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Metallic sodium (Na) is an appealing anode material for high-energy Na batteries. However, Na metal suffers from low coulombic efficiencies and severe dendrite growth during plating/stripping cycles, causing short circuits. As an effective strategy to improve the deposition behavior of Na metal, a 3D carbon foam is developed that is sputter-coated with gold nanoparticles (Au/CF), forming a functional gradient through its thickness. The highly porous Au/CF host is proven to have gradually varying sodiophilicity, which in turn facilitates initially preferential Na deposition on the gold-rich, sodiophilic region in a "bottom-up growth" mode, leading to uniform plating over the entire Au/CF host. This finding contrasts with dendrite formation in the pristine CF host, as proven by in situ microscopy. The Na-predeposited Au/CF (Na@Au/CF) composite anode operates steadily for 1000 h at a low overpotential of ≈20 mV at 2 mA cm-2 in a symmetric cell. When the composite anode is coupled with a Na3 V2 (PO4 )2 F3 cathode, the full cell has a high capacity of 102.1 mAh g-1 after 500 cycles at 2 C. The sodiophilicity gradient design that is explored in this study offers new insight into developing porous Na metal hosts with highly stable plating/stripping performance for next-generation Na batteries.

IGBT short-circuit protection is the key factor to improve the reliability of the power electronics system. The conventional short-circuit protection method based on $V_{CE}$ measurement detects the collector–emitter voltage of an IGBT to determine whether the IGBT short-circuit fault occurs. The blanking circuit is needed in this kind of protection method to avoid the false triggering of the short-circuit protection during IGBT turn-on transient. However, this blanking circuit should be carefully designed for different types of IGBT modules. In order to make the IGBT short-circuit protection circuit suitable for the tolerance of IGBT modules, a self-adaptive blanking circuit combined with the aforementioned short-circuit protection method based on $V_{CE}$ measurement is proposed. The proposed method is achieved by feeding back the required minimum blanking time interval which is decided by comparing the desaturation reference voltage with the collector–emitter voltage. The short-circuit protection delay time for the conventional circuit and the proposed circuit are compared. Experimental results are included to prove the effectiveness of the proposed circuit.

Sodium-ion batteries (SIBs) are considered promising low-cost alternatives to prevailing lithium-ion batteries (LIBs). The inherently sluggish kinetics of their anode materials, however, poses a great challenge to the SIBs' rate capabilities. This work reports the synthesis of novel MoS2/Carbon (MoS2/C) microspheres with three-dimensional (3D) architecture as an anode for SIBs using a facile hydrothermal strategy. The MoS2/C electrode delivers a reversible capacity of 498 mA h g−1 at 100 mA g−1, which stabilizes at 450 mA h g−1 after 100 cycles. Even at 4 A g−1, the electrode maintains a high reversible capacity above 310 mA h g−1 after 600 cycles, demonstrating its superior rate capability and long-term cyclic stability. Quantitative kinetics analysis reveals a pseudocapacitance-dominated Na+ storage mechanism, especially at high current densities. Furthermore, density functional theory (DFT) calculations show that the Na transport rates are faster through the MoS2/C heterointerface, due to a low diffusion energy barrier, than along the MoS2/MoS2 bilayers.

Red phosphorus has thus far the highest theoretical capacity among all known anode materials for sodium ion batteries (SIBs). However, its low electronic conductivity and large volume expansion during cycles cause rapid capacity fading, leading to poor electrochemical stability. Herein, we report a facile and scalable ball milling approach to synthesize NiP3/carbon nanotube (CNT) composites consisting of NiP3 particles chemically bonded with functionalized CNTs. The conductive CNTs play an important role in stabilizing the composite electrode through an enhanced Na+ diffusion coefficient by two orders of magnitude and six-fold reduction in its charge transfer resistance. The NiP3/CNT composite anode delivers a high initial reversible capacity of 853 mA h g−1 with more than 80% capacity retention after 120 cycles at 200 mA g−1 and an excellent high-rate capacity of 363.8 mA h g−1 after 200 cycles at 1600 mA g−1. The density functional theory (DFT) calculations combined with ab initio molecular dynamics (AIMD) simulations elucidate strong chemical interactions between the red P in NiP3 and the functional groups on CNTs to form P–C and P–O–C bonds by ball milling for the first time. The facile synthesis strategy devised in this study can be applied to other alloy-based composites with relatively low carbon content for use as high performance anodes for SIBs.

