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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Increasing energy demands and environment awareness have promoted extensive research on the development of alternative energy conversion and storage technologies with high efficiency and environmental friendliness. Among them, water splitting is very appealing, and is receiving more and more attention. The critical challenge of this renewable-energy technology is to expedite the oxygen evolution reaction (OER) because of its slow kinetics and large overpotential. Therefore, developing efficient electrocatalysts with high catalytic activities is of great importance for high-performance water splitting. In the past few years, much effort has been devoted to the development of alternative OER electrocatalysts based on transition-metal elements that are low-cost, highly efficient, and have excellent stability. Here, recent progress on the design, synthesis, and application of OER electrocatalysts based on transition-metal elements, including Co, Ni, and Fe, is summarized, and some invigorating perspectives on the future developments are provided.

Transition-Metal (Co, Ni, and Fe)-Based Electrocatalysts for the Water Oxidation Reaction

Progress in material selection for solid oxide fuel cell technology: A review

Poor oxygen evolution reaction (OER) catalysis limits the efficiency of H2 production from water electrolysis and photoelectrolysis routes to large-scale energy storage. Despite nearly a century of research, the factors governing the activity of OER catalysts are not well understood. In this Perspective, we discuss recent advances in understanding the OER in alkaline media for earth-abundant, first-row, transition-metal oxides and (oxy)hydroxides. We argue that the most-relevant structures for study are thermodynamically stable (oxy)hydroxides and not crystalline oxides. We discuss thin-film electrochemical microbalance techniques to accurately quantify intrinsic activity and in situ conductivity measurements to identify materials limited by electronic transport. We highlight the dramatic effect that Fe cations—added either intentionally or unintentionally from ubiquitous electrolyte impurities—have on the activity of common OER catalysts. We find new activity trends across the first-row transition metals...

Oxygen Evolution Reaction Electrocatalysis on Transition Metal Oxides and (Oxy)hydroxides: Activity Trends and Design Principles

Lithium ion batteries are now the dominant power for electronics and will change the power supply for vehicles and help to smoothly integrate renewable energy sources such as solar and wind to grid. In lithium ion batteries with liquid electrolytes, the organic solvents are flammable and unstable at high voltage. Especially in lithium metal batteries (LMB) where lithium dendrites can grow, the solvents can be ignited once the dendrites shortcircuit with the cathodes. To meet the high energy density and safety requirement, it is desirable to develop solid state electrolytes with high stability and mechanical strength. The solid state electrolytes can be classified into two categories: inorganic electrolytes and solid polymer electrolytes (SPE). Inorganic electrolytes typically have ionic conductivity at room temperature (10−2–10−4 S cm−1) close to or even higher than liquid electrolyte. However, their stiffness and friability result in poor film processability and high interface resistance with electrodes.[1–7] SPE are composed of lithium salts dissociated in the polymer matrix in which Li+ is allowed to transport along with the segment motion of the polymer chains. As a result, SPE are stretchable and flexible, and thus compatible with the current film-based battery technology. However, the low ionic conductivity (<10−6 S cm−1) of SPE at ambient temperature and high-temperature instability restrict their wide utilization.[8–15] Great efforts have been devoted to improving the performance of SPE. Increasing the content of Li salts or decreasing the crystallinity of polymers with composite polymers or block copolymers were able to increase the ionic conductivity by orders of magnitude.[16–18] However, other properties of SPE such as the film forming property were decreased, leading to poor mechanical strength and thermal resistance. A successful strategy was rigid-flexible coupling that applied cellulose nonwoven to support the softened SPE.[11] Another widely employed approach is to add ceramic fillers which can interact with both the salt anions and the polymer segments to promote local amorphization and enhance Li+ transport.[19–24] Accordingly, the interaction can be tailored by screening fillers with Solid state electrolytes are the key components for high energy density lithium ion batteries and especially for lithium metal batteries where lithium dendrite growth is an inevitable obstacle in liquid electrolytes. Solid polymer electrolytes based on a complex of polymers and lithium salts are intrinsically advantageous over inorganic electrolytes in terms of processability and film-forming properties. But other properties such as ionic conductivity, thermal stability, mechanical modulus, and electrochemical stability need to be improved. Herein, for the first time, 2D additives using few-layer vermiculite clay sheets as an example to comprehensively upgrade poly(ethylene oxide)-based solid polymer electrolyte are introduced. With clay sheet additives, the polymer electrolyte exhibits improved thermal stability, mechanical modulus, ionic conductivity, and electrochemical stability along with reduced flammability and interface resistance. The composite polymer electrolyte can suppress the formation and growth of lithium dendrites in lithium metal batteries. It is anticipated that the clay sheets upgraded solid polymer electrolyte can be integrated to construct high performance solid state lithium ion and lithium metal batteries with higher energy and safety.

Simultaneously Enhancing the Thermal Stability, Mechanical Modulus, and Electrochemical Performance of Solid Polymer Electrolytes by Incorporating 2D Sheets

Lithium-metal batteries can fulfill the ever-growing demand of the high-energy-density requirement of electronics and electric vehicles. However, lithium-metal anodes have many challenges, especially their inhomogeneous dendritic formation and infinite dimensional change during cycling. 3D scaffold design can mitigate electrode thickness fluctuation and regulate the deposition morphology. However, in an insulating or ion-conducting matrix, Li as the exclusive electron conductor can become disconnected, whereas in an electron-conducting matrix, the rate performance is restrained by the sluggish Li+ diffusion. Herein, the advantages of both ion- and electron-conducting paths are integrated into a mixed scaffold. In the mixed ion- and electron-conducting network, the charge diffusion and distribution are facilitated leading to significantly improved electrochemical performance. By incorporating Li6.4 La3 Zr2 Al0.2 O12 nanoparticles into 3D carbon nanofibers scaffold, the Li metal anodes can deliver areal capacity of 16 mAh cm-2 , volumetric capacity of 1600 mAh cm-3 , and remain stable over 1000 h under current density of 5 mA cm-2 . The volumetric and areal capacities as well as the rate capability are among the highest values reported. It is anticipated that the 3D mixed scaffold could be combined with further electrolytes and cathodes to develop high-performance energy systems.

Cuijuan Zhang

Papers

Simultaneously Enhancing the Thermal Stability, Mechanical Modulus, and Electrochemical Performance of Solid Polymer Electrolytes by Incorporating 2D Sheets

Incorporating Ionic Paths into 3D Conducting Scaffolds for High Volumetric and Areal Capacity, High Rate Lithium-Metal Anodes.

Electrical conduction behavior of La, Co co-doped SrTiO3 perovskite as anode material for solid oxide fuel cells

Modified aging process for silica aerogel

Membranes in non-aqueous redox flow battery: A review