High Power Stability Research Articles

Facile synthesis of composite tin oxide nanostructures for high-performance planar perovskite solar cells

Metal oxide carrier transporting layers have been investigated widely in organic/inorganic lead halide perovskite solar cells (PSCs). Tin oxide (SnO2) is a promising alternative to the titanium dioxide commonly used in the electron transporting layer (ETL), due to its tunable carrier concentration, high electron mobility, amenability to low-temperature annealing processing, and large energy bandgap. In this study, a facile method was developed for the preparation of a room-temperature-processed SnO2 electron transporting material that provided a high-quality ETL, leading to PSCs displaying high power conversion efficiency (PCE) and stability. A novel physical ball milling method was first employed to prepare chemically pure ground SnO2 nanoparticles (G-SnO2), and a sol–gel process was used to prepare a compact SnO2 (C-SnO2) layer. The effects of various types of ETLs (C-SnO2, G-SnO2, composite G-SnO2/C-SnO2) on the performance of the PSCs are investigated. The composite SnO2 nanostructure formed a robust ETL having efficient carrier transport properties; accordingly, carrier recombination between the ETL and mixed perovskite was inhibited. PSCs incorporating C-SnO2, G-SnO2, and G-SnO2/C-SnO2 as ETLs provided PCEs of 16.46, 17.92, and 21.09%, respectively. In addition to their high efficiency, the devices featuring the composite SnO2 (G-SnO2/C-SnO2) nanostructures possessed excellent long-term stability—they maintained 89% (with encapsulation) and 83% (without encapsulation) of their initial PCEs after 105 days (>2500 h) and 60 days (>1400 h), respectively, when stored under dry ambient air (20 ± 5 RH %).

Radio Frequency Performance Projection and Stability Tradeoff of h-BN Encapsulated Graphene Field-Effect Transistors

Hexagonal boron nitride (h-BN) encapsulation significantly improves carrier transport in graphene. This work investigates the benefit of implementing the encapsulation technique in graphene field-effect transistors (GFET) in terms of their radio frequency (RF) performance. For such a purpose, a drift-diffusion self-consistent simulator is prepared to get the GFET electrical characteristics. Both the mobility and saturation velocity information are obtained by means of an ensemble Monte Carlo simulator upon considering the relevant scattering mechanisms that affect carrier transport. RF figures of merit are simulated using an accurate small-signal model that includes non-reciprocal capacitances. Results reveal that the cutoff frequency could scale up to the physical limit given by the inverse of the transit time. Projected maximum oscillation frequencies, in the order of few THz, are expected to exceed the values demonstrated by InP and Si based RF transistors. The existing trade-off between power gain and stability and the role played by the gate resistance are also studied. High power gain and stability are feasible even if the device is operated far away from current saturation. Finally, the benefits of device unilateralization and the exploitation of the negative differential resistance region to get negative-resistance gain are discussed.

Advanced aqueous energy storage devices based on flower-like nanosheets-assembled Ni0.85Se microspheres and porous Fe2O3 nanospheres

The design and development of novel aqueous energy storage devices with high specific energy has recently become the research hotspot. The traditional energy storage devices are severely hindered because of the relatively low specific capacity of carbon anode materials. In this work, a novel aqueous energy storage device is assembled based on flower-like nanosheets-assembled Ni0.85Se microspheres as the cathode and porous Fe2O3 nanospheres as the anode. The flower-like nanosheets-assembled Ni0.85Se microspheres are synthesized by a two-step hydrothermal method and the porous Fe2O3 nanospheres are prepared through a facile one-step ionic liquid-assisted hydrothermal method. Due to their unique structures and superior electrochemical properties, the as-fabricated Ni0.85Se//Fe2O3 asymmetric device manifests high specific energy (39.2 Wh kg−1), high specific power (8.56 kW kg−1) and good cycling stability (82.6% of capacity retention after 5000 cycles). Moreover, two asymmetric devices are connected in series and can easily light a white light-emmitting diode for more than 5 min after being charged to 3.0 V. These impressive results indicate that the rational design of cathode and anode materials for energy storage devices is vitally important, and therefore this work can provide a valuable reference for the design and fabrication of novel energy storage devices with high specific energy and high specific power.

