Development of Surface Grating Distributed Feedback Quantum Cascade Laser for High Output Power and Low Threshold Current Density

We report on the room-temperature cascade laser （QCL） at λ -4.7μm. cw operation of a surface grating Both grating design and material distributed feedback （DFB） quantum optimization are used to decrease the threshold current density and to increase the output power. For a high-reflectivity-coated 13-μm-wide and 4- mm-long laser, high wall-plug efficiency of 6% is obtained at 20℃ from a single facet producing over I W of ew output power. The threshold current density of DFB QCL is as low as 1.13kA/cm^2 at 10℃ and 1.34kA/cm2 at 30℃ in cw mode. Stable single-mode emission with a side-mode suppression ratio of about 30 dB is observed in tile working temperature range of 20-50℃.

Nitrogen-doped carbon stabilized Li Fe0.5Mn0.5PO4/rGO cathode materials for high-power Li-ion batteries

Exploring high ion/electron conductive olivine-type transition metal phosphates is of vital significance to broaden their applicability in rapid-charging devices.Herein,we report an interface engineered Li Fe0.5Mn0.5PO4/rGO@C cathode material by the synergistic effects of r GO and polydopamine-derived N-doped carbon.The well-distributed Li Fe0.5Mn0.5PO4nanoparticles are tightly anchored on r GO nanosheet benefited by the coating of N-doped carbon layer.The design of such an architecture can effectively suppress the agglomeration of nanoparticles with a shortened Li+transfer path.Meantime,the high-speed conducting network has been constructed by r GO and N-doped carbon,which exhibits the face-to-face contact with Li Fe0.5Mn0.5PO4nanoparticles,guaranteeing the rapid electron transfer.These profits endow the Li Fe0.5Mn0.5PO4/rGO@C hybrids with a fast charge-discharge ability,e.g.a high reversible capacity of 105 m Ah·g^-1at 10 C,much higher than that of the Li Fe0.5Mn0.5PO4@C nanoparticles(46 mA·h·g^-1).Furthermore,a 90.8%capacity retention can be obtained even after cycling 500 times at 2 C.This work gives a new avenue to fabricate transition metal phosphate with superior electrochemical performance for high-power Li-ion batteries.

Recent Developments of Transition Metal Compounds-Carbon Hybrid Electrodes for High Energy/Power Supercapacitors

Due to their rapid power delivery,fast charging,and long cycle life,supercapacitors have become an important energy storage technology recently.However,to meet the continuously increasing demands in the fields of portable electronics,transportation,and future robotic technologies,supercapacitors with higher energy densities without sacrificing high power densities and cycle stabilities are still challenged.Transition metal compounds(TMCs)possessing high theoretical capacitance are always used as electrode materials to improve the energy densities of supercapacitors.However,the power densities and cycle lives of such TMCs-based electrodes are still inferior due to their low intrinsic conductivity and large volume expansion during the charge/discharge process,which greatly impede their large-scale applications.Most recently,the ideal integrating of TMCs and conductive carbon skeletons is considered as an effective solution to solve the above challenges.Herein,we summarize the recent developments of TMCs/carbon hybrid electrodes which exhibit both high energy/power densities from the aspects of structural design strategies,including conductive carbon skeleton,interface engineering,and electronic structure.Furthermore,the remaining challenges and future perspectives are also highlighted so as to provide strategies for the high energy/power TMCs/carbon-based supercapacitors.

