Zinc Bromine Redox Flow Battery Research Articles

Improved electro-kinetics of new electrolyte composition for realizing high-performance zinc-bromine redox flow battery

Aqueous Redox Flow Batteries (ARFB) are the most prominent technology for large-scale energy storage applications. The energy density of the ARFBs is mainly determined by the electrolyte components, which highly influence the flow battery performance. In the present work, we acutely investigated the various electrolyte compositions and optimized the best electrolyte for realizing the high performance of Zn-Br2 ARFBs. The electrode kinetics, such as rate constant, exchange current density, conductivity, and diffusion coefficient, were analyzed using electrochemical techniques, cyclic voltammetry, and electrochemical impedance analysis. It was observed that zinc bromide (ZnBr2) + perchloric acid (HClO4) + 1-Ethyl-1-methylmorpholinium bromide (MEM) + N-ethyl-N-methylpyrrolidinium bromide (MEP) and ZnBr2 + zinc chloride (ZnCl2) + MEM + MEP electrolytes showed improved performance, where the redox kinetics of 2Br-/Br2 redox couple is greatly enhanced. The presence of perchloric acid unlocks the capacity of full electro-oxidation of bromide (Br-) to bromine (Br2) as it involves 1e- per Br-, which would be highly beneficial to attain high energy density. Further, Zn-Br2 RFB adopted with optimized electrolyte formulation ZnBr2 + HClO4 + MEM+ MEP shows a better round-trip efficiency and displays a stable long cycling performance over 200 cycles with an energy (EE) and coulombic efficiency (CE) of > 68% and > 92%, respectively.

Tungsten oxide embedded graphene oxide doped with SPEEK composite membrane for zinc–bromine redox flow batteries

Zinc-bromine redox flow batteries (Zn/Br2 RFBs) are fingerprint candidates for large-scale energy storage applications owing to their low cost, flexibility, high energy density, and astonishing round-trip efficiency. However, during the charging and discharging process, the diffusion of bromine through the porous membrane creates significant capacity decay and reduces the membrane efficiency of Zn/Br2 RFBs. In this respect, we developed various amounts of tungsten trioxide (WO3) nanoparticle-decorated graphene oxide (WO3@GO)-loaded sulfonated poly (ether ether ketone) (SPEEK) membranes and investigated their Zn/Br2 redox flow battery performance. The optimum amount of WO3@GO-loaded WO3@GO/SPEEK-3 membrane exhibits higher mechanical stability and ionic conductivity, significantly restricting the bromine crossover through the membrane. Due to their higher hydrophilic ability and uniform dispersion, WO3-loaded GO nanosheets provide strong interaction between the sulfonic acid group of the SPEEK membrane, which acts as an effective barrier for bromine crossover and significantly alters the Zn/Br2 battery performance. As a result, at a current density of 40 mA cm−2, the Zn/Br2 single cell of the WO3@GO/SPEEK-3 demonstrated higher coulombic efficiency (96.6 %), voltage efficiency (89.6 %), and energy efficiency (86.6 %), better than the WO3@GO/SPEEK-5 and pristine SPEEK membranes. These performances indicate that the proposed low-cost WO3@GO/SPEEK membrane can be highly applicable to other energy-related fields, including fuel cells and water treatment.

Hollow Nitrogen-Doped Carbon Spheres as Zincophilic Sites for Zn Flow Battery.

Severe dendrite growth on Zn anodes poses a significant challenge to the development of Zn-based batteries. An effective strategy for inhibiting the formation of Zn dendrites involves electrode modification. In this study, hollow nitrogen-doped carbon spheres (HNCS) are synthesized and used as electrodes to regulate Zn deposition in Zn-based flow batteries. The electrochemical performance of HNCS reveals that the pyrrole nitrogen of HNCS changes the electrode surface state. Therefore, HNCS can inhibit the hydrogen evolution reaction and achieve uniform Zn deposition. HNCS can effectively inhibit dendrite growth and improve the reversibility of the Zn plating/stripping process to regulate the reversibility of Zn-based batteries. The zinc-bromine redox flow battery assembled with HNCS significantly reduces the hydrogen evolution reaction and exhibits a coulombic efficiency of 90 % and energy efficiency of 73 % at a current density of 60 mA cm-2. Similarly, an alkaline zinc-iron flow battery can maintain high Coulombic efficiency and energy efficiency of 83 %.

