, flexibility to increase storage, and minimum chemical hazard compared to conventional batteries Method: In this research, the engineering design and fabrication of a locally made Iron flow battery prototype is described. Then, electrolyte flow simulation was carried out through COMSOL Multiphysics to compare the fluid velocity and pressure profiles in three different flow geometries such as plain, parallel, and serpentine, to select the most compatible flow pattern for the Iron flow battery. Result: The resulting velocity profiles indicated that plain flow had stagnated points, the parallel flow had uneven velocity distribution, and serpentine flow had a uniform and high-velocity profile. The simulation results of pressure profiles showed the serpentine, parallel, and plain flows had inlet pressures of 34.38 Pa, 10.01 Pa, and 0.254 Pa, respectively. Conclusion: Given that pumping power is directly proportional to the pressure gradient, the power requirement of electrolyte pumps from highest to lowest is as serpentine flow, parallel flow, and plain flow.

Surface engineered carbon felt toward highly reversible Fe anode for all-iron flow batteries

Low-cost all-iron flow batteries recently promise a great alternative to conventional flow battery technologies for large-scale energy storage. However, inferior Fe deposition/dissolution reversibility at anode largely impedes further advance of all-iron flow battery in application. Here, we report a surface engineered carbon felt with abundant carbon defects, which realizes highly reversible Fe deposition/dissolution for all-iron flow batteries. By introducing nano-scale pores on carbon fibers via a multistep electrode treatment approach, the modified carbon felt features a high degree of defects and proves effective in promoting Fe/Fe2+ kinetics and improving Fe nucleation and growth morphology, which is beneficial for both uniform Fe deposition and complete Fe dissolution rendering a substantially enhanced reversibility for Fe anode. Theoretical calculations further ascribe the enhanced Fe/Fe2+ reversibility to strong adsorption and intensified hybridization between Fe2+ and carbon defects, while all-iron flow cell tests adopting the modified carbon felt finally demonstrates a high power density of 80 mW cm−2 as well as stable charge–discharge operation over 250 cycles with a Coulombic efficiency of 99 %, which highlights the importance of electrode design in developing stable Fe anode for use in high-performance all-iron flow batteries.

Carbon cloth modified by direct growth of nitrogen-doped carbon nanofibers and its utilization as electrode for zero gap flow batteries

The synthetic procedure and characterization of carbon nanofibers (CNFs) grown on carbon cloth (CC) are explored in this study, with a focus on their potential application as electrodes in vanadium redox flow batteries (VRFBs). CC offers an attractive platform for surface modification owing to its conductive properties and three-dimensional architecture, while the N-doped CNFs formed by nitrogen (N) rich composition of melamine precursor enhance wettability of electrolyte and redox reactivity of vanadium ions. Electrochemical assessments reveal that NCC electrodes significantly increase voltage efficiency (VE) and capacity retention in VRFBs compared to bare CC (BCC) electrodes. Notably, NCC demonstrates a VE of 65.9%, surpassing the 55.9% of BCC electrodes. Additionally, NCC maintains superior capacity retention under varying current densities, a crucial factor for VRFBs. Long-term stability tests over 1000 cycles highlight the NCC electrode's durability, with only a minimal decrease in VE. Post-experiment analysis confirms the structural integrity of the CNFs on the CC electrodes, validating their resilience in VRFB operations. In summary, the study introduces a novel approach for fabricating N-doped CNFs on CC, resulting in electrodes that significantly boost VRFB performance in terms of efficiency, capacity retention, and stability, marking a notable advancement in flow battery technology.