Sustainable Lignin-Derived Carbon as Capacity-Kinetics Matched Cathode and Anode towards 4.5 V High-Performance Lithium-Ion Capacitors

The Li-ion capacitors(LICs)develop rapidly due to their double-high features of high-energy density and high-power density.However,the relative low capacity of cathode and sluggish kinetics of anode seriously impede the development of LICs.Herein,the precisely pore-engineered and heteroatomtailored defective hierarchical porous carbons(DHPCs)as large-capacity cathode and high-rate anode to construct high-performance dual-carbon LICs have been developed.The DHPCs are prepared based on triple-activation mechanisms by direct pyrolysis of sustainable lignin with urea to generate the interconnected hierarchical porous structure and plentiful heteroatominduced defects.Benefiting from these advanced merits,DHPCs show the well-matched high capacity and fast kinetics of both cathode and anode,exhibiting large capacities,superior rate capability and long-term lifespan.Both experimental and computational results demonstrate the strong synergistic effect of pore and dopants for Li storage.Consequently,the assembled dual-carbon LIC exhibits high voltage of 4.5 V,high-energy density of 208 Wh kg^(−1),ultrahigh power density of 53.4 kW kg^(−1)and almost zerodecrement cycling lifetime.Impressively,the full device with high mass loading of 9.4 mg cm^(−2)on cathode still outputs high-energy density of 187 Wh kg^(−1),demonstrative of their potential as electrode materials for high-performance electrochemical devices.

Dielectric size optimization for high power density in large-scale triboelectric nanogenerators

Triboelectric nanogenerators(TENGs)have emerged as a promising technology to harvest electrical energy from natural motions such as human movement,wind,and water flow.Although TENGs show significant potential in small-scale applications,developing large-scale TENGs capable of generating high power remains a significant challenge.Several factors that can affect the performance of large-scale TENGs are being investigated to overcome this challenge,including the size and configuration of dielectric materials.This study optimizes dielectrics regarding surface area,thickness,and multicell configuration to improve harvested electrical power density in large-scale TENGs.In the studies,glass fiber was used as the positive dielectric,and multipurpose white silicone was used as the negative dielectric because of their high tribo-potential,durability,and easy accessibility.In the size optimization phase,dielectric thicknesses and surface areas that provide the maximum power density were determined.Subsequently,horizontal and vertical multicell configurations were examined to efficiently integrate size-optimized dielectrics.The results reveal that large-scale TENGs with vertical multicell configurations can achieve high and usable energy density for electronics.The findings provide valuable insight into the development of large-scale TENGs with advanced power generation capabilities.

All-solid-state flexible asymmetric supercapacitors with high energy and power densities based on NiCo_2S_4@MnS and active carbon

Electrode material based on a novel core–shell structure consisting of NiCoS（NCS） solid fiber core and Mn S（MS） sheet shell（NCS@MS） in situ grown on carbon cloth（CC） has been successfully prepared by a simple sulfurization-assisted hydrothermal method for high performance supercapacitor. The synthesized NiCoS@Mn S/CC electrode shows high capacitance of 1908.3 F gat a current density of 0.5 A gwhich is higher than those of NiCoSand Mn S at the same current density. A flexible all-solid-state asymmetric supercapacitor（ASC） is constructed by using NiCoS@Mn S/CC as positive electrode, active carbon/CC as negative electrode and KOH/poly（vinyl alcohol）(PVA) as electrolyte. The optimized ASC shows a maximum energy density of 23.3 Wh kgat 1 A g, a maximum power density of about7.5 kw kgat 10 A gand remarkable cycling stability. After 9000 cycles, the ASC still exhibited67.8% retention rate and largely unchanged charge/discharge curves. The excellent electrochemical properties are resulted from the novel core–shell structure of the NiCoS@Mn S/CC electrode, which possesses both high surface area for Faraday redox reaction and superior kinetics of charge transport. The NiCoS@Mn S/CC electrode shows a promising potential for energy storage applications in the future.

In situ XRD and electrochemical investigation on a new intercalation-type anode for high-rate lithium ion capacitor

