There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Redox‐Based Resistive Switching Memories – Nanoionic Mechanisms, Prospects, and Challenges

Electrochemical energy storage technology is based on devices capable of exhibiting high energy density (batteries) or high power density (electrochemical capacitors). There is a growing need, for current and near-future applications, where both high energy and high power densities are required in the same material. Pseudocapacitance, a faradaic process involving surface or near surface redox reactions, offers a means of achieving high energy density at high charge–discharge rates. Here, we focus on the pseudocapacitive properties of transition metal oxides. First, we introduce pseudocapacitance and describe its electrochemical features. Then, we review the most relevant pseudocapacitive materials in aqueous and non-aqueous electrolytes. The major challenges for pseudocapacitive materials along with a future outlook are detailed at the end.

https://hal.archives-ouvertes.fr/hal-01171774/document

Pseudocapacitive oxide materials for high-rate electrochemical energy storage

Approaches, Derivatives and Applications Vasilios Georgakilas,† Michal Otyepka,‡ Athanasios B. Bourlinos,‡ Vimlesh Chandra, Namdong Kim, K. Christian Kemp, Pavel Hobza,‡,§,⊥ Radek Zboril,*,‡ and Kwang S. Kim* †Institute of Materials Science, NCSR “Demokritos”, Ag. Paraskevi Attikis, 15310 Athens, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo naḿ. 2, 166 10 Prague 6, Czech Republic

Functionalization of Graphene: Covalent and Non-Covalent Approaches, Derivatives and Applications

A Si thin film of thickness 275 nm was deposited on rough Cu foil by magnetron sputtering for use as lithium ion battery anode material. X-ray diffraction (XRD) and TEM analysis revealed that the Si thin film was completely of amorphous structure. The electrochemical performance of the Si thin film was investigated by cyclic voltammetry and constant current charge/discharge test. The film exhibited a high capacity of 3,134 mAh g−1 at 0.025 C rate. The capacity retention was 61.3% at 0.5 C rate for 500 cycles. An island structure formed on the Cu foil substrate after cycling adhered to the substrate firmly and provided electrical connection. This is the possible reason for the long cycling life of Si thin film anode. Moreover, the cycling performance was further improved by annealing at 300 °C. The Li+ diffusion coefficients (D
 0) of Si thin film, measured by cyclic voltammetry, are 1.47 × 10−9 cm2 s−1 and 2.16 × 10−9 cm2 s−1 for different reduced peaks.

An amorphous Si thin film anode with high capacity and long cycling life for lithium ion batteries

Size- and shape-controllable preparation of WO3 nanoplates has been successfully realized through topochemical transformation of corresponding H2WO4 precursors synthesized by a facile solution-phase method. The fluoroboric acid was found to not only provide acid source but also act as a structure-directing agent during the growth process of H2WO4 nanoplates in the solution phase. WO3 nanoplates could be obtained by the two different topochemical transformation methods, hydrothermal treatment of H2WO4 nanoplates at the temperature (above 160 °C) and calcination at higher temperatures in air, based on their similarity of the W–O octahedral layers in both H2WO4 and WO3. Furthermore, the enhanced ethanol-sensing performance could be attributed to the plate-like morphology, especially the high crystallinity, due to the advantages of the effective adsorption and rapid diffusion of the ethanol molecules.

Topochemical Preparation of WO3 Nanoplates through Precursor H2WO4 and Their Gas-Sensing Performances

Nanoscale porous carbon fibers (CNFs) were synthesized successfully by pyrolysis of conducting polymer in an argon atmosphere, which were synthesized by the self-degradation template method. The diameter and length of the fibers are 100 nm and 2−3 μm, respectively. Owing to the high porosity and conducting one-dimension network, these porous carbon nanofibers show enhanced lithium-ion storage properties when used as anode material in lithium-ion battery. The reversible specific capacity of the CNFs at a 0.5C rate is about 400 mAhg−1. Moreover, they exhibit considerably specific capacity even at a high charge−discharge current; i.e., the reversible capacities are around 250 and 194 mAhg−1 at a rate of 10 and 20C, respectively.

Porous Carbon Nanofibers Derived from Conducting Polymer: Synthesis and Application in Lithium-Ion Batteries with High-Rate Capability

Stable field emission is realized from well-separated tetrapod-like ZnO nanostructures with high purity. The ZnO nanostructures are painted on a highly doped silicon substrate covered by a Au layer with a thickness of 300nm. An emission current density of 18mA∕cm2 is obtained and degradation was not observed over a three day period. The fluctuations of the emission current are less than 2%. These experimental results indicate that tetrapod-like ZnO nanostructures are promising materials as cold cathodes for mass production.

Stable field emission from tetrapod-like ZnO nanostructures

Hierarchical nanostructures that can be directly grown on a conducting substrate are a new trend in the design of active materials for high-performance lithium-ion batteries (LIBs). This article reports our design and fabrication of a 3D hierarchical ZnCo2O4 nanostructure (3D-ZCO-NS) directly grown on Ni foams. The goose-feather-like ZnCo2O4 bundled into a loose array structure with a large electrolyte contact area and good electrical and mechanical connection to the current collector. Electrochemical measurements confirmed the good performance of the electrode for reversible Li+ storage (specific capacity of 932 mAh g–1 in the 50th cycle at 1 A g–1) relative to a pasted electrode of 3D-ZCO-NSs (599 mAh g–1 in the 50th cycle at 0.1 A g–1).

Taihong Wang

Papers

An amorphous Si thin film anode with high capacity and long cycling life for lithium ion batteries

Topochemical Preparation of WO3 Nanoplates through Precursor H2WO4 and Their Gas-Sensing Performances

Porous Carbon Nanofibers Derived from Conducting Polymer: Synthesis and Application in Lithium-Ion Batteries with High-Rate Capability

Stable field emission from tetrapod-like ZnO nanostructures

High-performance lithium-ion battery anode by direct growth of hierarchical ZnCo2O4 nanostructures on current collectors.