Моделирование индукционного генератора двойного питания вертикально-осевой ветроэнергетической установки

Global energy demand forms the challenge of selecting a proper power source. The choice is either to continue using traditional fossil fuels, projected to expire in 50–70 years, or to speed up the development of renewables, which could be used considerably longer. Today the advanced choice is the second option. Hence, the new methods and approaches have to be developed, diversified, and/or improved. The paper presents a new MATLAB Simulink simulation model used to estimate the integrated power generated by Vertical Axis Wind Turbine (VAWT). The material presents a step by step description of the model development. The value of generated power fluctuations is accounted for and verified in accordance with the grid capacity available at the moment. The parameters under analysis are as follows: Efficiency, Cost, and System Response Time. The benefits are comprehensively analyzed against disadvantages. A special advantage is considered as a combination of two systems, getting high performance and power stability.

Optimal coordination-site exposure engineering in porous platinum for outstanding oxygen reduction performance.

In this study, we report that optimal coordination-site exposure engineering in porous platinum brings ultrahigh activity and durability for the fuel cell oxygen reduction reaction (ORR). The porous platinum with numerous grain boundaries (GBP-Pt) consisting of 3nm crystals exhibits 7 times higher ORR activity than commercial Pt. For fuel-cell measurements, the GBP-Pt catalyst based MEA exhibits high power density (1.49 W cm-2, 0.71 A mg-1 Pt for mass activity) and stability (12.9% loss after 30 K cycles), all of which far surpass the U.S. DOE target in 2020 (0.44 A mg-1 Pt for mass activity and 40% loss for stability). Density Functional Theory (DFT) calculation and X-ray Absorption Fine Structure (XAFS) results suggest that proper Pt coordination site exposure in grain boundaries provides optimal adsorption energies for oxygen species and high stability in the ORR, even superior to Pt(111) sites. We anticipated that coordination-site exposure engineering would open a new avenue to offer robust electrocatalysts for the fuel-cell oxygen reduction reaction.

Blended cathode materials for all-solid-state Li-ion batteries

In this article, we report the effects of blended cathode materials in all solid-state lithium-ion batteries (ASLBs) with oxide-based inorganic-organic-hybrid electrolytes. A high capacity Ni-rich cathode material was used for high energy density in an ASLB, and LiFePO4, with its robust olivine structure, was added to compensate for the degradation of the Ni-rich cathode material during cycling. In case of the blended cathode, the shortcomings of the parent material can be minimized by blending two cathode materials, and the blending ratio can be tailored to produce stable high energy and power densities. For these reasons, the structure, cycling stability, and rate performance of the blended LiNi0.7Co0.15Mn0.15O2/LiFePO4 cathode material, for use in ASLBs with oxide-based inorganic–organic-hybrid electrolytes, was investigated by powder X-ray diffraction, field-emission scanning electron microscopy, Brunauer–Emmett–Teller sorption experiments, electrochemical impedance spectroscopy, and galvanostatic testing.

Flexible Asymmetric Microsupercapacitors from Freestanding Hollow Nickel Microfiber Electrodes

AbstractThe increasing demand for flexible and wearable microelectronics is a major driving force for the development of high‐performance small‐volume energy sources. Microsupercapacitors exhibit significant potential in energy storage as they provide high power and good cycle stability. Yet, most microsupercapacitors display low energy densities limiting their practical use in microelectronics. Here, synthesis of high surface area freestanding electrodes comprising hollow nickel microfibers is demonstrated. The microfiber nickel electrodes constitute a platform for flexible asymmetric microsupercapacitors exhibiting excellent mechanical resilience as well as high energy density (0.11 mWh cm−2) and power density (37.5 mW cm−2). The freestanding nature and extensive surface area of the electrodes contribute to pronounced areal and volumetric capacitance, energy storage values, and stability after numerous (hundreds) physical bending cycles. The simple preparation scheme and use of an inexpensive building block (e.g., nickel) underscore potential uses as light and flexible energy storage devices.