Lithium–sulfur (Li–S) batteries have attracted increasing attention in the past few decades due to the extremely high energy density, low cost and non-toxicity of sulfur. But the poor conductivity of sulfur and particularly the migration of soluble polysulfides greatly hindered the application of Li–S batteries. Herein, we report a novel strategy for trapping polysulfides by coating a separator with an interwoven framework of MoO3 nanorods and carbon nanotubes (CNTs) as the interlayer in Li–S batteries. The interwoven scaffold-like MoO3@CNT network provides abundant conducting channels and pathways for ions and electrons, leading to high rate capabilities. While the MoO3@CNT interlayer acting as a barrier effectively mitigates the shuttle effect in Li–S batteries, the MoO3 nanorods enfolded by CNTs uniformly play an important role in immobilizing sulfur species. Consequently, the electrochemical performances of Li–S batteries are improved, giving rise to higher capacities with a longer cycling life. The Li–S batteries with the MoO3@CNT interlayer can deliver a specific capacity of 755 mA h g−1 after 200 cycles at a current density of 0.3C, and show an excellent rate capability with a capacity of 655 mA h g−1 at 3C.

Solid electrolyte interphase (SEI) is an electrically insulating and ionically conductive passivation layer which is formed on the electrode surface through electrolyte decomposition. SEI is crucial to battery performance because it plays a vital role to determine the Coulombic efficiency, cycle life, capacity, and safety. Given the intricated formation mechanisms and the complicated structures and compositions of SEI, the in-depth understanding of SEI is still challenging. This review is dedicated to critical discussion on recent advances in understanding the formation mechanisms of SEI. The important factors, including electrolyte components, temperature, areal current, and electrode materials, that affect the formation, morphology, structure, composition, and properties of SEI layers are discussed. In situ/operando characterization techniques used to look into the surface morphology, electrochemical performance, chemical composition, structure, and mechanical properties of SEI layers are emphasized. The recent progress of the state-of-the-art cryogenic electron microscopy aimed at atomistic visualization of SEI is highlighted. Multi-scale theoretical simulations employed to study the thermodynamic and kinetic properties of SEI are also discussed. In addition, the SEIs formed on various anodes using solid-state electrolytes are also presented. Finally, the outstanding challenges and future directions in understanding SEI are presented. This review is envisioned to offer new insights into rationally designing the SEI layers for the development of next-generation high-performance rechargeable batteries.

The potential application of metallic Na anodes for high energy density batteries is plagued by dendrite formation accompanied by rapid consumption of electrolyte and Na metal. Herein, coaxially electrospun, hollow and mesoporous carbon nanofiber (HpCNF) hosts possessing strong affinity with Na are developed for Na metal batteries. The combined in situ and cryogenic microscopy along with theoretical simulations reveal that the highly sodiophilic HpCNFs with abundant defects and nitrogen functional groups enable compact, uniform plating of Na with excellent reversibility aided by the resilient, fluorine-rich SEI layer. Thanks to the optimized Na deposition in the entire structure, the Na@HpCNF anodes present an average Coulombic efficiency of 99.7% after 1,400 cycles at a current density of 3 mA cm−2 and a plating/striping capacity of 6 mAh cm−2. Their symmetric cell maintains stable cycles for over 1000 hr at 5 mA cm−2 and 5 mAh cm−2, which is among the best when compared with state-of-the-art electrodes. The full cells paired with a Na3V2(PO4)2F3 cathode deliver remarkable specific capacities of 115 and 93 mAh cm−2 after 500 cycles at 1 C and 200 cycles at 4 C, respectively. These findings highlight new insight into rationally-designed metal anodes towards the development of high-performance metal batteries.

