A Passivation-Free Solid Electrolyte Interface Regulated by Magnesium Bromide Additive for Highly Reversible Magnesium Batteries.

Highly reversible Mg battery chemistry demands a suitable electrolyte formulation highly compatible with currently available electrodes. In general, conventional electrolytes form a passivation layer on the Mg anode, requiring the use of MgCl2 additives that lead to severe corrosion of cell components and low anodic stability. Herein, for the first time, we conducted a comparative study of a series of Mg halides as potential electrolyte additives in conventional magnesium bis(hexamethyldisilazide)-based electrolytes. A novel electrolyte formulation that includes MgBr2 showed unprecedented performance in magnesium plating/stripping, with an average Coulombic efficiency of 99.26% over 1000 cycles at 0.5 mA/cm2 and 0.5 mAh/cm2. Further analysis revealed the in situ formation of a robust Mg anode-electrolyte interface, which leads to dendrite-free Mg deposition and stable cycling performance in a Mg-Mo6S8 battery over 100 cycles. This study demonstrates the rational formulation of a novel MgBr2-based electrolyte with high anodic stability of 3.1 V for promising future applications.

Chloride-Free Electrolyte Based on Tetrabutylammonium Triflate Additive for Extended Anodic Stability in Magnesium Batteries.

Rechargeable magnesium batteries (RMBs) have been proposed as a promising alternative to currently commercialized lithium-ion batteries. However, Mg anode passivation in conventional electrolytes necessitates the use of highly corrosive Cl- ions in the electrolyte. Herein for the first time, we design a chloride-free electrolyte for RMBs with magnesium bis(hexamethyldisilazide) (Mg(HMDS)2) and magnesium triflate (Mg(OTf)2) as the main salts and tetrabutylammonium triflate (TBAOTf) as an additive. The TBAOTf additive improved the dissolution of Mg salts, consequently enhancing the charge-carrying species in the electrolyte. COMSOL studies further revealed desirable Mg growth in our modulated electrolyte, substantiated by homogeneous electric flux distribution across the electrolyte-electrode interface. Post-mortem chemical composition analysis uncovered a MgF2-rich solid electrolyte interphase (SEI) that facilitated exceptional Mg deposition/dissolution reversibility. Our study illustrates a highly promising strategy for synthesizing a corrosion-free and reversible Mg battery electrolyte with a widened anodic stability window of up to 4.43 V.

High-Performance NiS2 Hollow Nanosphere Cathodes in Magnesium-Ion Batteries Enabled by Tunable Redox Chemistry.

Two-dimensional metal dichalcogenides have demonstrated outstanding potential as cathodes for magnesium-ion batteries. However, the limited capacity, poor cycling stability, and severe electrode pulverization, resulting from lack of void space for expansion, impede their further development. In this work, we report for the first time, nickel sulfide (NiS2) hollow nanospheres assembled with nanoparticles for use as cathode materials in magnesium-ion batteries. Notably, the nanospheres were prepared by a one-step solvothermal process in the absence of an additive. The results show that regulating the synergistic effect between the rich anions and hollow structure positively affects its electrochemical performance. Crystallographic and microstructural characterizations reveal the reversible anionic redox of S2-/(S2)2-, consistent with density functional theory results. Consequently, the optimized cathode (8-NiS2 hollow nanospheres) could deliver a large capacity of 301 mA h g-1 after 100 cycles at 50 mA g-1, supporting the promising practical application of NiS2 hollow nanospheres in magnesium-ion batteries.

High Utilization of Composite Magnesium Metal Anodes Enabled by a Magnesiophilic Coating.

Metallic magnesium is a promising high-capacity anode material for energy storage technologies beyond lithium-ion batteries. However, most reported Mg metal anodes are only cyclable under shallow cycling (≤1 mAh cm-2) and thus poor Mg utilization (<3%) conditions, significantly compromising their energy-dense characteristic. Herein, composite Mg metal anodes with high capacity utilization of 75% are achieved by coating magnesiophilic gold nanoparticles on copper foils for the first time. Benefiting from homogeneous ionic flux and uniform deposition morphology, the Mg-plated Au-Cu electrode exhibits high average Coulombic efficiency of 99.16% over 170 h cycling at 75% Mg utilization. Moreover, the full cell based on Mg-plated Au-Cu anode and Mo6S8 cathode achieves superior capacity retention of 80% after 300 cycles at a low negative/positive ratio of 1.33. This work provides a simple yet effective general strategy to enhance Mg utilization and reversibility, which can be extended to other metal anodes as well.

In Situ Formed Magnesiophilic Sites Guiding Uniform Deposition for Stable Magnesium Metal Anodes.

Owing to its high volumetric capacity and natural abundance, magnesium (Mg) metal has attracted tremendous attention as an ideal anode material for rechargeable Mg batteries. Despite Mg deposition playing an integral role in determining the cycling lifespan, its exact behavior is not clearly understood yet. Herein, for the first time, we introduce a facile approach to build magnesiophilic In/MgIn sites in situ on a Mg metal surface using InCl3 electrolyte additive for rechargeable Mg batteries. These magnesiophilic sites can regulate Mg deposition behaviors by homogenizing the distributions of Mg-ion flux and electric field at the electrode-electrolyte interphase, allowing flat and compact Mg deposition to inhibit short-circuiting. The as-designed Mg metal batteries achieve a stable cycling lifespan of 340 h at 1.0 mA cm-2 and 1.0 mAh cm-2 using Celgard separators, while the full cell coupled with Mo6S8 cathode maintains a high capacity retention of 95.5% over 800 cycles at 1 C.

Triggering Water and Methanol Activation for Solar-Driven H2 Production: Interplay of Dual Active Sites over Plasmonic ZnCu Alloy.

