Performance Of Flow Batteries Research Articles

Designer Fluorescent Redoxmer Self‐Reports Side Reactions in Nonaqueous Redox Flow Batteries

The state of health (SOH) is a critical measure for evaluating and predicting performance of redox flow batteries (RFBs). However, diagnosing SOH of RFBs is often challenging due to the overwhelming complexity of the electrolytes and associated electrochemical reactions. Designing active molecules or redoxmers that can autonomously exhibit property changes upon specific stimuli may provide a viable way for early diagnosis of SOH. Herein, a dimerized redoxmer, DGL‐N‐CH3, was designed and synthesized by linking blue‐green fluorescent monomers through a diglycolamide linker. While DGL‐N‐CH3 still maintains similar electrochemical behavior and strong fluorescence, we observe a unique side reaction when cycling DGL‐N‐CH3 in H‐cells, which leads to a side product, NHCH3‐BzNSN via linker cleavage. Interestingly, NHCH3‐BzNSN also emits fluorescence but at a longer wavelength. By taking advantage of this unique fluorescent change that corresponds to the growth of NHCH3‐BzNSN, we successfully established the capacity decay of DGL‐N‐CH3 H‐cell cycling, exemplifying a proof‐of‐concept self‐reporting redoxmer design towards in situ SOH monitoring.

A convection-enhanced flow field with height-changing ribs for redox flow batteries

Serpentine flow fields with flat ribs can effectively improve the performance of redox flow batteries. However, the marginal pressure difference between adjacent channels near the end side of ribs in conventional designs leads to weak convection in the regions, increasing the local concentration overpotential. This problem will be exacerbated in scaled-up redox flow battery stacks due to enlarged under-rib regions near the end side of ribs. In this work, two modified serpentine flow fields with height-changing ribs are proposed to adjust the electrode compression ratio at the under-rib region, thereby enhancing the convection in the electrode near the end side of ribs. Therefore, the active species are distributed more uniformly, resulting in an improved battery performance. Specifically, the uniformity of V2+, the energy efficiency and the system efficiency of the vanadium redox flow batteries with the ramp ribs are improved by 21 %, 2.7 %, and 2.7 % respectively compared with that of the conventional flat ribs, at the current density of 200 mA cm−2, the flow rate of 3.4 mL min−1 cm−2, and the active area of 117 cm2.

Enhancing Vanadium Redox Flow Battery Performance with ZIF-67-Derived Cobalt-Based Electrode Materials.

Vanadium redox flow batteries (VRFBs) have emerged as a promising energy storage solution for stabilizing power grids integrated with renewable energy sources. In this study, we synthesized and evaluated a series of zeolitic imidazolate framework-67 (ZIF-67) derivatives as electrode materials for VRFBs, aiming to enhance electrochemical performance. Four materials-Co/NC-700, Co/NC-800, Co3O4-350, and Co3O4-450-were prepared through thermal decomposition under different conditions and coated onto graphite felt (GF) electrodes. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses confirmed the structural integrity and distribution of the active materials. Electrochemical evaluations revealed that electrodes with ZIF-67-derived coatings exhibited significantly lower charge transfer resistance (Rct) and higher energy efficiency (EE) compared to uncoated GF electrodes. Co/NC-800//GF delivered the highest energy efficiency and discharge capacity among the tested configurations, maintaining stable performance over 100 charge-discharge cycles. These results indicate that Co/NC-800 holds great potential for use in VRFBs due to its superior electrochemical activity, stability, and scalability.

State of Charge (SoC) of the Vanadium and Other Redox Flow Batteries: Identification of the Electrode and Bipolar Plate Contributions

In this paper attention is directed toward one of the key measures of performance, State of Charge (SoC) for vanadium and other battery chemistries. Explored are its simple definition, as well as a more complete examination of just what is meant by this terminology. Developed is a more sophisticated exposition of how to calculate it properly, including spatial distributions, and what consequences arise from various simplifications. Open Circuit voltage through the Nernst equation, is related to the SoC. Non-equilibrium overpotential is also related to the concentrations when treated as averaged field variables. Other chemistries examined include iron-chromium, all-iron, and hydrogen-bromine. For the first time, a rigorous decomposition of the spatial variation of the electrode and bipolar plate contributions is identified, allowing new formulas to be obtained. This may allow optimization of redox flow battery performance. Finally, an expression is found for the open circuit voltage cost going between no bipolar plates and their incorporation into the redox flow battery.

