Secondary-Phase-Induced Charge–Discharge Performance Enhancement of Co-Free High Entropy Spinel Oxide Electrodes for Li-Ion Batteries

High entropy oxide (HEO) has emerged as a new class of anode material for Li-ion batteries (LIBs) by offering infinite possibilities to tailor the charge–discharge properties. While the advantages of single-phase HEO anodes are realized, the effects of a secondary phase are overlooked. In this study, two kinds of Co-free HEOs are prepared, containing Cr, Mn, Fe, Ni, and Zn, for use as LIB anodes. One is a plain cubic-structure high entropy spinel oxide HESO (C) prepared using a solvothermal method. The other HESO (C+T) contains an extra secondary phase of tetragonal spinel oxide and is prepared using a hydrothermal method. It is demonstrated that the secondary tetragonal spinel phase introduces phase boundaries and defects/oxygen vacancies within HESO (C+T), which improve the redox kinetics and reversibility during electrode lithiation/delithiation. Density functional theory calculation is performed to assess the phase stability of cubic spinel, tetragonal spinel, and rock-salt structures, and validate the cycling stability of the electrodes upon charging–discharging. The secondary-phase-induced rate capability and cyclability enhancement of HEO electrodes are for the first time demonstrated. A HESO (C+T)||LiNi_0.8Co_0.1Mn_0.1O₂ full cell is assembled and evaluated, showing a promising gravimetric energy density of ≈610 Wh kg⁻¹ based on electrode-active materials.     

Features of the Characteristics of Field-Resistant Silicon–Ultrathin Oxide–Polysilicon Structures

Semiconductors - Results of studying the features of the current–voltage (I–V) and capacitance–voltage characteristics of field-resistant silicon–ultrathin...     

Physical Principles of Self-Consistent Simulation of the Generation of Interface States and the Transport of Hot Charge Carriers in Field-Effect Transistors Based on Metal–Oxide–Semiconductor Structures

A detailed simulation of degradation (caused by hot charge carriers) based on self-consistent consideration of the transport of charge carriers and the generation of defects at the SiO₂/Si interface is carried out for the first time. The model is tested using degradation data obtained with decananometer n-type-channel field-effect transistors. It is shown that the mutual influence of the above aspects is significant and their independent simulation gives rise to considerable quantitative errors. In calculations of the energy distribution for charge carriers, the actual band structure of silicon and such mechanisms as impact ionization, scattering at an ionized impurity, and also electron–phonon and electron–electron interactions are taken into account. At the microscopic level, the generation of defects is considered as the superposition of single-particle and multiparticle mechanisms of breakage of the Si–H bond. A very important applied aspect of this study is the fact that our model makes it possible to reliably assess the operating lifetime of a transistor subjected to the effects of “hot” charge carriers.     

S-Shaped I–V Characteristics of High-Power Schottky Diodes at High Current Densities

Semiconductors - The effect of a set of quasi-neutral regimes of carrier transport in semiconductors, including, along with diffusion and drift, recently discovered diffusion stimulated by...     

Dielectric Loss in the Polymer–Semiconductor–Composite System with Allowance for Nonlinear Dependence of Electric Characteristics on Temperature Resulting from Microwave Irradiation

An electrothermophysical model that makes it possible to estimate dielectric loss and predict energy-dissipation characteristics in dielectric materials is proposed. Heat and mass transfer is numerically simulated in the presence of microwave irradiation of an electronic device (polymer–semiconductor–composite system) with allowance for local heat liberation and nonlinear dependence of dielectric characteristics on temperature. Distributions of permittivity and tangent of dielectric loss with respect to thickness of the system under study are presented for a typical interval of variations in the parameters of electromagnetic radiation. It is demonstrated that dissipation of electromagnetic energy leads to a significant (by a factor of 1.6) increase in the tangent of dielectric loss.     

Synergistic Effect of Crosslinked Organic–Inorganic Composite Protective Layer for High Performance Lithium Metal Batteries

Maintaining a stable interface of lithium metal anodes (LMAs) by implementing a protective layer is a promising approach in extending the cycle life of lithium metal batteries (LMBs). Nevertheless, designing a protective layer with desired physicochemical properties is still a challenging task. Herein, an inorganic–organic composite protective layer consisting of fluorinated graphene oxide (FGO) (inorganic part) and polyacrylic acid (PAA) (organic part) that are in situ crosslinked via poly(ethylene glycol) diglycidyl ether (PEGDE) into a robust network is reported. The mechanical strength of FGO and the elasticity of the polymeric network jointly suppress the unwanted dendritic Li growth while fluorine-functional groups in FGO induce an LiF-enriched interface. This balanced inorganic–organic composite protective layer facilitates charge transfer kinetics for enhanced lithium-ion diffusion at the interface. Utilizing this protective layer, LMB full-cells with LiFePO₄ demonstrate negligible capacity loss for 100 cycles even under an extreme negative/positive capacity (N/P) ratio of 1.0. This study uncovers the possibility of highly robust, reliable LMBs by a sophisticatedly designed protective layer of widely used inorganic and organic components.     

