Titanium-Oxygen Clusters Brazing Li with Li6.5La3Zr1.5Ta0.5O12 for High-Performance All-Solid-State Li Batteries.

Garnet-based solid-state electrolytes are considered crucial candidates for solid-state Li batteries due to their high Li+ conductivity and nonflammability; however, poor interfacial contact with the Li anode and growth of Li dendrites limit their application. Herein, a high-activity titanium-oxygen cluster is used as a brazing filler to braze the Li6.5La3Zr1.5Ta0.5O12 (LLZTO) with an Li anode into the whole unit. The brazing layer leads to a significantly lower interfacial impedance of 8.32 Ω cm2. Furthermore, the brazing layer is an isotropic amorphous ion-electron hybrid conductive layer, which significantly promotes Li+ transport and regulates the distribution of the electric field, therefore inhibiting the growth of Li dendrites. The cell exhibits an ultrahigh critical current density of 2.3 mA cm-2 and stable cycling of over 4000 h at 0.5 mA cm-2 (25 °C).

Efficient Polysulfide Trapping and Conversion on N-Doped CoTe2 via Enhanced Dual-Anchoring Effect.

Polysulfide shuttling and sluggish sulfur redox kinetics hinder the cyclability and rate capability of lithium-sulfur (Li-S) batteries. The intrinsic redox kinetics of sulfur cathodes strongly depends on the interaction between catalysts and sulfur species. Herein, N-doped CoTe2 is proposed as an effective dual-anchoring electrocatalyst, which can simultaneously bind Li and S atoms in lithium polysulfides via ionic Te-Li/N-Li bonding and coordinate covalent Co-S bonding. The incorporated N not only serves as enhanced lithiophilic site, but also an agent to improve the sulfiphilicity of the Co site as revealed by a series of experimental and computational results. Benefiting from these superiorities, the use of N-doped CoTe2 as a catalytic interlayer enables efficient operation of Li-S batteries in terms of impressive rate capability of 758 mAh g-1 at 4 C and very low capacity decay of 0.021% per cycle over 1000 cycles. The material and strategy demonstrated in this work may open the door toward developing more advanced Li-S electrocatalysts.

Powerful Acoustogeometric Streaming from Dynamic Geometric Nonlinearity.

Past forms of acoustic streaming, named after their progenitors Eckart (1948), Schlichting (1932), and Rayleigh (1884), serve to describe fluid and particle transport phenomena from the macro to micro-scale. Governed by the fluid viscosity, traditional acoustic streaming arises from second-order nonlinear coupling between the fluid's density and particle velocity, with the first-order acoustic wave time averaging to zero. We describe a form of acoustogeometric streaming that has a nonzero first-order contribution. Experimentally discovered in nanochannels of a height commensurate with the viscous penetration depth of the fluid in the channel, it arises from nonlinear interactions between the surrounding channel deformation and the leading order acoustic pressure field, generating flow pressures three orders of magnitude greater than any known acoustically mediated mechanism. It enables the propulsion of fluids against significant Laplace pressure, sufficient to produce 6 mm/s flow in a 130-150 nm tall nanoslit. We find quantitative agreement between theory and experiment across a variety of fluids and conditions, and identify the maximum flow rate with a channel height 1.59 times the viscous penetration depth.

An investigation of maximum particle velocity as a universal invariant-Defined by a statistical measure of failure or plastic energy loss for acoustofluidic applications.

Materials under vibration experience internal stress waves that can cause material failure or energy loss due to inelastic vibration. Traditionally, failure is defined in terms of material acceleration, yet this approach has many drawbacks, principally because it is not invariant with respect to scale, type of vibration, or material choice. Here, the likelihood of failure is instead considered in terms of the maximum vibration or particle velocity for various metals, polymers, and structural materials. The exact relationship between the maximum particle velocity and the maximum induced stress may be derived, but only if one knows the details of the vibration, material, flaws, and geometry. Statistical results with over thousands of individual trials are presented here to demonstrate a wide variety of vibrations across a sufficient variety of these choices. Failure in this context is defined as either fracture or plastic yield, the latter associated with inelastic deformation and energy loss during vibration. If the maximum permissible cyclical stress in material vibration is known, to at least an order of magnitude, the probability of this type of failure may be computed for a range of vibration velocities in each material. The results support the notion that a maximum particle velocity on the order of 1 m/s is a universal and critical limit that, upon exceeding, causes the probability of failure to become significant regardless of the details of the material, geometry, or vibration. We illustrate this in a specific example relevant to acoustofluidics, a simple surface acoustic wave device. The consequences of particle velocity limit analysis can effectively be used in materials and structural engineering to predict when dynamic material particle velocity can cause inelastic losses or failure via brittle fracture, plastic deformation, or fatigue failure.

