Dual-Defect Engineering Strategy Enables High-Durability Rechargeable Magnesium-Metal Batteries.

Rechargeable magnesium-metal batteries (RMMBs) are promising next-generation secondary batteries; however, their development is inhibited by the low capacity and short cycle lifespan of cathodes. Although various strategies have been devised to enhance the Mg2+ migration kinetics and structural stability of cathodes, they fail to improve electronic conductivity, rendering the cathodes incompatible with magnesium-metal anodes. Herein, we propose a dual-defect engineering strategy, namely, the incorporation of Mg2+ pre-intercalation defect (P-Mgd) and oxygen defect (Od), to simultaneously improve the Mg2+ migration kinetics, structural stability, and electronic conductivity of the cathodes of RMMBs. Using lamellar V2O5·nH2O as a demo cathode material, we prepare a cathode comprising Mg0.07V2O5·1.4H2O nanobelts composited with reduced graphene oxide (MVOH/rGO) with P-Mgd and Od. The Od enlarges interlayer spacing, accelerates Mg2+ migration kinetics, and prevents structural collapse, while the P-Mgd stabilizes the lamellar structure and increases electronic conductivity. Consequently, the MVOH/rGO cathode exhibits a high capacity of 197 mAh g-1, and the developed Mg foil//MVOH/rGO full cell demonstrates an incredible lifespan of 850 cycles at 0.1 A g-1, capable of powering a light-emitting diode. The proposed dual-defect engineering strategy provides new insights into developing high-durability, high-capacity cathodes, advancing the practical application of RMMBs, and other new secondary batteries.

H2O-Mg2+ Waltz-Like Shuttle Enables High-Capacity and Ultralong-Life Magnesium-Ion Batteries.

Mg-ion batteries (MIBs) are promising next-generation secondary batteries, but suffer from sluggish Mg2+ migration kinetics and structural collapse of the cathode materials. Here, an H2O-Mg2+ waltz-like shuttle mechanism in the lamellar cathode, which is realized by the coordination, adaptive rotation and flipping, and co-migration of lattice H2O molecules with inserted Mg2+, leading to the fast Mg2+ migration kinetics, is reported; after Mg2+ extraction, the lattice H2O molecules rearrange to stabilize the lamellar structure, eliminating structural collapse of the cathode. Consequently, the demo cathode of Mg0.75V10O24·nH2O (MVOH) exhibits a high capacity of 350 mAh g-1 at a current density of 50 mA g-1 and maintains a capacity of 70 mAh g-1 at 4 A g-1. The full aqueous MIB based on MVOH delivers an ultralong lifespan of 5000 cycles The reported waltz-like shuttle mechanism of lattice H2O provides a novel strategy to develop high-performance cathodes for MIBs as well as other multivalent-ion batteries.

Study on the High-Temperature Interaction between Coke and Iron Ores with Different Layer Thicknesses.

Coke plays a key role as the skeleton of the charge column in BF. The gas path formed by the coke layer in the BF has a decisive influence on gas permeability. At high temperatures, the interface between coke and ore undergoes a melting reaction of coke and a reduction reaction of ore. The better the reducibility of the ore, the more conducive it is to the coupling reaction of ore and coke. The melting loss reaction of coke becomes more intense, and the corresponding strength of coke will decrease, which will affect the permeability of the blast furnace and is not conducive to the smooth operation of the blast furnace. Especially with a deterioration in iron ore quality, BF operation faces severe challenges, which makes it necessary to find an effective way to strengthen BF operation. In this study, a melting-dropping furnace was used to develop and clarify the high-temperature interaction between coke and iron ores with different layer thicknesses. The influencing factors were studied by establishing a gas permeability mathematical model and observing the metallographic microscope images of samples after the coke solution loss reaction. The relationships between coke layer thickness, distribution of gas flow, and pressure drop were obtained. The results showed that, under certain conditions, the gas permeability property of a furnace burden has been improved after the coke layer thickness increased. Upon observing the size of coke particles at the interface reaction site, the degree of melting loss reaction can be determined. A smaller particle size indicates more melting loss reaction. A dripping eigenvalue for molten metal was introduced to evaluate the dynamic changes in the comprehensive dripping properties of molten metal of furnace burden, which showed that the dripping eigenvalue for the molten metal could deteriorate because of the unruly thickness and the coke layer thickness should be limited through considering the operational indicators of the blast furnace.

Magnesiation roasting kinetics exploration of vanadium slag toward minimization of tailing toxicity.

In order to minimize the toxicity of vanadium extraction tailings, the vanadium extraction efficiency should be as high as possible to minimize the residual V(V) content in tailings. In this work, the kinetics of the novel magnesiation roasting of vanadium slag, including the roasting mechanism and kinetic models, is explored to intensify the vanadium extraction. By combination of various characterizations, the microscopic mechanism of magnesiation roasting is revealed, which indicates the simultaneous occurrence of the salt-formation→oxidation routine (major) and the oxidation→salt-formation routine (minor). Macroscopic kinetic model studies show the magnesiation roasting of vanadium slag proceeds in two stages. In the initial 50 min, the roasting follows the Interface Controlled Reaction Model, during which the stable roasting temperature is essential to intensify the magnesiation. In the long-time range (50-90 min), the roasting follows the Ginstling-Brounstein Model, during which the acceleration of air blow rate is most favorable. With intensified roasting kinetics, the vanadium extraction efficiency is as high as 96.65%. This work has provided the guideline to intensify the magnesiation roasting of vanadium slag for vanadium extraction, which can not only minimize the tailing toxicity of vanadium extraction but also accelerate the industrial application of the novel magnesiation roasting technique.