Enhanced Vanadium Redox Flow Battery Performance with New Amphoteric Ion Exchange Membranes.

Vanadium redox flow batteries (VRFBs) depend on the separator membrane for their efficiency and cycle life. Herein, two amphoteric ion exchange membranes are synthesized, based on sulfonic acid group-grafted poly(p-terphenyl piperidinium), for VRFBs. Using ether-free poly(p-terphenyl piperidine) (PTP) as the polymer matrix, and sodium 2-bromoethanesulphonate (ES) and 1,4-butane sultone (BS) as grafting agents, We achieve quaternization of PTP through an environmentally friendly process without alkaline catalysts. PTP-ES and PTP-BS membranes exhibit low area resistance, high H+ permeability, and significantly reduced vanadium ion permeability, leading to exceptional ion selectivity, which is 3.06×106Smincm-3 and 4.34×106Smincm-3, respectively,three orders of magnitude higher than that of Nafion115 (0.27×104Smincm-3). The VRFB with PTP-BS achieves a self-discharge duration of 190h, compared to 86h for Nafion 115. Additionally, under current densities of 40-160mAcm-2, PTP-BS shows coulombic efficiencies of 98.1-99.1% and energy efficiencies of 92.0-82.1%, outperforming Nafion 115. The VRFB with PTP-BS also demonstrates excellent cycle stability and discharge capacity retention over 300 cycles at 100mAcm-2. Therefore, the amphoteric PTP-BS membrane shows remarkable performance, offering significant potential for VRFB applications.

Balancing current density and electrolyte flow for improved zinc-air battery cyclability

Zinc-air batteries (ZABs), known for their high energy density and environmental friendliness, are emerging as promising solutions for sustainable energy storage. However, the irregular deposition of zinc on electrodes hinders the widespread utilization of rechargeable ZABs due to limited durability and stability. This study investigates the role of electrolyte flow in enhancing zinc electrodeposition and overall performance in zinc-air flow batteries (ZAFBs) at high current densities. We explore the interplay between current density, flow rate, and their influence on electrode surface morphology and the removal of the passivating zinc oxide layer to improve battery efficiency and lifespan. Using advanced in-situ synchrotron radiation x-ray tomography, we found that incorporating flowing electrolyte at specific current densities results in rounded dendrite tips, thinner and more uniform deposition layers, and improved zinc adhesion. Imaging and electrochemical analyses further reveal that flowing electrolyte enhances zinc morphology, reduces charge transfer resistance, diminishes passivation, and lowers galvanostatic charge/discharge polarization across various current densities, thereby improving battery cycling performance. Notably, the impact of flowing electrolyte is more pronounced at a moderate current density of 50 mA/cm2 compared to lower or higher currents. Our findings underscore the importance of electrolyte flow and current density management in developing high-performance ZAFBs, providing valuable insights for their future commercialization.

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.

Semi-Analytical Model for Hybrid and Redox Targeting Flow Battery Systems

Redox flow battery represents an economically viable energy storage technology that can integrate intermittent renewable energies from solar and wind power into existing electric grids. Besides the conventional all-liquid redox flow battery, there are two different architectures of flow batteries: hybrid and redox targeting flow batteries. Because the reactive solid phase is involved in the system, the energy storage density increases significantly. Therefore, they are considered as ones of the potential solutions for the future large-scale deployment of long-duration energy storage systems (LDES). A digital twin (DT) has been demonstrated as a promising numerical framework and platform to assist in the design, deployment, and operation of LDES. DTs usually require a fast-response model to provide an estimation of the flow battery's performance, which can be a fast-forward physics-based model or a machine learning-based regression model. Many pioneering works and our previous studies have introduced several fast-forward physics-based models for the conventional all-liquid redox flow battery in both inorganic and organic systems. In this study, a semi-analytical model, which can adapt to DTs, is proposed to provide an estimation of the performance of the hybrid and the redox targeting flow battery at different operating conditions.

