Zinc-bromine Flow Batteries Research Articles

Function regionalized catalyst promoted bromine redox kinetics for bromine-based flow battery

Bromine-based flow batteries are considered as ideal large-scale energy storage devices, due to their attractive high energy density and low cost. However, the inferior redox activity of the Br3−/Br− couple leads to limited power density, which cannot meet the practical application requirements. Herein, a flexible catalytic electrode is constructed by interweaving a nitrogen-doped porous carbon (NPC) coated TiO2 (TiO2@NPC) nanofiber, via electrospinning technique. In the electrode, the NPC component with superior affinity to the reactant Br−, could assistant rapid charge transfer, and facilitate the conversion from Br− to Br3−, which plays an excellent catalytic function. With a stronger adsorption for the oxidation product Br3− than NPC, the TiO2 component can transfer Br3− from NPC, releasing the catalytic active sites on NPC timely and enabling the reaction smoothly proceeded. Consequently, the regional differentiation strategy of the catalysis and adsorption functions significantly boosts the redox kinetic of the bromine chemistry. The Zinc-bromine flow batteries equipped with TiO2@NPC can run 200 cycles stably at 80 mA cm−2, with the voltage efficiency and energy efficiency of 82.8 % and 81.6 %, respectively. This design provides a brand-new improvement strategy for bromine cathode from the perspective of accelerating the reaction rate-determining step.

(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.

High-Rate and Durable Zinc-Based Flow Batteries for Large-Scale Energy Storage

Large-scale energy storage is a key enabling technology for the widespread adoption of renewable energy such as wind and solar power. Among various technologies, zinc-based flow batteries stand out as one of the most promising candidates due to the high energy density, low cost, and use of earth-abundant active materials. However, the low operating current density and short cycle life resulting from notorious zinc dendrite formation, large internal resistance, and sluggish reaction kinetics pose a great challenge for their practical applications. Although great efforts have been made to address these issues, previous works mainly focused on one specific aspect, making it challenging to boost the overall performance of zinc-based flow batteries. In this presentation, a systematic study on the effects of key components on the electrochemical performance of zinc-bromine flow batteries will be presented. Our results show that all key components (electrodes, electrolytes, membranes, and flow fields) can exert a significant influence on the electrochemical performance. More impressively, a high areal capacity of >200 mAh/cm2 and an operating current density of as high as 400 mA/cm2 can be achieved by optimizing the design and operating parameters. Underlying mechanisms and perspectives for further improvement will be discussed during the presentation.

A high-rate and long-life zinc-bromine flow battery

Zinc-bromine flow batteries (ZBFBs) offer great potential for large-scale energy storage owing to the inherent high energy density and low cost. However, practical applications of this technology are hindered by low power density and short cycle life, mainly due to large polarization and non-uniform zinc deposition. In this work, a systematic study is presented to decode the sources of voltage loss and the performance of ZBFBs is demonstrated to be significantly boosted by tailoring the key components (electrolyte, electrodes, and membranes) and operating conditions (flow rate and temperature). Results show that the optimized battery exhibits an energy efficiency of 74.14 % at a high current density of 400 mA cm−2 and is capable of delivering a current density up to 700 mA cm−2. Furthermore, a peak power density of 1.363 W cm−2 and a notable limiting discharge current density of ∼1.5 A cm−2 are achieved at room temperature. More remarkably, the battery is stably operated for over 1200 cycles (∼710 h) at 200 mA cm−2 and 60 mAh cm−2, which sheds light on the development of high-rate and long-life ZBFBs for next-generation energy storage.

Regulated adsorption capability by Interface–Electric–Field enabling promoted electrochemical kinetics of Zinc–Bromine flow batteries

Zinc–bromine flow batteries (ZBFB) are gaining significant attention for large–scale energy storage due to the high energy density and affordable cost. Nevertheless, the diffusion of Br2 and the relatively low activity of Br2/Br− impede their broader application. Herein, a bi–phasic rutile/anatase–TiO2 embedded in carbon composite with hollow sphere structure (R/A–TiO2@HCS) is proposed as the catalyst for the Br2/Br− electrode. The internal electric field (IEF) formed between rutile–TiO2 and anatase–TiO2 regulates the adsorption capability for active bromine species. The appropriate adsorption capability can rapidly transfer the generated Br2 complex (QBrn) to the adsorbent component R/A–TiO2 during charging, liberating the carbon active sites, and release QBrn back to the carbon reaction sites timely during discharging, satisfying the both adsorption and desorption requirements of QBrn in different processes. The kinetics for oxidation and reduction are simultaneously enhanced. Moreover, the hollow construction offers storage space for QBrn, relieving its penetration problem. Under the synergistical cooperation, the ZBFB assembled with R/A–TiO2@HCS demonstrates the energy efficiency (EE) of 83.6 % at 80 mA cm−2, without significant decay over 500 cycles. And the EE still maintains 70.0 % even under 160 mA cm−2. This work highlights the significance of tailored electrocatalyst for ZBFB.

