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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Ongoing technological advances in diverse fields including portable electronics, transportation, and green energy are often hindered by the insufficient capability of energy-storage devices By taking advantage of two different electrode materials, asymmetric supercapacitors can extend their operating voltage window beyond the thermodynamic decomposition voltage of electrolytes while enabling a solution to the energy storage limitations of symmetric supercapacitors This review provides comprehensive knowledge to this field We first look at the essential energy-storage mechanisms and performance evaluation criteria for asymmetric supercapacitors to understand the wide-ranging research conducted in this area Then we move to the recent progress made for the design and fabrication of electrode materials and the overall structure of asymmetric supercapacitors in different categories We also highlight several key scientific challenges and present our perspectives on enhancing the electrochemical performance of future asymmetric supercapacitors

Design and Mechanisms of Asymmetric Supercapacitors.

Review on recent progress of nanostructured anode materials for Li-ion batteries

We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

Nanostructured materials are advantageous in offering huge surface to volume ratios, favorable transport properties, altered physical properties, and confinement effects resulting from the nanoscale dimensions, and have been extensively studied for energy-related applications such as solar cells, catalysts, thermoelectrics, lithium ion batteries, supercapacitors, and hydrogen storage systems. This review focuses on a few select aspects regarding these topics, demonstrating that nanostructured materials benefit these applications by (1) providing a large surface area to boost the electrochemical reaction or molecular adsorption occurring at the solid–liquid or solid–gas interface, (2) generating optical effects to improve optical absorption in solar cells, and (3) giving rise to high crystallinity and/or porous structure to facilitate the electron or ion transport and electrolyte diffusion, so as to ensure the electrochemical process occurs with high efficiency. It is emphasized that, to further enhance the capability of nanostructured materials for energy conversion and storage, new mechanisms and structures are anticipated. In addition to highlighting the obvious advantages of nanostructured materials, the limitations and challenges of nanostructured materials while being used for solar cells, lithium ion batteries, supercapacitors, and hydrogen storage systems have also been addressed in this review.

Nanomaterials For Energy Conversion And Storage

Self-supported Li(4) Ti(5) O(12) nanowire arrays with high conductivity architectures are designed and fabricated for application in a Li-ion battery. The Li(4) Ti(5) O(12) nanowire arrays grow directly on Ti foil by a facile solution-based method, further enhancing Li-ion storage properties by creating Ti(3+) sites through hydrogenation. This configuration ensures that every Li(4) Ti(5) O(12) nanowire participates in the fast electrochemical reaction, enabling remarkable rate performance and a long cycle life.

Hydrogenated Li(4)Ti(5)O(12) nanowire arrays for high rate lithium ion batteries.

A mesoporous Li4Ti5O12/C nanocomposite is synthesized by a nanocasting technique using the porous carbon material CMK-3 as a hard template. Modified CMK-3 template is impregnated with Li4Ti5O12 precursor, followed by heat treatment at 750 °C for 6 h under N2. Li4Ti5O12 nanocrystals of up to several tens of nanometers are successfully synthesized in micrometer-sized porous carbon foam to form a highly conductive network, as confirmed by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and nitrogen sorption isotherms. The composite is then evaluated as an anode material for lithium ion batteries. It exhibits greatly improved electrochemical performance compared with bulk Li4Ti5O12, and shows an excellent rate capability (73.4 mA h g−1 at 80 C) with significantly enhanced cycling performance (only 5.6% capacity loss after 1000 cycles at a high rate of 20 C). The greatly enhanced lithium storage properties of the mesoporous Li4Ti5O12/C nanocomposite may be attributed to the interpenetrating conductive carbon network, ordered mesoporous structure, and the small Li4Ti5O12 nanocrystallites that increase the ionic and electronic conduction throughout the electrode.

Li4Ti5O12 Nanoparticles Embedded in a Mesoporous Carbon Matrix as a Superior Anode Material for High Rate Lithium Ion Batteries

Amorphous and nanocrystalline vanadium pentoxide (V2O5) were prepared through a combination of sol–gel processing paired with electrochemical deposition and investigated as cathodes for sodium-ion batteries. Amorphous V2O5 demonstrated superior electrochemical properties upon sodiation as compared to its crystalline counterpart. More specifically, amorphous vanadium pentoxide had a measured capacity of 241 mA h g−1, twice the capacity of its crystalline contemporary at 120 mA h g−1. In addition, the amorphous vanadium pentoxide demonstrated a much higher discharge potential, energy density, and cycle stability. The development of amorphous materials could enable the usage and design of previously unexplored electrode materials; herein, the possible relationship between the improved sodiation properties and the amorphous structure is discussed.

Better than crystalline: amorphous vanadium oxide for sodium-ion batteries

The need for economical and sustainable energy storage drives battery research today. While Li-ion batteries are the most mature technology, scalable electrochemical energy storage applications benefit from reductions in cost and improved safety. Sodium- and magnesium-ion batteries are two technologies that may prove to be viable alternatives. Both metals are cheaper and more abundant than Li, and have better safety characteristics, while divalent magnesium has the added bonus of passing twice as much charge per atom. On the other hand, both are still emerging fields of research with challenges to overcome. For example, electrodes incorporating Na+ are often pulverized under the repeated strain of shuttling the relatively large ion, while insertion and transport of Mg2+ is often kinetically slow, which stems from larger electrostatic forces. This review provides an overview of cathode and anode materials for sodium-ion batteries, and a comprehensive summary of research on cathodes for magnesium-ion batteries. In addition, several common experimental discrepancies in the literature are addressed, noting the additional constraints placed on magnesium electrochemistry. Lastly, promising strategies for future study are highlighted.

/pdf/beyond-li-ion-electrode-materials-for-sodium-and-magnesium-1wicnjebmm.pdf

Evan Uchaker

Papers

Nanomaterials For Energy Conversion And Storage

Hydrogenated Li(4)Ti(5)O(12) nanowire arrays for high rate lithium ion batteries.

Li4Ti5O12 Nanoparticles Embedded in a Mesoporous Carbon Matrix as a Superior Anode Material for High Rate Lithium Ion Batteries

Better than crystalline: amorphous vanadium oxide for sodium-ion batteries

Beyond Li-ion: electrode materials for sodium- and magnesium-ion batteries