A new intercalation-type anode material is reported herein to improve the lithium storage kinetics for high-rate lithium ion capacitors.The crystal structure of orthorhombic NaNbO3 indicates two possible tunnels for lithium ions insertion into NaNbO3 host along the<101>and<141>directions.Moreover,in situ XRD is conducted to investigate the lithium storage mechanism and structural evolution of the NaNb O_(3) anode,demonstrating its intercalation behavior through(101)and(141)planes.Furthermore,the rGO nanosheets are introduced to facilitate the charge transfer,which also effectively prevent the aggregation of NaNbO3 nanocubes.As expected,the NaNbO_(3)/rGO nanocomposites possess remarkable reversible capacity(465 mA h g^(-1) at 0.1 A g^(-1)),superior rate capability(325 mA h g^(-1) at 1.0 A g^(-1))and cycling stability,attributed to their synergistic effect and high Li+diffusion coefficient DLi[D(NaNbO_(3)/rGO)/D(NaNbO_(3))≈31.54].Remarkably,the NaNbO3/rGO-based LIC delivers a high energy density of 166.7 W h kg^(-1) at 112.4 W kg^(-1) and remains 24.1 W h kg^(-1) at an ultrahigh power density of26621.2 W kg^(-1),with an outstanding cycling durability(90%retention over 3000 cycles at 1.0 A g^(-1)).This study provides new insights on novel intercalation-type anode material to enrich the materials system of LICs.

Recent progress on garnet phosphor ceramics for high power solid-state lighting

As the fourth-generation light source,solid-state lighting has developed rapidly in the past 30 years due to its advantages of high efficiency and environmental protection.It is widely used in various scenes such as automobile headlights,projection displays,industrial production,and remote lighting.High-power,high-brightness white light-emitting diodes(LEDs)and laser diodes(LDs)technology put forward new requirements for the service stability of color conversion materials.Garnet phosphor ceramics have emerged with their unique advantages of withstanding high power excitation density and the flexibly tunable spectrum.In this article,the research progress of garnet based phosphor ceramics for high-power solid-state lighting was comprehensively reviewed.Firstly,the band gap and coordination environment regulations of luminescence centers of garnet phosphor were summarized.Secondly,the improvement of luminous efficacy via defects regulation was discussed.Thirdly,the relationship between the geometric design and the lighting performance was elucidated.Fourthly,the characterization methods of phosphor ceramics for laser lighting were introduced and illustrated.Finally,the development trend of garnet phosphor ceramics in solid state lighting and display was prospected.

Niobium Tungsten Oxide in a Green Water‑in‑Salt Electrolyte Enables Ultra‑Stable Aqueous Lithium‑Ion Capacitors

Aqueous hybrid supercapacitors are attracting increasing attention due to their potential low cost,high safety and eco-friendliness.However,the narrow operating potential window of aqueous electrolyte and the lack of suitable negative electrode materials seriously hinder its future applications.Here,we explore high concentrated lithium acetate with high ionic conductivity of 65.5 mS cm−1 as a green“water-in-salt”electrolyte,providing wide voltage window up to 2.8 V.It facilitates the reversible function of niobium tungsten oxide,Nb18W16O93,that otherwise only operations in organic electrolytes previously.The Nb18W16O93 with lithium-ion intercalation pseudocapacitive behavior exhibits excellent rate performance,high areal capacity,and ultra-long cycling stability.An aqueous lithium-ion hybrid capacitor is developed by using Nb18W16O93 as negative electrode combined with graphene as positive electrode in lithium acetate-based“water-in-salt”electrolyte,delivering a high energy density of 41.9 W kg−1,high power density of 20,000 W kg−1 and unexceptionable stability of 50,000 cycles.

High-Voltage and Fast-Charging Lithium Cobalt Oxide Cathodes: From Key Challenges and Strategies to Future Perspectives

