Solid–Liquid Coexisting LiNO₃ Electrolyte for Extremely Stable Lithium Metal Anodes on a Bare Cu Foil

Li dendrite growth restricts the promising application of lithium (Li) metal anodes in high-energy-density batteries. The host matrix, solid electrolyte, and surface modification of Li were widely studied to suppress Li dendrite growth. However, material preparation and process modification are complex and high-cost. Herein, a simple and effective solid–liquid coexisting lithium nitrate (SLC-LiNO3) electrolyte was proposed, and excellent Li plating/stripping properties were obtained on a planar and bare Cu foil without a host matrix and surface modification. It is confirmed that a robust LiF-rich solid electrolyte interface (SEI) layer was formed in the SLC-LiNO3 electrolyte and the Li+ transference number was obviously enlarged due to the induced action of solid LiNO3 particles. As a result, uniform Li deposition without uncontrollable Li dendrite growth was achieved. In the SLC-LiNO3 electrolyte, a high coulombic efficiency (98% for 300 cycles) was obtained on a planar Cu foil and the stable Li plating/stripping cycling times were up to 2500 and 700 h (i.e., 1250 and 700 cycles) at 1 and 2 mA cm–2, respectively. This provides a promising and convenient method to suppress lithium dendrite growth in lithium metal batteries

Metal–Organic Framework-Derived Co₃O₄@MWCNTs Polyhedron as Cathode Material for a High-Performance Aluminum-Ion Battery

Because of the unprecedented development and popularization of portable electronics, electric vehicles, and smart grid, rechargeable batteries have become one of the hottest topics within worldwide research for the past decade. Among all of the proposed nonlithium-based battery systems, rechargeable aluminum-ion batteries (RAIBs) are considered as a promising candidate due to aluminum’s abundance and safety. Naturally, exploring compatible and high-performance cathode materials for RAIBs becomes a key issue for pushing RAIBs from lab-level to industrialization. In this work, we report a novel high-performance RAIB system using MOF-derived Co3O4@MWCNTs polyhedron composite as cathode. The well-defined morphology of MOF-derived Co3O4 and enhancement brought by MWCNTs allow Co3O4@MWCNTs polyhedrons to deliver an initial discharge capacity of ca. 266.3 mAh g–1, and the reversible specific capacity can reach 125 mAh g–1 at 100 mA g–1 over 150 cycles. The energy storage mechanism has been verified to be a reversible valence-change reaction between Co3O4 and Co. These findings can enlighten future research regrading MOF derivatives as advanced cathode materials for RAIBs

Molecule Engineering of Dual-Electron-Withdrawing Groups for Rechargeable Aluminum Batteries

A rechargeable aluminum battery is expected to be the next-generation energy storage system due to abundant resources and good safety. Inorganic positive electrodes face the bottleneck to develop high-energy-density Al batteries. Organic molecules with active groups provide a promising opportunity to solve the restrictive problems. In this work, novel dual-electron-withdrawing group organic molecules are proposed as positive electrode materials of Al batteries. Molecule engineering of electron-withdrawing carbonyl groups is developed by introducing heterogeneous electron-withdrawing chloride groups and regulating the benzene ring. It is confirmed that the molecular polarity, orbital energy level, and reaction activity of carbonyl organic molecules can be effectively regulated by molecule engineering. By introducing electron-withdrawing chloride groups and decreasing the benzene ring number, discharge voltage and conductivity of organic molecules are obviously enlarged. However, the solubility in the ionic liquid electrolyte increases, which leads to poor cycling stability. The theoretical capacity depends on the weight ratio of carbonyl groups and organic molecules. 2,3-Dichloro-1,4-naphthalenedione (2Cl-NQ) with dual-electron-withdrawing carbonyl and chloride groups delivers an initial specific capacity of 150 mA h g–1. Particularly, the stable discharge voltage and energy density of 2Cl-NQ are up to1.5 V and 159 W h kg–1, respectively. Electron-withdrawing carbonyl groups as active sites contribute to the capacity by coordinating with positively charged AlCl2+. The charge/discharge mechanism is independent of the molecule structure and heterogeneous chloride groups. This work provides a clear insight to understand the design principle of organic positive electrodes. A novel dual-electron-withdrawing group organic molecule with high energy density for Al batteries is obtained