(Invited) Relationship of Pseudo-Capacitive Current in Sulphuric Acid and Vanadium Flow Battery Reaction Kinetics at Carbon Electrodes

Flow battery technologies are promising solutions to the need for electricity storage driven by the increasing demand for energy supply at the same time as the electricity grid becomes more and more dependent on renewable sources such as solar, wind and ocean energy. Vanadium flow batteries (VFBs) are perhaps the most promising of these technologies and a growing number of commercial systems are in operation worldwide.The energy efficiency of vanadium flow batteries (VFBs) largely depends upon the performance of the electrodes. Poor electrode kinetics cause large overpotentials, which reduce the voltage efficiency. They can also lead to side reactions, such as hydrogen evolution at the negative electrode and oxidation of the positive electrode, which reduce the coulombic efficiency and the overall performance and durability.There is considerable variation in the data regarding the kinetics of vanadium redox reactions at carbon electrodes. We have previously reported that cathodic treatment enhances the kinetics of the positive (VIV-VV) electrode in VFBs but inhibits the kinetics of the negative (VII-VIII) electrode, while anodic treatment inhibits the kinetics of the positive electrode but enhances the kinetics of the negative electrode1-3. We also showed that the activity of carbon-based material is strongly dependent on the surface history, in particular the most positive and the most negative potential used to treat an electrode4. In this presentation we will further investigate the effect of electrochemical treatment of the carbon surface and show the relationship between the observed pseudo-capacitive behavior and the kinetics of the different vanadium redox couples. References Bourke, M. A. Miller, R. P. Lynch, X. Gao, J. Landon, J. S. Wainright, R. F. Savinell and D. N. Buckley, J. Electrochem. Soc. 163, A5097 (2016). A. Bourke, M. A. Miller, R. P. Lynch, J. S. Wainright, R. F. Savinell and D. N. Buckley, J. Electrochem. Soc., 162, A1547 (2015). M. A. Miller, A. Bourke, N. Quill, J. S. Wainright, R. P. Lynch, D. N. Buckley and R. F. Savinell, J. Electrochem. Soc., 163, A2095 (2016). M. Al Hajji Safi, A. Bourke, D. N. Buckley, R. P. Lynch, ECS Trans., 109, 67-84 (2022).

Molecular Design for Organic Redox Flow Batteries

Redox flow batteries have in recent years become an increasingly researched alternative to lithium-ion batteries for stationary energy storage, stabilizing fluctuations between demand and the intermittent electricity production from solar and wind. The most common vanadium redox flow battery technology suffers from high market volatility for vanadium metal. As a potentially more sustainable alternative to the electrolytes based on metal-ions used in e.g. the vanadium RFB, organic redox active species are being developed to store charge. The organic electrolytes used in aqueous organic redox flow batteries (AORFBs) are reaching closer to economic viability in terms of stability and electrochemical properties but is still inferior to its vanadium counterpart in long-term performance.[1]The degrees of freedom when designing organic electrolytes are endless. However, to improve strategies to designing new electrolytes more systematic studies on the working principles behind what makes organic compounds accept and store charge has to be made. Using less electronegative organo-metallic compounds, radical stabilization and multiple electron reactions, are some of these strategies that can be utilized. Figure 1 shows how examples of current parent molecules with functional groups modifications to tailor stability, solubility and electrochemical properties and in various pH regions.[Image]Molecular design can be divided into three important factors that will impact the performance of the electrolyte; electrochemical properties, solubility and stability. The electrochemical properties of the redox active species are essential for the application towards RFBs, regarding potential, electrochemical reversibility, coulombic- and voltaic efficiencies. The second criteria to maintain a reasonable operating energy density of the RFB is to optimise the water solubility, being proportional to capacity and energy density. The organic compounds solubility is highly pH dependent, thus pairings of posolyte and negolyte will need to operate within the same pH range. By substituting different functional groups to the parent molecule, the operating pH of the species can be tailored. Electrolyte conductivity is also an important factor when altering pH or co-electrolytes in terms of efficiency. Stability or capacity decay is the main focal point for AORFBs and limitation of the redox active species. These decay mechanisms can be further categorized into three different types of degradation, all which result in loss of active electrolyte. First, radical-induced reactions given rise to disproportionation or dimerization reactions, second, pH dependent chemical reactions such as hydrolysis, addition, substitution and elimination reactions and third, physical reactions dependent on molecular size and charge, that can supress or promote crossover through the membrane.As of designing structurally novel molecules, the electrochemical properties are the first property that must be assessed followed by solubility and stability. Since there are already some well explored compounds such as anthraquinones and viologens, much research has been put into increasing the solubility and stability for these.[2] The poster aims to highlight the interconnection between the parameters that make these compounds viable for use in AORFBs. Issues such as what has been explored in terms of posolytes, negolytes, alkaline, neutral and acidic electrolytes and what important components are missing for development of AORFB will be discussed.[1] J. Luo, A. P. Wang, M. Hu, and T. L. Liu, “Materials challenges of aqueous redox flow batteries,” MRS Energy and Sustainability, 9, 1–12, 2022, doi: 10.1557/s43581-022-00023-1.[2] Z. Li, T. Jiang, M. Ali, C. Wu, and W. Chen, “Recent Progress in Organic Species for Redox Flow Batteries,” Energy Storage Materials, 50, 105–138, 2022. doi: 10.1016/j.ensm.2022.04.038. Figure 1