Recent Advances in Bromine Complexing Agents for Zinc–Bromine Redox Flow Batteries

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

Operational Parameter Analysis and Performance Optimization of Zinc–Bromine Redox Flow Battery

Zinc–bromine redox flow battery (ZBFB) is one of the most promising candidates for large-scale energy storage due to its high energy density, low cost, and long cycle life. However, numerical simulation studies on ZBFB are limited. The effects of operational parameters on battery performance and battery design strategy remain unclear. Herein, a 2D transient model of ZBFB is developed to reveal the effects of electrolyte flow rate, electrode thickness, and electrode porosity on battery performance. The results show that higher positive electrolyte flow rates can improve battery performance; however, increasing electrode thickness or porosity causes a larger overpotential, thus deteriorating battery performance. On the basis of these findings, a genetic algorithm was performed to optimize the batter performance considering all the operational parameters. It is found that the battery energy efficiency can reach 79.42% at a current density of 20 mA cm−2. This work is helpful to understand the energy storage characteristics and high-performance design of ZBFB operating at various conditions.

Laser ablated uniform deposition of bismuth oxide film as efficient anode for zinc based flow battery

Zinc based redox flow batteries are the most proficient and attractive candidature for large scale energy storage applications. However, zinc dendritic formation and inhomogeneous deposition of zinc hamper the cyclability of zinc-based flow batteries. Herein, we have successfully decorated Bi2O3 on the felt by using the pulsed laser deposition (PLD) technique and tested it as a negative electrode in zinc bromine redox flow battery. The Bi2O3 felt provides more robust nucleation sites for zinc nuclei, lowers the potential of hydrogen evolution reaction, minimizes the surface diffusion of zinc, lowers zinc nucleation overpotential, and triggers homogenous zinc deposits. Compared to pristine (57.7 %), Bi2O3 felt exhibited an energy efficiency of 70.6 % at 100 mA cm−2. Interestingly, the morphological evolution of zinc deposits demonstrates that zinc deposition on the Bi2O3 felt is more homogeneous than pristine at an initial time (30 sec of charging at 20 mA cm−2). Moreover, Bi2O3 felt shows a stable long cycling performance over 200 cycles with minimized charge discharge overpotential and exhibited an avg. coulombic efficiency of 96.78 % which is superior than pristine. Thus, Bi2O3 felt is a prominent anode material for improving the electrochemical performance of zinc based redox flow batteries.

Synthesis and characterization of highly durable hydrocarbon-based composite membrane for zinc-bromine redox flow battery

Low-cost, durable, and high-performance membranes are urgent requirements for zinc bromine redox flow battery (ZBFB) applications. Sulfonated poly (ether ether ketone), SPEEK is a low-cost, ion-exchange membrane with excellent ionic conductivity, but its backbone is susceptible to the harsh bromine environment. Herein, the successful incorporation of a multifunctional nanofiller, perovskite-structured cerium titanate nanoparticles dispersed on smooth carbon nanofibers (p-CT/CNF) with varying carbon content into the polymer matrix protects the SPEEK backbone, reduces the crossover of active species and improves the selectivity of the composite membrane. At high current density of 100 mA cm−2, the SP-p-CT350 membrane in ZBFB shows an energy efficiency of 73.34% compared to pristine SPEEK and SP-p-CT320 with 70.32 and 69.71%, respectively. Interestingly, the excellent dispersion of the nanofiller notably reduces the self-discharge rate of SP-p-CT350, retaining the OCV at 1.70 V for 117 h which is 1.86 and 1.75 times greater than pristine SPEEK and SP-p-CT320. Furthermore, with the effect of loading to determine the durability of the SP-p-CT350 membrane, SP-p-CT350 with a nanofiller loading of 0.5 wt% demonstrates stable battery performance across 500 cycles at a current density of 40 mA cm−2 with an outstanding energy efficiency of 81.13%.