Hierarchical Mn3 O4 Anchored on 3D Graphene Aerogels via C-O-Mn Linkage with Superior Electrochemical Performance for Flexible Asymmetric Supercapacitor.

Flexible asymmetric supercapacitors are more appealing in flexible electronics because of high power density, wide cell voltage, and higher energy density than symmetric supercapacitors in aqueous electrolyte. In virtues of excellent conductivity, rich porous structure and interconnected honeycomb structure, three dimensional graphene aerogels show great potential as electrode in asymmetric supercapacitors. However, graphene aerogels are rarely used in flexible asymmetric supercapacitors because of easily re-stacking of graphene sheets, resulting in low electrochemical activity. Herein, flower-like hierarchical Mn3 O4 and carbon nanohorns are incorporated into three dimensional graphene aerogels to restrain the stack of graphene sheets, and are applied as the positive and negative electrode for asymmetric supercapacitors devices, respectively. Besides, a strong chemical coupling between Mn3 O4 and graphene via the C-O-Mn linkage is constructed and can provide a good electron-transport pathway during cycles. Consequently, the asymmetric supercapacitor device shows high rate cycle stability (87.8 % after 5000 cycles) and achieves a high energy density of 17.4 µWh cm-2 with power density of 14.1 mW cm-2 (156.7 mW cm-3 ) at 1.4 V.

SnS2 /SnO2 Heterostructures towards Enhanced Electrochemical Performance of Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have been recognized as outstanding candidates for energy storage systems due to their superiority in terms of energy density. To meet the requirements for practical use, it is necessary to develop an effective method to realize Li-S batteries with high sulfur utilization and cycle stability. Here, a strategy to construct heterostructure composites as cathodes for high performance Li-S batteries is presented. Taking the SnS2 /SnO2 couple as an example, SnS2 /SnO2 nanosheet heterostructures on carbon nanofibers (CNFs), named C@SnS2 /SnO2 , were designed and synthesized. Considering the electrochemical performance of SnS2 /SnO2 heterostructures, it is interesting to note that the existence of heterointerfaces could efficiently improve lithium ion diffusion rate so as to accelerate the redox reaction significantly, thus leading to the enhanced sulfur utilization and more excellent rate performance. Benefiting from the unique structure and heterointerfaces of C@SnS2 /SnO2 materials, the battery exhibited excellent cyclic stability and high sulfur utilization. This work may provide a powerful strategy for guiding the design of sulfur hosts from selecting the material composition to constructing of microstructure.

A Conductive Ni2 P Nanoporous Composite with a 3D Structure Derived from a Metal-Organic Framework for Lithium-Sulfur Batteries.

Sulfur cathodes have attracted significant attention as next-generation electrode material candidates due to their considerable theoretical energy density. The main challenge in developing long-life Li-S batteries is to simultaneously suppress the shuttle effect and high areal mass loading of sulfur required for practical applications. To solve this problem, we have designed a novel nickel phosphide nanoporous composite derived from metal-organic frameworks (MOFs) as sulfur host materials. Homogeneous distribution of Ni2 P nanoparticles significantly avoids soluble polysulfides migrating out of the framework through strong chemical interactions, and the conductive 3D skeleton offers an accelerating electron transport. As a result, S@Ni2 P/NC has exhibited an enhanced performance of 1357 mAh g-1 initially at 0.2 C (1 C=1675 mA g-1 ) and remaining at 946 mAh g-1 after 300 cycles. Even at an areal mass loading of sulfur as high as 4.6 mg cm-2 , the electrode still showed an excellent specific capacity of 918 mAh g-1 .

Graphene Aerogels with Anchored Sub-Micrometer Mulberry-Like ZnO Particles for High-Rate and Long-Cycle Anode Materials in Lithium Ion Batteries.