Switchable and Strain-Releasable Mg-Ion Diffusion Nanohighway Enables High-Capacity and Long-Life Pyrovanadate Cathode.

Rechargeable magnesium batteries (RMBs) suffer from low capacity and poor cyclability of cathode materials, which is due to the sluggish Mg2+ diffusion kinetics and large lattice strain. Here, a layer-interweaving mechanism in lamellar cathode to simultaneously facilitate Mg2+ diffusion and release Mg2+ -insertion strain is reported. In the Cu3 V2 O7 (OH)2 ·2H2 O (CVOH) cathode, Mg2+ diffusion highways are generated by the vertical interweaving of CVOH layers and V6 O13 layers that nucleate in CVOH during discharging, which are switchable by Mg2+ insertion/extraction. These highways enhance the Mg2+ diffusion coefficient by three orders of magnitude and release 50% Mg2+ -insertion strain. This enables CVOH to exhibit a high capacity of 262 mAh g-1 at high current density of 250 mA g-1 in aqua, and extremely low capacity loss of 0.0004% per cycle in the activated carbon//CVOH cell. This work inspires designing the magnesiation phase transformation of electrodes to resolve both kinetic and strain issues for high-performance RMBs.

A novel process for comprehensive resource utilization of hazardous chromium sludge: Progressive recovery of Si, V, Fe and Cr.

Chromium sludge is a hazardous solid waste which cannot be effectively treated but only piled up and abandoned, causing serious environment pollution and resource wasting. This work proposes an effective novel process to separately recover all resources in chromium sludge via a sustainable way. The obtained acid solving liquid from chromium sludge is desiliconized by cationic flocculant (PCAM) to induce coprecipitation of polysilicate gel and PCAM, which mixture is calcinated to generate the product of white carbon black in purity of 94.35% with a recovery of 92.58%. After desiliconization, V in the solving liquid is selectively extracted by microemulsion (ME), which is recovered as V2O5 in purity of 99.34% with a recovery of 95.53% by the subsequent procedure of stripping-precipitation-calcination. The Fe3+ in raffinate is reduced to Fe2+ cations by Na2SO3, and is then recovered by H2C2O4 precipitation to generate the FeC2O4 product in purity of 99.12% with a recovery of 98.25%. Cr3+ cations in residual solution are recovered by alkaline precipitation and calcination to generate the Cr2O3 product in purity of 98.25% with a recovery of 92.68%. This work provides fresh penetrations into the synchronous detoxification, resource recovery and value-added utilization of hazardous industrial solid wastes.

Microemulsion extraction: An efficient way for simultaneous detoxification and resource recovery of hazardous wastewater containing V(V) and Cr(VI).

Vanadium (V) metallurgy industry produces significant amount of ammonium polyvanadate (APV) wastewater containing V(V) and Cr(VI), thereby polluting the ecological environment and adversely affecting human health and wasting natural resources. Herein, an efficient method for separating V and chromium (Cr) from APV wastewater is proposed based on an artful pretreatment of the selective transformation of Cr(VI) using microemulsion extraction to realize harmless treatment of the wastewater and recycling of V and Cr resources. The influence of various factors on the V and Cr extraction efficiencies has been investigated, including the extractant concentration, aqueous phase-to-microemulsion volume ratio, contact time, and temperature. Furthermore, the principle of Cr transformation and microemulsion extraction and stripping has been illustrated and the recyclability of the microemulsion has been evaluated. Under optimum conditions, 96.29 % of V(V) and 95.56 % of Cr(VI) were separately recovered from the AVP wastewater, confirming the efficient separation and recovery of V and Cr. This study highlights a new approach for the separate recovery of V(V) and Cr(VI) from hazardous wastewater and provides new insights into the simultaneous detoxification and resource utilization of industrial hazardous wastes.

Steering polyoxometalate transformation from octahedral to tetrahedral coordination by counter-cations.

Polyoxometalates (POMs) are intriguing catalysts for various reactions. However, the function of their counter-cations is overlooked. Here, we show that flexible counter-cations of methyltrioctylammonium can trigger polyoxovanadates to transform from octahedrally coordinated H2V10O284- to tetrahedrally coordinated V10O262-. This structural transformation enhances the performance tunability of POM chemistry and improves catalyst design.

[Research on reducing mold flux's radiative heat transfer based on FTIR and XRD].

The mold fluxes samples containing transition metal oxides TiO2 were designed based on the composition of commercial mold fluxes in continuous casting of steel, and the relation between radiative heat transfer and the content of TiO2 was obtained through FTIR spectrum analysis and XRD analysis. The result of FTIR analysis indicates that TiO2 has a great negative effect on infrared transmittance of flux samples in the wavelength range of 1-6 microm. The result of XRD analysis indicates that crystallization of cuspidine was restrained with addition of TiO2, and CaTiO3 and other phases were found in the samples. The decrease in cuspidine phase is beneficial to strand lubrication in the mold. Radiation heat flux from the strand to the mold was calculated using a radiative heat transfer model concluded in previous study. Addition of TiO2 was found to result in a remarkable decrease in radiation heat flux for both glassy and crystalline samples, and the heat flux tended to decrease with increasing TiO2, with the maximal decrease reaching 30%. As a result of great refraction and scatter at surface and grain boundaries of samples, the negative effect of crystalline samples was much larger than that of the glassy ones.