Preventing Dissolution of Cathode Active Materials by Ion-anchoring Zeolite-based Separators for Durable Aqueous Zinc Batteries.

Aqueous zinc batteries have emerged as promising energy storage devices due to their safety and low cost. However, they face challenges such as anodic dendrite formation and cathodic compound dissolution. Here, we present the development of a polymer-matrixed zeolite separator (SZ) by synthesizing zeolite materials on a flexible polymeric membrane. This separator acts as an effective ionic barrier, preventing the leaching and shuttling of vanadium from the cathode, while significantly inhibiting the formation of by-products and zinc dendrites. The SZ cells demonstrate stable operation for more than 400 cycles at 0.5 A g-1 , with an initial capacity of 375.4 mAh g-1 , and over 10,000 cycles at 15 A g-1 . Notably, when pre-anchored with vanadium ions, the SZ-V cells exhibited excellent capacity retention of up to 94.6 % over 1000 cycles. The SZ separator featuring an ion barrier represents a crucial advancement towards the commercialization of zinc storage devices.

Insight into the removal of vanadium ions from model and real wastewaters using surface grafted zirconia-based adsorbents: Batch experiments, equilibrium and mechanism study.

This study concerns the fabrication of CTAB- and N,N-dimethyltetradecylamine-grafted zirconia and evaluation of their ability to adsorb vanadium ions. The effectiveness of ZrO2 functionalization and the different nature of the modifiers used were confirmed by differences in the porosity (ZrO2: SBET = 347 m2/g; ZrO2-CTAB: SBET = 375 m2/g, ZrO2-NH+: SBET = 155 m2/g), types of functional groups, and isoelectric points (the ZrO2 and CTAB-modified samples have IEPs = 3.8 and 3.9, ZrO2-NH+ has IEP = 7.1) of the prepared adsorbents. The designed materials were tested in batch adsorption experiments involving the removal of vanadium ions from model wastewaters at various process parameters, among which pH proved to be the most important. Based on equilibrium and kinetic evaluations, it was proved that the sorption of V(V) ions followed pseudo-second-order and intraparticle diffusion models, and the data were better fitted to the Langmuir model, suggesting the following order of the sorbents in terms of favorability for V(V) ion adsorption: ZrO2-NH+ > ZrO2 > ZrO2-CTAB. The estimated maximum monolayer capacity of ZrO2-NH+ for V(V) (87.72 mg/g) was the highest among the tested materials. Additionally, it was confirmed that adsorption of V(V) ions onto synthesized materials is a heterogeneous, exothermic, and spontaneous reaction, as evidenced by the calculated values of thermodynamic parameters. The key goals included the transfer of experimental findings obtained using model solutions to the adsorption of V(V) ions from solutions arising from the leaching process of spent catalysts. The highest adsorption efficiencies of 70.8% and 47.5% were recorded for the ZrO2-NH+ material in acidic solution; this may be related to the protonization of -NH+ groups, which favors the sorption of V(V) ions. Based on desorption tests as well as the results of infrared and X-ray photoelectron spectroscopy, irrespective of the process conditions, the physical nature of the adsorbent/adsorbate interaction was confirmed.

Enhanced selective separation of vanadium(V) and chromium(VI) using the CeO2 nanorod containing oxygen vacancies.

Adsorption of vanadium from wastewater defends the environment from toxic ions and contributes to recover the valuable metal. However, it is still challenging for the separation of vanadium (V5+) and chromium (Cr6+) because of their similar properties. Herein, a kind of CeO2 nanorod containing oxygen vacancies is facilely synthesized which displays ultra-high selectivity of V5+ against various competitive ions (i.e., Fe, Mn, Cr, Ni, Cu, Zn, Ga, Cd, Ba, Pb, Mg, Be, and Co). Moreover, a large separation factor (SFV/Cr) of 114,169.14 for the selectivity of V5+ is achieved at the Cr6+/V5+ ratio of 80 with the trace amount of V5+ (~ 1 mg/L). The results show that the process of V5+ uptake is the monolayer homogeneous adsorption and is controlled by external and intraparticle diffusions. In addition, it also shows that V5+ is reduced to V3+ and V4+ and then formation of V-O complexation. This work offers a novel CeO2 nanorod material for efficient separation of V5+ and Cr6+ and also clarifies the mechanism of the V5+ adsorption on the CeO2 surface.