Lithium-ion batteries(LIBs)with the“double-high”characteristics of high energy density and high power density are in urgent demand for facilitating the development of advanced portable electronics.However,the lithium ion(Li+)-storage performance of the most commercialized lithium cobalt oxide(LiCoO_(2),LCO)cathodes is still far from satisfactory in terms of high-voltage and fast-charging capabilities for reaching the double-high target.Herein,we systematically summarize and discuss high-voltage and fast-charging LCO cathodes,covering in depth the key fundamental challenges,latest advancements in modification strategies,and future perspectives in this field.Comprehensive and elaborated discussions are first presented on key fundamental challenges related to structural degradation,interfacial instability,the inhomogeneity reactions,and sluggish interfacial kinetics.We provide an instructive summary of deep insights into promising modification strategies and underlying mechanisms,categorized into element doping(Li-site,cobalt-/oxygen-site,and multi-site doping)for improved Li+diffusivity and bulkstructure stability;surface coating(dielectrics,ionic/electronic conductors,and their combination)for surface stability and conductivity;nanosizing;combinations of these strategies;and other strategies(i.e.,optimization of the electrolyte,binder,tortuosity of electrodes,charging protocols,and prelithiation methods).Finally,forward-looking perspectives and promising directions are sketched out and insightfully elucidated,providing constructive suggestions and instructions for designing and realizing high-voltage and fast-charging LCO cathodes for next-generation double-high LIBs.

Numerical simulation of the flow field of a flat torque converter

A flexible flat torque converter was proposed to fulfill the requirement of miniaturization and power density maximization for automobiles.Constructed by two arcs joined by lines,the torus was designed directly from design path.The influence of flatness on the performance of the torque converter was evaluated.The software CFX and standard k-ε model were adopted to simulate the internal flow fields of the torque converter under different flatness ratios.The results indicated that the performance of the torque converter got worse as the flatness declined,but the capacity of pump increased.The efficiency and the torque ratio dropped slightly as the flatness ratio decreased.So the torque converter could be squashed appropriately to get high power density without too much efficiency sacrifice.But when the flatness ratio was below 0.2,there was a significant drop in the efficiency.

A review of ferroelectric materials for high power devices

Compact autonomous ultrahigh power density energy storage and power generation devices that exploitthe spontaneous polarization of ferroelectric materials are capable of producing hundreds of kilovoltvoltages,multi-kiloampere currents,and megawatt power levels for brief interval of time.The storagelife of these devices is four orders of magnitude longer than that for electrochemical batteries andelectrochemical capacitors.Herein is an up to date survey of ferroelectric materials used for these highpower devices.Several types of ferroelectric ceramics possess the ability to be depolarized under adia-batic compression and can be successfully used for high power applications.In addition to bulk ferro-electric ceramics,multilayer ferroelectric films are very efficient materials for high power systems.Ofparticular importance is the ability of relaxor ferroelectric single crystals to produce significantly higherelectric charge density and energy density than ceramics,making them promising materials for highpower applications.Also provided is a brief survey of recent developments of ferroelectric materials forhigh energy density and power density dielectric capacitors.Numerous ceramics have been developed,including antiferroelectric and relaxor antiferroelectric solid solutions,providing high energy densityand efficiency simultaneously.

Revisiting the electrode manufacturing: A look into electrode rheology and active material microenvironment

The microstructures on electrode level are crucial for battery performance, but the ambiguous understanding of both electrode microstructures and their structuring process causes critical challenges in controlling and evaluating the electrode quality during fabrication. In this review, analogous to the cell microenvironment well-known in biology, we introduce the concept of ‘‘active material microenvironment”(ME@AM)that is built by the ion/electron transport structures surrounding the AMs, for better understanding the significance of the electrode microstructures. Further, the scientific significance of electrode processing for electrode quality control is highlighted by its strong links to the structuring and quality control of ME@AM. Meanwhile, the roles of electrode rheology in both electrode structuring and structural characterizations involved in the entire electrode manufacturing process(i.e., slurry preparation, coating/printing/extrusion, drying and calendering) are specifically detailed. The advantages of electrode rheology testing on in-situ characterizations of the electrode qualities/structures are emphasized. This review provides a glimpse of the electrode rheology engaged in electrode manufacturing process and new insights into the understanding and effective regulation of electrode microstructures for future high-performance batteries.

