다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Recent advancements in supercapacitor technology

Composite Titanium Dioxide Nanomaterials

Carbon-oxide and carbon-sulfide nanocomposites have attracted tremendous interest as the anode materials for Li and Na ion batteries. Such composites are fascinating as they often show synergistic effect compared to their singular components. Carbon nanomaterials are often used as the matrix due to their high conductivity, tensile strength, and chemical stability under the battery condition. Metal oxides and sulfides are often used as active material fillers because of their large capacity. Numerous works have shown that by taking one step further into fabricating nanocomposites with rational structure design, much better performance can be achieved. The present review aims to present and discuss the development of carbon-based nanocomposite anodes in both Li ion batteries and Na ion batteries. The authors introduce the individual components in the composites, i.e., carbon matrices (e.g., carbon nanotube, graphene) and metal oxides/sulfides; followed by evaluating how advanced nanostructures benefit from the synergistic effect when put together. Particular attention is placed on strategies employed in fabricating such composites, with examples such as yolk–shell structure, layered-by-layered structure, and composite comprising one or more carbon matrices. Lastly, the authors conclude by highlighting challenges that still persist and their perspective on how to further develop the technologies.

A Review on Design Strategies for Carbon Based Metal Oxides and Sulfides Nanocomposites for High Performance Li and Na Ion Battery Anodes

Electrochemical capacitors (best known as supercapacitors) are high‐performance energy storage devices featuring higher capacity than conventional capacitors and higher power densities than batteries, and are among the key enabling technologies of the clean energy future. This review focuses on performance enhancement of carbon‐based supercapacitors by doping other elements (heteroatoms) into the nanostructured carbon electrodes. The nanocarbon materials currently exist in all dimensionalities (from 0D quantum dots to 3D bulk materials) and show good stability and other properties in diverse electrode architectures. However, relatively low energy density and high manufacturing cost impede widespread commercial applications of nanocarbon‐based supercapacitors. Heteroatom doping into the carbon matrix is one of the most promising and versatile ways to enhance the device performance, yet the mechanisms of the doping effects still remain poorly understood. Here the effects of heteroatom doping by boron, nitrogen, sulfur, phosphorus, fluorine, chlorine, silicon, and functionalizing with oxygen on the elemental composition, structure, property, and performance relationships of nanocarbon electrodes are critically examined. The limitations of doping approaches are further discussed and guidelines for reporting the performance of heteroatom doped nanocarbon electrode‐based electrochemical capacitors are proposed. The current challenges and promising future directions for clean energy applications are discussed as well.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/aenm.202001239

Heteroatom-Doped and Oxygen-Functionalized Nanocarbons for High-Performance Supercapacitors

Anatase/rutile titania anchored carbon nanotube (TiO2@CNT) porous nanocomposites are fabricated using TiCl3 and polymer nanotubes as the titanium and carbon sources, respectively, by a hydrothermal process with subsequent heat treatment. As anodes for lithium ion batteries, the electrochemical performance of the nanocomposites is highly dependent on the crystal phase and content of TiO2. Compared with anatase TiO2/C nanocomposites, the TiO2@CNT nanocomposites exhibit high reversible capacity, excellent rate capability and superior long-term cycling stability at high current densities. The enhanced electrochemical performance of the nanocomposites results from the shortened Li+ diffusion distance, large contact surface area and sufficient conductivity. In addition, the crystal interface effect of mixed-phase TiO2 could improve the dispersion rate of electrons, which is conducive to the rapid transport of Li+ and the electrons.

Anatase/rutile titania anchored carbon nanotube porous nanocomposites as superior anodes for lithium ion batteries

Na3V2(PO4)2F3 is one of the most studied polyanion type cathode materials for sodium-ion batteries (SIBs) and offers great promises. However, the inferior rate capability induced by its sluggish diffusion of electrons and ions greatly limits the practical application of electrode materials in SIBs. Herein, we develop an efficient method to fabricate in situ carbon-coated Na3V2(PO4)2F3 nanosheets by using cost-effective amylopectin. The amylopectin not only could induce the nucleation of Na3V2(PO4)2F3 along its backbone to form a 2D nanostructure, but also act as a source of amorphous carbon for in situ coating on the active material surface. The composite exhibits extraordinary rate capability (104 mA h g-1 at 40 C, 51 mA h g-1 at 150 C) and desirable cycling stability. Such satisfactory achievements, especially the superior rate performance, should be ascribed to its unique 2D nanostructure which shortens the Na+ diffusion length, and the in situ carbon coating endows the composites with effective electron transport. Even applied to full cells, the obtained devices still display an exceptionally high energy density (94.8 W h kg-1), high power density (7295 W kg-1), and excellent cyclic stability.

Amylopectin-Assisted Fabrication of In Situ Carbon-Coated Na3V2(PO4)2F3 Nanosheets for Ultra-Fast Sodium Storage.

NiFe nanoalloys in-situ immobilized on coal based activated carbons through one-step pyrolysis as magnetically recoverable catalysts for reduction of 4-nitrophenol

Carbon Nanotube-Encapsulated Bi2S3 Nanorods as Electrodes for Lithium-Ion Batteries and Lithium–Sulfur Batteries

Silicon waste from industrial cutting silicon rod process is assessed as an anode for lithium-ion batteries (LIBs) to expand utilization of silicon waste and effectively reduce the cost. However, it is still a big challenge to achieve a large-scale and green-effective manufacture. Hence, it is important to propose a facile, low-cost, and scalable method which prepares porous silicon as an anode by chemical etching of silicon waste using acid and alkaline solution. The silicon etched by HF solution possesses porous structure, which exhibits higher capacity than unetched samples. Comparatively, the silicon etched by NaOH solution has the flaky shape with about 110 nm and shows superior cycling performance and stability (600.7 mAh g−1 after 200 cycles at 420 mA g−1), which can be ascribed to its abundant porous structure, as well as the amorphous SiOx layer accommodating the volume expansion of embedded Si. The silicon waste modified by scalable etching reveals greatly enhanced electrochemical properties for LIB anodes. It is a promising method of improving the electrochemical properties of porous Si anode materials for commercial LIBs. The two kinds of porous silicon were cleverly fabricated using KL-Si through facile ball-milling and chemical etching. H-Si owns the high initial coulombic efficiency and reversible capacity at lower current density. However, N-Si exhibits the superior cycling stability, which can be attributed to larger specific area and the SiOx layer to buffer enormous volume expansion of Si during discharge/charge process.

Porous silicon from industrial waste engineered for superior stability lithium-ion battery anodes

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