The discovery of new hydrogen storage materials has greatly driven the entire hydrogen storage technology forward in the past decades. Magnesium hydride, which has a high hydrogen capacity and low ...cost, has been considered as one of the most promising candidates for hydrogen storage. Unfortunately, extensive efforts are still needed to better improve its hydrogen storage performance, since MgH2 suffers from high operation temperature, poor dehydrogenation kinetic, and unsatisfactory thermal management. In this paper, we present an overview of recent progress in improving the hydrogenation/de-hydrogenation performance of MgH2, with special emphases on the additive-enhanced MgH2 composites. Other widely used strategies（e. g. alloying,nanoscaling, nanoconfinement） in tuning the kinetics and thermodynamics of MgH2 are also presented. A realistic perspective regarding to the challenges and opportunities for further researches in MgH2 is proposed.
Lithium-sulfur (Li-S) batteries are attracting much attention due to their high energy densities. However, Li-S batteries often suffer from low Coulombic efficiency, severe degradation of cyclic ...capacity, and low utilization of active sulfur material because of the low electrical conductivity of sulfur and the severe shuttle effect. To solve these issues, various nanostructured carbon-based materials have been developed to serve as the sulfur host materials, modify separators and protect lithium (Li) anode due to their good conductivity, large surface area, and electrochemical stability. In this review, a brief introduction of electrochemical principles and prospects of the Li-S batteries are discussed firstly. Then the recent achievements and challenges of nanostructured carbon-based materials in Li-S batteries are summarized. The nanostructured carbon-based materials focus on active carbon, carbon nanotubes, graphene and their composites. The role of these carbon-based materials in Li-S batteries emphasize on the design of sulfur host materials, the modification of functional separators as well as the protection of the Li anode. Furthermore, various flexible Li-S batteries based on freestanding nanostructured carbon/sulfur electrodes are also presented. Finally, the further developments and prospects in this field are also discussed.
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Sodium–ion batteries (SIBs) have received extensive attention as ideal candidates for large‐scale energy storage systems (ESSs) owing to the rich resources and low cost of sodium (Na). However, the ...larger size of Na+ and the less negative redox potential of Na+/Na result in low energy densities, short cycling life, and the sluggish kinetics of SIBs. Therefore, it is necessary to develop appropriate Na storage electrode materials with the capability to host larger Na+ and fast ion diffusion kinetics. 1D materials such as nanofibers, nanotubes, nanorods, and nanowires, are generally considered to be high‐capacity and stable electrode materials, due to their uniform structure, orientated electronic and ionic transport, and strong tolerance to stress change. Here, the synthesis of 1D nanomaterials and their applications in SIBs are reviewed. In addition, the prospects of 1D nanomaterials on energy conversion and storage as well as the development and application orientation of SIBs are presented.
1D nanomaterials (e.g., nanofibers, nanorods, nanowires, nanobelts, etc.) are considered promising electrode materials due to their orientated electronic and ionic transport, short radial distance, and strong tolerance to stress change. The success of numerous 1D nanomaterials fabricated via various methods and their application in sodium–ion batteries is described.
This paper considers the problem of fault-tolerant tracking control for linear and Lipschitz nonlinear multi-agent systems subject to actuator faults and the leader's bounded unknown input. The ...communication topology is the undirected subgraph with directed connections between the leader and the followers. Based on the relative states of neighbors and a general actuator fault model, an adaptive fault-tolerant control protocol is proposed to compensate for the failure effects on consensus tracking where the feedback matrices update the parameters by the online estimation of actuator faults. The criteria of reaching consensus tracking despite the actuator faults for both linear and Lipschitz nonlinear agents are derived, respectively. Finally, two examples are included to illustrate the theoretical results.
Distinguished by particular physical and chemical properties, metal oxide materials have been a focus of research and exploitation for applications in energy storage devices. Used as supercapacitor ...electrode materials, metal oxides have certified attractive performances for fabricating various supercapacitor devices in a broad voltage window. In comparison with single metal oxides, bimetallic oxide materials are highly desired for overcoming the constraint of the poor electric conductivity of single metal oxide materials, achieving a high capacitance and raising the energy density at this capacitor-level power. Herein, we investigate the principal elements affecting the properties of bimetallic oxide electrodes to reveal the relevant energy storage mechanisms. Thus, the influences of the chemical constitution, structural features, electroconductivity, oxygen vacancies and various electrolytes in the electrochemical behavior are discussed. Moreover, the progress, development and improvement of multifarious devices are emphasized systematically, covering from an asymmetric to hybrid configuration, and from aqueous to non-aqueous systems. Ultimately, some obstinate and unsettled issues are summarized as well as a prospective direction has been given on the future of metal oxide-based supercapacitors.