Core‐shell Ni/NiO heterostructures as catalytic cathodes enabling high‐performance zinc bromine flow batteries

AbstractZinc bromine flow batteries (ZBFBs) are well suited for stationary energy storage due to their attractive features of high energy density and low cost. Nevertheless, the ZBFBs suffer from low power density and limited efficiency owing to the relatively severe polarization of the Br2/Br− redox couple. Herein, a three‐dimensional (3D) hierarchical composite electrode based on core‐shell Ni/NiO heterostructures anchored on graphite felt (Ni/NiO@GF) is designed to promote the kinetics of the Br2/Br− couple, so as to improve the power density and efficiency of the ZBFB. In this design, the highly conductive carbon felt and Ni cores provide a composite electrode with a 3D electron transporting framework to guarantee excellent electronic conductivity, while the NiO shells possess great absorption ability to Br2 and brilliant catalytic activity for the Br2/Br− redox reaction to reduce the electrochemical polarization. As a result, an enhanced ZBFB with Ni/NiO@GF electrode shows an outstanding energy efficiency of 86% at 20 mA cm−2 and can be operated at a current density of up to 160 mA cm−2 with a respectable energy efficiency of 67%. These results exhibit a promising strategy to fabricate catalytic electrodes for high‐performance ZBFBs.

Double-Doped Carbon-Based Electrodes with Nitrogen and Oxygen to Boost the Areal Capacity of Zinc–Bromine Flow Batteries

Double-Doped Carbon-Based Electrodes with Nitrogen and Oxygen to Boost the Areal Capacity of Zinc–Bromine Flow Batteries

Molecular polarity regulation of polybromide complexes for high-performance low-temperature zinc–bromine flow batteries

Polybromide molecular polarity regulation ensures the optimal performance of zinc–bromine flow batteries at room temperature and −20 °C.

A Choline-Based Antifreezing Complexing Agent with Selective Compatibility for Zn-Br2 Flow Batteries.

The high freezing point of polybromides, charging products, is a significant obstacle to the rapid development of zinc-bromine flow batteries (Zn-Br2 FBs). Here, a choline-based complexing agent (CCA) is constructed to liquefy the polybromides at low temperatures. Depending on quaternary ammonium group, choline can effectively complex with polybromide anions and form dense oil-phase that has excellent antifreezing property. Benefiting from indispensable strong ion-ion interaction, the highly selectively compatible CCA, consisting of choline and N-methyl-N-ethyl-morpholinium salts (CCA-M), can be achieved to further enhance bromine fixing ability. Interestingly, the formed polybromides with CCA-M are able to keep liquid even at -40°C. The CCA-M endows Zn-Br2 FBs at 40mAcm-2 with unprecedented long cycle life (over 150cycles) and high Coulombic efficiency (CE, average ≈98.8%) at -20°C, but also at room temperature (over 1200cycles, average CE: ≈94.7%). The CCA shows a promising prospect of application and should be extended to other antifreezing bromine-based energy storage systems.

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.

Bi-layer graphite felt as the positive electrode for zinc-bromine flow batteries: Achieving efficient redox reaction and stable mass transport

Zinc-bromine flow battery (ZBFB) is one of the most promising energy storage technologies due to their high energy density and low cost. However, their efficiency and lifespan are limited by ultra-low activity and stability of carbon-based electrode toward Br2/Br− redox reactions. Herein, chitosan-derived bi-layer graphite felt (CS-GF) with stable physical structure and abundant active sites is proposed and developed as cathodes for ZBFBs. In this uniquely developed electrode, the catalyst layer possesses oxygen and nitrogen co-doped surface enables high activity for redox reaction, whilst the wrapping structure enhances bonding force between catalyst layer and supporting layer to keep the stability against electrolyte flow. Moreover, the closely-bonding and partially-cracked catalyst layer ensures low electrical resistance between two layers and further emerges more inside active sites for bromine ions reactions. Consequently, the bi-layer electrode is demonstrated high electrochemical activity towards bromine ion redox reactions by cyclic voltammetry and electrochemical impedance spectra test. In battery charge-discharge measurements, a ZBFB employing CS-GF electrode yields a high current density of 120 mA cm−2, with an ultra-high coulombic efficiency of 99 % and improved energy efficiency of 69 %. Furthermore, the proposed bi-layer electrode enables stable battery performance, which cycle for more than 100 cycles with minor 0.057 % energy efficiency decay per cycle. This work provides a promising strategy to develop high-activity and high-stability electrode that possesses great application potentials in ZBFBs and other energy storage systems.