(Invited) Operando Visualization of the Electrolyte Distribution in Vanadium Redox Flow Electrodes

Electrolyte transport losses are among the main factors that limit the performance of Vanadium Redox Flow Batteries (VRFBs)1. The electrolyte must percolate into the electrode and reach the reaction sites with minimum resistance to reduce such losses. The optimized electrolyte flow ensures that the reactants and products are transported to and away from the reaction sites freely and decreases the pumping losses of the electrochemical cell, increasing the overall efficiency of the battery system.The electrolyte distribution in a porous electrode is crucial for the stability and performance of the electrode. The presence of gas bubbles in the electrode reduces the electrochemically active surface, resulting in cell potential fluctuations. In addition, the gas bubbles cause poor contact between the electrolyte and the electrode, and the ionic conductivity could be locally blocked2. These effects lead to inhomogeneous potential distribution (spikes), accelerating the electrode material's corrosion. Gas bubbles are very common in VRFBs, and they result from parasitic side reactions, such as carbon corrosion, hydrogen evolution (HER), or incomplete electrode wetting3.Synchrotron X-ray imaging is a powerful tool for tracking these bubbles in porous carbon materials. We have designed an experimental setup resembling an operating VRFB cell to image the flow through the porous carbon electrode. With its modular structure, the setup offers excellent flexibility to evaluate different designs and operational aspects of VRFBs4, 5. The findings of our investigations over the years will be discussed in this presentation. References J. Kim and H. Park, Journal of Power Sources, 2022, 545, 231904. K. Krause, C. Lee, J. K. Lee, K. F. Fahy, H. W. Shafaque, P. J. Kim, P. Shrestha and A. Bazylak, ACS Sustainable Chemistry & Engineering, 2021, 9, 5570-5579. M.-A. Goulet, M. Skyllas-Kazacos and E. Kjeang, Carbon, 2016, 101, 390-398. L. Eifert, N. Bevilacqua, K. Köble, K. Fahy, L. Xiao, M. Li, K. Duan, A. Bazylak, P.-C. Sui and R. Zeis, ChemSusChem, 2020, 13, 3154-3165. K. Köble, L. Eifert, N. Bevilacqua, K. F. Fahy, A. Bazylak and R. Zeis, Journal of Power Sources, 2021, 492, 229660. Figure 1

Mitigation of Negative-Electrode Degradation in Vanadium Redox Flow Batteries

Electrode overpotentials are among the major factors that impact the performance of redox flow batteries (RFBs). However, even though the all-vanadium redox flow battery (VRFB) is the most mature flow-battery chemistry, a recent review article has pointed out that “there is poor agreement between the reported values of kinetic parameters” [1]. Major contributors to this disagreement are the wide variety of carbon materials that are used as electrodes and because the kinetics of both the V(II)/V(III) and V(IV)/V(V) reactions on carbon depend on the electrode pretreatments. The role of surface functional groups and the mechanisms of electron transfer for these reactions is not well understood [1]. There is general agreement that the V(IV)/V(V) kinetics are more facile than the V(II)/V(III) kinetics [2, 3]. Multiple researcher groups have reported electrode overpotential increases with time, and “there is evidence that it occurs mainly on the negative electrode” [1]. Additionally, “reversing the polarity of the VRFB has been suggested as one strategy to recover lost performance but not all investigators have found this strategy effective” [1]. Exposing the V(II)/V(III) electrode to V(IV)/V(V) electrolyte may increase the roughness and oxidize the electrode, which can both improve the activity. It has also been suggested that reversing the polarity may remove impurities, such as copper metal from the negative electrode [4]. More recently, it has been proposed that surface activity may be improved by oxidizing adsorbed V(II) [5]. We hypothesize that V(II)/V(III) electrode degradation on graphitic carbon-fiber electrodes is primarily due to the adsorption of a contaminate that is oxidized when exposed to V(IV)/V(V) electrolyte. We will describe what we suspect is the relevant contaminate species, and we will show the stability of the V(II)/V(III) electrode can be substantially improved by simply removing certain electrolyte-wetted components from the VRFB test apparatus. References A. Bourke, D. N. Buckley, et.al., “JES, 170 (2020). 10.1149/1945-7111/acbc99 D. Aaron, T. A. Zawodzinski, et. al., ECS Electrochem. Letters, 2 (2013) 10.1149/2.001303eel N. Pour, Y. Shao-Horn, et.al., J. of Physical Chemistry C, 119 (2015).10.1021/jp5116806 D. Reynard, H. Girault, et.al., ChemSusChem, 12 (2019). 10.1002/cssc201802895T. Greese and G. Reichennauer, J. Power Sources, 500 (2021). 10.1016/j/jpowsour.2021.229958