We investigate the principal elements affecting the properties of bimetallic oxide electrodes to reveal the relevant energy storage mechanisms.
This paper develops the disturbance observer-based integral sliding-mode control approach for continuous-time linear systems with mismatched disturbances or uncertainties. The disturbance observer is ...proposed to generate the disturbance estimate, which can be incorporated in the controller to counteract the disturbance. With the help of the proposed disturbance observer, both the memoryless and memory-based integral sliding surfaces and integral sliding-mode controllers are developed, respectively, and two approaches, i.e., H ∞ control and steady-state output-based approaches, are proposed to design the controller and disturbance rejection gains. Finally, the effectiveness and applicability of the proposed technique are illustrated by a numerical example and a real-time experiment.
Lithium–sulfur (Li–S) batteries have arousing interest because of their high theoretical energy density. However, they often suffer from sluggish conversion of lithium polysulfides (LiPS) during the ...charge/discharge process. Single nickel (Ni) atoms on nitrogen‐doped graphene (Ni@NG) with Ni–N4 structure are prepared and introduced to modify the separators of Li–S batteries. The oxidized Ni sites of the Ni–N4 structure act as polysulfide traps, efficiently accommodating polysulfide ion electrons by forming strong Sx
2−⋅⋅⋅NiN bonding. Additionally, charge transfer between the LiPS and oxidized Ni sites endows the LiPS on Ni@NG with low free energy and decomposition energy barrier in an electrochemical process, accelerating the kinetic conversion of LiPS during the charge/discharge process. Furthermore, the large binding energy of LiPS on Ni@NG also shows its ability to immobilize the LiPS and further suppresses the undesirable shuttle effect. Therefore, a Li–S battery based on a Ni@NG modified separator exhibits excellent rate performance and stable cycling life with only 0.06% capacity decay per cycle. It affords fresh insights for developing single‐atom catalysts to accelerate the kinetic conversion of LiPS for highly stable Li–S batteries.
Single Ni atoms on nitrogen‐doped graphene with a unique Ni–N4 structure are used to modify the separator of a lithium–sulfur battery to improve its electrochemical performance. The oxidized Ni state of the Ni–N4 structure not only serves as an active site for immobilizing lithium polysulfides, but also accelerates their kinetic conversion via electrocatalysis.
A novel composite of magnetite (Fe3O4) nanoparticles (NPs) grown on reduced graphene oxide (rGO) has been synthesized by a facile hydrothermal technique without any surfactants or templates. In this ...method, the growth of Fe3O4 NPs and the reduction of graphene oxide (GO) are completed in one single step. Moreover, we have prepared Fe3O4 microcubes and Fe3O4/carbon nanotubes (CNTs) composite under the same condition. The electrochemical properties of the as-prepared samples are investigated as advanced electrode materials for supercapacitors. It is found that the Fe3O4/rGO nanocomposite displays much higher specific capacitances and better cycle stability than those of pure Fe3O4 and Fe3O4/CNTs composite. Specifically, it exhibits a high specific discharge capacitance of 220.1 F ga1 at 0.5 A ga1 and remains stable after 3000 charge/discharge cycles. The improvement of the electrochemical performances of Fe3O4/rGO may be attributed to the chemical interaction between rGO and Fe3O4, lower agglomeration and smaller particle size of Fe3O4.
Actualmente, las animaciones de no ficción, de desarrollo ágil, se han extendido ampliamente y empiezan a comprender las culturas y experiencias de minorías étnicas. Los medios de la animación ...permiten a los investigadores y a las minorías étnicas llevar a cabo una cooperación entre sí para visualizar, mediante imágenes animadas, materiales no escritos tales como la historia oral de las minorías étnicas y las antiguas canciones populares. No obstante, los diferentes enfoques de las animaciones y de las situaciones reales de los sujetos lleva a la necesidad de que los investigadores consideren la manera de aplicar estrategias de representación artística y métodos cooperativos adecuados para llevar su práctica al contenido de la animación. El presente artículo analiza diferentes estrategias de representación en los documentales animados, los métodos de aplicación de los elementos artísticos locales de las minorías étnicas y el modo de cooperación en el trabajo de campo, con el objetivo de mejorar la base teórica y el sistema práctico de la animación etnográfica, y explorar la animación etnográfica como un nuevo método de documental etnográfico que puede transmitir eficazmente las verdaderas opiniones de las minorías étnicas al tiempo que muestra sus fenómenos culturales.
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