The Use of Zinc-Bromine Battery Technology to Remove and Recover Zinc from Scrap and Waste Steel Resources

ZBBs have a high open circuit voltage (1.82 V), a high theoretical energy (> 400 W h-1 kg-1) and high demonstrated power densities (> 100 mW cm-2). Typically, ZBBs adopt a redox flow design involving the use of a Nafion membrane to separate aqueous zinc bromide anolyte and catholyte solutions [1]. In this study, the use of a membrane-free non-flow design was investigated for the purposes of recovering zinc from scrap and waste steel resources [2]. The rationale for this work stems from the greenhouse gas emissions produced by the iron and steel industry, which accounts for between 4-7 % of the anthropogenic CO2 emissions globally [3]. Blast furnace technology is likely to account for most stainless steel production in the coming decades, and therefore a transition to low-carbon and green steel production will require increased steel recycling rates and significantly improved waste and scrap management. To the best of our knowledge, this is the first time a zinc-bromine battery has been investigated for the recovery of materials rather than energy storage.Galvanization of steel is required to prevent rusting and degradation and involves coating the surface of steel in a protective layer of zinc. Galvanization processes account for over 50 % of global zinc consumption and by 2050 the demand for zinc will be 2.7 times greater than that of 2012 [4]. In order to enable recycling of scrap steel directly into blast furnaces, zinc is removed and recovered via mineral acid leaching. This method of recovery has a high zinc extraction efficiency but creates problematic waste streams and has poor energetic efficiency.In this work, the use of a membrane-free zinc-bromine battery has been studied for the purposes of extracting zinc from steel substrates and subsequently re-electroplating onto a conventional carbon foam electrode. The electrical performance of the cell was characterised by charge-discharge profiles and I-V curves. Zinc removal and recovery onto electrodes was characterised using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The work successfully demonstrates that ZBB technology could enable efficient and clean recovery of zinc from metal and waste substrates including scrap steel, slurries generated from basic oxygen steelmaking processes, and secondary vent dust from the primary steelmaking off gas streams. The cell studied in this work enabled dipping of zinc-containing steel substrates directly into the electrolyte solution without disassembly of the battery housing. In addition, the design involved the use of low-cost materials and reagents and potentially offers low balance-of-plant costs.The results show that zinc could be removed from steel surfaces during cell discharge with greater than 99.9 % yield. The Figure shows the extracted zinc could subsequently be re-electroplated onto a standard carbon foam electrode upon re-charging the cell. When a 0.5 V cut-off voltage was used upon discharge, the zinc was recovered selectively from the steel (see Fig. (a)); the surface elemental composition of the carbon electrode measured by EDS after charging was: carbon (26.79 wt%), oxygen (18.06 wt%), zinc (30.03 wt%) and bromine (25.11 wt%). Using a lower cut-off voltage (0.2 V) resulted in the co-extraction of iron from the substrate as well as zinc (see Fig. (b)); in this case, the elemental composition of the carbon electrode after charging was: carbon (27.53 wt%), oxygen (22.65 wt%), iron (4.72 wt%), zinc (24.44 wt%) and bromine (20.65 wt%). Provided a cut-off voltage of no less than 0.5 V was used for discharging, high purity zinc was recovered, and the cell showed good initial durability, with 30 cycles of charge-discharge demonstrated in this work.[1] S. Suresh, M. Ulaganathan, N. Venkatesan, P. Periasamy, P. Ragupathy, High performance zinc-bromine redox flow batteries: Role of various carbon felts and cell configurations. J. Energy Storage, 2018. 20: pp. 134-139.[2] S. Biswas, A. Senju, R. Mohr, T. Hodson, N. Karthikeyan, K. Knehr, A.G. Hsieh, X. Yang, B.E. Koel, D.A. Steingart, Minimal architecture zinc-bromine battery for low-cost electrochemical storage. Energy Environ. Sci., 2017. 10: pp. 114-120.[3] Iron and Steel Technology Roadmap: Towards More Sustainable Steelmaking, Energy Technology Perspectives, International Energy Agency, IEA Publications, Paris, 2020. https://www.iea.org/reports/iron-and-steel-technology-roadmap [accessed 12 April 2022].[4] K.S. Ng, I. Head, G.C. Premier, K. Scott. E. Yu, J. Lloyd, J. Sadhukhan. A multilevel sustainability analysis of zinc recovery from wastes. Resour. Conserv. Recycl., 2016. 113: pp. 88-105.Figure. SEM images showing the carbon foam zinc electrodes after charging the cell. (a) is an electrode when a discharge cut-off voltage of 0.5 V was used, (b) is an electrode when a discharge cut-off voltage of 0.2 V was used. Figure 1