Enlarging Zn deposition space via regulating Sn-induced effective interface for high areal capacity zinc-based flow battery

Zinc-based flow batteries (ZFBs) have aroused great favor in large-scale energy storage due to the high security and low cost. However, the low areal capacity arising from the limited space for Zn plating hinders the further development. Herein, a novel carbon felt-Sn-carbon felt sandwich host (CSCH) is designed and constructed. Benefiting from the strong chemical absorption and the dehydration effect on Zn(H2O)62+, the Sn activation layer in the CSCH demonstrates the lowest comprehensive resistance for Zn deposition. Thus, Zn is induced to nucleate preferentially on the Sn activation layer, and grows towards the membrane, regulating the spatial distribution of Zn electrochemical deposits, which remarkably improves the areal capacity and cyclic stability of Zn anode. Consequently, the zinc-bromine flow batteries equipped with CSCH electrodes can achieve the ultra-high areal capacity of 120 mA h cm−2 at 80 mA cm−2, and run stably for 140 h with average energy efficiency of 80.3% in the extreme condition (80 mA cm−2, 80 mA h cm−2). This innovative work will inspire future advanced designs for high areal capacity electrodes in ZFBs.

Scientific issues of zinc-bromine flow batteries and mitigation strategies.

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

A Mesoporous Tungsten Oxynitride Nanofibers/Graphite Felt Composite Electrode with High Catalytic Activity for the Cathode in Zn-Br Flow Battery.

High electrochemical polarization during a redox reaction in the electrode of aqueous zinc-bromine flow batteries largely limits its practical implementation as an effective energy storage system. This study demonstrates a rationally-designed composite electrode that exhibits a lower electrochemical polarization by providing a higher number of catalytically-active sites for faster bromine reaction, compared to a conventional graphite felt cathode. The composite electrode is composed of electrically-conductive graphite felt (GF) and highly active mesoporous tungsten oxynitride nanofibers (mWONNFs) that are prepared by electrospinning and simple heat treatments. Addition of the 1D mWONNFs to porous GF produces a web-like structure that significantly facilitates the reaction kinetics and ion diffusion. The cell performance achieves in this study demonstrated high energy efficiencies of 89% and 80% at current densities of 20 and 80mA cm-2 , respectively. Furthermore, the cell can also be operated at a very high current density of 160mA cm-2 , demonstrating an energy efficiency of 62%. These results demonstrate the effectiveness of the mWONNF/GF composite as the electrode material in zinc-bromine flow batteries.

Економічний аналіз технологій акумулювання електричної енергії

The use of cost-effective large-scale electrical energy storage systems is necessary for the reliability of the power system due to the rapid growth of its production by powerful renewable energy sources. The article examines stationary electric energy storage devices, namely: sodium-sulfur; lead-acid; lithium-ion; nickel-cadmium; vanadium reduction, polysulfide-bromine and zinc-bromine flow batteries; supercapacitors; superconducting magnetic energy. Information from open sources on technologies of electric energy storage has been analyzed. As a criterion of optimality in world practice, the weighted average cost of electric energy for the life cycle is used, which ensures the self-sufficiency of the source of its production or accumulation for the entire cycle of its existence. A comparison of modern technical and economic indicators of various electrical energy storage technologies is made. Calculated average cost of electrical energy storage over the life cycle (LCOS) of various storage devices. It was determined that supercapacitors and superconductors of magnetic energy have the lowest cost of storage, and lithium-ion ones have the highest. Therefore, to minimize short-term power fluctuations in power systems, superconducting magnetic and supercapacitor storage devices are preferable. They have a lower cost of electric energy storage, short response time and high specific power.

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 Performance of Zn/Br Flow Battery Using N-Methyl-N-Propylmorpholinium Bromide as Complexing Agent.

Redox flow batteries (RFB) are one of the most interesting technologies in the field of energy storage, since they allow the decoupling of power and capacity. Zinc–bromine flow batteries (ZBFB) are a type of hybrid RFB, as the capacity depends on the effective area of the negative electrode (anode), on which metallic zinc is deposited during the charging process. Gaseous bromine is generated at the positive electrode (cathode) during the charging process, so the use of bromine complexing agents (BCA) is very important. These BCAs are quaternary amines capable of complexation with bromine and generating an organic phase, immiscible with the aqueous electrolyte. One of the most commonly used BCAs in RFB technology is 4-methylethylmorpholinium bromide (MEM-Br). In this work, an alternative quaternary amine 4-methylpropylmorpholinium bromide (MPM-Br) was studied. MPM-Br was integrated into the electrolyte, and 200 charge–discharge cycles were performed on the resulting ZBFBs. The obtained results were compared with those when MEM-Br was used, and it was observed that the electrolyte with MPM-Br displays a higher resistance in voltage and higher energy efficiency, making it a promising alternative to MEM-Br.

