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Sodium-ion batteries (SIBs) are potential candidates for large energy storage usage because of the natural abundance and cheap sodium. Nevertheless, improving the energy density and cycling steadiness of SIB cathodes remains a challenge. In this work, F-doping Na3Al2/3V4/3(PO4)3(NAVP) microspheres (Na3Al2/3V4/3(PO4)2.9F0.3(NAVPF)) are synthesized via spray drying and investigated as SIB cathodes. XRD and Rietveld refinement reveal expanded lattice parameters for NAVPF compared to the undoped sample, and the successful cation doping into the Na superionic conductor (NASICON) framework improves Na+ diffusion channels. The NAVPF delivers an ultrahigh capacity of 148 mAh g-1 at 100 mA g-1 with 90.8% retention after 200 cycles, enabled by the activation of V2+/V5+ multielectron reaction. Notably, NAVPF delivers an ultrahigh rate performance, with a discharge capacity of 83.6 mAh g-1 at 5000 mA g-1. In situ XRD demonstrates solid-solution reactions occurred during charge-discharge of NAVPF without two-phase reactions, indicating enhanced structural stability after F-doped. The full cell with NAVPF cathode and Na+ preintercalated hard carbon anode shows a large discharge capacity of 100 mAh g-1 at 100 mA g-1 with 80.2% retention after 100 cycles. This anion doping strategy creates a promising SIB cathode candidate for future high-energy-density energy storage applications.
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Sodium-ion batteries (SIBs) have emerged as a compelling alternative to lithium-ion batteries (LIBs), exhibiting comparable electrochemical performance while capitalizing on the abundant availability of sodium resources. In SIBs, P2/O3 biphasic cathodes, despite their high energy, require furthur improvements in stability to meet current energy demands. This study introduces a systematic methodology that leverages the meta-heuristically assisted NSGA-II algorithm to optimize multi-element doping in electrode materials, aiming to transcend conventional trial-and-error methods and enhance cathode capacity by the synergistic integration of P2 and O3 phases. A comprehensive phase analysis of the meta-heuristically designed cathode material Na0.76Ni0.20Mn0.42Fe0.30Mg0.04Ti0.015Zr0.025O2 (D-NFMO) is presented, showcasing its remarkable initial reversible capacity of 175.5 mAh g-1 and exceptional long-term cyclic stability in sodium cells. The investigation of structural composition and the stabilizing mechanisms is performed through the integration of multiple characterization techniques. Remarkably, the irreversible phase transition of P2âOP4 in D-NFMO is observed to be dramatically suppressed, leading to a substantial enhancement in cycling stability. The comparison with the pristine cathode (P-NFMO) offers profound insights into the long-term electrochemical stability of D-NFMO, highlighting its potential as a high-voltage cathode material utilizing abundant earth elements in SIBs. This study opens up new possibilities for future advancements in sodium-ion battery technology.
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A plug-flow fixed-bed cell for synchrotron powder X-ray diffraction (PXRD) and X-ray absorption fine structure (XAFS) idoneous for the study of heterogeneous catalysts at high temperature, pressure and under gas flow is designed, constructed and demonstrated. The operating conditions up to 1000°C and 50â bar are ensured by a set of mass flow controllers, pressure regulators and two infra-red lamps that constitute a robust and ultra-fast heating and cooling method. The performance of the system and cell for carbon dioxide hydrogenation reactions under specified temperatures, gas flows and pressures is demonstrated both for PXRD and XAFS at the P02.1 (PXRD) and the P64 (XAFS) beamlines of the Deutsches Elektronen-Synchrotron (DESY).
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We report on the fabrication of a novel design of GaAs/(In,Ga)As/GaAs radial nanowire heterostructures on a Si 111 substrate, where, for the first time, the growth of inhomogeneous shells on a lattice mismatched core results in straight nanowires instead of bent. Nanowire bending caused by axial tensile strain induced by the (In,Ga)As shell on the GaAs core is reversed by axial compressive strain caused by the GaAs outer shell on the (In,Ga)As shell. Progressive nanowire bending and reverse bending in addition to the axial strain evolution during the two processes are accessed byin situby x-ray diffraction. The diameter of the core, thicknesses of the shells, as well as the indium concentration and distribution within the (In,Ga)As quantum well are revealed by 2D energy dispersive x-ray spectroscopy using a transmission electron microscope. Shell(s) growth on one side of the core without substrate rotation results in planar-like radial heterostructures in the form of free standing straight nanowires.