An organic imidazolium derivative additive inducing fast and highly reversible redox reactions in zinc-bromine flow batteries

In zinc-bromine redox flow batteries (ZBBs), the weak molecular structure and stability of bromine-complexing agent (BCA) can sometime negatively affect battery's performance. To address this issue, this paper introduces a 1,2-dimethyl-3-ethylimidazolium bromide (DMEIm∙Br, C7H13BrN2), comprising planar molecular structure with strong molecular-polarizability and low steric hindrance. The effectiveness of the DMEIm∙Br is compared and verified with those of two popular BCAs through various electrochemical experiments including full-cell tests for 200 cycles. Experimental results show that the DMEIm∙Br significantly contributes to apparently enhancing reaction kinetics and reversibility of Zn2+/Zn(s) and Br−/Br2 redox couples by inducing highly reversible zinc-plating/stripping (by strong electrostatic shielding effect) and bromine-capture/release (along with strong bromine-binding strength) in anolyte and catholyte solutions, respectively. The superior chemical and electrochemical properties are clearly demonstrated by the fact that the DMEIm∙Br-supported solution in ZBBs exhibits 5.53 (24.19) and 7.29 (16.99) % higher current and voltaic efficiencies than the pristine solution at the temperature of 25 (60) °C, respectively. It also exhibits remarkably improved discharge-capacity retention of averagely 99.17% for 200 cycles along with a slight discharge-capacity loss of only 1.46% vs. 1st cycle at 200th cycle, even at the high temperature of 60 °C.

Enhanced electrochemical performance of zinc/bromine redox flow battery with carbon-nanostructured felt generated by cobalt ions

Surface properties of graphite fibers greatly determine the performance of flow batteries. In this work, graphite felt is modified with transition metal ion (cobalt)-assisted thermal treatment process. This multi-step thermal treatment process generated well aligned carbon nanostructures as well as large amount of oxygen functional groups on graphite fiber surface. Such an electrode surface architecture is highly beneficial for the performance of Zinc-Bromine redox flow batteries, as it facilitates superior charge as well as mass transfer, associated with dense organic polybromide phase formed during charging. Consequently, the flow cell with modified felt, decorated with carbon nanostructures, operates at higher energy efficiency (84%) compared to pristine felt (68%) and conventionally thermally treated felt (68%). Postmortem analysis using scanning electron microscopy reveals the durability of carbon nanostructure on the felt, as these structures are observed to remain intact after long-term cycling (100 cycles) experiments.

Active material crossover suppression with bi-ionic transportability by an amphoteric membrane for Zinc–Bromine redox flow battery