Ideal lithium-ion batteries (LIBs) should possess a high power density, be charged extremely fast (e.g., 100C), and have a long service life. To achieve them all, all battery components, including anodes, cathodes, and electrolytes should have excellent structural and functional characteristics. The present work reports ultrafast-charging and long-life LIB anodes made from TiO2-B/anatase dual-phase nanowires. The dual-phase nanowires are fabricated with anatase TiO2 nanoparticles through a facile and cost-effective hydrothermal process, which can be easily scaled up for mass production. The anodes exhibit remarkable electrochemical performance with reversible capacities of ∼225, 172, and 140 mAh g–1 at current rates of 1C, 10C, and 60C, respectively. They deliver exceptional capacity retention of not less than 126 and 93 mAh g–1 after 1000 cycles at 60C and 100C, respectively, potentially worthwhile for high-power applications. These values are among the best when the high-rate capabilities are compared w...

Porous Fe3O4/carbon microspheres (PFCMs) were successfully fabricated via a facile electrospray method and subsequent heat treatment, using ferrous acetylacetonate, carbon nanotubes (CNTs), Ketjen black (KB), polyvinylpyrrolidone (PVP), and polystyrene (PS) as raw materials. The porous carbon sphere framework decorated with well-dispersed CNTs and KB exhibits excellent electronic conductivity and acts as a good host to confine the Fe3O4 nanoparticles. The abundant mesopores in the carbon matrix derived from polymer pyrolysis can effectively accommodate the volume changes of Fe3O4 during the charge/discharge process, facilitate electrolyte penetration, and promote fast ion diffusion. Moreover, a thin amorphous carbon layer on the Fe3O4 nanoparticle formed during polymer carbonization can further alleviate the mechanical stress associated with volume changes, and preventing aggregation and exfoliation of Fe3O4 nanoparticles during cycling. Therefore, as anode materials for lithium-ion batteries, the PFCMs exhibited excellent cycling stability with high specific capacities, and outstanding rate performances. After 130 cycles at a small current density of 0.1 A·g–1, the reversible capacity of the PFCM electrode is maintained at almost 1,317 mAh·g–1. High capacities of 746 and 525 mAh·g–1 were still achieved after 300 cycles at the larger currents of 1 and 5 A·g–1, respectively. The optimized structure design and facile fabrication process provide a promising way for the utilization of energy storage materials, which have high capacities but whose performance is hindered by large volume changes and poor electrical conductivity in lithium or sodium ion batteries.

The rapid development of electrochemical energy storage systems requires new electrode materials with high performance. As a two-dimensional material, molybdenum disulfide (MoS2 ) has attracted increasing interest in energy storage applications due to its layered structure, tunable physical and chemical properties, and high capacity. In this review, the atomic structures and properties of different phases of MoS2 are first introduced. Then, typical synthetic methods for MoS2 and MoS2 -based composites are presented. Furthermore, the recent progress in the design of diverse MoS2 -based micro/nanostructures for rechargeable batteries, including lithium-ion, lithium-sulfur, sodium-ion, potassium-ion, and multivalent-ion batteries, is overviewed. Additionally, the roles of advanced in situ/operando techniques and theoretical calculations in elucidating fundamental insights into the structural and electrochemical processes taking place in these materials during battery operation are illustrated. Finally, a perspective is given on how the properties of MoS2 -based electrode materials are further improved and how they can find widespread application in the next-generation electrochemical energy-storage systems.

The pursuit of sustainable energy utilization arouses increasing interest in efficiently producing durable battery materials and catalysts with minimum environmental impact. As green, safe, and cheap eutectic mixtures, deep eutectic solvents (DESs) provide tremendous opportunities and open up attractive perspectives as charge transfer and reaction media for electrochemical energy storage and conversion (EESC). In this review, the fundamental properties of DESs are first summarized. Then, the important roles that DESs play in various EESC technologies including advanced electrolytes for batteries/supercapacitors, media for the preparation of electrode materials and catalysts, and extracting agents for battery recycling are systematically reviewed. A particular focus is placed on the fundamental understanding of structure–composition–property–performance relationships. Finally, the challenges for the controllable design of DESs for EESC applications and future developments are presented. This review is expected to shed light on developing advanced DESs for next-generation EESC systems.