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With increasing applications for voltage-controlled magnetism, the need to more fully understand magnetoelectric coupling and strain transfer in nanostructured multiferroic composites has also increased. Here, multiferroic nanocomposites were synthesized using block copolymer templating to create mesoporous cobalt ferrite (CFO), followed by partly filling the pores with ferroelectric zirconium-substituted hafnia (HZO) using atomic layer deposition (ALD) to produce a porous multiferroic composite with enhanced mechanical flexibility. Upon electrical poling of the nanocomposite, we observed large changes in the magnetization. These changes partly relaxed upon removing the electric field, suggesting a strain-mediated mechanism. Both the anisotropic strain transfer from HZO to CFO and the strain relaxation after the field was removed were confirmed using high-resolution X-ray diffraction measurements collected during in-situ poling. The in-situ observation of both anisotropic strain transfer and large magnetization changes allows us to directly characterize the strong multiferroic coupling that can occur in flexible, nanostructured composites.
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Wadsley-Roth niobium oxide phases have attracted extensive research interest recently as promising battery anodes. We have synthesized the niobium-molybdenum oxide shear phase (Nb, Mo)13 O33 with superior electrochemical Li-ion storage performance, including an ultralong cycling lifespan of at least 15000â cycles. During electrochemical cycling, a reversible single-phase solid-solution reaction with lithiated intermediate solid solutions is demonstrated using in situ X-ray diffraction, with the valence and short-range structural changes of the electrode probed by in situ Nb and Mo K-edge X-ray absorption spectroscopy. This work reveals that the superior stability of niobium molybdenum oxides is underpinned by changes in octahedral distortion during electrochemical reactions, and we report an in-depth understanding of how this stabilizes the oxide structure during cycling with implications for future long-life battery material design.
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SiOx anode has a more durable cycle life than Si, being considered competitive to replace the conventional graphite. SiOx usually serves as composites with carbon to achieve more extended cycle life. However, the carbon microstructure dependent Li-ion storage behaviors in SiOx /C anode have received insufficient attention. Herein, this work demonstrates that the disorder of carbon can determine the ratio of inter- and intragranular Li-ion diffusions. The resulted variation of platform characteristics will result in different compatibility when matching SiOx . Rational disorder induced intergranular diffusion can benefit phase transition of SiOx /C, benefiting the electrochemical performance. Through a series of quantitative calculations and in situ X-ray diffraction characterizations, this work proposes the rational strategy for the future optimization, thus achieving preferable performance of SiOx /C anode.
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The commercialization of high-energy Li-metal batteries is impeded by Li dendrites formed during electrochemical cycling and the safety hazards it causes. Here, a novel porous copper current collector that can effectively mitigate the dendritic growth of Li is reported. This porous Cu foil is fabricated via a simple two-step electrochemical process, where Cu-Zn alloy is electrodeposited on commercial copper foil and then Zn is electrochemically dissolved to form a 3D porous structure of Cu. The 3D porous Cu layers on average have a thickness of ≈14 um and porosity of ≈72%. This current collector can effectively suppress Li dendrites in cells cycled with a high areal capacity of 10 mAh cm-2 and under a high current density of 10 mA cm-2 . This electrochemical fabrication method is facile and scalable for mass production. Results of advanced in situ synchrotron X-ray diffraction reveal the phase evolution of the electrochemical deposition and dealloying processes.
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The reduction of metal oxides with hydrogen is widely used for the production of fine chemicals and metals both on the laboratory and industry scale. In situ methods can help to elucidate reaction pathways and to gain control over such synthesis reactions. In this study, the reduction of WO3 and V2 O5 with hydrogen was investigated by in situ X-ray powder diffraction with regard to intermediates and the influence of heating rates and hydrogen flow rates. Mixtures of V4 O9 , V6 O13 and VO2 in two modifications were identified as intermediates on the way to phase-pure V2 O3 . None of the intermediates occurs in a single phase and therefore cannot be prepared this way. In contrast, the intermediates of the WO3 reduction, H0.23 WO3 and W10 O29 , appear consecutively and can be isolated. For both reactions, the heating and flow rates have little influence on the formation of intermediates.
