Functionalized carbon black modified sulfonated polyether ether ketone membrane for highly stable vanadium redox flow battery

Nature of Solvent/Nonsolvent Strategy in Achieving Superior Polybenzimidazole Membrane for Vanadium Redox Flow Battery

The tightly connected structure of polybenzimidazole (PBI) membrane can be relaxed by solvent/nonsolvent solution to achieve a high proton conductivity for vanadium redox flow battery (VRFB). However, the nature behind the solvent/nonsolvent strategy is not unraveled. This work proposes a guideline to analyze the effect of PBI membrane relaxing formulas based on the interactions between different components in membranes. The supreme-efficient PBI membrane derived by the DMSO/formamide formula according to the guideline displays a marvelous performance for VRFB, with the proton conductivity boosted by 4300 % (from 1.93 to 83.33 mS cm-1), and VRFB assembled with this membrane achieves an outstanding energy efficiency of 82.5 % under 200 mA cm-2. Moreover, this work profoundly unravels the structure, property and performance relationship of PBI membrane, which is of great value for the development of membranes.

A Comprehensive Review of Nanoparticles: From Classification to Application and Toxicity

Nanoparticles are structures that possess unique properties with high surface area-to-volume ratio. Their small size, up to 100 nm, and potential for surface modifications have enabled their use in a wide range of applications. Various factors influence the properties and applications of NPs, including the synthesis method and physical attributes such as size and shape. Additionally, the materials used in the synthesis of NPs are primary determinants of their application. Based on the chosen material, NPs are generally classified into three categories: organic, inorganic, and carbon-based. These categories include a variety of materials, such as proteins, polymers, metal ions, lipids and derivatives, magnetic minerals, and so on. Each material possesses unique attributes that influence the activity and application of the NPs. Consequently, certain NPs are typically used in particular areas because they possess higher efficiency along with tenable toxicity. Therefore, the classification and the base material in the NP synthesis hold significant importance in both NP research and application. In this paper, we discuss these classifications, exemplify most of the major materials, and categorize them according to their preferred area of application. This review provides an overall review of the materials, including their application, and toxicity.

An Ultra-Low Self-Discharge Aqueous|Organic Membraneless Battery with Minimized Br2 Cross-Over

Batteries dissolving active materials in liquids possess safety and size advantages compared to solid-based batteries, yet the intrinsic liquid properties lead to material cross-over induced self-discharge both during cycling and idle when the electrolytes are in contact, thus highly efficient and cost-effective solutions to minimize cross-over are in high demand. An ultra-low self-discharge aqueous|organic membraneless battery using dichloromethane (CH2 Cl2 ) and tetrabutylammonium bromide (TBABr) added to a zinc bromide (ZnBr2 ) solution as the electrolyte is demonstrated. The polybromide is confined in the organic phase, and bromine (Br2 ) diffusion-induced self-discharge is minimized. At 90% state of charge (SOC), the membraneless ZnBr2 |TBABr (Z|T) battery shows an open circuit voltage (OCV) drop of only 42 mV after 120 days, 152 times longer than the ZnBr2  battery, and superior to 102 previous reports from all types of liquid active material batteries. The 120-day capacity retention of 95.5% is higher than commercial zinc-nickel (Zn-Ni) batteries and vanadium redox flow batteries (VRFB, electrolytes stored separately) and close to lithium-ion (Li-ion) batteries. Z|T achieves >500 cycles (2670 h, 0.5 m electrolyte, 250 folds of membraneless ZnBr2  battery) with ≈100% Coulombic efficiency (CE). The simple and cost-effective design of Z|T provides a conceptual inspiration to regulate material cross-over in liquid-based batteries to realize extended operation.