Based on the Friedel-Crafts alkylation reaction, epichlorohydrin is applied to decorate the meta aramid to enhance the comfort of the fabrics. It is obviously more perfect that the samples are treated with the hydrophilic soft finishing agent. In this paper, the effects of modification and finishing time on the structure and properties of meta aramid are studied. The results indicate that the surface roughness, polarity, active point, and wetting property of the modified fabrics are increased, and the loading rate and fastness of the finishing agent on the meta aramid are enhanced. After finishing, the wetting time and the time of water transfer from the surface to the bottom become shorter in the fabrics, and the water absorption rate becomes faster, the core absorption height rises by 60%, the bending stiffness lowers by 39%, the moisture permeability increases by 5.9%, the permeability decreases by 3.6%, and the friction electric voltage reduces by 78%, The longitudinal and weft secondary combustion time increase by 0.3 s and 0.2 s, the smoldering time increase by 0.3 s, and the improving rate of damage length are 5.4% and 7.6%, respectively.

The silicon/carbon (Si/C) hybrid fibers with a hierarchical core–shell structure are prepared by encapsulating Si nanoparticles in the interconnected hollow carbon fibers (Si@IHCFs) based on a dual coaxial electrospinning technique. For the hierarchical structure, Si nanoparticles are embedded in the honeycomb-like carbon framework in the fiber core, which is further wrapped by the interlocked cobweb-like carbon shell network. As lithium-ion battery anode, the well-defined Si@IHCFs demonstrates a reversible capacity of 903 mAh g −1 and a capacity retention of 89% after 100 cycles with a current density of 0.2 A g −1 . With the current density gradually increasing to 2.0 A g −1 , the electrode shows a specific capacity of 743 mAh g −1 , exhibiting superior rate capability compared to the Si/C fibers with a core–shell but unconnected structure. The excellent electrochemical properties are attributed to the hierarchical core–shell structure and cross-linked network for the Si/C composite fibers. The carbon framework in the core region accommodates the volume expansion of Si by the honeycomb-like pores. And the interconnected carbon shell can not only prevent electrolyte from permeating into the core section, but also improve the electronic conductivity by the connections in the fiber network.

Lithium–sulfur (Li–S) batteries are seriously constrained by the diffusion and crossover of intermediary product polysulfides and their further reductions on the anode surface. Although carbon-based interlayers have been widely used to inhibit the detrimental shuttle effect in Li–S batteries, the weak physical adsorption of pure carbon materials for trapping polysulfides still leads to low recycle efficiency of active species and short cycle life for cells. Herein, we report a cyclized-polyacrylonitrile-cast carbon nanofiber (CP@CNF) film as an interlayer in Li–S batteries. By exploiting the CP@CNF interlayer, the batteries assembled with bare sulfur cathodes deliver superior rate capability and cycle stability. The reversible capacity could be maintained at 710 mA h g−1 after 200 cycles at 0.3C and a capacity of 560 mA h g−1 can be obtained even at a 2C rate. The improved performances are attributed to both the abundant pyridine groups in the cyclized polyacrylonitrile matrix, which can entrap polysulfides by strong interatomic attraction, and the three-dimensional porous conductive network composed of the carbon nanofiber skeleton and conjugated polymer matrix, giving rise to highly effective transfer pathways for electrons and ions.