The effect of Fe as an impurity element for sustainable resynthesis of Li[Ni1/3Co1/3Mn1/3]O2 cathode material from spent lithium-ion batteries

We synthesize Li[Ni1/3Co1/3Mn1/3]O2 (NCM) and Li[Ni1/3Co1/3Mn1/3]FexO2 (NCMF) cathode active materials with various amounts of Fe via hydroxide coprecipitation and calcination processes, which simulate the resynthesis of NCM in leach liquor containing Fe from spent lithium-ion batteries (LIBs). The crystal structure and electrochemical performances of the synthesized NCMF (i.e., NCMF (0.05%), NCMF (0.25%) and NCMF (1.0%)), are investigated and compared with NCM. The structural perfection of NCMF gradually deteriorates with increasing the amount of Fe because of undesirable cation mixing between Ni2+/Fe3+ and Li+ sites. In LIB performances, NCMF (0.05%) and NCMF (0.25%) present relatively reduced overpotential leading to superior rate performance at high C-rates to NCM with NCMF (1.0%) having the poorest. In terms of cycling stability, however, capacity retention improves as the Fe content in NCMF increases. The thermal stability of NCM and NCMF is also measured by differential scanning calorimetry, and the post-mortem analysis of X-ray photoelectron spectroscopy reveals that the ratio of Mn3+ becomes lower after cycling tests as the amount of Fe in NCMF increases. Moreover, the additional post-mortem analysis of energy dispersive spectroscopy on graphite surface after full cell cycling tests further confirms the positive effect of Fe on the improved capacity retention performance of NCMF. Therefore, even if Fe is regarded as an impurity component in the LIB recycling process, a small amount of Fe in the resynthesized NCM cathode material could favor high power and high cycling stability.

3D 3C-SiC/Graphene Hybrid Nanolaminate Films for High-Performance Supercapacitors.

High-performance supercapacitors feature big and stable capacitances and high power and energy densities. To fabricate high-performance supercapacitors, 3D 3C-SiC/graphene hybrid nanolaminate films are grown via a microwave plasma-assisted chemical vapor deposition technique. Such films consist of 3D alternating structures of vertically aligned 3C-SiC and graphene layers, leading to high surface areas and excellent conductivity. They are further applied as the capacitor electrodes to construct electrical double layer capacitors (EDLCs) and pseudocapacitors (PCs) in both aqueous and organic solutions. The capacitance for an EDLC in aqueous solutions is up to 549.9 µF cm-2 , more than 100 times higher than that of an epitaxial 3C-SiC film. In organic solutions, it is 297.3 µF cm-2 . The pseudocapacitance in redox-active species (0.05 Fe(CN)6 3-/4- ) contained aqueous solutions is as high as 62.2 mF cm-2 . The capacitance remains at 98% of the initial value after 2500 charging/discharging cycles, indicating excellent cyclic stability. In redox-active species (0.01 m ferrocene) contained organic solutions, it is 16.6 mF cm-2 . Energy and power densities of a PC in aqueous solution are 11.6 W h kg-1 and 5.1 kW kg-1 , respectively. These vertically aligned 3C-SiC/graphene hybrid nanolaminate films are thus promising electrode materials for energy storage applications.

Simultaneous removal of organic matter and iron from hydraulic fracturing flowback water through sulfur cycling in a microbial fuel cell

