Oxygen release and irreversible cation migration are the main causes of voltage fade in Li-rich transition metal oxide cathode. But their correlation is not very clear and voltage decay is still a ...bottleneck. Herein, we modulate the oxygen anionic redox chemistry by constructing Li
ZrO
slabs into Li
MnO
domain in Li
Ni
Mn
O
, which induces the lattice strain, tunes the chemical environment for redox-active oxygen and enlarges the gap between metallic and anionic bands. This modulation expands the region in which lattice oxygen contributes capacity by oxidation to oxygen holes and relieves the charge transfer from anionic band to antibonding metal-oxygen band under a deep delithiation. This restrains cation reduction, metal-oxygen bond fracture, and the formation of localized O
molecule, which fundamentally inhibits lattice oxygen escape and cation migration. The modulated cathode demonstrates a low voltage decay rate (0.45 millivolt per cycle) and a long cyclic stability.
An adaptive Kalman filter is proposed in this paper for actuator fault diagnosis in discrete time stochastic time varying systems. By modeling actuator faults as parameter changes, fault diagnosis is ...performed through joint state-parameter estimation in the considered stochastic framework. Under the classical uniform complete observability–controllability conditions and a persistent excitation condition, the exponential stability of the proposed adaptive Kalman filter is rigorously analyzed. In addition to the minimum variance property of the combined state and parameter estimation errors, it is shown that the parameter estimation within the proposed adaptive Kalman filter is equivalent to the recursive least squares algorithm formulated for a fictive regression problem. Numerical examples are presented to illustrate the performance of the proposed algorithm.
In China, urban land is allocated by leasehold sales by local officials. Attempting to end widespread corruption, the government now requires sales to be conducted publicly, by either English or ..."two-stage" auctions. However, corruption persists through the choice of auction format and preauction side deals between favored bidders and local officials. Two-stage auctions have a first stage where favored developers signal that auctions are "taken," deterring entry of other bidders. Empirics show that both sales prices and competition are significantly less for two-stage than English auctions. Selection on unobserved property characteristics is positive: officials divert hotter properties to two-stage auctions.
Herein we report a new high ionic conductivity and wide electrochemical window solid polymer electrolyte (SPE), which is developed via grafting sulfobetaine zwitterion (ZI) and poly (ethylene oxide) ...(PEO) chains on highly flexible polysiloxane backbone followed by crosslinking of tri(ethylene glycol) divinyl ether. The synergistic effect of zwitterion and PEO endows the SPE with an excellent ionic conductivity of 3.39 × 10−4 S cm−1 and the wide electrochemical stable window of 5.0 V (vs. Li/Li+) at room temperature. LiFePO4/Li half-cells with as-prepared solid polymer electrolyte present a high initial discharge capacity of 155 mAh g−1 and superior cycle stability with a capacity retention of 93% at 0.1 C after 100 cycles at 30 °C. In addition, LiNi0.5Mn1.5O4/Li half-cells employing such polymer electrolyte also deliver excellent cycle performance and stability. The above results indicate that the designed zwitterionic SPE appears to be a potential candidate for application in all-solid-state lithium-ion batteries.
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•A new bifunctional polysiloxane solid polymer electrolyte is synthesized.•It shows high ionic conductivity of 3.39 × 10−4 S cm−1 at room temperature.•The electrolyte has a wide electrochemical stable window of 5.0 V (vs. Li/Li+).•The SPE exhibits impressive battery performance.•The SPE can used in high voltage lithium-ion batteries.
•The SED method is used for fatigue evaluation of rib-to-deck welded joints.•Fatigue test results are applied to validate the proposed SED method.•Effect of weld geometrical variables on fatigue ...failure mode is evaluated.•W-N curve is derived using the SED method to evaluate full-scale specimens.
This paper investigates the feasibility of an averaged strain energy density (SED) method for fatigue evaluation of rib-to-deck weld joint in orthotropic steel deck. The effect of weld geometry on fatigue resistance of rib-to-deck joint is evaluated. The analysis results of the presented average SED method are validated against fatigue testing data and compared with the results of the conventional hot-spot stress and effective notch stress methods. A W-N curve is derived using the averaged SED method and used for evaluating the fatigue strength of rib-to-deck welded joints. The averaged SED method is also used to investigate the effect of weld geometrical variables on the fatigue failure mode transition, and the fatigue strength of full-scale orthotropic steel deck specimens. The results indicate that the averaged SED method provides superior ability in evaluating fatigue resistance and failure mode of rib-to-deck welded joint.
A porous and mat-like polyaniline/sodium alginate (PANI/SA) composite with excellent electrochemical properties was polymerized in an aqueous solution with sodium sulfate as a template. ...Ultraviolet–visible spectra, X-ray diffraction pattern, and Fourier transform infrared spectra were employed to characterize the PANI/SA composite, indicating that the PANI/SA composite was successfully prepared. The PANI/SA nanofibers with uniform diameters from 50 to 100 nm can be observed on scanning electron microscopy. Cyclic voltammetry and galvanostatic charge/discharge tests were carried out to investigate the electrochemical properties. The PANI/SA nanostructure electrode exhibits an excellent specific capacitance as high as 2093 F g–1, long cycle life, and fast reflect of oxidation/reduction on high current changes. The remarkable electrochemical characteristic is attributed to the nanostructured electrode materials, which generates a high electrode/electrolyte contact area and short path lengths for electronic transport and electrolyte ion. The approach is simple and can be easily extended to fabricate nanostructural composites for supercapacitor electrode materials.