Graphene aerogels (GAs) anchoring hierarchical, mulberry-like ZnO particles are fabricated in situ using a one-step solvothermal reaction. The resulting composites can function as anodes in lithium ion batteries, where they exhibit a high capacity and cyclic stability. The reversible capacities obtained are 365, 320, and 230 mA h g-1 at current densities of 1, 2, and 10 A g-1 . Their high reversible capacity is 445 mA h g-1 at a current density of 1.6 A g-1 ; this value is maintained even after the 500th cycle, The excellent electrochemical performance is attributed to strong oxygen bridges between ZnO and graphene, where C-O-Zn linkages provide a good pathway for electron transport during charge/discharge cycles. Additionally, the hierarchical structure of the ZnO microballs suppresses stacking among the graphene layers, allowing the GAs to accelerate the transport of lithium ions. Furthermore, the GA framework enhances the electrical conductivity and buffer any volume expansion.

pH-controllable on-demand oil/water separation on the switchable superhydrophobic/superhydrophilic and underwater low-adhesive superoleophobic copper mesh film.

Recently, materials with controlled oil/water separation ability became a new research focus. Herein, we report a novel copper mesh film, which is superhydrophobic and superhydrophilic for nonalkaline water and alkaline water, respectively. Meanwhile, the film shows superoleophobicity in alkaline water. Using the film as a separating membrane, the oil/water separating process can be triggered on-demand by changing the water pH, which shows a good controllability. Moreover, it is found that the nanostructure and the appropriate pore size of the substrate are important for realization of a good separation effect. This paper offers a new insight into the application of surfaces with switchable wettability, and the film reported here has such a special ability that allows it to be used in other applications, such as sewage purification, filtration, and microfluidic device.

Confined iron fluoride@CMK-3 nanocomposite as an ultrahigh rate capability cathode for Li-ion batteries.

A facile and advanced architecture design of FeF3·0.33H2O impregnated CMK-3 nanocomposite (FeF3·0.33H2O@CMK-3) is presented. In the FeF3·0.33H2O@CMK-3 nanocomposite, mesoporous carbon CMK-3 can provide enough passageways for electron and Li(+) transport to the confined nanosized FeF3·0.33H2O. The intimate conductive contact between the FeF3·0.33H2O nanoparticles and the carbon framework not only provides an expressway of electron transfer for Li(+) insertion/extraction but also suppresses the growth and agglomeration of FeF3·0.33H2O during the crystallization process. As expected, the nanostructured materials exhibit impressive rate capability and excellent cyclicity. Remarkably, even under an ultrahigh charge/discharge rate of 50 C (the charge or discharge process takes a mere 72 s), the confined FeF3·0.33H2O@CMK-3 still shows a high specific capacity of 78 mAh g(-1). By combining confined nanosized active material, high electron conductivity, and open framework, the FeF3·0.33H2O@CMK-3 nanocomposite demonstrates excellent high-rate capability and good cycling properties.

Construct Robust Epitaxial Growth of (101) Textured Zinc Metal Anode for Long Life and High Capacity in Mild Aqueous Zinc-Ion Batteries.

Aqueous zinc-metal batteries are considered to have the potential for energy storage due to their high safety and low cost. However, the practical applications of zinc batteries are limited by dendrite growth and side reactions. Epitaxial growth is considered an effective method for stabilizing Zn anode, especially for manipulating the (002) plane of deposited zinc. However, (002) texture zinc is difficult to achieve stable cycle at high capacity due to its large lattice distortion and uneven electric field distribution. Here, a novel zinc anode with highly (101) texture (denoted as (101)-Zn) is constructed. Due to unique directional guidance and strong bonding effect, (101)-Zn can achieve dense vertical electroepitaxy in near-neutral electrolytes. In addition, the low grain boundary area inhibits the occurrence of side reactions. The resultant (101)-Zn symmetric cells exhibit excellent stability over 5300 h (4 mA cm-2 for 2 mAh cm-2 ) and 330 h (15 mA cm-2 for 10 mAh cm-2 ). Meanwhile, the cycle life of Zn//MnO2 full cell is meaningfully improved over 1000 cycles.

Multifunctional electrolyte additive for realizing high-temperature and high-voltage lithium metal batteries.

Methyl 1H-1,2,4-triazole-3-carboxylate (MTC) was added into lithium metal batteries as an electrolyte additive, and not only did this addition lead to formation of solid electrolyte interfaces to protect both the anode and cathode, but the added MTC also served as a Lewis base in removing HF from the electrolyte to prevent the electrolyte from deteriorating. Therefore, the addition of MTC, in an appropriate amount, can be very effective at improving the electrochemical performance of lithium metal batteries.

Isolated Fe-Co heteronuclear diatomic sites as efficient bifunctional catalysts for high-performance lithium-sulfur batteries.