Sodium-ion batteries have been considered a cost-effective alternative to lithium-ion batteries because of the cheap and abundant sodium reserves. However, the sluggish kinetics arising from the slow ion and electron transport, particularly at high rates, is the main bottleneck of fast sodium storage. Here, few-layer MoSe2 encapsulated by nitrogen/phosphorus (N/P) co-doped carbon and reduced graphene oxide (MoSe2@NPC/rGO) composites are fabricated through a simple polymerization reaction followed by selenization. The two-dimensional composite nanosheets effectively shorten the ion diffusion length while the few-layer MoSe2 exposes a large surface area to the electrolyte. The NPC/rGO sheets intercalated within the composites function as channels for fast electron transfer and surface reactions. First-principles calculations show quick Na transport rates on the surface of MoSe2, and quantitative kinetics analysis reveals a pseudocapacitance-dominated Na+ storage mechanism at high rates. Thanks to the ameliorating functional features and highly reversible conversion reactions, the MoSe2@NPC/rGO electrode delivers a reversible capacity of ~340 mA h g−1 after 500 cycles at 0.5 A g−1 with a high contribution by surface capacitance. It also possesses a high reversible capacity of ~100 mA h g−1 even at an extremely high current density of 50 A g−1, presenting potential application as anodes for high-power sodium-ion batteries.

Rechargeable batteries have significantly helped to effectively use renewable energy sources as well as to intensively expand the electrification of vehicles. To achieve such goals, new advanced materials are urgently required. Atomically dispersed materials (ADMs) with single-atom metals supported on substrates feature uniform metallic sites and represent the utmost utilization of atoms, demonstrating wide applications in catalysis. These structural and morphological characteristics also make ADMs attractive materials for rechargeable batteries. Herein, we highlight and summarize the recent advances in synthetic methods for ADMs by physical confinement and chemical bonding. Subsequently, we summarize the recent progress in the design of diverse ADMs for lithium metal, lithium-sulfur, sodium-sulfur, lithium-oxygen, and zinc-air batteries and unveil the corresponding roles of ADMs from atomistic perspectives. Finally, the challenges and perspectives in this field are discussed.

Nanostructured metal chalcogenides (MCs) and their composites are studied for high performance sodium-ion batteries (SIBs). Herein, we report the assembly of an emerging MC, Sb2Te3, with functionalized carbon nanotubes (CNTs) to form composite anodes. The role of oxygenated functional groups on CNTs in fostering the chemical interactions with Sb2Te3 for enhanced structural integrity of electrodes is elucidated by density functional theory combined with ab-initio molecular dynamics simulations and X-ray photoelectron spectroscopy analysis. Remarkably, cryogenic transmission electron microscopy (TEM) analysis reveals a uniform and thin solid electrolyte interface (SEI) layer of ~19.1 nm on the Sb2Te3/CNT composite while the neat Sb2Te3 presents an irregular and ~67.3 nm thick SEI. The ex-situ X-ray diffraction (XRD) and ex-situ/in-situ TEM analyses offer mechanistic explanations of phase transition and volume changes during sodiation. The Sb2Te3/CNT composite electrode with an optimal content of 10 wt% CNTs delivers excellent reversible gravimetric and volumetric capacities of 422 mA h g−1 and 1232 mA h cm−3, respectively, at 100 mA g−1 with ~97.5% capacity retention after 300 cycles. The excellent high-rate capability of 318 mA h g−1 at 6400 mA g−1 corroborates the structural robustness of the composite electrode. Sodium-ion full cells (SIFCs) are assembled by pairing the above anode with a Na3V2(PO4)2F3 cathode, which exhibit remarkable energy density of ~229 Wh kg−1 at 0.5 C and excellent cyclic stability of over 71% and 66% capacity retention at 5 C and 10 C, respectively, after 200 cycles. Even at 40 C, an ultrahigh power density of 5384 W kg−1 is delivered. Furthermore, the pouch-type SIFCs prove excellent flexibility with ~85% capacity retention after 1000 bending cycles and satisfactory operation under temperatures ranging from 40 to −20 °C. The design strategy developed here can also be employed to other electrode materials to achieve better SEI stability and excellent Na storage performance.