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Bimetallic alloy nanomaterials are promising anode materials for potassium-ion batteries (KIBs) due to their high electrochemical performance. The most well-adopted fabrication method for bimetallic alloy nanomaterials is tube furnace annealing (TFA) synthesis, which can hardly satisfy the trade-off among granularity, dispersity and grain coarsening due to mutual constraints. Herein, we report a facile, scalable and ultrafast high-temperature radiation (HTR) method for the fabrication of a library of ultrafine bimetallic alloys with narrow size distribution (≈10-20â nm), uniform dispersion and high loading. The metal-anchor containing heteroatoms (i.e., O and N), ultrarapid heating/cooling rate (≈103 â K s-1 ) and super-short heating duration (several seconds) synergistically contribute to the successful synthesis of small-sized alloy anodes. As a proof-of-concept demonstration, the as-prepared BiSb-HTR anode shows ultrahigh stability indicated by negligible degradation after 800â cycles. The in situ X-ray diffraction reveals the K+ storage mechanism of BiSb-HTR. This study can shed light on the new, rapid and scalable nanomanufacturing of high-quality bimetallic alloys toward extended applications of energy storage, energy conversion and electrocatalysis.
Asunto(s)
Aleaciones , Potasio , Biblioteca de Genes , Frío , Electrodos , IonesRESUMEN
Tin chalcogenides are regarded as promising anode materials for potassium ion batteries (PIBs) due to their considerable specific capacity. However, the severe volume effect, limited electronic conductivity, and the shuttle effect of the potassiation product restrict the application prospect. Herein, based on the metal evaporation reaction, a facile structural engineering strategy for yolk-shell SnSe encapsulated in carbon shell (SnSe@C) is proposed. The internal void can accommodate the volume change of the SnSe core and the carbon shell can enhance the electronic conductivity. Combining qualitative and quantitative electrochemical analyses, the distinguished electrochemical performance of SnSe@C anode is attributed to the contribution of enhanced capacitive behavior. Additionally, first-principles calculations elucidate that the heteroatomic doped carbon exhibits a preferable affinity toward potassium ions and the potassiation product K2 Se, boosting the rate performance and capacity retention consequently. Furthermore, the phase evolution of SnSe@C electrode during the potassiation/depotassiation process is clarified by in situ X-ray diffraction characterization, and the crystal transition from the SnSe Pnma(62) to Cmcm(63) point group is discovered unpredictably. This work demonstrates a pragmatic avenue to tailor the SnSe@C anode via a facile structural engineering strategy and chemical regulation, providing substantial clarification for the phase evolution mechanism of SnSe-based anode for PIBs.
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Li3 V2 (PO4 )3 (LVP) is a promising cathode material for lithium-ion batteries, especially when used in a wide temperature range, due to its high intrinsic ionic mobility and theoretical capacity. Herein, Ru- and Cl-codoped Li3 V2 (PO4 )3 (LVP-Rux -Cl3 x ) coated with/without a nitrogen-doped carbon (NC) layer are synthesized. Among them, the optimized sample (LVP-Ru0.05 -Cl0.15 @NC) delivers remarkable performances at both room temperature and extreme temperatures (-40, 25, and 60 °C), indicating temperature adaptability. It achieves intriguing capacities (49 mAh g-1 at -40 °C, 128 mAh g-1 at 25 °C, and 123 mAh g-1 at 60 °C, all at 0.5 C), long cycle life (94% capacity retention after 2000 cycles at 25 °C and 5 C), and high-rate capabilities (up to 20 C). The structural evolution features and capacity loss mechanisms of LVP-Ru0.05 -Cl0.15 @NC are further investigated using in situ X-ray diffraction (XRD) at different temperatures (-10, 25, and 60 °C) during redox reactions. Theoretical calculations elucidate that Ru- and Cl-codoping can greatly improve the intrinsic diffusion coefficient of LVP by reducing its bandgap energy and lowering the energy barrier of lithium-ion diffusion. In "all-weather" conditions, the dual-element co-doping strategy is critical for increasing electrochemical performance.