Selective Ion Conducting Polymers for Non-Aqueous Redox Flow Battery Applications

Providing sustainable supplies of clean energy is a critical global challenge for the future. As intermittent renewable energy sources are increasingly deployed, grid-scale energy storage solutions are increasingly needed. One approach to addressing this challenge is to use flow battery technology to store and deliver grid-scale amounts of energy. Non-aqueous redox flow batteries can be operated at higher voltages and energy densities compared to aqueous systems and, as such, may offer high volumetric energy density compared to other flow batteries. A significant challenge facing non-aqueous flow batteries, however, is the lack of selective membrane separators engineered for the unique challenges of non-aqueous electrochemical systems. Suitable membranes for non-aqueous redox flow battery applications must be stable in aggressive solvent environments, offer high conductivity, and provide selectivity to prevent cross-over of redox active molecules. Here, we report the synthesis and characterization of a series of negatively charged ion conductive polymeric membranes for non-aqueous flow battery applications. Fixed negative charges were added to a poly(phenylene oxide) backbone via a custom sulfonate group-based side chain. Lithium ion conductivity and ferrocene permeability properties were characterized to evaluate the selectivity of the membrane for ion transport relative to redox active molecule cross-over (as ferrocene is a representative redox active molecule). The polymers exhibited combinations of conductivity and selectivity that are favorable compared to other Nafion-based materials, and the materials appear to be dimensionally stable in a non-aqueous electrolyte over a period of several months. Redox active molecule cross-over was analyzed within a thermodynamic regular solution framework to highlight how thermodynamic factors contribute to cross-over properties. Ultimately, the data suggest a decoupling of ion and redox active molecule transport that could inform future efforts to develop advanced non-aqueous redox flow battery membrane separators. Altogether, this presentation discusses the transport properties and stability of these materials that show promise for non-aqueous flow battery applications.

Multi-Purpose Structure-Integrated Zinc-Polyiodide Hybrid Flow Battery As Sustainable Energy Storage System for Extraterrestrial Environments

For the energy supply of spacecrafts, such as space stations, satellites or orbiters, primarily solar power is used, which conversion, however, is subject to constant fluctuations due to rotational and orbital movements. In order to secure energy security for technical operations, the maintenance of scientific test series as well as life-support measures even during dark phases, various types of batteries such as nickel-hydrogen or nickel-cadmium batteries have been used as buffer storage over the years. However, due to the isolated locations in which they are used, energy storage systems for space applications must have a particularly long service life and operational reliability in order to be able to reduce resource-intensive replacement missions as well as hazards to people and technology.Since the battery systems used in space applications have in some cases shown significant deficits in these areas, a novel storage concept was developed in the "SpaceFlow" project, which was awarded third place in the europewide idea competition INNOspace Masters DLR Challenge, using the particularly safe and durable flow battery technology. The energy storage concept is based on the space-efficient integration of pressure-stable yet flexible flow battery cells into the supporting structure of spacecraft. In this way, in addition to energy storage as the primary task, other functions such as mechanical stiffening of the modules, support of thermal management or absorption of radiation can be realized.The "SpaceFlow"battery is realized as a zinc-polyiodide hybrid flow battery, which achieved incomparably high energy densities in laboratory tests. An energy density of 167 Wh/l was demonstrated and the potential to increase the energy density even up to 350 Wh/l was shown. The currently most widely used all-vanadium flow battery achieves energy densities of about 30 Wh/l. To optimize the cell chemistry zinc-polyiodide, various additives will be tested in the project. For a controlled formation of dendrites, for example, polyethylene glycol, methanesulfonic acid, chromium ions and, in general, alcohols, especially ethanol, could be added to the electrolytes as additives. In organic compounds, the presence of hydroxyl groups is an important factor in stabilizing the Zn ions. The deposition is also influenced by these. The search for additional alcohol and ether compounds offers the potential to find new additives. Chromium ions provide electrostatic shielding during zinc deposition, inhibiting dendrite growth.The iodine side (cathode) can be optimized mainly by improving the solubility of I2 in water. Stabilization of I2 without the binding of I- provides more free I-, which can react and help increase the capacity of the battery. Bromine ions or polyvinylpyrrolidone can be used to stabilize I2. Other additives such as KI and NH4Cl can be used for improved conductivity. Another approach is to improve diffusion at the cathode. For this purpose, a molybdenum sulfide coating can be applied, which improves the reaction rate with only a slight overpotential.The talk will present the novel storage concept and achievable functionalities as well as the latest project results of the flow cell design development and the design of a zinc polyiodide electrolyte, which must not be hazardous to humans and and at the same time must have a high energy density, to meet the requirements of space applications.