High-voltage,low-temperature supercapacitors enabled by localized“water-in-pyrrolidinium chloride”electrolyte

Aqueous electrolytes offer superior prospects for advanced energy storage.“Water-in-salt”(WIS)electrolytes exhibit a wide electrochemical stability window(ESW),but their low conductivity,high viscosity,and precipitation at low temperatures restrict their application.Herein,we report a novel localized“water-in-pyrrolidinium chloride”electrolyte(LWIP;1 mol/L,N-propyl-N-methylpyrrolidinium chloride/(water and N,Ndimethylformamide,1:4 by molality))enabling high-voltage,low-temperature supercapacitors(SCs).The greatly improved ESW(3.451 V)is mainly attributed to the strong solvation between Cl-and water molecules,which broadens the negative stability.This water-binding mechanism is very different from that of a WIS electrolyte based on alkali metal salt.SCs using LWIP electrolytes not only yield a high operating voltage of 2.4 V and excellent capacity retention(82.8%after 15,000 cycles at 5 A g^(-1))but also operate stably at-20℃.This work provides new approaches for the design and preparation of novel electrolytes.

Introduction of 35-kV kilometer-scale high-temperature superconducting cable demonstration project in Shanghai

In December 2021,the 35-kV kilometer-level high-temperature superconducting(HTS)demonstration cable was officially connected to the grid in Xuhui District,Shanghai,China.A three-in-one HTS cable with a rated current of 2.2 kA,which replaces four-parallel lines XLPE cables,has been used in this project.This cable powers one of the busiest districts of Shanghai and serves to demonstrate and study the stability and reliability of a superconducting cable in the municipal power system.This project officially started in February 2019,and the type test of the prototype cable system was completed in November 2019.The commissioning test will be completed in November 2021.This paper introduces the main operating parameters,relevant research studies,and tests of this project.

Fe_(2)TiO_(5)nanochains as anode for high-performance lithium-ion capacitor

The unique crystal structure and multiple redox couples of iron titanate(Fe_(2)TiO_(5)) provide it a high theoretical capacity and good cycling stability when used as an electrode. In this study, the electrospinning method is employed to synthesize one-dimensional(1 D) Fe_(2)TiO_(5) nanochains. The as-prepared Fe_(2)TiO_(5) nanochains exhibited superior specific capacity(500 mAh·g^(-1) at 0.10 A·g^(-1)),excellent rate performance(180 mAh·g^(-1) at 5.00 A·g^(-1)),and good cycling stability(retaining 100% of the initial specific capacity at a current density of 1.00 A·g^(-1) after1000 cycles). The as-assembled Fe_(2)TiO_(5)/SCCB lithiumion capacitor(LIC) also delivered a competitive energy density(137.8 Wh·kg^(-1))andpowerdensity(11,250 W·kg^(-1)). This study proves that the as-fabricated1 D Fe_(2)TiO_(5) nanochains are promising anode materials for high-performance LICs.

Perspectives and challenges for lead-free energy-storage multilayer ceramic capacitors

The growing demand for high-power-density electric and electronic systems has encouraged the development of energy-storage capacitors with attributes such as high energy density,high capacitance density,high voltage and frequency,low weight,high-temperature operability,and environmental friendliness.Compared with their electrolytic and film counterparts,energy-storage multilayer ceramic capacitors(MLCCs)stand out for their extremely low equivalent series resistance and equivalent series inductance,high current handling capability,and high-temperature stability.These characteristics are important for applications including fast-switching third-generation wide-bandgap semiconductors in electric vehicles,5G base stations,clean energy generation,and smart grids.There have been numerous reports on state-of-the-art MLCC energy-storage solutions.However,lead-free capacitors generally have a low-energy density,and high-energy density capacitors frequently contain lead,which is a key issue that hinders their broad application.In this review,we present perspectives and challenges for lead-free energy-storage MLCCs.Initially,the energy-storage mechanism and device characterization are introduced;then,dielectric ceramics for energy-storage applications with aspects of composition and structural optimization are summarized.Progress on state-of-the-art energy-storage MLCCs is discussed after elaboration of the fabrication process and structural design of the electrode.Emerging applications of energy-storage MLCCs are then discussed in terms of advanced pulsed power sources and high-density power converters from a theoretical and technological point of view.Finally,the challenges and future prospects for industrialization of lab-scale lead-free energy-storage MLCCs are discussed.