Self-Assembled Construction of Ion-Selective Nanobarriers in Electrolyte Membranes for Redox Flow Batteries

Ion-conducting membranes (ICMs) with high selectivity are important components in redox flow batteries. However it is still a challenge to break the trade-off between ion conductivity and ion selectivity, which can be resolved by the regulation of their nanostructures. Here, polyoxometalate (POM)-hybridized block copolymers (BCPs) are used as self-assembled additives to construct proton-selective nanobarriers in the ICM matrix to improve the microscopic structures and macroscopic properties of ICMs. Benefiting from the co-assembly behavior of BCPs and POMs and their cooperative noncovalent interactions with the polymer matrix, ∼50 nm ellipsoidal functional nanoassemblies with hydrophobic vanadium-shielding cores and hydrophilic proton-conducting shells are constructed in the sulfonated poly(ether ether ketone) matrix, which leads to an overall enhancement of proton conductivity, proton selectivity, and cell performance. These results present a self-assembly route to construct functional nanostructures for the modification of polymer electrolyte membranes toward emerging energy technologies.

Two-Dimensional Materials Applied in Membranes of Redox Flow Battery

Redox flow batteries (RFBs) are one of the most promising techniques to store and convert green and renewable energy, benefiting from their advantages of high safety, flexible design and long lifespan. Membranes with fast and selective ions transport are required for the advances of RFBs. Remarkably, two-dimensional (2D) materials with high mechanical and chemical stability, strict size exclusion and abundantly modifiable functional groups, have attracted extensive attentions in the applications of energy fields. Herein, the improvements and perspectives of 2D materials working for ionic transportation and sieving in RFBs membranes are presented. The characteristics of various materials and their advantages and disadvantages in the applications of RFBs membranes particularly are focused. This review is expected to provide a guidance for the design of membranes based on 2D materials for RFBs.

Electrospun Nanofibers Based on Polymer Blends with Tunable High-Performance Properties for Innovative Fire-Resistant Materials

The main concern of materials designed for firefighting protective clothing applications is heat protection, which can be experienced from any uncomfortably hot objects or inner spaces, as well as direct contact with flame. While textile fibers are one of the most important components of clothing, there is a constant need for the development of innovative fire-retardant textile fibers with improved thermal characteristics. Lately, inherently fire-resistant fibers have become very popular to provide better protection for firefighters. In the current study, the electrospinning technique was applied as a versatile method to produce micro-/nano-scaled non-woven fibrous membranes based on various ratios of a poly(ether-ether-ketone) (PEEK) and a phosphorus-containing polyimide. Rheological measurements have been performed on solutions of certain ratios of these components in order to optimize the electrospinning process. FTIR spectroscopy and scanning electron microscopy were used to investigate the chemical structure and morphology of electrospun nanofiber membranes, while thermogravimetric analysis, heat transfer measurements and differential scanning calorimetry were used to determine their thermal properties. The water vapor sorption behavior and mechanical properties of the optimized electrospun nanofiber membranes were also evaluated.

Simultaneous Regulation of Solvation Shell and Oriented Deposition toward a Highly Reversible Fe Anode for All-Iron Flow Batteries

Developing low-cost all-iron hybrid redox flow batteries (RFBs) presents a practical alternative to the high-cost all-vanadium RFBs and is deemed vital for grid-scale energy storage applications. However, the intrinsically poor Fe anode reversibility associated with the deposition and dissolution of metallic iron greatly limits the cycling performance and long-term stability of all-iron hybrid RFBs. Herein, a highly reversible and dendrite-free Fe anode is reported for all-iron RFBs through regulation of polar solvent dimethyl sulfoxide (DMSO) on FeCl₂ anolyte, which simultaneously reshapes Fe²⁺ solvation structure and induces controllable oriented Fe deposition. Combining both experimental and theoretical analyses, the polar DMSO additives prove effective in replacing H₂ O molecule from the primary solvation shell of Fe²⁺ cation via the Fe²⁺ -O (DMSO) bond and meanwhile induces a fine-grained Fe nucleation on the preferred Fe (110) plane, which are responsible for the minimized hydrogen evolution and dendrite-free Fe deposition that significantly enhance Fe anode reversibility. The all-iron RFB based on the proposed FeCl₂ -DMSO anolyte demonstrates an excellent combination of peak power density of 134 mW cm^-2 , high energy efficiency of 75% at 30 mA cm^-2 , and high capacity retention of 98.6% over 200 cycles, which presents the best performance of all-iron RFBs among previously reported research.