Sulfonated calixarene modified Poly(methyl methacrylate) nanoparticles:A promising adsorbent for Removal of Vanadium Ions from aqueous media.

The poly (methyl methacrylate) (PMMA)-based nanoparticle was synthesized by surfactant-free emulsion polymerization method and then post modified with Calixarene using (3-Aminopropyl)triethoxysilane organo-silane as a linker after OH-treatment. The prepared structure was applied for efficient adsorption of Vanadium ions in the aqueous solution after characterization by FT-IR, SEM, TEM, DLS, and EDX. Additional investigations discovered that the prepared adsorbent has a good capacity to adsorb vanadium ions. The effect of key experimental factors was studied to find the optimal point of adsorbent efficiency including the initial concentration of analyte, sorbent dosage, pH of the solution, contact time, and type/quantity of the eluents. It was specified, the maximum adsorption capacity for the synthesized nanoparticles was obtained about 322 mg g-1. The adsorption mechanism was revealed that the model of Langmuir isotherm well-matched compared to the others due to the calculated equilibrium data. Besides, the kinetics of the adsorption process was fitted with pseudo-second-order. Eventually, the prepared adsorbent was successfully applied in vanadium adsorption from real water media.

Electrochemical Characteristics and Transport Properties of V(II)/V(III) Redox Couple in a Deep Eutectic Solvent: Magnetic Field Effect.

Compared with conventional aqueous electrolytes, deep eutectic solvent (DES) has a wider electrochemical stability window, simple preparation, potential biodegradability, and lower cost, leading to its utilization as electrolyte for non-aqueous redox flow batteries (RFB). However, the large viscosity and inferior transport properties hinder the wide spread of DES electrolyte. To circumvent these issues, various additives as well as external fields can be applied separately or synergistically. This work reports a study on the inclusion of a DC magnetic field to the glycol-based DES electrolyte of a RFB. The effects of magnetic field on the physical and electrochemical characteristics of the electrolyte and the active redox couple on mass transfer are studied by cyclic voltammetry and electrochemical impedance spectroscopy. The experimental results show that the viscosity of the vanadium DES electrolyte decreases and the conductivity increases after adding a magnetic field. With the intensity of the added magnetic field increases, the oxidation and reduction peak current densities of the vanadium DES electrolyte keep increasing. Under the magnetic field intensity of 605 mT, the oxidation peak current density and the reduction peak current density increases 41.56 and 30.74%, respectively, compared with those of no added magnetic field. The ohmic resistance and electrochemical reaction resistance of the vanadium DES electrolyte are reduced when adding the magnetic field, reaching to 40.55 and 43.28%, respectively, with a magnetic field intensity of 605 mT. This study shows an effective yet simple way to improve the physical and electrochemical properties of DES electrolyte, which owns the potential to be widely applied in non-aqueous redox flow batteries.

Application of Novel Anion-Exchange Blend Membranes (AEBMs) to Vanadium Redox Flow Batteries.

Both cation-exchange membranes and anion-exchange membranes are used as ion conducting membranes in vanadium redox flow batteries (VRFBs). Anion-exchange membranes (AEMs) are applied in vanadium redox flow batteries due to the high blocking property of vanadium ions via the Donnan exclusion effect. In this study, novel anion-exchange blend membranes (AEBMs) were prepared, characterized, and applied in VRFBs. Bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide), poly[(1-(4,4′-diphenylether)-5-oxybenzimidazole)-benzimidazole] (PBI-OO) and sulfonated polyether sulfone polymer were combined to prepare 3-component AEBMs with 1,2,4,5-tetramethylimidazole (TMIm) for quaternization. 3-component AEBMs showed significantly enhanced chemical and mechanical properties compared with those of 2-component AEBMs, resulting in an improved performance in VRFBs. The compositions of the anion-exchange polymers in 3-component AEBMs were systematically varied to optimize the AEBMs for the redox-flow battery application. While the 3-component AEBMs showed comparable efficiencies with Nafion® 212 membranes, they displayed improved vanadium ions cross-over as was confirmed by open circuit voltage tests and capacity fade tests conducted in VRFBs. In addition, one of the synthesized 3-component AEBM had a superior coulombic efficiency and capacity retention in a charging⁻discharging test over 300 cycles at a current density of 40 mA/cm². It can thus be concluded that 3-component AEBMs are promising candidates for long-term operation in VRFBs.