Upcycling of Titanium by Molten Salt Electrorefining

Molten salt electrorefining is expected to be a powerful technology for upcycling titanium scrap because of its robust ability of removing impurities. However, realizing the stable operation of electrorefining, for example, the current efficiency of the anode and the cathode is still a key challenge from the viewpoint of industrial applications. Here, we study titanium’s anodic dissolution and cathodic deposition processes via a direct three-dimensional visualization method based on a computed tomography technology under high-temperature operational conditions. Real-time quantitative results show that the current efficiency is obviously affected by the concentration of titanium ions in the melt. Visual analysis of the local dissolution rate and the curvature of the titanium anode at different electrolysis stages reveals the kinetic origin of the concentration-induced current efficiency changes, which arise from the priority of the side reactions being dependent on the concentration of titanium ions. Finally, we show that employing the high concentration and single existence forms of titanium ions is an effective strategy to prevent the side reactions and improve the current efficiency. This work provides a fresh and fundamental understanding of the side reactions occurring at the interface of electrodes and is significant for facilitating the stability of electrorefining engineering of titanium

Hierarchically Plasmonic Z‑Scheme Photocatalyst of Ag/AgCl Nanocrystals Decorated Mesoporous Single-Crystalline Metastable Bi₂₀TiO₃₂ Nanosheets

The hierarchical photocatalysts of Ag–AgCl@Bi₂₀TiO₃₂ composites have been successfully synthesized by anchoring Ag–AgCl nanocrystals on the surfaces of mesoporous single-crystalline metastable Bi₂₀TiO₃₂ nanosheets via a two-stage strategy for excellent visible-light-driven photocatalytic activities in the Z-scheme system. First, the single-crystalline metastable Bi₂₀TiO₃₂ nanosheets with tetragonal structures were prepared via a facile hydrothermal process in assistance with the post-heat-treatment route using benzyl alcohol. Especially, the mesoporous Bi₂₀TiO₃₂ nanosheets showed high photocatalytic activity for the degradation of rhodamine B dye under visible-light irradiation. Then, the as-prepared mesoporous Bi₂₀TiO₃₂ nanosheets were used as a support for loading Ag–AgCl nanocrystals using the deposition–precipitation method and irradiation–reduction process to fabricate the Ag–AgCl@Bi₂₀TiO₃₂ composites. Inspiringly, the hierarchical Ag–AgCl@Bi₂₀TiO₃₂ photocatalyst has the higher photocatalytic performance than Ag–AgCl nanocrystals and mesoporous Bi₂₀TiO₃₂ nanosheets over the degradation of rhodamine B and acid orange 7 dyes, which is attributed to the effective charge transfer from plasmon-excited Ag nanocrystal to Bi₂₀TiO₃₂ for the construction of a Z-scheme visible-light photocatalyst. This work could provide new insights into the fabrication of hierarchically plasmonic photocatalysts with high performance and facilitate their practical application in environmental issues

Surface Engineering Based on Conductive Agent Dispersion Uniformity: Strategies toward Performance Consistency of Lithium-Ion Batteries

The consistency of lithium-ion battery performance is the key factor affecting the safety and cycle life of battery packs. Surface engineering of electrodes in production processes plays an important role in improving the consistency of battery performance. In this study, the drying process in the electrode manufacturing process is studied as the effect on surface engineering of the electrode materials, with consideration on impacting the battery performance. Specifically, the solid content of the slurry and drying temperature are considered to be the two factors that affect conductive agent dispersion uniformity in the porous electrodes. To achieve surface engineering on the dispersion uniformity of the conductive agent, the optimal processing parameters can be obtained by adjusting the temperature and solid content of the slurry. The mechanism of dispersion uniformity of the conductive agent is mainly related to the polyvinylidene fluoride grid structure. In the manufacturing of lithium-ion batteries, the electrode coated with 66% solid slurry and dried at 90–100 °C presents stable energy storage performance, which is beneficial to maintain the stable performance of the battery pack in the application