Prediction of the Magnitude of the Trapped Charge in the Buried Oxide of Silicon-on-Insulator Structures Using the Poole–Frenkel Effect

Semiconductors - The possibility of predicting the magnitude of the trapped charge in the buried oxide of silicon-on-insulator structures using the Poole–Frenkel effect is investigated. The...     

Multi-Stage Porous Nickel–Iron Oxide Electrode for High Current Alkaline Water Electrolysis

Alkaline water electrolysis (AWE) is the promising technical pathway of large-scale green hydrogen production. The sluggish oxygen evolution reaction seriously hampers the water decomposition reaction kinetics for AWE, especially at high current density above 500 mA cm⁻². It is closely related with bubbles removal dynamic performance of porous electrodes. In this study, the multi-stage porous nickel–iron oxide electrode is prepared by a two-step electro-deposition method. The electrode shows good oxygen evolution reaction performance at high current densitiy of 1000 mA cm⁻², which is attributed to both the good electro-catalytic performance of NiFeO_x with nano-cone structure and good bubbles removal performance of porous Ni interlayer with the curved pore channels. Bubbles motion inside the pore channels is deeply analyzed by Lattice Boltzmann simulation of gas–liquid two-phase flows, combining with the experiments. The results indicate that bubbles motion speed is faster in curved pore channels than that in straight pore channels due to the role of bubble buoyancy. It illuminates the effects of pore channel curvature on bubbles motion for porous electrodes prepared by electro-deposition. It provides the possibility of designing porous electrodes with both good electro-catalytic performance and good bubbles removal performance by the electro-deposition method, from the view of industrial applications.     

Study on Photocapacitance in PN Junction of High Resistivity P—type Silicon

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Generation of Dynamic Chaos in a Range of 10–30 GHz

The possibility of generation of ultrawideband chaotic oscillation in a frequency band of 10–30 GHz on the basis of the state-of-the-art microelectronic technology has been investigated. Schematic and topological models of a generator of chaotic oscillations based on elements from the 130-nm SiGe technology library have been proposed, developed, and investigated. The dynamics of the oscillation conditions and the energy efficiency of the generator has been analyzed.     

Atomic-Precision Tailoring of Au–Ag Core–Shell Composite Nanoparticles for Direct Electrochemical-Plasmonic Hydrogen Evolution in Water Splitting

Traditionally, bandgap materials are a prerequisite to photocatalysis since they can harness a reasonable range of the solar spectrum. However, the high impedance across the bandgap and the low concentration of intrinsic charge carriers have limited their energy conversion. By contrast, metallic nanoparticles possess a sea of free electrons that can effectively promote the transition to the excited state for reactions. Here, an atomic layer of a bimetallic concoction of silver–gold shells is precisely fabricated onto an Au core via a sonochemical dispersion approach to form a core–shell of Au–Ag that exploits the wide availability of excited states of Ag while maintaining an efficient localized surface plasmon resonance (LSPR) of Au. Catalytic results demonstrate that this mix of Ag and Au can convert solar energy to hydrogen at high efficiency with an increase of 112.5% at an optimized potential of −0.5 V when compared to light-off conditions under the electrochemical LSPR. This outperforms the commercial Pt catalysts by 62.1% with a hydrogen production rate of 1870 µmol g⁻¹ h⁻¹ at room temperature. This study opens a new route for tuning the range of light capture of hydrogen evolution reaction catalysts using fabricated core–shell material through the combination of LSPR with electrochemical means.     

Engineering Crystallinity and Oxygen Vacancies of Co(II) Oxide Nanosheets for High Performance and Robust Rechargeable Zn–Air Batteries

Efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes highly rely on the rational design and synthesis of high-performance electrocatalysts. Herein, comprehensive characterizations and density functional theory (DFT) calculations are combined to verify the important roles of the crystallinity and oxygen vacancy levels of Co(II) oxide (CoO) on ORR and OER activities. A facile and controllable vacuum-calcination strategy is utilized to convert Co(OH)₂ into oxygen-defective amorphous-crystalline CoO (namely ODAC-CoO) nanosheets. With the carefully controlled crystallinity and oxygen vacancy levels, the optimal ODAC-CoO sample exhibits dramatically enhanced ORR and OER electrocatalytic activities compared with the pure crystalline CoO counterpart. The assembled liquid and quasi-solid-state Zn–air batteries with ODAC-CoO as cathode material achieve remarkable specific capacity, power density, and excellent cycling stability, outperforming the benchmark Pt/C + IrO₂ catalysts. This study theoretically proposes and experimentally demonstrates that the simultaneous introduction of amorphous structures and oxygen vacancies could be an effective avenue towards high-performance electrocatalytic ORR and OER.     

