Performance Of Vanadium Redox Flow Battery Research Articles

Discussion of the Performance of VRB Based on Modeling by Using EKF to Estimate SOC

There are several ongoing researchers on searching for an appropriate model to describe the characteristic of Vanadium redox flow batteries(VRB) .Based on one of these models, a SOC estimator of VRB- Extended Kalman Filter (EKF) is advanced. And then, update the VRB model by using EKF to estimate SOC when simulation in SIMULINK. At last, the effects of the temperature and operating current on performance of VRB, including battery capacity, output voltage, efficiencies are discussed.

Directly fluorinated polyaromatic composite membranes for vanadium redox flow batteries

Abstract Fluorinated sulfonated poly(fluorenyl ether ketone) (F-SPFEK) membranes and composites with 3-aminopropyltriethoxylsilane (F-SPFEK–APTES) were prepared for evaluation in vanadium redox flow battery (VRB) devices. Improved oxidative stability as well as increased water uptake and proton conductivity were found after direct fluorination of a sulfonated poly(fluorenyl ether ketone) (SPFEK) sample with fluorine gas. The incorporation of a polysilsesquioxane network within the fluorinated membrane effectively suppressed vanadium permeation without a large decrease in proton conductivity, leading to a membrane with a more optimized balance of proton conductivity and VO 2+ permeability for good VRB performance. Both F-SPFEK and F-SPFEK–APTES membranes showed promising characteristics for VRB application, but the coulombic efficiency of the VRB with the F-SPFEK–APTES composite membrane was 21.5% higher than the VRB with a SPFEK membrane.

Synthesis and characterization of EFFE-g-(VBTAC-co-HEMA) anion exchange membranes prepared by a 60Co radiation-induced graft copolymerization for redox-flow battery applications

Vinyl benzyl trimethyl ammonium chloride (VBTAC) was grafted onto poly(ethylene-co-tetrafluoroethylene) (ETFE) film by γ-ray using simultaneous irradiation graft copolymerization in the presence of 2-hydroxyl ethyl methacrylate (HEMA). The structure of the ETFE-g-(VBTAC-co-HEMA) anion membrane was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis. The degree of grafting (DG) of the membrane increased with total irradiation dose and VBTAC monomer concentration. The highest DG of an ETFE-g-(VBTAC-co-HEMA) membrane was 92%, which was synthesized by the treating of an ETFE film with a 0.8 M solution of VBTAC monomer in the presence of 50 kGy irradiation. Different properties of the anion membrane, such as water uptake and ion exchange capacity, increased as DG increased. The permeability and vanadium redox-flow battery performance were measured for a membrane with a DG of 92%. The average voltage efficiency, coulombic efficiency, and energy efficiency were 0.79, 0.88, and 0.70, respectively, all of which remained stable as the number of cycles increased. Open image in new window

An optimal strategy of electrolyte flow rate for vanadium redox flow battery

Electrolyte flow rate is a key factor that affects the performance of vanadium redox flow battery (VRFB). A kilo-watt class VRFB system is fabricated to investigate the effects of electrolyte flow rate on the performance of VRFB. The experiments show that the capacity increases, but the system efficiency decreases with the increase of electrolyte flow rate. An optimal strategy of electrolyte flow rate is proposed to improve the system efficiency and keep the high capacity simultaneously, which is corresponding to optimize the electrolyte flow rate at different stages of charge and discharge processes. The results show that the system efficiency can be improved as high as 8% when keeping high capacity simultaneously.

A multilayered membrane for vanadium redox flow battery

In order to reduce the vanadium ions permeability of membranes used in vanadium redox flow battery (VRB) while keeping its chemical stability, sulfonated poly(ether ether ketone) (SPEEK)/polypropylene (PP)/perfluorosulfonic acid (PFSA) layered composite membrane (we name it as S/P/P membrane) has been fabricated and characterized. In the S/P/P membrane, polypropylene plays a role of central layer, which is sandwiched by SPEEK and PFSA layer. Results show that S/P/P membrane presents a very low permeability of vanadium ions, accompanied by slightly higher area resistance than that of Nafion 212 membrane (N212). The VRB single cell with S/P/P membrane shows higher coulombic efficiency but lower voltage efficiency in comparison with the one with N212. The performance of VRB with S/P/P membrane can be maintained after more than 50 cycles. Our experimental results suggest that the S/P/P membrane approach is a promising strategy to suppress the migration of vanadium ions in VRB, while retaining an outstanding VRB performance.

Nafion/SiO 2 hybrid membrane for vanadium redox flow battery

Sol–gel derived Nafion/SiO 2 hybrid membrane is prepared and employed as the separator for vanadium redox flow battery (VRB) to evaluate the vanadium ions permeability and cell performance. Nafion/SiO 2 hybrid membrane shows nearly the same ion exchange capacity (IEC) and proton conductivity as pristine Nafion 117 membrane. ICP-AES analysis reveals that Nafion/SiO 2 hybrid membrane exhibits dramatically lower vanadium ions permeability compared with Nafion membrane. The VRB with Nafion/SiO 2 hybrid membrane presents a higher coulombic and energy efficiencies over the entire range of current densities (10–80 mA cm −2), especially at relative lower current densities (<30 mA cm −2), and a lower self-discharge rate compared with the Nafion system. The performance of VRB with Nafion/SiO 2 hybrid membrane can be maintained after more than 100 cycles at a charge–discharge current density of 60 mA cm −2. The experimental results suggest that the Nafion/SiO 2 hybrid membrane approach is a promising strategy to overcome the vanadium ions crossover in VRB.

Study of the Mechanism of the Vanadium 4+/5+ Redox Reaction in Acidic Solutions

The mechanism of the vanadium redox couple has been examined in acidic aqueous solutions. A detailed understanding of this chemistry is of interest for improving and optimizing the performance of vanadium redox-flow batteries, a promising electrochemical electricity storage technology. The vanadium 4+/5+ redox reactions were studied at a rotating disk graphite electrode and polarization curves were obtained in sulfuric acid and perchloric acid, with varying pH and vanadium concentrations. The results were compared to model predictions for different mechanisms. The data were consistent with a model with a multistep chemical-electrochemical-chemical mechanism at low overpotentials, which changes to a multistep electrochemical-chemical-chemical mechanism at higher anodic or cathodic overpotentials. Unusually high Tafel slopes (350-450 mV/decade) were observed for the reduction of at higher overpotentials. While this could not be directly explained by the model, insights gained through the use of the model can provide the basis for some suggestions. © 2003 The Electrochemical Society. All rights reserved.