Harnessing redox flow batteries for industrial applications: Opportunities and future directions

This paper provides a brief introduction to flow battery technology as an energy storage device, with a particular focus on the all-vanadium redox flow battery (VRFB). These rechargeable batteries are well suited for reducing greenhouse gas (GHG) emissions for small commercial or multi-family residential dwellings. This paper will explore, in greater depth, the specific industrial and marketing mechanisms by which a storage battery, that does not generate electricity, is able to actually reduce CO2 gas emissions, while at the same time benefiting all stakeholders. The startup company, Ashlawn Energy, is discussed by way of example of the process being followed to push this technology into the mass market, and thus realize this technology's full potential.

Redox flow battery technology development from the perspective of patent applications: A review

With the continuous increase in global energy consumption, the development and utilization of renewable energy become imperative. However, the intermittency and fluctuation of wind and solar power generation prevent direct grid integration, resulting in energy waste. As a large-scale electrochemical energy storage technology, redox flow batteries (RFBs) can effectively store renewable energy and smooth the power output. This paper summarizes the development history of RFBs technology in China by analyzing relevant patent application data, elaborates on the working principles, advantages and disadvantages of various RFBs, and their latest research progress. It analyzes the technical challenges in current RFBs research and presents the application prospects of RFBs commercialization. The results show that although RFBs technology has made significant progress in China, it still faces issues like high battery cost and limited cycle life. To realize the efficient utilization of renewable energy and green low-carbon development, RFBs technology needs continuous optimization and upgrade. This paper can provide references for the development of RFBs technology.

Monitoring the State of Charge Imbalance of Vanadium Redox Flow Batteries Via Dual Online UV/Visible Spectroscopy

Electrolyte imbalance in Redox Flow Batteries (RFBs) is known to result in significant capacity decay over cycling [1]. This drawback is inherent to the flow battery technology and is caused by unwanted physico-chemical phenomena, such as species and water crossover, hydrogen evolution, air oxidation and precipitation of vanadium ions. The time evolution of electrolyte imbalance is often disregarded or underestimated when measuring the open-circuit voltage (OCV) for keeping track of the battery State of Charge (SOC). In order to correct such asymmetry, in operando real-time monitoring of the SOC of the positive and negative electrolytes would be highly desirable.In this work, we present an experimental test bench for the continuous online monitoring of the anolyte and catholyte SOCs via UV/visible spectroscopy during cycling of an all-vanadium redox flow battery (VRFB). The system notably includes 3D printed microfluidic optical flow cells, an optical switch, and an in-house microfluidic electrochemical cell. Key steps for the calibration of UV/visible spectroscopy with vanadium are presented and applied independently to both electrolytes to accurately estimate the SOC while taking into account the total vanadium concentration [2]. An experimental campaign is then carried out under varying conditions (initial average oxidation state (AOS), air oxidation, crossover, etc.) to illustrate the real-time evolution of electrolyte imbalance during VRFB battery cycling. The results suggest that the imbalance may arise from asymmetric initial Average Oxidation State (AOS ≠ 3.5) [3], vanadium crossover and also hydrogen evolution, which notably reduces the charging speed of the negative electrolyte [4]. The results highlight the benefits of UV/Visible spectroscopy to obtain SOC data for any of the three stable vanadium electrolytes: i) negative, VII/VIII ii) positive VIV/VV and even the iii) VIII/VIV pair. Moreover, the measurements are online, non-invasive and could provide real-time data to a battery management system either in conventional or microfluidic VRFBs to correct the SOC imbalance and maintain the battery capacity and efficiency [1]. Acknowledgments This work has been partially funded by FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación Project PID2019-106740RB-I00, and by Grant IND2019/AMB-17273 of the Comunidad de Madrid. A. A. Maurice Energy acknowledges the support of an MCSF-Cofund “Energy for Future” (E4F) postdoctoral research fellowship by the Spanish Iberdrola Foundation (GA-101034297).