Dielectric Properties of Nanocrystalline Tungsten Oxide in the Temperature Range of 223–293 K

The dielectric properties of nanocrystalline tungsten oxide are studied in the temperature range of 223–293 K and in the frequency range ν = 10^–2–10⁶ Hz. Powders of WO₃ with particle sizes of 110, 150, and 200 nm are prepared by the heat treatment of ammonium paratungstate at various temperatures. It is established that the frequency dependences of the conductivity for all samples increase with an increase in frequency, while the polarization characteristics ε'(ν) and ε"(ν) decrease. It is found that the frequency dependences of the conductivity are described by a function of the form ν ^s with an index in the range of (0.83–0.90) ± 0.01, which is characteristic of the “hopping” mechanism of charged-particle motion (complexes) over localized states confined by potential barriers and structural defects.     

Two-Dimensional Siloxene–Graphene Heterostructure-Based High-Performance Supercapacitor for Capturing Regenerative Braking Energy in Electric Vehicles

The development of high-performance electrodes that increase the energy density of supercapacitors (SCs) (without compromising their power density) and have a wide temperature tolerance is crucial for the application of SCs in electric vehicles. Recent research has focused on the preparation of multicomponent materials to form electrodes with enhanced electrochemical properties. Herein, a siloxene–graphene (rGO) heterostructure electrode-based symmetric SC (SSC) is designed that delivers a high energy density (55.79 Wh kg⁻¹) and maximum power density of 15 000 W kg⁻¹. The fabricated siloxene–rGO SSC can operate over a wide temperature range from –15 to 80 °C, which makes them suitable for applications in automobiles. This study shows the practical applicability of siloxene–rGO SSC to drive an electric car as well as to capture the braking energy in a regenerative brake-electric vehicle prototype. This work opens new directions for evaluating the use of siloxene–rGO SSC as suitable energy devices in electric vehicles.     

Bulk Incorporation of Molecular Dopants into Ruddlesden–Popper Organic Metal–Halide Perovskites for Charge Transfer Doping

Organic metal-halide perovskites (OHPs) have recently attracted much attention as next-generation semiconducting materials due to their outstanding opto-electrical properties. However, OHPs currently suffer from the lack of efficient doping methods, while the traditional method of atomistic doping having clear limitations in the achievable doping range. While doping with molecular dopants, has been suggested as a solution to this problem, the action of these dopants is typically restricted to perovskite surfaces, therefore significantly reducing their doping potential. In this study, successful bulk inclusion of “magic blue”, a molecular dopant, into 2D Ruddlesden–Popper perovskites is reported. This doping strategy of immersing the perovskite film in dopant solution increases the electrical current up to ≈60 times while maintaining clean film surface. A full mechanistic picture of such immersion doping is provided, in which the solvent molecule facilitates bulk diffusion of dopant molecule inside the organic spacer layer. Physical criteria for judicious choice of solvents in immersion doping are developed based on readily available solvent properties. The immersion doping method developed in this study that enables bulk molecular doping in OHPs will provide a strategic doping methodology for controlling electrical properties of OHPs for electronic and optoelectronic devices.     

The Frenkel–Poole Effect in the Ionization of an Acceptor Impurity of Boron in Diamond in a Strong Electric Field

Journal of Communications Technology and Electronics - The conductivity of epitaxial diamond films lightly doped with boron has been studied at strong electric fields up to ~5 × 105 V/ cm. It...     

Impact of the Percolation Effect on the Temperature Dependences of the Capacitance–Voltage Characteristics of Heterostructures Based on Composite Layers of Silicon and Gold Nanoparticles

Semiconductors - The temperature dependences of the capacitance–voltage characteristics and deep-level spectra of a Au–n-Si:Au–Si–p-Si heterostructure based on a composite...     

On the Electret Effect in Polymer–Ferroelectric Piezoceramic Composites with Various Values of the Electronegativity of the Polymer Matrix and Piezophase Cations

The influence of the electronegativity of phases, which is controlled by composite crystallization under the conditions of the effect of the electric discharge and covalence of piezophase cations, on the formation mechanism of the stable electret effect is determined. The specific features of the formation of the electret effect in composites based on polyolefins (HDPE, PP), fluorine-containing polymers (F42), and ferroelectric piezoelectric ceramics of the family of lead zirconate–titanate (Pb(Zr,Ti)O₃) crystallized under conditions of the effect of electric discharge plasma, are revealed. A physical model of electret composites taking into account the role of homocharges and heterocharges formed in a composite by its dispersion with piezoceramic particles of various structures—rhombohedral, tetragonal, and heterogeneous—is proposed.