Recent advances in the synthesis of non-carbon two-dimensional electrode materials for the aqueous electrolyte-based supercapacitors

Supercapacitors(SCs) with high power density and long cycling span life are demanding energy storage devices that will be an attractive power solution to modern electronic and electrical applications. Numerous theoretical and experimental works have been devoted to exploring various possibilities to increase the functionality and the specific capacitance of electrodes for SCs. Non-carbon two-dimensional(2D)materials have been considered as encouraging electrode candidates for their chemical and physical advantages such as tunable surface chemistry, high electronic conductivity, large mechanical strength, more active sites, and dual non-faradaic and faradaic electrochemical performances. Besides, these 2D materials also play particular roles in constructing highway channels for fast ion diffusion. This concise review summarizes cutting-edge progress of some representative 2D non-carbon materials for the aqueous electrolyte-based SCs, including transition metal oxides(TMOs), transition metal hydroxides(TMHs), transition metal chalcogenides(TMCs), MXenes, metal-organic frameworks(MOFs) and some emerging materials. Different synthetic methods, effective structural designs and corresponding electrochemical performances are reviewed in detail. And we finally present a detailed discussion of the current intractable challenges and technical bottlenecks, and highlight future directions and opportunities for the development of next-generation high-performance energy storage devices.

Plasma-grating-induced breakdown spectroscopy

.Laser-induced breakdown spectroscopy(LIBS)is a useful tool for determination of elements in solids,liquids,and gases.For nanosecond LIBS(ns-LIBS),the plasma shielding effect limits its reproducibility,repeatability,and signal-to-noise ratios.Although femtosecond laser filament induced breakdown spectroscopy(FIBS)has no plasma shielding effects,the power density clamping inside the filaments limits the measurement sensitivity.We propose and demonstrate plasma-grating-induced breakdown spectroscopy(GIBS).The technique relies on a plasma excitation source-a plasma grating generated by the interference of two noncollinear femtosecond filaments.We demonstrate that GIBS can overcome the limitations of standard techniques such as ns-LIBS and FIBS.Signal intensity enhancement with GIBS is observed to be greater than 3 times that of FIBS.The matrix effect is also significantly reduced with GIBS,by virtue of the high power and electron density of the plasma grating,demonstrating great potential for analyzing samples with complex matrix.

Rational construction of phosphate layer to optimize Cu-regulated Fe_(3)O_(4) as anode material with promoted energy storage performance for rechargeable Ni-Fe batteries

Flexible aqueous energy storage devices with high security and flexibility are crucial for the progress of wearable energy storage.Particularly,aqueous rechargeable Ni-Fe batteries owning a large theoretical capacity,low cost and outstanding safety characteristics have emerged as a promising candidate for flexible aqueous energy storage devices.Herein,Cu-doped Fe_(3)O_(4)(CFO)with 3D coral structure was prepared by doping Cu^(2+) based on Fe_(3)O_(4)nanosheets(FO).Furthermore,the Fe-based anode material(CFPO)grown on carbon fibers was obtained by reconstructing the surface of CFO to form a low-crystallization shell which can enhance the ion transport.Excitingly,the newly developed CFPO electrode as an innovative anode material further exhibited a high capacity of 117.5 mAh g^(-1)(or 423 F g^(-1))at 1 A g^(-1).Then,the assembled aqueous Ni-Fe batteries with a high cell-voltage output of 1.6 V deliver a high capacity of 49.02 mAh g^(-1) at 1 A g^(-1) and retention ratio of 96.8%for capacitance after 10000 continuous cycles.What’s more,the aqueous quasi-solid-state batteries present a remarkable maximal energy density of 45.6 Wh kg^(-1) and a power density of 12 kW kg^(-1).This work provides an innovative and feasible way and optimization idea for the design of high-performance Fe-based anodes,and may promote the development of a new generation of flexible aqueous Ni-Fe batteries.