The slow redox kinetics of polysulfides and the difficulties in decomposition of Li2S during the charge and discharge processes are two serious obstacles to the practical application of lithium-sulfur batteries. Herein, we construct the Fe-Co diatomic catalytic materials supported by hollow carbon spheres to achieve high-efficiency catalysis for the conversion of polysulfides and the decomposition of Li2S simultaneously. The Fe atom center is beneficial to accelerate the discharge reaction process, and the Co atom center is favorable for charging process. Theoretical calculations combined with experiments reveal that this excellent bifunctional catalytic activity originates from the diatomic synergy between Fe and Co atom. As a result, the assembled cells exhibit the high rate performance (the discharge specific capacity achieves 688 mAh g-1 at 5 C) and the excellent cycle stability (the capacity decay rate is 0.018% for 1000 cycles at 1 C).

Unlocking the Capacity of Bismuth Oxide by a Redox Mediator Strategy for High-Performance Aqueous Zn-Ion Batteries.

Many cathode materials store zinc ions based on the intercalation reaction mechanism in neutral aqueous Zn-ion batteries, and the structural design of the cathodes has been stuck in the curing mode by extending the ion diffusion channel. Here, we first develop halide ions to unlock the electrochemical activity of conversion-type Bi2O3 in aqueous Zn-ion batteries. Notably, the iodide ion shows the best performance compatibility with the Bi2O3 cathode. The electrochemical reaction mechanism studies show that iodide ions can be regarded as a redox medium to reduce the charge-transfer activation energy and motivate the conversion of Bi2O3 from Bi3+ to Bi0 during the cycle. Unsurprising, the discharge-specific capacity can reach 436.8 mAh g-1 at 0.5 A g-1 and achieve a cyclic lifespan of 6000 cycles at a current density of 3 A g-1. The activation of the Bi2O3 conversion reaction by iodide ions is of great significance for broadening the research range of ZIB cathode materials.

A Dynamic and Self-Adapting Interface Coating for Stable Zn-Metal Anodes.

The zinc (Zn)-ion battery has attracted much attention due to its high safety and environmental protection. At present, the critical issues of the generation of dendrites and the accumulation of dead Zn on the surface will lead to a sharp decline of the battery life. Zn dendrites can be inhibited to some extent by constructing an interface protective coating. However, the existing rigid coating method cannot maintain conformal contact with Zn due to the volume change of Zn deposition and will cause fracture irreversibly during the cycle. Here, a highly self-adaptable poly(dimethylsiloxane) (PDMS)/TiO2- x coating is developed that can dynamically adapt to volume changes and inhibit dendrites growth. PDMS has high dynamic and self-adaptability due to the crosslinking of the B-O bond. In addition, the rapid and uniform transfer of Zn2+ is induced by the oxygen-vacancy-rich TiO2- x . The assembled cells still achieve 99.6% coulombic efficiency after 700 cycles at a current density of 10 mA cm-2 . The adaptive interface coating constructed provides a sufficient guarantee for the stable operation of the Zn anode.

Manipulation and Mixing of 200 Femtoliter Droplets in Nanofluidic Channels Using MHz-Order Surface Acoustic Waves.

Controllable manipulation and effective mixing of fluids and colloids at the nanoscale is made exceptionally difficult by the dominance of surface and viscous forces. The use of megahertz (MHz)-order vibration has dramatically expanded in microfluidics, enabling fluid manipulation, atomization, and microscale particle and cell separation. Even more powerful results are found at the nanoscale, with the key discovery of new regimes of acoustic wave interaction with 200 fL droplets of deionized water. It is shown that 40 MHz-order surface acoustic waves can manipulate such droplets within fully transparent, high-aspect ratio, 100 nm tall, 20-130 micron wide, 5-mm long nanoslit channels. By forming traps as locally widened regions along such a channel, individual fluid droplets may be propelled from one trap to the next, split between them, mixed, and merged. A simple theory is provided to describe the mechanisms of droplet transport and splitting.