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In this study, the conceptual design and performance of a multimodal X-ray probe station recently installed at the 9C coherent X-ray scattering beamline of the Pohang Light Source-II are presented. The purpose of this apparatus is to measure coherent X-ray diffraction, X-ray fluorescence and electrical properties simultaneously. A miniature vacuum probe station equipped with a four-point probe was mounted on a six-axis motion hexapod. This can be used to study the structural and chemical evolution of thin films or nanostructures, as well as device performance including electronic transport properties. This probe station also provides the capability of varying sample environments such as gas atmosphere using a mass-flow-control system and sample temperatures up to 600°C using a pyrolytic boron nitride heater. The in situ annealing of ZnO thin films and the performance of ZnO nanostructure-based X-ray photodetectors are discussed. These results demonstrate that a multimodal X-ray probe station can be used for performing in situ and operando experiments to investigate structural phase transitions involving electrical resistivity switching.
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Engineering intriguing electrode with exceptional kinetics behaviors is imperative for boosting sodium storage systems. Herein, the uniform nanoframes are threaded by the interwoven carbon nanotube (CNT) conductive network to form an ingenious beads-on-a-string structured NiFePBA nanoframe/CNT (NFPB-NF/CNT) cathode and the corresponding derivative NiFeSe nanoframe/CNT (NFS-NF/CNT) anode. NFPB-NF/CNT exhibited remarkable cycling life along with outstanding rate capability and low voltage decay per cycle. The fast Na+ conduction and sufficient sodiation reaction is proved using Na+ diffusion models. Meanwhile, an exceptional sodium storage capacity and prolonged cycling life is achieved using binary NFS-NF/CNT anode at a high rate. In situ and ex situ investigations are used to reveal the sodium storage mechanisms and structural evolution process. Furthermore, a sodium-ion full battery based on the above electrodes shows stable performance accompanied by high energy conversion efficiency. The material design strategy provides a new solution for exploiting smart multicomponent composites toward advanced energy storage devices.
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Transition metal chalcogenides have received great attention as promising anode candidates for sodium-ion batteries (SIBs). However, the undesirable cyclic life and inferior rate capability still restrict their practical applications. The design of micro-nano hierarchitectures is considered as a possible strategy to facilitate the electrochemical reaction kinetics and strengthen the electrode structure stability upon repeated Na+ insertion/extraction. Herein, urchin-like Fe3 Se4 hierarchitectures are successfully prepared and developed as a novel anode material for SIBs. Impressively, the as-prepared urchin-like Fe3 Se4 can present an ultrahigh rate capacity of 200.2 mAh g-1 at 30 A g-1 and a prominent capacity retention of 99.9% over 1000 cycles at 1 A g-1 , meanwhile, a respectable initial coulombic efficiency of ≈100% is achieved. Through the conjunct study of in situ X-ray diffraction, ex situ X-ray absorption near-edge structure spectroscopy, as well as cyclic voltammetry curves, it is intriguing to reveal that the phase transformation from monoclinic to amorphous structure accompanied by the pseudocapacitive Na+ storage behavior accounts for the superior electrochemical performance. When paired with the Na3 V2 (PO4 )3 cathode materials, the assembled full cell enables high energy density and decent cyclic stability, demonstrating potential practical feasibility of the present urchin-like Fe3 Se4 anode.
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Electrochemical actuators are devices that convert electrical energy into mechanical energy via electrochemical processes. They are used in soft robotics, artificial muscles, micropumps, sensors, and other fields. The design of flexible and stable electrode materials remains a major challenge. MXenes, an emerging family of 2D materials, have found applications in energy storage. Here, we report an actuator device using MXene (Ti3C2Tx) as a flexible electrode material. The electrode in 1 M H2SO4 electrolyte exhibits a curvature change up to 0.083 mm-1 and strain of 0.29%. Meanwhile, the MXene-based actuator with a symmetric configuration separated by gel electrolyte (PVA-H2SO4) has curvature and strain changes up to 0.038 mm-1 and 0.26% with excellent retention after 10,000 cycles. In situ X-ray diffraction analysis demonstrates that the actuation mechanism is due to the expansion and shrinkage of the interlayer spacing of MXenes. This research shows promise of this new family of materials for electrochemical actuators.