This paper aims to develop a new finite‐time convergent guidance law for intercepting maneuvering targets accounting for second‐order autopilot lag. The guidance law is applied to guarantee that the line of sight (LOS) angular rate converges to zero in finite time and results in a direct interception. The effect of autopilot dynamics can be compensated based on the finite‐time backstepping control method. The time derivative of the virtual input is avoided, taking advantage of integral‐type Lyapunov functions. A finite‐time disturbance observer (FTDOB) is used to estimate the lumped uncertainties and high‐order derivatives to improve the robustness and accuracy of the guidance system. Finite‐time stability for the closed‐loop guidance system is analyzed using the Lyapunov function. Simulation results and comparisons are presented to illustrate the effectiveness of the guidance strategy.

This paper investigates the possibility of improving power density of three-phase grid inverter by adopting SiC MOSFET. Static and dynamic characteristics of trench gate SiC MOSFET, planar gate SiC MOSFET and Si IGBT are compared. The efficiency performance of planar gate SiC MOSFET inverter, trench gate SiC MOSFET inverter and Si IGBT inverter are estimated and compared with increased switching frequency. Finally, these results are verified with 10 kW inverter prototypes.

Fe3O4 nanoparticles encapsulated in porous carbon fibers (Fe3O4@PCFs) as anode materials in lithium ion batteries are fabricated by a facile single-nozzle electrospinning technique followed by heat treatment. A mixed solution of polyacrylonitrile (PAN) and polystyrene (PS) containing Fe3O4 nanoparticles is utilized to prepare hybrid precursor fibers of Fe3O4@PS/PAN. The resulted porous Fe3O4/carbon hybrid fibers composed of compact carbon shell and Fe3O4-embeded honeycomb-like carbon core are formed due to the thermal decomposition of PS and PAN. The Fe3O4@PCF composite demonstrates an initial reversible capacity of 1015 mAh g−1 with 84.4% capacity retention after 80 cycles at a current density of 0.2 A g−1. This electrode also exhibits superior rate capability with current density increasing from 0.1 to 2.0 A g−1, and capacity retention of 91% after 200 cycles at 2.0 A g−1. The exceptionally high performances are attributed to the high electric conductivity and structural stability of the porous carbon fibers with unique structure, which not only buffers the volume change of Fe3O4 with the internal space, but also acts as high-efficient transport pathways for ions and electrons. Furthermore, the compact carbon shell can promote the formation of stable solid electrolyte interphase on the fiber surface.

Silicon (Si) has been regarded as one of the most attractive anode materials for the next generation lithium-ion batteries because of its large theoretical capacity, high safety, low cost and environmental benignity. However, the architecture of Si-based anode material still needs to be well designed to overcome the structure degradation and instability of the solid-electrolyte interphase caused by a large volume change during cycling. Here we report the electrochemical performances of a novel binder-free Si/carbon composite film consisting of alternatively stacked Si-porous carbon layers and graphene layers, which is synthesized by electrostatic spray deposition followed by heat treatment. For this composite film, Si nanoparticles are embedded in the porous carbon layer composed of nitrogen-doped carbon framework, carbon black and carbon nanotubes. And the combined Si-porous carbon layer is further sandwiched by flexible and conductive graphene sheets. The multilayered Si-porous carbon/graphene electrode shows a maximum reversible capacity of 1020 mAh g −1 with 75% capacity retention after 100 cycles and a good rate capability on the basis of the total electrode weight. The excellent electrochemical performances are attributed to the fact that the layer-by-layer porous carbon matrix can accommodate the volume change of Si particles and maintain the structural and electrical integrities.

Core–shell silicon/carbon (Si/C) fibers with an internal honeycomb-like carbon framework are prepared based on the coaxial electrospinning technique. For this hierarchical structure, the fiber's core is composed of a porous carbon framework and embedded Si nanoparticles, which is further wrapped by a compact carbon shell. The well-defined Si/C composite anode shows high specific capacities, good capacity retention, and high accessibility of Si in lithium-ion batteries. An initial reversible capacity of 997 mA h g−1 and a capacity retention of 71% after 150 cycles are demonstrated with a current density of 0.2 A g−1. At a higher current density of 0.5 A g−1, a reversible capacity of 603 mA h g−1 can be maintained after 300 cycles. The accessibility of Si in the Si/C anode is up to 3612 mA h g−1 in the 1st cycle. The excellent electrochemical properties are attributed to the hierarchical structure of Si/C fibers. The porous carbon framework in the core region could not only accommodate the volume expansion of Si, but also enhance the conductivity inside these fibers. The compact carbon shell is able to prevent the electrolyte from permeating into the core section, therefore a stable solid-electrolyte interphase can be formed on the fiber surface.