Zinc-bromine redox flow batteries (Zn/Br2 RFBs) are gaining attention as a next-generation energy storage system with the advantages of a cost-effective redox couple material price, high output, and high energy density. However, bromine (Br2) crossover through a commercial porous membrane causes self-discharge to lower the capacity retention. Nafion, a commercial ion exchange membrane, can lower the crossover but has low voltage efficiency due to high membrane resistance. To address this trade-off, the amphoteric functionalized silica (Am-SiO2) is introduced into the Nafion membrane (Nafion/Am-SiO2). It suppresses the crossover of active materials such as Br2 and polybromide (Brn−) and possesses high ionic conductivity due to the quaternary ammonium and sulfonic groups on the Am-SiO2 surface. In addition, increasing the water content in the membrane prevents the expansion of the water cluster size, which could help balance bi-ionic transport. As a result, the composite membrane showed 83.3 and 19.0 times higher ion selectivity than the commercial porous membrane (SF600) and ion-exchange membrane (NRE-212). Compared to SF600 and NRE-212, the energy efficiency of Nafion/Am-SiO2 was improved by 4.2 and 6.4%, respectively. Balancing anion and cation transport can be successfully applied in Zn/Br2 RFBs by introducing an amphoteric group into an ion-exchange membrane.

Carbon Nanotube Scaffolds Entrapped in a Gel Matrix for Realizing the Improved Cycle Life of Zinc Bromine Redox Flow Batteries.

Herein, we have successfully demonstrated a nanofiller (such as multiwalled carbon nanotubes (MWCNT)) dispersed in a polymer matrix (such as polyacrylonitrile (PAN)) as an effective pore filling agent to a microporous Daramic membrane for inhibiting bromine diffusion in zinc bromine redox flow batteries. A simple protocol of the MWCNT/PAN-Daramic membrane renders a major benefit for inhibiting bromine diffusion relative to the conventional microporous membrane. As a result, the MWCNT/PAN composite Daramic membrane exhibits remarkable electrochemical performance in zinc bromine redox flow batteries at various current densities. More impressively, the MWCNT/PAN composite Daramic membrane shows a 90% Coulombic efficiency compared to the pristine Daramic membrane and the PAN composite Daramic membrane with only 68.53 and 71.20% efficiencies at 160 mA cm-2, respectively. Moreover, the MWCNT/PAN composite Daramic membrane displays an extraordinary long cycling performance with a >97% Coulombic efficiency, whereas the Daramic membrane withstands only 200 cycles due to severe water transport from the catholyte to the anolyte. The zinc bromine redox flow battery assembled with the MWCNT/PAN composite Daramic membrane significantly reduces the self-discharge rate and retains an open circuit voltage of 1.69 V for 13.40 h in comparison to the Daramic membrane (10.83 h) and the PAN composite membrane (11.13 h). Thus, the extraordinary flow cell performance and stability of the MWCNT/PAN composite Daramic membrane lead to the development of an alternative to the microporous Daramic membrane in zinc bromine redox flow batteries.

Modulated Zn Deposition by Glass Fiber Interlayers for Enhanced Cycling Stability of Zn–Br Redox Flow Batteries

The zinc bromine redox flow battery (ZBB) is one of the most promising candidates for next-generation energy storage systems due to its low cost, inflammability, and high power and energy densities. However, dendritic Zn growth, which intensifies at higher current densities and larger deposition capacities, practically hinders the high-current and high-capacity operation of ZBBs. Herein, we demonstrate that a non-conductive, highly porous, and zincophilic glass fiber (GF) layer on top of a carbon felt electrode notably suppresses dendritic Zn growth. The ZBB with the GF layer successfully operates for more than 4000 cycles at 80 mA cm–2 and 20 mA h cm–2, in contrast to the cell failure outcome at the 45th cycle for a GF-free ZBB. Electrochemical analysis and simulations suggest that the surface polar groups of the GF facilitate Zn ion transport and matrix-guided Zn deposition. A GF layer decorated with negatively charged polymer achieves highly superior uniform Zn deposition and remarkable cycling stability at 200 mA cm–2 and 50 mA h cm–2, verifying the validity of this approach.