Basal-Plane-Activated Molybdenum Sulfide Nanosheets with Suitable Orbital Orientation as Efficient Electrocatalysts for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are one of the most promising candidates for next-generation energy storage systems because of their high theoretical energy density. However, the shuttling behavior and sluggish conversion kinetics of lithium polysulfides (LiPSs) limit their practical application. Herein, B-doped MoS2 nanosheets are synthesized on carbon nanotubes (denoted as CNT@MoS2-B) to function as catalysts to boost the performance of Li-S batteries. The poor catalytic performance of the pristine MoS2 is revealed to be the result of unsuitable orbital orientation of the basal plane, which hinders the orbital overlap with sulfur species. B in CNT@MoS2-B is sp3 hybridized, and it has a vacant σ orbital perpendicular to the basal plane, which can maximize the head-on orbital overlap with S. The incorporation of B significantly increases the reactivity of MoS2 basal plane, which can facilitate the kinetics of Li2S formation and dissolution. With these merits, the S/CNT@MoS2-B cathodes deliver high rate capability and outstanding cycling stability, holding great promise for both scientific research and practical application. This work affords fresh insights for developing effective catalysts to accelerate LiPS conversion.

High-Index Faceted Nanocrystals as Highly Efficient Bifunctional Electrocatalysts for High-Performance Lithium-Sulfur Batteries.

Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium-sulfur (Li-S) batteries. Herein, high-index faceted iron oxide (Fe2O3) nanocrystals anchored on reduced graphene oxide are developed as highly efficient bifunctional electrocatalysts, effectively improving the electrochemical performance of Li-S batteries. The theoretical and experimental results all indicate that high-index Fe2O3 crystal facets with abundant unsaturated coordinated Fe sites not only have strong adsorption capacity to anchor polysulfides but also have high catalytic activity to facilitate the redox transformation of polysulfides and reduce the decomposition energy barrier of Li2S. The Li-S batteries with these bifunctional electrocatalysts exhibit high initial capacity of 1521 mAh g-1 at 0.1 C and excellent cycling performance with a low capacity fading of 0.025% per cycle during 1600 cycles at 2 C. Even with a high sulfur loading of 9.41 mg cm-2, a remarkable areal capacity of 7.61 mAh cm-2 was maintained after 85 cycles. This work provides a new strategy to improve the catalytic activity of nanocrystals through the crystal facet engineering, deepening the comprehending of facet-dependent activity of catalysts in Li-S chemistry, affording a novel perspective for the design of advanced sulfur electrodes.

Microliter ultrafast centrifuge platform for size-based particle and cell separation and extraction using novel omnidirectional spiral surface acoustic waves.

Asymmetric surface acoustic waves have been shown useful in separating particles and cells in many microfluidics designs, mostly notably sessile microdroplets. However, no one has successfully extracted target particles or cells for later use from such samples. We present a novel omnidirectional spiral surface acoustic wave (OSSAW) design that exploits a new cut of lithium niobate, 152 Y-rotated, to rapidly rotate a microliter sessile drop to ∼10 g, producing efficient multi-size particle separation. We further extract the separated particles for the first time, demonstrating the ability to target specific particles, for example, platelets from mouse blood for further integrated point-of-care diagnostics. Within ∼5 s of surface acoustic wave actuation, particles with diameter of 5 µm and 1 µm can be separated into two portions with a purity of 83% and 97%, respectively. Red blood cells and platelets within mouse blood are further demonstrated to be separated with a purity of 93% and 84%, respectively. These advancements potentially provide an effective platform for whole blood separation and point-of-care diagnostics without need for micro or nanoscale fluidic enclosures.

Circulating purification of cutting fluid: an overview.

Cutting fluid has cooling and lubricating properties and is an important part of the field of metal machining. Owing to harmful additives, base oils with poor biodegradability, defects in processing methods, and unreasonable emissions of waste cutting fluids, cutting fluids have serious pollution problems, which pose challenges to global carbon emissions laws and regulations. However, the current research on cutting fluid and its circulating purification technique lacks systematic review papers to provide scientific technical guidance for actual production. In this study, the key scientific issues in the research achievements of eco-friendly cutting fluid and waste fluid treatment are clarified. First, the preparation and mechanism of organic additives are summarized, and the influence of the physical and chemical properties of vegetable base oils on lubricating properties is analyzed. Then, the process characteristics of cutting fluid reduction supply methods are systematically evaluated. Second, the treatment of oil mist and miscellaneous oil, the removal mechanism and approach of microorganisms, and the design principles of integrated recycling equipment are outlined. The conclusion is concluded that the synergistic effect of organic additives, biodegradable vegetable base oils and recycling purification effectively reduces the environmental pollution of cutting fluids. Finally, in view of the limitations of the cutting fluid and its circulating purification technique, the prospects of amino acid additive development, self-adapting jet parameter supply system, matching mechanism between processing conditions and cutting fluid are put forward, which provides the basis and support for the engineering application and development of cutting fluid and its circulating purification.