Methanol steam reforming (MSR) is a promising reaction that enables efficient production and safe transportation of hydrogen, but it requires a relatively high temperature to achieve high activity, leading to large energy consumption. Here, we report a plasmonic ZnCu alloy catalyst, consisting of plasmonic Cu nanoparticles with surface-deposited Zn atoms, for efficient solar-driven MSR without additional thermal energy input. Experimental results and theoretical calculations suggest that Zn atoms act not only as the catalytic sites for water reduction with lower activation energy but also as the charge transfer channel, pumping hot electrons into water molecules and subsequently resulting in the formation of electron-deficient Cu for methanol activation. These merits together with photothermal heating render the optimal ZnCu catalyst a high H2 production rate of 328 mmol gcatalyst-1 h-1 with a solar energy conversion efficiency of 1.2% under 7.9 Suns irradiation, far exceeding the reported conventional photocatalytic and thermocatalytic MSR. This work provides a potential strategy for efficient solar-driven H2 production and various other energy-demanding industrial reactions through designing alloy catalysts.

Facile Top-Down Strategy for Direct Metal Atomization and Coordination Achieving a High Turnover Number in CO2 Photoreduction.

Developing unique single atoms as active sites is vitally important to boosting the efficiency of photocatalytic CO2 reduction, but directly atomizing metal particles and simultaneously adjusting the configuration of individual atoms remain challenging. Herein, we demonstrate a facile strategy at a relatively low temperature (500 °C) to access the in situ metal atomization and coordination adjustment via the thermo-driven gaseous acid. Using this strategy, the pyrolytic gaseous acid (HCl) from NH4Cl could downsize the large metal particles into corresponding ions, which subsequently anchored onto the surface defects of a nitrogen-rich carbon (NC) matrix. Additionally, the low-temperature treatment-induced C═O motifs within the interlayer of NC could bond with the discrete Fe sites in a perpendicular direction and finally create stabilized Fe-N4O species with high valence status (Fe3+) on the shallow surface of the NC matrix. It was found that the Fe-N4O species can achieve a highly efficient CO2 conversion when accepting energetic electrons from both homogeneous and heterogeneous photocatalysts. The optimized sample achieves a maximum turnover number (TON) of 1494 within 1 h in CO generation with a high selectivity of 86.7% as well as excellent stability. Experimental and theoretical results unravel that high valence Fe sites in Fe-N4O species can promote the adsorption of CO2 and lower the formation barrier of key intermediate COOH* compared with the traditional Fe-N4 moiety with lower chemical valence. Our discovery provides new points of view in the construction of more efficient single-atom cocatalysts by considering the optimization of the atomic configuration for high-performance CO2 photoreduction.

Universal Access to Two-Dimensional Mesoporous Heterostructures by Micelle-Directed Interfacial Assembly.

Two-dimensional (2D) mesoporous heterostructures combining ultrathin nanosheet morphology, periodic porous surface structures, and diverse hybrid compositions have become increasingly important for renewable energy storage and electronics. However, it remains a great challenge to develop a universal method to prepare 2D mesoporous heterostructures. Herein, we report a composite-micelle-directed interfacial assembly method to synthesize heterostructures of an ultrathin 2D material covered with mesoporous monolayers assembled on both sides. To demonstrate the concept, we first fabricated a new sandwichlike carbon@MXene@carbon mesoporous heterostructure through the self-assembly of exfoliated MXene nanosheets and block copolymer F127/melamine-formaldehyde resin composite micelles and subsequent thermal treatment. Finally, we demonstrate that the carbon@MXene@carbon mesoporous heterostructured nanosheets manifest remarkably enhanced electrochemical performance as a cathode material for lithium-sulfur batteries.

Recycling of Spent Lithium Iron Phosphate Cathodes: Challenges and Progress.

The number of spent lithium iron phosphate (LiFePO4, LFP) batteries will increase sharply in the next few years, owing to their large market share and development potential. Therefore, recycling of spent LFP batteries is necessary and urgent from both resource utilization and environmental protection standpoints. In this review, the significance of pretreatment for LFP recycling is first underscored, and its technical challenges and recent advancements are presented. Following that, the current recycling methods for spent LFP cathodes are outlined in terms of the respective treating processes, advantages, and disadvantages. Additionally, the preparation methods of LFP cathode material are reviewed to guide the resynthesis of LFP that uses salts obtained from spent LFP, which are beneficial for closed-loop recycling of LFP batteries. Lastly, we explore the future development direction of spent LFP battery recycling, highlighting the importance of technological innovation to advance the sustainable growth of the LFP battery industry.

A Recyclable Ionogel with High Mechanical Robustness Based on Covalent Adaptable Networks.

Ionogels are an emerging class of soft materials for flexible electronics, with high ionic conductivity, low volatility, and mechanical stretchability. Recyclable ionogels are recently developed to address the sustainability crisis of current electronics, through the introduction of non-covalent bonds. However, this strategy sacrifices mechanical robustness and chemical stability, severely diminishing the potential for practical application. Here, covalent adaptable networks (CANs) are incorporated into ionogels, where dynamic covalent crosslinks endow high strength (11.3 MPa tensile strength), stretchability (2396% elongation at break), elasticity (energy loss coefficient of 0.055 at 100% strain), and durability (5000 cycles of 150% strain). The reversible nature of CANs allows the ionogel to be closed-loop recyclable for up to ten times. Additionally, the ionogel is toughened by physical crosslinks between conducting ions and polymer networks, breaking the common dilemma in enhancing mechanical properties and electrical conductivity. The ionogel demonstrates robust strain sensing performance under harsh mechanical treatments and is applied for reconfigurable multimodal sensing based on its recyclability. This study provides insights into improving the mechanical and electrical properties of ionogels toward functionally reliable and environmentally sustainable bioelectronics.