Silicon/carbon composite microspheres with hierarchical core–shell structure were prepared by spray drying polyvinyl alcohol (PVA) solution containing silicon (Si) nanoparticles, followed by surface coating with polyacrylonitrile (PAN) and heat treatment. For the hierarchical structure, the core section (Si/po-C) was composed of PVA-based porous carbon framework and the embedded Si nanoparticles, and the desired Si/po-C@C microspheres were formed by encapsulating the Si/po-C core with PAN-based carbon shell. The Si/po-C@C anode gave rise to stable cycling performances with high capacity and excellent rate capability attributed to the hierarchical structure. The compact PAN-based carbon shell was able to block electrolyte to contact with Si effectively, promoting the formation of stable solid-electrolyte interphase. The porous carbon framework could accommodate the volume change of embedded Si nanoparticles and enhance the internal conductivity. Keywords: Si/C anode, Core–shell structure, Electrochemical properties, Lithium ion battery, Spray drying

Although lithium-sulfur (Li-S) batteries deliver high specific energy densities, lots of intrinsic and fatal obstacles still restrict their practical application. Electrospun carbon nanofibers (CNFs) decorated with ultrafine TiO2 nanoparticles (CNF-T) were prepared and used as a multifunctional interlayer to suppress the volume expansion and shuttle effect of Li-S battery. With this strategy, the CNF network with abundant space and superior conductivity can accommodate and recycle the dissolved polysulfides for the bare sulfur cathode. Meanwhile, the ultrafine TiO2 nanoparticles on CNFs work as anchoring points to capture the polysulfides with the strong interaction, making the battery perform with remarkable and stable electrochemical properties. As a result, the Li-S battery with the CNF-T interlayer delivers an initial reversible capacity of 935 mA h g(-1) at 1 C with a capacity retention of 74.2% after 500 cycles. It is believed that this simple, low-cost and scalable method will definitely bring a novel perspective on the practical utilization of Li-S batteries.

In order to further increase power density of residential PV inverter, a Zero-Voltage Switching (ZVS) full-bridge inverter with increased switching frequency of 500 kHz is investigated. According to the loss model, the loss distribution of the ZVS inverter is analyzed. In order to maintain high efficiency at 500 kHz switching frequency, resonant inductor design, optimized modulation of the ZVS inverter and layout are discussed. The main results are verified on a 1.5kW ZVS inverter prototype with 500 kHz switching frequency.

Dense and crack-free barium titanate (BaTiO₃, BTO) thin films with a thickness of less than 4 μm were prepared by using sub-micrometric scale, layer-by-layer electrohydrodynamic jet (E-jet) deposition of the suspension ink which is composed of BTO nanopowder and BTO sol. Impacts of the jet height and line-to-line pitch of the deposition on the micro-structure of BTO thin films were investigated. Results show that crack-free BTO thin films can be prepared with 4 mm jet height and 300 μm line-to-line pitch in this work. Dielectric constant of the prepared BTO thin film was recorded as high as 2940 at 1 kHz at room temperature. Meanwhile, low dissipation factor of the BTO thin film of about 8.6% at 1 kHz was also obtained. The layer-by-layer E-jet deposition technique developed in this work has been proved to be a cost-effective, flexible and easy to control approach for the preparation of high-quality solid thin film.