Swelling-Induced Quaternized Anthrone-Containing Poly(aryl ether ketone) Membranes with Low Area Resistance and High Ion Selectivity for Vanadium Flow Batteries

A vanadium flow battery (VFB) is one of the most promising electrochemical energy storage technologies. However, membranes for VFBs still suffer from high cost or low conductivity and poor stability. Here, we report new quaternized anthrone-containing poly(aryl ether ketone) (QAnPEK) membranes for VFBs. QAnPEK membranes with moderate ion exchange capacity (1.26 mmol g^-1) were swelling-induced in H₃PO₄ (50 wt %) to form wider ion transport pathways that significantly enhanced membrane conductivity (e.g., 0.49 Ω cm² for the QAnPEK-virgin membrane and 0.12 Ω cm² for the swelling-induced QAnPEK-90 membrane). The bulky rigid anthrone-containing backbone provided high swelling resistance and enabled QAnPEK membranes to have high ion selectivity. As a result, QAnPEK membranes displayed low area resistance, high ion selectivity, and robust mechanical strength. The QAnPEK-90 membrane yielded excellent energy efficiencies (92.4% at 80 mA cm^-2, 85.1% at 200 mA cm^-2, and 80.3% at 280 mA cm^-2). Moreover, QAnPEK membranes exhibited outstanding in situ and ex situ stability, for example, the VFB with the QAnPEK-40 membrane demonstrated highly stable battery performance for 3000 cycles at 160 mA cm^-2. QAnPEK membranes are attractive candidates for VFB application.

Surface-Modified Approach to Fabricate Nafion Membranes Covalently Bonded with Polyhedral Oligosilsesquioxane for Vanadium Redox Flow Batteries

An aminopropyl isobutyl polyhedral oligosilsesquioxane (NH₂-POSS) surface-modified Nafion membrane has been designed by chemical grafting for vanadium redox flow batteries (VRFBs). NH₂-POSS is a cage-like macromer consisting of an inorganic Si₈O₁₂ core surrounded by seven inert isobutyl groups and one active aminopropyl group. The sulfonic acid groups on the surface of Nafion can be activated by 1,1-carbonyldiimidazole for further modification with NH₂-POSS. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) prove that NH₂-POSS has been successfully grafted on the surface of a Nafion 115 membrane. Although the proton conductivity decreases slightly, the organic-inorganic hybrid membranes display enhanced ion selectivity and excellent dimensional stability with lower water uptake and swelling ratio than Nafion 115. Moreover, two-dimensional-grazing incidence X-ray diffraction (2D-GIXRD) reveals that the introduction of NH₂-POSS forms a POSS layer on the surface of the membrane and narrows the space of Nafion clusters, which helps to block VO²⁺ permeation. A VRFB with the surface-modified Nafion membrane displays an outstanding performance with an average Coulombic efficiency (CE) of 98.7% and energy efficiency (EE) of 84.5% at a current density of 80 mA cm^-2, superior to those of the Nafion 115 membrane (CE = 95.7%, EE = 81.7%). Furthermore, the cell holds a high capacity retention of 49.2% after 1000 charge-discharge cycles, in contrast to that of 41.9% for the cell with Nafion 115 after only 200 cycles. The results suggest that the surface-modified hybrid membrane is a promising strategy to overcome the vanadium ion crossover in VRFBs.

Enhanced Specific Mechanism of Separation by Polymeric Membrane Modification-A Short Review

Membrane technologies have found a significant application in separation processes in an exceeding range of industrial fields. The crucial part that is decided regarding the efficiency and effectivity of separation is the type of membrane. The membranes deal with separation problems, working under the various mechanisms of transportation of selected species. This review compares significant types of entrapped matter (ions, compounds, and particles) within membrane technology. The ion-exchange membranes, molecularly imprinted membranes, smart membranes, and adsorptive membranes are investigated. Here, we focus on the selective separation through the above types of membranes and detect their preparation methods. Firstly, the explanation of transportation and preparation of each type of membrane evaluated is provided. Next, the working and application phenomena are evaluated. Finally, the review discusses the membrane modification methods and briefly provides differences in the properties that occurred depending on the type of materials used and the modification protocol.