An optimistic approach on flow rate and supporting electrolyte for enhancing the performance characteristics of Zn-Br2 redox flow battery

Herein for the first time, we have successfully demonstrated the influence of flow rate on the polarization effect caused by the sluggish kinetics of Br−/Br2 redox couple in zinc-bromine redox flow battery (ZBRFB). Besides, the effect of perchloric acid (HClO4) on Br−/Br2 redox reaction has also been explored. The optimized electrolyte flow rate condition shows significant improvisation on the round-trip efficiency (> 95%) due to the balanced kinetics. Further, the double-layer formation was substantially minimized with the help of HClO4 as evidenced by cyclic voltammetry studies. The electrode kinetics towards Br−/Br2 also was enhanced by increasing the concentration of HClO4. The enhanced voltage efficiency (~85%) of the flow cell employing HClO4 as a supporting electrolyte is mainly accredited to the balanced conductivity of the redox electrolyte. Moreover, optimized flow cell design exhibits good cycle life and improved ohmic region over the prolonged cycle studies in comparison. Thus, the optimistic flow rate and the selection of such an efficient electrolyte additive can be proficient candidates for improving the zinc-bromine battery performances.

Low loading of Pt@Graphite felt for enhancing multifunctional activity towards achieving high energy efficiency of Zn–Br2 redox flow battery

Polyhalides based hybrid redox flow batteries are highly appropriated for long term stationary charge storage applications due to their high practical energy density, long cycle life, low cost, etc. Among various metal-halide redox flow batteries, zinc-bromine redox flow battery system received much attention due to its reasonable cell voltage, energy density and life-time. However, the poor kinetics of bromine/bromide redox reaction at the electrodes and bromine vapour formation during the charge process are the major issues associated with this flow system. In the present work, low loading of platinum is used as electrocatalyst for improving the Br2/Br-reaction kinetics where platinum particles are deposited on the graphite felt using pulsed laser deposition. Platinum decorated graphite felt is investigated as an active electrode material in the positive compartment of this flow system to study the improvement in the reaction kinetics of Br2/Br− redox couple reaction. This approach is highly influenced in bromine/bromide redox reaction kinetics, as a result, avg. Coulombic efficiency of 99.96% and ever best avg. energy efficiency of ~88% is observed for the zinc-bromine based flow cell tested at 50 mA cm−2. Thus, graphite felt having low loading platinum is considered as a potential candidate for enhancing the Br2/Br-kinetics at any given condition.

Effect of positive electrode modification on the performance of zinc-bromine redox flow batteries

Abstract Performance of the zinc-bromine redox flow battery is correlated to the surface properties of the positive electrode. Herein, we have modified the graphite felt electrode by thermal treatment and plasma treatment under oxygen and nitrogen atmospheres. These treatments induced specific changes to the electrode surface. Under the experimental conditions, thermal treatment increased overall surface area whereas, the O2 and N2 plasma increased the defects in the felt, by generating oxygen functional groups as well as N doping respectively. By combining both thermal and O2 plasma treatment, an increase in both surface area, as well as oxygen functional groups, were achieved. The performance of the cell was influenced by the surface area and surface functional groups. Most importantly surface oxygen functionalization proved to be a decisive factor for the enhanced performance especially when the concentration of organic polybromide phase is higher. A better charge transfer/adhesion between the electrode and polybromide phase is expected through halogen/hydrogen bonding between the complexed Br and oxygen/proton of the phenolic or carboxyl functional groups.