Layered materials, such as graphite/graphene, boron nitride, transition metal dichalcogenides, represent materials in which reduced size, dimensionality, and symmetry play critical roles in their physical properties. Here, we report on a comprehensive investigation of the phonon properties in the topological insulator ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ and ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ two-dimensional (2D) crystals, with the combination of Raman spectroscopy, first-principles calculations, and group theory analysis. Low frequency $(l30\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1})$ interlayer vibrational modes are revealed in few-quintuple-layer (QL) $\mathrm{B}{\mathrm{i}}_{2}\mathrm{T}{\mathrm{e}}_{3}\text{/}\mathrm{B}{\mathrm{i}}_{2}\mathrm{S}{\mathrm{e}}_{3}$ 2D crystals, which are absent in the bulk crystal as a result of different symmetries. The experimentally observed interlayer shear and breathing mode frequencies both show blueshifts, with decreasing thickness in few-QL ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ (down to 2QL) and ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ (down to 1QL), in agreement with first-principles calculations and a linear chain model, from which the interlayer coupling force constants can be estimated. Besides, an intense ultralow $(l12\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1})$ frequency peak is observed in 2--4QL ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$, which is tentatively attributed to a substrate-induced interface mode supported by a linear chain model analysis. The high frequency Raman peaks exhibit frequency shifts and broadening from 3D to 2D as a result of the phonon confinement effect. Our studies shed light on a general understanding of the influence of dimensionality and crystal symmetry on the phonon properties in layered materials.

This paper studies the distributed cooperative tracking problem for several typical second-order nonlinear uncertain multi-agent systems with bounded external and internal disturbances. In the first place, a distributed control algorithm is proposed for Von Der Pol oscillators which do not satisfy the Lipschitz condition by using extended state observer. In this case, the velocity measurements are not available for state feedback. Then the extended case when only absolute position and relative position measurements are available is studied, we develop the proposed algorithm by introducing distributed filter for each follower, and results shown that the state of follower converge to the time-varying leader. In addition, the consensus problem of a group of non-identical pendulums is studied and the distributed cooperative tracking can be achieved under the algorithm.

Semicontinuous niobium and silver films were made in an ultra-high-vacuum (UHV) chamber and in-situ d.c. resistance measurements were performed. After interrupting the deposition, we investigated the immediate ageing phenomenon (relaxation) of the sample resistance on a time scale of about 10 min. Resistance increase and decrease were observed for niobium and silver samples, respectively. The intensity of the relaxation is sensitive to substrate temperature and film thickness. We suggest that edge diffusion and coalescence of islands due to thermomigration of the metal atoms are responsible for the resistance relaxation.

In situ DC resistance measurements were performed on semicontinuous niobium and silver films, which were made on mica and fullerene substrates in an ultra-high-vacuum(UHV) chamber. Right after the interruption of the deposition, we investigated the changes(relaxation) of the sample resistance on a time scale of about 10 minutes. Resistance increase was observed for Nb/mica and Ag C 60 systems, and decrease for Ag/mica system. The relaxation is sensitive to substrate temperature and film thickness. We suggest that the edge diffusion and mergence of islands due to thermomigration of the metal atoms are responsible for the resistance relaxation. The intensity and direction of the relaxation reflect the interfacial activity of the metal/substrate system. The heterogeneities on substrate may also play an important role during this process.

Fullerene (${\mathrm{C}}_{60}$ and ${\mathrm{C}}_{70}$) films were epitaxially grown on fresh (001) mica with the fcc closed-packed plane parallel to the substrate surface. Metal overlayers were deposited onto these fullerene films in an ultrahigh-vacuum chamber, and in situ resistance measurements were performed. With increasing current, we observed a reversible resistance variation and irreversible breakdown. Near the percolation threshold, we find the power law scaling behavior ${\mathit{I}}_{\mathit{b}}$\ensuremath{\sim}${\mathit{R}}^{\mathrm{\ensuremath{-}}\mathit{a}}$, where ${\mathit{I}}_{\mathit{b}}$ is the breakdown current and R the sample resistance. The exponent a is much smaller than the values given by previous experiments and the prediction of the conventional Nodes-Links-Blobs model. A possible explanation of these phenomena based on metal-fullerene interfacial interactions is discussed. \textcopyright{} 1996 The American Physical Society.