A Stable Polymer-Blended Anion-Exchange Membrane for Enhanced Performance in Redox Flow Batteries

Redox flow batteries (RFBs) operate with a membrane, responsible for the separation of cationic active species and allowing the passage of counter-ions, to preserve electroneutrality on each side of RFBs. Commercial cation-exchange membranes (CEMs), such as Nafion®, possess excellent ionic conductivity and chemical stability. However, they face challenges in blocking cationic active species common in RFBs, leading to significant capacity loss over time. Anion-exchange membranes (AEMs) efficiently block active species with the assistance of the Donnan effect. Nevertheless, commercial AEMs lack acid stability and conductivity compared to their cationic counterparts.Polytetrafluoroethylene (PTFE)-reinforced quaternary ammonium cardo poly(ether)ketone (QPEK-C)-based membranes with Al2O3 additives (PQPAM), a heterogeneous AEM developed in our lab1, possess excellent ionic conductivity with low permeability of active species and good mechanical properties. PQPAM has demonstrated better acid stability than commercial AEMs. However, its acidic and oxidative stability require improvement, as evidenced by degradation after 250 hours of in-situ harsh RFB cycling due to the heterogeneous nature of PQPAM and the exposure of the susceptible QPEK-C-rich side to the electrolytes2. To address this issue, we propose a strategy to enhance the chemical stability of QPEK-C-based membranes by inhibiting the exposure of QPEK-C to oxidation agents through blending with a hydrophobic engineering thermoplastic like polybenzimidazole (PBI)3,4. Furthermore, PBI's known ability to protonate in acidic media will reinforce ionic conductivity and the separation of active species, thus improving the Donnan effect, in addition to enhancing chemical and mechanical stability.Elemental analyses and microscopy images confirm a homogeneous blending of PBI and QPEK-C, promising stability improvement. The results of ex-situ tests on ionic conductivity, cation permeability, and chemical stability align with the mentioned hypotheses, showcasing that blend of PBI/QPEK-C outperforms pure PBI and QPEK-C AEMs. Additionally, the mechanical properties of the PBI/QPEK-C blended AEMs are improved compared to pure QPEK-C AEMs and PBI/QPEK-C blended AEMs outperform pure PBI and QPEK-C AEMs in in-situ cycling tests with our patented titanium-cerium RFBs5. Moreover, this work will explore other strategies to improve the blended AEM properties, such as utilizing inorganic fillers or PTFE reinforcement.

Synergetic Functionalization of the ZnS@ASCs Biocomposite: For Enhanced Electrochemical Performance of Redox Flow Batteries and Supercapacitors

Synergetic Functionalization of the ZnS@ASCs Biocomposite: For Enhanced Electrochemical Performance of Redox Flow Batteries and Supercapacitors

Surfactant-Driven Dynamic Changes in Rheology of Activated Carbon Slurry Electrodes.

Carbon black slurry electrodes are an effective means to improve flow battery performance by increasing the active surface area necessary for electrochemical reactions with a cost-effective material. Current challenges with this specific flow battery chemistry include the stability and flowability of the carbon black suspensions, especially in response to formulation choices. Advancing the manufacturing, operation, and performance of these redox flow batteries requires a deeper understanding of how slurry formulation impacts its rheological profile and ultimately battery performance. In response to this need, the linear and nonlinear rheological responses of activated carbon (AC) based slurry electrode materials used in an all-iron flow battery in the presence of a nonionic surfactant (Triton X-100) were measured. Results from these measurements show the slurry is a colloidal gel with elasticity remaining constant despite increasing surfactant concentration until α (= Csurf/CAC) < 0.65. However, at α ≥ 0.65, the slurry abruptly transitions to a fluid with no measurable yield stress. This critical surfactant concentration at which the rheological profile undergoes a dynamic change matches the concentration found previously for gel collapse of this system. Moreover, this transition is accompanied by a complete loss of electrical conductivity. From these data we conclude the site specific adsorption of surfactant molecules often used in slurry formulation has a significant and dramatic impact on the stability and flowability of these suspensions. Work presented herein demonstrates the importance of additive choices when formulating a slurry electrode.