The high volume of flowback water (FW) generated during shale gas exploitation is highly saline, and contains complex organics, iron, heavy metals, and sulfate, thereby posing a significant challenge for the environmental management of the unconventional natural gas industry. Herein, the treatment of FW in a sulfur-cycle-mediated microbial fuel cell (MFC) is reported. Simultaneous removal efficiency for chemical oxygen demand (COD) and total iron from a synthetic FW was achieved, at 72 ± 7% and 90.6 ± 8.7%, respectively, with power generation of 2667 ± 529 mW/m3 in a closed-circuit MFC (CC-MFC). However, much lower iron removal (38.5 ± 4.5%) occurred in the open-circuit MFC (OC-MFC), where the generated FeS fine did not precipitate because of sulfide supersaturation. Enrichment of both sulfur-oxidizing bacteria (SOB), namely Helicobacteraceae in the anolyte and the electricity-producing bacteria, namely Desulfuromonadales on the anode likely accelerated the sulfur cycle through the biological and bioelectrochemical oxidation of sulfide in the anodic chamber, and effectively increased the molar ratio of total iron to sulfide, thus alleviating sulfide supersaturation in the closed circuitry. Enrichment of SOB in the anolyte might be attributed to the formation of FeS electricity wire and likely contributed to the stable high power generation. Bacteroidetes, Firmicutes, Proteobacteria, and Chloroflexi enriched in the anodic chamber were responsible for degrading complex organics in the FW. The treatment of real FW in the sulfur-cycle-mediated MFC also achieved high efficiency. This research provides a promising approach for the treatment of wastewater containing organic matters, heavy metals, and sulfate by using a sulfur-cycle-mediated MFC.

One-Pot Synthesis of Co3 O4 /Ag Nanoparticles Supported on N-Doped Graphene as Efficient Bifunctional Oxygen Catalysts for Flexible Rechargeable Zinc-Air Batteries.

Flexible rechargeable zinc-air batteries are considered as one of the most promising power supplies for the emerging flexible and wearable electronic devices. However, the development of flexible zinc-air batteries is stagnant due to the lack of efficient bifunctional catalysts with high oxygen catalytic activity and flexible solid-state electrolytes with high mechanical stability and ionic conductivity. In this work, Co3 O4 /Ag@NrGO composite was synthesized by a facile one-pot method, and the catalyst shows remarkable oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional catalytic activity and good long-term stability. In particular, the OER overpotential of Co3 O4 /Ag@NrGO reaches 437 mV, outperforming that of the commercial IrO2 catalyst. This can be attributed to the combined effects of Co3 O4 , Ag, and N-rGO. Furthermore, PAA (polyacrylic acid) and PVA (polyvinyl alcohol) based gel-electrolytes have been developed as flexible solid-state electrolytes for zinc-air batteries. The results show that PAA-based electrolyte is more favorable to the flexible zinc-air battery with a high power density due to its relatively high ionic conductivity. The maximum power density of flexible zinc-air batteries with Co3 O4 /Ag@NrGO catalyst and PAA-based electrolyte can reach 108 mW cm-2 , which is almost the highest value reached in recent reports. This work will provide valuable guidance for the development of flexible rechargeable zinc-air batteries with high power density and stability.

Design a high power pulse transformer for c-band klystron modulator

Shanghai soft X-ray Free Electron Lasers (SXFEL) used C-band accelerator structure to accelerate electrons at SINAP (Shanghai Institute of Applied Physics). 50MW C-band klystron and 110MW modulator are used to provide power supply for accelerator structure. In order to meet the modulator-klystron demands, a reliable and stable high power pulse transformer is indispensable. In this paper, the key design points for the high voltage pulse transformer are presented. The methods of shortening rise time and diminishing flattop droop are highlighted.

Stable and widely tunable single-/dual-wavelength erbium-doped fiber laser by cascading a twin-core photonic crystal fiber based filter with Mach-Zehnder interferometer

A stable and widely tunable single-/dual-wavelength erbium-doped fiber laser (EDFL) is proposed by cascading a homemade twin-core photonic crystal fiber (TCPCF) based filter with Mach-Zehnder interferometer (MZI). By bending the TCPCF, single-wavelength lasing can be tuned from 1560.4 nm to 1583.44 nm with the tuning step of ∼0.78 nm and the widely tunable wavelength range over 23.04 nm can be achieved. Furthermore, by adjusting polarization controller, the output lasing can be switched from single-wavelength to dual-wavelength; the dual-wavelength lasing with wavelength interval of 0.78 nm can be tuned over a range of 33.82 nm from 1559.72 nm/1560.48 nm to 1593.54 nm/1594.32 nm. The tuning step and the interval of dual-wavelength is determined by the MZI. The SMSR of single- and dual-wavelength are higher than 45 dB and 42 dB, respectively. In addition, the stability of output lasing is measured experimentally. Excremental results demonstrate that the wavelength drift is less than 0.02 nm and peak power fluctuations of single-/dual-wavelengths are less than 0.47 dB and 0.8 dB, respectively. Such wide tuning range, small wavelength drift and high power stability makes this tunable EDFL have a potential application in the fields of optical fiber communication and sensing.

