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Redox flow batteries (RFBs) are promising choices for stationary electric energy storage. Nevertheless, commercialization is impeded by high-cost electrolyte and membrane materials. Here, we report a low-cost all-iron RFB that features inexpensive FeSO 4 electrolytes, microporous membrane along with a glass fiber separator. The addition of 0.1 м 1-ethyl-3-methylimidazolium chloride (EMIC) overcomes the low solubility of FeSO 4 in water which is raised to 2.2 м. DFT calculations demonstrate that EMI+ can strengthen the interaction between sulfate anions and water molecules. This electrolyte composition also allows both anode and cathode reactions to operate without actively maintaining a pH gradient between them, thus eliminating the need for expensive ion exchange membranes. The all-iron RFB demonstrates stable operation at a current density of 20 mA cm−2 for more than 800 cycles via a simple, periodic regeneration process. Furthermore, the system cost of FeSO 4 /EMIC RFBs is projected to be $ 50 per kWh due to its low-cost active materials and the inexpensive microporous membrane. This low-cost, high-concentration all-iron RFB is a promising stationary energy‐storage system for storing renewable energy. • An all-iron aqueous flow battery based on 2 м FeSO 4 /EMIC electrolyte is proposed. • EMI+ improves FeSO 4 solubility by strengthening the water-anion interaction. • EMIC improves the uniformity of iron metal deposition in carbon felt electrodes. • The system cost of the 2 м FeSO 4 /EMIC flow battery is estimated to be $ 50 per kWh. • The 2 м FeSO 4 /EMIC flow battery can cycle over 800 times with a regeneration process. [ABSTRACT FROM AUTHOR]

The demand for lithium batteries with energy densities beyond those of lithium-ion has driven the recent studies on lithium metal anode. High-efficiency electrochemical cycling of lithium requires improved lithium deposition morphology and reduced parasitic reactions between lithium and the liquid electrolyte. A protective layer on lithium metal is expected to reduce contact between lithium metal and the organic solvent, exert compressive mechanical force on the anode, and improve the selectivity and uniformity of lithium ion transport at the electrode surface. This review covers recent advancements in this topic. We first establish the design criteria for an effective coating followed by a brief description of the methods for depositing the layer, characterizing its structure and morphology, and evaluating its electrochemical performance. Our discussion of the literature is organized on resultant layer composition and corresponding ion conduction mechanisms. In the case of polymeric materials, the polarity difference between the polymer and electrolyte solvents determines the degree of swelling and selectivity of lithium ion transport. We conclude by advocating for the need of increased mechanistic study for the functioning mechanism, improved understanding of layer degradation, and demonstration of the protective function in realistic cell environment, namely lean electrolytes and coupled with appropriate cathodes. • This review covers recent advancements in protective coatings for Li metal anode. • The design criteria for an effective coating are proposed. • Ion conduction mechanisms of inorganic and polymeric coatings are discussed. • Demonstration of the protective function in realistic cell condition is advocated. [ABSTRACT FROM AUTHOR]

Single-phase and Dy 3+ /Eu 3+ co-doped novel phosphor LiY(MoO 4 ) 2−x (WO 4 ) x :Dy 3+ ,Eu 3+ , emitting white luminescence under near ultraviolet (NUV) light, was prepared through sol-gel method. The preparation and characterization of this phosphor were systematically studied by X-ray diffraction and spectrofluorophotometric measurements. The molar ratio of metal ions and citric acid (R m/c ) and calcination temperature greatly influenced the phase purity of sample, revealing that the pure phase could be obtained by using R m/c = 1:2.5 and calcination temperature = 800 °C. Under NUV excitation, the as-prepared phosphor exhibited the emissions of 485, 572 and 612 nm, which intensities could be affected by the pH and the concentrations of molybdenum and tungsten ions. By doping appropriate concentrations of Dy 3+ and Eu 3+ , white light emitting phosphor LiY(MoO 4 ) 1.2 (WO 4 ) 0.8 :6%Dy 3+ ,7%Eu 3+ with good responsiveness to NUV light was obtained. The Commission Internationale de L’Eclairage chromaticity coordinates were calculated to be (x = 0.334, y = 0.322), close to the D 65 illuminant (x = 0.313, y = 0.329), indicating the potential application for NUV WLEDs. [ABSTRACT FROM AUTHOR]

This novel electrolyte stabilizes both lithium metal anode and SPAN cathode for high energy density batteries with low cost. Raising the coulombic efficiency of lithium metal anode cycling is the deciding step in realizing long-life rechargeable lithium batteries. Here, we designed a highly concentrated salt/ether electrolyte diluted in a fluorinated ether: 1.8 M LiFSI in DEE/BTFE (diethyl ether/bis(2,2,2-trifluoroethyl)ether), which realized an average coulombic efficiency of 99.37% at 0.5 mA cm−2 and 1 mAh cm−2 for more than 900 cycles. This electrolyte also maintained a record coulombic efficiency of 98.7% at 10 mA cm−2, indicative of its ability to provide fast-charging with high cathode loadings. Morphological studies reveal dense, dendrite free Li depositions after prolonged cycling, while surface analyses confirmed the formation of a robust LiF-rich SEI layer on the cycled Li surface. Moreover, we discovered that this ether-based electrolyte is highly compatible with the low-cost, high-capacity SPAN (Sulfurized polyacrylonitrile) cathode, where the constructed Li||SPAN cell exhibited reversible cathode capacity of 579 mAh g−1 and no capacity decay after 1200 cycles. A cell where a high areal loading SPAN electrode (>3.5 mAh cm−2) is paired with only onefold excess Li was constructed and cycled at 1.75 mA cm−2, maintaining a coulombic efficiency of 99.30% for the lithium metal. Computational simulations revealed that at saturation, the Li-FSI complex forms contact ion pairs, with a first solvation shell comprising DEE molecules, and a second solvation shell with a mix of DEE/BTFE. This study provides a path to enable high energy density Li||SPAN batteries with stable cycling. [ABSTRACT FROM AUTHOR]

Well-crystallized, layered, two-dimensional bismuth oxyhalide (BiOX; X = Cl, Br, or I) ultrathin nanosheets have been synthesized via a simple and low-cost hydrothermal method. The nanosheets are assessed as oxygen reduction reaction (ORR) catalysts for the air electrodes of aluminum-air batteries using linear polarization, constant-current discharge and rotating ring-disk electrode techniques. Electrochemical results show that the obtained BiOI with the highly reactive (001) facets demonstrates higher electrochemical activity than BiOCl and BiOBr under high discharge current density. Koutecky-Levich analysis of the ORR current densities of all compositions indicates that BiOCl and BiOI are mainly dominated by a four-electron pathway. [ABSTRACT FROM AUTHOR]