Rechargeable Nickel Telluride/Aluminum Batteries with High Capacity and Enhanced Cycling Performance

Rechargeable aluminum-ion batteries (AIBs) possess significant advantages of high energy density, safety performance, and abundant natural resources, making them one of the desirable next-generation substitutes for lithium battery systems. However, the poor reversibility, short lifespan, and low capacity of positive materials have limited its practical applications. In comparison with semiconductors, the metallic nickel telluride (NiTe) alloy with enhanced electrical conductivity and fast electron transmission is a more favorable electrode material that could significantly decrease the kinetic barrier during battery operation for energy storage. In this paper, the NiTe nanorods prepared through a simple hydrothermal routine enable an initial reversible capacity of approximately 570 mA h g–1 (under the current density of 200 mA g–1) to be delivered on the basis of the ionic liquid electrolyte, along with the average voltage platform of about 1.30 V. Moreover, the cycling performance could be easily enhanced using a modified separator to prevent the diffusion of soluble intermediate species to the negative electrode side. At a high rate of 500 mA g–1, the NiTe nanorods could retain a specific capacity of about 307 mA h g–1 at the 100th cycle. The results have important implications for the research of transition metal tellurides as positive electrode materials for AIBs

High-Performance Aluminum-Ion Battery with CuS@C Microsphere Composite Cathode

On the basis of low-cost, rich resources, and safety performance, aluminum-ion batteries have been regarded as a promising candidate for next-generation energy storage batteries in large-scale energy applications. A rechargeable aluminum-ion battery has been fabricated based on a 3D hierarchical copper sulfide (CuS) microsphere composed of nanoflakes as cathode material and room-temperature ionic liquid containing AlCl₃ and 1-ethyl-3-methylimidazolium chloride ([EMIm]­Cl) as electrolyte. The aluminum-ion battery with a microsphere electrode exhibits a high average discharge voltage of ∼1.0 V <i>vs</i> Al/AlCl₄^–, reversible specific capacity of about 90 mA h g^–1 at 20 mA g^–1, and good cyclability of nearly 100% Coulombic efficiency after 100 cycles. Such remarkable electrochemical performance is attributed to the well-defined nanostructure of the cathode material facilitating the electron and ion transfer, especially for chloroaluminate ions with large size, which is desirable for aluminum-ion battery applications

Natural Convection in Molten Salt Electrochemistry

Molten salt electrochemistry has been widely used in many fields, especially for metal extraction/refinement. The understanding of mass transfer in molten salts under harsh operation conditions is of great importance to reveal reaction mechanisms and advance fine technologies. It has been generally assumed that natural convection is negligible in stagnant molten salt electrochemistry. Herein, we report an abnormal natural convection in molten LiCl–KCl, with the arising time from 2.37 s at 873 K to 10.13 s at 673 K. Using the concentration correction factor, the derived thickness of the natural convection–diffusion layer (δconv.) was found to be ranging from 128 to 163 μm, much thinner than those in aqueous solutions (∼200 μm). The simulations showed that the notable natural convection resulted from convection–diffusion layer (CDL) convection dominated over the density-driven convection even at high redox concentrations, implying the severe vibration of molten salt systems. To suppress the intense natural convection, we predicted that the use of microelectrodes (with radii less than 23.2 μm for δconv. = 150 μm) would be a promising tool, regardless of their inferior stabilities in high-temperature molten salts at this stage. These innovative findings offer insights into the impact of natural convection on mass transfer in molten salts that have not been previously revealed