Single noble metal atoms and ultrafine metal clusters catalysts tend to sinter into aggregated particles at elevated temperatures, driven by the decrease of metal surface free energy. Herein, we ...report an unexpected phenomenon that noble metal nanoparticles (Pd, Pt, Au-NPs) can be transformed to thermally stable single atoms (Pd, Pt, Au-SAs) above 900 °C in an inert atmosphere. The atomic dispersion of metal single atoms was confirmed by aberration-corrected scanning transmission electron microscopy and X-ray absorption fine structures. The dynamic process was recorded by in situ environmental transmission electron microscopy, which showed competing sintering and atomization processes during NP-to-SA conversion. Further, density functional theory calculations revealed that high-temperature NP-to-SA conversion was driven by the formation of the more thermodynamically stable Pd-N
structure when mobile Pd atoms were captured on the defects of nitrogen-doped carbon. The thermally stable single atoms (Pd-SAs) exhibited even better activity and selectivity than nanoparticles (Pd-NPs) for semi-hydrogenation of acetylene.
As unique building blocks for next‐generation optoelectronics, high‐quality 2D p–n junctions based on semiconducting transition metal dichalcogenides (TMDs) have attracted wide interest, which are ...urgent to be exploited. Herein, a novel and facile electron doping of WSe2 by cetyltrimethyl ammonium bromide (CTAB) is achieved for the first time to form a high‐quality intramolecular p–n junction with superior optoelectronic properties. Efficient manipulation of charge carrier type and density in TMDs via electron transfer between Br− in CTAB and TMDs is proposed theoretically by density functional theory (DFT) calculations. Compared with the intrinsic WSe2 photodetector, the switching light ratio (Ilight/Idark) of the p–n junction device can be enhanced by 103, and the temporal response is also dramatically improved. The device possesses a responsivity of 30 A W−1, with a specific detectivity of over 1011 Jones. In addition, the mechanism of charge transfer in CTAB‐doped 2D WSe2 and WS2 are investigated by designing high‐performance field effect transistors. Besides the scientific insight into the effective manipulation of 2D materials by chemical doping, this work presents a promising applicable approach toward next‐generation photoelectronic devices with high efficiency.
A novel and facile electron doping of 2D WSe2 by cetyltrimethyl ammonium bromide (CTAB) is achieved to form a high‐quality lateral p–n homojunction with superior optoelectronic properties. The high switching light ratio (≈105), superior photoresponsivity (30 A W−1), and specific detectivity (over 1011 Jones) of the device demonstrate its promising applications for highly sensitive photodetectors and low‐power photoelectronic devices.
The rational design and synthesis of anisotropic 3D nanostructures with specific composition, morphology, surface structure, and crystal phase is of significant importance for their diverse ...applications. Here, the synthesis of well‐crystalline lotus‐thalamus‐shaped Pt‐Ni anisotropic superstructures (ASs) via a facile one‐pot solvothermal method is reported. The Pt‐Ni ASs with Pt‐rich surface are composed of one Ni‐rich “core” with face‐centered cubic (fcc) phase, Ni‐rich “arms” with hexagonal close‐packed phase protruding from the core, and facet‐selectively grown Pt‐rich “lotus seeds” with fcc phase on the end surfaces of the “arms.” Impressively, these unique Pt‐Ni ASs exhibit superior electrocatalytic activity and stability toward the hydrogen evolution reaction under alkaline conditions compared to commercial Pt/C and previously reported electrocatalysts. The obtained overpotential is as low as 27.7 mV at current density of 10 mA cm−2, and the turnover frequency reaches 18.63 H2 s−1 at the overpotential of 50 mV. This work provides a new strategy for the synthesis of highly anisotropic superstructures with a spatial heterogeneity to boost their promising application in catalytic reactions.
Well‐crystalline lotus‐thalamus‐shaped Pt‐Ni anisotropic superstructures (ASs) with unique hexagonal‐close‐packed/face‐centered‐cubic crystal phases and Pt‐rich surface are synthesized via a simple one‐pot solvothermal method. The obtained Pt‐Ni ASs exhibit superior electrocatalytic activity and stability toward the hydrogen evolution reaction under alkaline conditions compared to commercial Pt/C and other reported electrocatalysts.
Use of green propellants is a trend for future space propulsion. Hypergolic ionic liquid propellants, which are environmentally‐benign while exhibiting energetic performances comparable to hydrazine, ...have shown great potential to meet the requirements of developing nontoxic high‐performance propellant formulations for space propulsion applications. This Concept article presents a review of recent advances in the field of ionic liquid propellants.
Up, up, and away: The use of green propellants is a trend for future space propulsion. Hypergolic ionic liquid propellants, which are environmentally benign and exhibit energetic performances comparable to hydrazine, have shown great potential to meet the requirements of developing nontoxic, high‐performance, propellant formulations for space propulsion applications (see figure).
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