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The growth of regular arrays of uniform III-V semiconductor nanowires is a crucial step on the route toward their application-relevant large-scale integration onto the Si platform. To this end, not only does optimal vertical yield, length, and diameter uniformity have to be engineered, but also, control over the nanowire crystal structure has to be achieved. Depending on the particular application, nanowire arrays with varying area density are required for optimal device efficiency. However, the nanowire area density substantially influences the nanowire growth and presents an additional challenge for nanowire device engineering. We report on the simultaneous in situ X-ray investigation of regular GaAs nanowire arrays with different area density during self-catalyzed vapor-liquid-solid growth on Si by molecular-beam epitaxy. Our results give novel insight into selective-area growth and demonstrate that shadowing of the Ga flux, occurring in dense nanowire arrays, has a crucial impact on the evolution of nanowire crystal structure. We observe that the onset of Ga flux shadowing, dependent on array pitch and nanowire length, is accompanied by an increase of the wurtzite formation rate. Our results moreover reveal the paramount role of the secondary reflected Ga flux for VLS NW growth (specifically, that flux that is reflected directly into the liquid Ga droplet).
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Solution studies have proposed that crystal nucleation can take more complex pathways than previously expected in classical nucleation theory, such as formation of prenucleation clusters or densified amorphous/liquid phases. These findings show that it is possible to separate fluctuations in the different order parameters governing crystal nucleation, that is, density and structure. However, a direct observation of the multipathways from aqueous solutions remains a great challenge because heterogeneous nucleation sites, such as container walls, can prevent these paths. Here, we demonstrate the existence of multiple pathways of nucleation in highly supersaturated aqueous KH2PO4 (KDP) solution using the combination of a containerless device (electrostatic levitation), and in situ micro-Raman and synchrotron X-ray scattering. Specifically, we find that, at an unprecedentedly deep level of supersaturation, a high-concentration KDP solution first transforms into a metastable crystal before reaching stability at room temperature. However, a low-concentration solution, with different local structures, directly transforms into the stable crystal phase. These apparent multiple pathways of crystallization depend on the degree of supersaturation.
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Tetragonal FeAl2 is a high-pressure phase and is predicted to exhibit semiconductor-like behavior. We investigated the pressure and temperature synthesizing conditions of tetragonal FeAl2, supported by in situ X-ray diffractions, using synchrotron radiation during heating the sample under a pressure of 20 GPa. Based on the determined optimal conditions, we synthesized the bulk polycrystalline samples of tetragonal FeAl2 at 7.5 GPa and 873 K, using a multi-anvil press and measured its thermoelectric properties. The Seebeck coefficient of tetragonal FeAl2 showed a large negative value of - 105 µV/K at 155 K and rapidly changed to a positive value of 75 µV/K at 400 K. Although these values are the largest among those of Fe-Al alloys, the maximum power factor remained at 0.41 mW/mK2 because the carrier concentration was not tuned. A comparison of the Gibbs free energy of tetragonal FeAl2, triclinic FeAl2 and FeAl+Fe2Al5 revealed that tetragonal FeAl2 became unstable as the temperature increased, because of its smaller contribution of vibrational entropy.
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The reactive metal-support interaction in the Cu-In2O3 system and its implications on the CO2 selectivity in methanol steam reforming (MSR) have been assessed using nanosized Cu particles on a powdered cubic In2O3 support. Reduction in hydrogen at 300 °C resulted in the formation of metallic Cu particles on In2O3. This system already represents a highly CO2-selective MSR catalyst with ~93% selectivity, but only 56% methanol conversion and a maximum H2 formation rate of 1.3 µmol gCu -1 s-1. After reduction at 400 °C, the system enters an In2O3-supported intermetallic compound state with Cu2In as the majority phase. Cu2In exhibits markedly different self-activating properties at equally pronounced CO2 selectivities between 92% and 94%. A methanol conversion improvement from roughly 64% to 84% accompanied by an increase in the maximum hydrogen formation rate from 1.8 to 3.8 µmol gCu -1 s-1 has been observed from the first to the fourth consecutive runs. The presented results directly show the prospective properties of a new class of Cu-based intermetallic materials, beneficially combining the MSR properties of the catalyst's constituents Cu and In2O3. In essence, the results also open up the pathway to in-depth development of potentially CO2-selective bulk intermetallic Cu-In compounds with well-defined stoichiometry in MSR.