Low-cost Zinc-Iron Flow Batteries for Long-Term and Large-Scale Energy Storage.

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.

Influence of NH4Cl additive in a VO2+/VO2+ - AQDS/AQDS2− solar redox flow battery

Solar redox flow batteries are a relatively new type of redox flow battery technology that uses solar energy to directly store chemical energy. Here we present a solar redox flow battery that uses a MoS2@TiO2 thin film with a Nafion protection layer supported on FTO glass substrate as photoanode, employing VO2+/VO2+ and AQDS/AQDS2− as redox active species. When the solar radiation strikes the photoelectrode, the photogenerated holes oxidize VO2+ to VO2+, while the photogenerated electrons reduce AQDS to AQDS2− at the counter electrode. The oxidized form of V5+ and reduced form of AQDS2− thus retain the chemical energy and can release the stored charged via the reverse electrochemical reaction. The addition of NH4Cl to the electrolyte was found to have a positive impact on the electrochemical performance of the redox flow cell. This effect was more evident for the VOSO4 electrolyte, leading to an enhancement of the voltaic and energy efficiencies of more than 17.5%. The results suggest that NH4Cl promotes both mass transport of the vanadium redox species and charge transfer of the AQDS in the electrolyte. The solar-to-output energy conversion efficiency (SOEE) of the solar redox flow battery using 1.6 g L−1 NH4Cl in both anolyte and catholyte reached 9.73%, and an energy density of 87.45% after 10 consecutive one-hour photocharging cycles. Additionally, the use of Nafion to protect the MoS2@TiO2 photoanode from photocorrosion was explored. The Nafion layer ensured an increased stability of MoS2@TiO2 against the strong acidic environment while maintaining effective light response, which translated into enhanced photon and mass transport. An energy storage capacity of ∼60 mAh L−1 after 1-hour photocharging was observed.

Development of flow battery technologies using the principles of sustainable chemistry.

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.

Vanadium (II) Sulfate for the Reductive Leaching of Chalcopyrite: Replacing Smelting with Electrolysis for Copper Production

AbstractThe demand for copper is expected to outpace supply in the coming decades due in part to the emergence of wind and solar technologies, which require about five times as much copper as traditional energy sources. This work introduces a potentially transformative hydrometallurgical process to extract copper from chalcopyrite, and thereby sustain a high rate of copper production throughout the 21st century. Chalcopyrite is reacted with vanadium (II) sulfate for the first time to enable the rapid, clean, and complete recovery of copper. Reactions between 39 g/L copper concentrate, 1 M vanadium (II) sulfate, and various concentrations of sulfuric acid yielded a final product of solid copper sulfate, which was characterized by X‐ray diffraction (XRD) and scanning electron microscopy‐energy dispersive X‐ray spectroscopy (SEM‐EDS) analysis. The solid products were leached in a subsequent step to demonstrate copper yields ranging from 95–99 %. The vanadium (II) ion may be regenerated by an electrolysis unit that leverages advances in vanadium flow battery technologies.