Techno-economic analysis of solar photo-voltaic/diesel generator hybrid system using different energy storage technologies for isolated islands of India

This paper exclusively investigates techno-economic performance of solar photo-voltaic (SPV)/diesel generator (DG) hybrid system using four different battery energy storage (BES) technologies namely lead acid battery, lithium ion battery, vanadium redox battery, and zinc bromine flow (ZBF) for the isolated Andaman & Nicobar and Lakshadweep islands of India. The analysis has been performed using Hybrid Optimization Model for Electric Renewables (HOMER) software at Baratang and Minicoy islands of Andaman & Nicobar and Lakshadweep, respectively, in which SPV/DG/ZBF hybrid system (20 kW SPV, 7 kW DG, 100 kWh ZBF batteries and 20 kW converter) found to be most techno-economic viable optimized solution for both locations. The net present cost, levelized cost of energy, and operating cost of this configuration are found to be $23927.21, $0.167/kWh and $338.20, respectively, for Baratang island; and $22366.64, $0.155/kWh and $217.49, respectively, for Minicoy island. Using this system as baseline configuration, analysis was extended to different BES technologies to evaluate the performance parameters like system cost, return of investment, simple payback period, energy produced, pollutant emissions, renewable penetration etc. The effectiveness of the ZBF technology is justified with the obtained results which show highest value of return of investment and renewable penetration with lowest simple payback period and pollutant emission. Finally, sensitivity analysis of the system was performed using a unique three-dimensional approach.

Carbon Electrocatalysts for High Performance Bromine and Iodine Redox Flow Battery Electrodes

Redox flow battery (RFB) electrodes act as bi-directional electrocatalysts, improving the kinetics of the electrolyte redox reactions of interest without being consumed in the reaction itself. This property of flow battery electrodes allows for the power and energy densities of RFBs to be uncoupled and designed separately. The power density is largely dependent on the activity of the electrocatalyst, whereas the energy density is determined by the solubility and volume of the electroactive species in the external electrolyte tank. Due to the advantages of RFBs, they have been heavily studied and implemented for applications in large-scale energy storage and are often used in tandem with renewable energy stations. Zinc-bromine flow batteries have arguably become the most promising and common flow battery technology behind that of the all-vanadium RFB, but are held back by low power densities that result from the slower Br2/Br- half-cell kinetics compared to that of the Zn2+/Zn half-cell. Fabrication of low-cost, high activity bromine electrodes will help increase the viability of this technology. Analogous zinc-iodine flow batteries have also been proposed for identical applications, as the electrolyte is much less toxic and corrosive to common battery materials than bromine, and a high solubility of electroactive species due to the formation of the triiodide ion (I3 -) (up to ~12 M). In addition, some scientific research has shifted towards flow batteries constructed from heteropolyhalides (such as I2Br- or Br2Cl-) by combining different halogen electrolytes.We investigated a variety of different carbon electrocatalysts for low-cost and durable electrodes for the I2/I-, Br2/Br, and mixed heteropolyhalide electrodes in RFB technology. A variety of carbon blacks, graphenes, and phosphorus-doped graphitic carbons (PCx) were drop-casted onto a glassy carbon electrode substrate and their electrocatalytic performance was assessed via a variety of techniques including cyclic voltammetry, rotating disc studies, and impedance spectroscopy. Phosphorus-doped graphitic carbon (PCx) was synthesized via the reaction of phosphorus chloride and benzene in different volumes ratios to obtain samples with variable amounts of phosphorus content (PC, PC3, PC5, PC8), characterized by X-ray diffraction analysis and 31P NMR.The electrochemical performance of various carbon blacks and graphenes were observed to have a strong dependence on their surface area and porosity. The electrocatalytic activity of the phosphorus-doped catalysts was seen to exhibit a volcano plot relationship with the degree of phosphorus-doping, where PC5 and PC3 exhibited higher electrocatalytic behaviour towards the halogen/halide redox reactions than PC and PC8. These observations can be explained by P31 NMR indicating an increased amount of P-O bonds with increasing amounts of doping, with the oxygen containing functional group being catalytic. Excessive doping leads to faults in the lattice structure of the P-doped graphite. The surface area of the electrocatalyst material had the largest impact overall on the electrocatalytic performance of the electrode.

Exploiting Buoyancy Driven Flow As an Alternative Flow Battery Design

It can be shown that the density gradients formed during operation of many traditional flow battery chemistries give rise to substantial natural convection. This convection tends to dominate transport within a cell with no forced flow. Using the zinc-bromine chemsitry as an example we show how this principle can be used to design a minimal architecture cell needing no pumps, membranes, or complexing agents. Density gradients are used to keep active materials separated while buoyancy driven flow is used to increase the transport of solution phase reactants during discharge. This design can maintain reasonably high efficiencies and energy density (90% CE, >45 Wh/L) while significantly cutting the balance of plant costs compared to traditional zinc-bromine flow batteries.