Erbium Ring Fiber Laser Cavity Based on Tip Modal Interferometer and Its Tunable Multi-Wavelength Response for Refractive Index and Temperature

A tunable multi-wavelength fiber laser is proposed and demonstrated based on two main elements: an erbium-doped fiber ring cavity and compact intermodal fiber structure. The modal fiber interferometer is fabricated using the cost-effective arc splice technique between conventional single-mode fiber and microfiber. This optical fiber structure acts as a wavelength filter, operated in reflection mode. When the refractive index and temperature variations are applied over the fiber filter, the ring laser cavity provides several quad-wavelength laser spectra. The multi-wavelength spectra are tuned into the C-band with a resolution of 0.05 nm. In addition, the spectra are symmetric with minimal power difference between the lasing modes involved, and the average of the side mode suppression ratio is close to 37 dB. This laser offers low-cost implementation, low wavelength drift, and high power stability, as well as an effect of easy controllability regarding tuned multi-wavelength.

Optimization of a fast rotating target to produce kHz X-ray pulses from laser-plasma interaction

We report the development of a fast rotating target to produce ultrashort incoherent X-ray pulses from bremsstrahlung. These short X-ray pulses are produced in the laser-plasma interaction of a 35 fs, 1 mJ pulse of a Ti:Sa laser of 1 kHz repetition rate, with a solid metallic target. In this paper, we report our developments to improve the stability of this micron size source of ultrashort X-rays. As the Rayleigh length is very small (<15 μm), wobbling of the rotatory stage can reduce the intensity on target and change the characteristics of the source. We describe the methods we have developed to measure and adjust the stability of the focus on target. These advances are important for the development of sources with high average power and good stability. The X-ray source has a broad Maxwellian-like distribution with temperatures of around 10 - 40 KeV and could be used for advanced X-ray imaging such as absorption or phase contrast tomography.

Investigation about the influence of longitudinal-mode structure of the laser on the relative intensity noise properties

The influence of the longitudinal-mode structure (LMS) of the laser on the relative intensity noise (RIN) properties was investigated in this paper after an all-solid-state continuous-wave (CW) single-frequency 1064 nm laser with output power of 50.3 W was achieved. The LMS of the laser was manipulated by controlling the temperature of the nonlinear lithium triborate (LBO) crystal deliberately introduced to the resonator. When the laser worked with single-longitudinal-mode (SLM) operation, the stable RIN spectrum was observed and measured. Moreover, with the decrease of the nonlinear conversion efficiency (NCE), the frequency and amplitude of the resonant-relaxation oscillation (RRO) peak regularly shifted to the higher frequencies and increased, respectively. However, with further decrease of the NCE, the laser began to work with the multi-longitudinal-mode (MLM) or mode-hopping operation and the unstable RIN spectra of the laser were both observed not only at low frequencies but also at high frequencies. Once the NCE was moved away, the MLM or mode-hopping can only enhance the fluctuation of the laser RIN spectrum at the low frequencies (lower than the frequency of RRO). The experimental results directly revealed the relationship between the LMS of the laser and the RIN spectra, and confirmed definitely that the key to achieve a stable high power laser with low intensity noise was to realize single-frequency operation of the laser with free MLM and mode-hopping.