Evaluation of the effect of hydrogen evolution reaction on the performance of all-vanadium redox flow batteries

The exceptional advantages of vanadium redox flow batteries (VRFBs) have garnered significant attention, establishing them as the preferred choice for large-scale and long-term energy storage solutions. However, side reactions such as hydrogen evolution reaction (HER) lead to suboptimal performance of VRFB parameters, resulting in an overall decrease in VRFB performance. Therefore, it is imperative to investigate the mechanism by which HER affects VRFB performance and identify effective methods to mitigate its impact. In light of this, critical parameters such as charge-discharge curve, internal resistance, pressure-drop, pump power consumption, efficiency, and capacity retention rate are selected to evaluate the impact of HER on VRFB performance. Experimental results demonstrate that HER causes an increases in voltage during charging and a decrease during discharging stages leading to voltage loss; additionally, bubble generation significantly increases pressure drop and pump power consumption; furthermore, blockage of flow channels and electrodes due to bubbles leads to an increase in ohmic resistance. Finally, HER has a substantial impact on efficiency and capacity with an average energy efficiency of 2.92 %. After 60 cycles, the capacity retention rate decreased by nearly 7.69 %.

2-Acrylamido-2-methylpropane sulfonic acid (AMPS) grafted poly(vinylidene fluoride) (PVDF) membrane for improved vanadium redox flow battery (VRFB) performance

Polymer modification techniques are crucial for customizing material properties to suit specific applications, particularly in energy storage systems. This study investigates the modification of poly(vinylidene fluoride) (PVDF) membranes via atom transfer radical polymerization (ATRP) to graft 2-acrylamido-2-methylpropane sulfonic acid (AMPS) onto the fluorinated backbone. The successful grafting was confirmed via nuclear magnetic resonance (NMR) spectroscopy, while the membrane structure was evaluated using infrared (IR) and X-ray photoelectron spectroscopies (XPS). Thermogravimetric analysis (TGA) and universal testing machine (UTM) tests verified the thermal and mechanical stability of the membranes. Electrochemical analysis showed sustained performance over 300 cycles. The FluorCat-25 membrane demonstrated high coulombic efficiency (>98 %), voltage efficiency (83 %), and energy efficiency (81 %) at a current density of 100 mA cm−2. Notably, FluorCat-25 achieved a peak power density of 353 mW cm⁻², surpassing that of Nafion-117 (304 mW cm⁻²), with >85 % capacity retention, indicating its superior performance and suitability for VRFB applications. These findings position FluorCat-25 as a promising candidate for efficient and durable energy storage solutions in VRFB technology.

3-Dimensional numerical study on carbon based electrodes for vanadium redox flow battery

Electrode materials are critical in determining the performance of Vanadium redox flow batteries (VRFB). This work aims at elucidating the difference between carbon-based electrodes for VRFB. The electrodes considered for the present study are Graphite felt, Carbon felt, Carbon paper, and Carbon cloth. To study the characteristic behavior of different electrode materials, a 3D unit cell numerical model was developed by coupling electrolyte flow and electrochemical reactions and mass transfer module apart from considering the electrode structural and material information such as porosity, permeability, thickness, conductivity, and specific area. The simulation results of this study suggest that the Graphite felt is the optimum choice as an electrode material for VRFB as it offers higher electrocatalytic activity, lower pressure drop, better performance, and lower cost. The study is also extended to a multilayer configuration of Carbon Paper and Carbon Cloth. The performance of multi-layered electrodes by stacking single sheets of Carbon Paper and Carbon Cloth electrodes are matched to meet the performance obtained with the Graphite felt electrode. It has been shown with the help of polarization curve and the pressure drop study that the performance of five layers of carbon cloth and nine layers of carbon paper match the performance of Graphite felt, approximately. The present study provides practical guidance for the design and optimization of VRFB electrodes.