Boron-Based Anolyte for Non-Aqueous Redox Flow Batteries

Redox flow batteries (RFBs) that employ dissolved electroactive materials to store energy have attracted growing attention because of their great potential to store renewable but intermittent solar and wind energy. The unique technological merits of decoupled energy and power leads to high flexibility and scalability in design for the RFBs to satisfy a wide range of energy/power applications[1,2]. In established traditional RFBs, the electroactive species are aqueous solutions of redox-active inorganic transition-metal salts including all-vanadium, iron-chromium and zinc-bromine RFBs. Despite immense progress, the attainable cell voltages in these aqueous systems are largely limited by the narrow electrochemical stability window of water (1.5V). As a result, aqueous RFBs suffer from low energy densities and in turn require more electroactive materials and supporting salts to achieve high storage capacity[3,4]. To address these limitations, recent research is shifting to non-aqueous RFBs (NARFBs) that utilize non-aqueous solvents, taking advantage of the wider electrochemical windows over ~5 V depending on the organic solvent employed. A variety of electro-active species including organic redox-active molecules and organometallic complexes have been used in NARFBs[5,6]. Here, we will introduce our research efforts on the development of boron-based redox active anode molecules for non-aqueous redox flow batteries. We have investigated the electrochemical properties of boron-based anode molecules with different substitution groups and the cyclic voltammetry (CV) results indicate that the boron-based redox active molecule with di-tert-butyl substituted (DTBF2) exhibits superior electrochemical reversibility and stability and low half wave potential of -1.82V. When paired with the catholyte 2,5-ditert-butyl-1-methoxy-4-[2′-methoxyethoxy]benzene (DBMMB), the cell voltage can reach up to 2.56V. The built redox flow cell demonstrates an energy efficiency of 80% and capacity retention of 99.3% per cycle, as shown in figure 2. These initial results proved that this readily synthesized boron-based redox active anode is promising anolyte for NARFBs.More experimental data and results will be disclosed during the meeting. Acknowledgement The work described in this paper was fully supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. T23-601/17-R)

An Aqueous Hybrid Zinc‐Bromine Battery with High Voltage and Energy Density

AbstractThe zinc‐bromine redox flow battery (ZBB) is an ideal device of energy storage systems. Nevertheless, its energy density is relatively low compared to those of Li‐ion batteries, due to its low output voltage. Herein, a high‐voltage aqueous hybrid zinc‐bromine battery system (AHZBBs) was developed, where K+‐conducting membrane was used to segregate neutral‐alkaline hybrid electrolytes and redox couples of Br2/Br−and [Zn(OH)4]2−/Zn at the positive and negative electrode. Benefited from an efficient and stable cathode catalyst (carbon‐manganite nanoflakes), this AHZBB delivered a high average output voltage of 2.15 V and energy density of 276.7 Wh/kg without capacity attenuation after 200 cycles. More importantly, this work provides an efficient avenue to elevating the output voltage and energy density, and will strongly encourage studies on redox flow batteries.

Modeling of Zinc Bromine redox flow battery with application to channel design

Here we present a 2-D combined mass transfer and electrochemical model of a zinc bromine redox flow battery (ZBFB). The model is successfully validated against experimental data. The model also includes a 3-D flow channel submodel, which is used to analyze the effects of flow conditions on battery performance. A comprehensive analysis of the effects of flow is included. We find that the zinc deposition decreases with flow distance during charging, and the opposite for the zinc de-plating process during discharging. The simulations also show that multiple curved flow channels can slightly improve the voltage efficiency of the ZBFB while the coulombic and energy efficiencies are slightly reduced. The model can be used for improving ZBFB design.

Activated Carbon‐Anchored 3D Carbon Network for Bromine Activity and its Enhanced Electrochemical Performance in Zn−Br2 Hybrid Redox Flow Battery

AbstractThere has been a huge demand on the usage of biomass‐derived activated carbon as an electrode and electrocatalyst for energy storage and conversion applications owing to its abundance, high surface area, good chemical stability, low cost, and eco‐friendliness. Herein, we report for the first time, activated carbon (AC) derived from Phyllanthus Emblica Leaves (PEL) (Indian gooseberry) biomass as an electrocatalyst for enhancing the bromine electro‐kinetics. The AC‐anchored graphite felt (AC−GF) showed excellent improvement in the bromine reversibility, which reinforces the overall performance of the zinc bromine redox flow battery (ZBRFB). Specifically, the AC−GF showed significant improvement in voltage efficiency. The flow cell employing AC in the positive electrode showed high Coulombic, voltage, and energy efficiency of 99, 83 and 82 %, respectively at a current density of 30 mA cm−2. Furthermore, the cell showed good cycle performance with 96.43 % Coulombic efficiency retention even after 100 cycles. Thus, the significant improvement in the cell performance unveils the good electrochemical/catalytic activity of the AC and therefore can be used as a potential low‐cost electrocatalyst in ZBRFB.