Facile synthesized Cu-SnO2 anode materials with three-dimensional metal cluster conducting architecture for high performance lithium-ion batteries

Metal oxide anode material is one of promising candidates for the next-generation LIBs, due to its high theoretical capacity and low cost. The poor conductivity and huge volume change during charge/discharge, however, restrict the commercialization of metal oxide anode material. In this work, we design a novel Cu-SnO2 composite derived from Cu6Sn5 alloy with three dimensional (3D) metal cluster conducting architecture. The novel Cu structure penetrates in the composite particles inducing high conductivity and space-confined SnO2, which restrict the pulverization of SnO2 during lithiation/delithiation process. The optimized Cu-SnO2 composite anode delivers an initial discharge capacity of 933.7mAh/g and retains a capacity of 536.1mAh/g after 200 cycles, at 25°C and a rate of 100mA/g. Even at the high rate of 300mA/g, the anode still exhibits a capacity of more than 29% of that tested at 50mA/g. Combining with the phase and morphology analysis, the novel Cu-SnO2 composite not only has good electrical conductivity, but also possesses high theoretical capacity (995mAh/g), which may pave a new way for the design and construction of next-generation metal oxide anode materials with high power and cycling stability.

Design of Carbon/Metal Oxide Hybrids for Electrochemical Energy Storage.

Next generation electrochemical energy storage materials that enable a combination of high specific energy, specific power, and cycling stability can be obtained by a hybridization approach. This involves electrode materials that contain carbon and metal oxide phases linked on a nanoscopic level and combine characteristics of supercapacitors and batteries. The combination of the components requires careful design to create synergistic effects for an increased electrochemical performance. Improved understanding of the role of carbon as a substrate has advanced the power handling and cycling stability of hybrid materials significantly in recent years. This Concept outlines different design strategies for the design of hybrid electrode materials: (1) the deposition of metal oxides on readily existing carbon substrates and (2) co-synthesizing both carbon and metal oxide phase during the synthesis procedure. The implications of carbon properties on the hybrid material's structure and performance will be assessed and the impact of the hybrid electrode architecture will be analyzed. The advantages and disadvantages of all approaches are highlighted and strategies to overcome the latter will be proposed.

Atomic Layer-Deposited Molybdenum Oxide/Carbon Nanotube Hybrid Electrodes: The Influence of Crystal Structure on Lithium-Ion Capacitor Performance.

Merging of supercapacitors and batteries promises the creation of electrochemical energy storage devices that combine high specific energy, power, and cycling stability. For that purpose, lithium-ion capacitors (LICs) that store energy by lithiation reactions at the negative electrode and double-layer formation at the positive electrode are currently investigated. In this study, we explore the suitability of molybdenum oxide as a negative electrode material in LICs for the first time. Molybdenum oxide-carbon nanotube hybrid materials were synthesized via atomic layer deposition, and different crystal structures and morphologies were obtained by post-deposition annealing. These model materials are first structurally characterized and electrochemically evaluated in half-cells. Benchmarking in LIC full-cells revealed the influences of crystal structure, half-cell capacity, and rate handling on the actual device level performance metrics. The energy efficiency, specific energy, and power are mainly influenced by the overpotential and kinetics of the lithiation reaction during charging. Optimized LIC cells show a maximum specific energy of about 70 W·h·kg-1 and a high specific power of 4 kW·kg-1 at 34 W·h·kg-1. The longevity of the LIC cells is drastically increased without significantly reducing the energy by preventing a deep cell discharge, hindering the negative electrode from crossing its anodic potential limit.

Glass Ceramic Phosphors: Towards Long‐Lifetime High‐Power White Light‐Emitting‐Diode Applications–A Review

AbstractWith the technological advancements of high‐quality lightings and high‐end displays, white light‐emitting‐diodes (w‐LEDs) are quickly developing towards high energy density excitation, high output power and high device stability, which requires outstanding thermal properties of the phosphor color converters. In this connection, all‐inorganic luminescent glass ceramic (GC), exhibiting excellent physical/chemical stability to address the serious aging and yellowing issues of conventional phosphor/silicone composite, receives great attention recently and is regarded as a new generation color converter with longevity. Herein, a thorough survey of the research progress of this kind of material is made, with focus put on the design principle, microstructure‐property relationship, packaging technology and the burgeoning application direction. Some challenging issues are discussed and potential directions are suggested for further developing the phosphor‐glass composite fulfilling various requirements in practical application. This Review can promote rapid progress of long‐lifetime high‐power w‐LEDs.