Bioinspired flow Fields: A numerical investigation into Nature-Mimicking designs for boosting vanadium redox flow batteries

Efficient flow field structures are crucial for improving the performance of all-vanadium redox flow batteries (VRFBs). Considering the large pressure drop and pump losses in traditional serpentine flow fields (SFF), this paper proposes a novel biomimetic flow field structure (BFF) for VRFB. A three-dimensional multiphysics model comparing SFF and BFF designs for VRFB is developed, the assessment was further enhanced by considering the impact of electrolyte flow rates on multiple performance indicators. The results show that BFF’s unique design substantially reduces pressure drop, especially at higher flow rates. For both SFF and BFF designs, at a low flow rate of 60 ml/min, the SFF has a slightly higher pump-based voltage efficiency, but as the flow rate increases to 120 ml/min and 180 ml/min, the BFF outperforms the SFF, demonstrating advantages of 2.057 % and 6.888 %, respectively. This comprehensive VRFB modeling analysis provides valuable insights into optimizing future flow battery designs.

Construction and Investigation of Novel Cross-Linked Fluorine-Containing Sulfonated Polyimide Membranes for VFB Application.

Membrane with remarkable proton conductance and selectivity plays a key role in obtaining high vanadium flow battery (VFB) performance. In this work, the trade-off effect between proton conductance and vanadium ion blocking was overcome by the introduction of a cross-linking structure to prepare covalent cross-linked fluorine-containing sulfonated polyimide (CFSPI-PVA) membranes. Herein, the CFSPI-PVA-15 membrane possesses excellent comprehensive properties, including acceptable area resistance (0.21 Ω cm2), lower vanadium ion permeability (0.76 × 10-7 cm2 min-1), and remarkable proton selectivity (3.11 × 105 min cm-3) compared with the commercial Nafion 212 membrane. At the same time, the CFSPI-PVA-15 membrane exhibits higher coulomb efficiencies (97.26%-99.34%) and energy efficiencies (68.65%-88.11%) and a longer self-discharge duration (29.2 h) in contrast with the Nafion 212 membrane. Moreover, 500 cycles of the CFSPI-PVA-15 membrane at 160 mA cm-2 are also stably executed. The internal reasons for the improved chemical stability of the CFSPI-PVA-15 membrane are clarified from theoretical calculations with the mean square displacement value and fractional free volume. Therefore, the CFSPI-PVA-15 membrane exhibits great potential for application in VFB.

A gradient electrospinning electrode structure both in the in/through-plane directions for non-aqueous iron-vanadium redox flow battery

To boost the performance of non-aqueous redox flow batteries (RFBs), it is important to synergistically improve the flow/mass transfer efficiencies and the uniformity of overpotential distribution into the porous electrode. In this work, electrostatic spinning technology is developed to propose a novel porous electrode with gradient pore distribution both in the in-plane and through-plane directions, and applied in deep eutectic solvent (DES) electrolyte-based iron-vanadium RFB. On the one hand, the new in-plane gradient design modifies the distribution of reactive species of electrode near the membrane side, resulting in the decreasing polarization loss. On the other hand, the increasing porosity of electrodes from the flow field side to the membrane side attains a trade-off between the charge transfer and the electrolyte flow resistances. According to the experimental results, compared to the graphite felt electrode, the energy efficiency of this RFB with three-dimensional gradient electrode improves by 74.2 % at a current density of 10 mA·cm−2. Moreover, the numerical simulation reveals the reactive transfer behaviors of three-dimensional gradient porous electrode. The results show that the proposed three-dimensional gradient design can enhance the uniformity of overpotential distribution and achieve the decrease of polarization resistance, thus improving the performance of DES electrolyte-based iron-vanadium RFB effectively.

The Performance of All Iron-Based Redox Flow Batteries Enhanced by Carbon Nanotube Catalysts

The Performance of All Iron-Based Redox Flow Batteries Enhanced by Carbon Nanotube Catalysts