University of Electronic Science and Technology of China

About: University of Electronic Science and Technology of China is a education organization based out in Chengdu, China. It is known for research contribution in the topics: Antenna (radio) & Dielectric. The organization has 50594 authors who have published 58502 publications receiving 711188 citations. The organization is also known as: UESTC.

Multi-Functional Layered WS2 Nanosheets for Enhancing the Performance of Lithium–Sulfur Batteries

Abstract: DOI: 10.1002/aenm.201601843 in order to restrict the loss of material. Furthermore, due to their scalability and flexibility, 3D flexible electronics (see Supporting Information (SI), where Table S1 contains a list) were considered revolutionary materials and were used in many fields such as imperceptible electronic devices, wearable electronic devices, and bionic technology.[11–13] Recently studies have shown the encapsulation of sulfur in the pores of carbon materials, such as meso-/microporous carbons,[11] cable-shaped carbon,[12] and carbon nanotubes/fibers,[13] can reduce the capacity fading. However, such nonpolar flexible carbon materials have a destructive disadvantage; they only have physical van der Waals (vdW) adsorption for polar Li2Sn, which leads to the facile detachment of Li2Sn from the carbon surface.[14] This proves that carbon-based materials alone cannot serve as the perfect host. In light of this new insight, various types of polar functional groups on carbon-based materials have been demonstrated to increase the interaction between Li2Sn species and the electrode; these materials can generally be categorized into three types: polymers (polyaniline, polypyrrole, poly(3,4ethylenedioxythiophene) (PEDOT)),[15] metal oxides (SiO2, TiO2, Al2O3, V2O5, MoO3), and transition-metal disulfides (TiS2, ZrS2,VS2). Zhang et al.[14] suggested that the moderate materials (such as TiS2, ZrS2, and VS2) are the best choices for battery electrodes. Recent research have revealed that the morphology of interconnected nanosheets, such as that found when MnO2 and MoS2 are vertically aligned on carbon materials, forms a 3D network producing electrodes with a stable cycling behavior.[13,17] Nevertheless, to obtain sophisticated pore structures and composites, tedious preparation methods were required for those materials, preventing them from having broad commercial applications. To further address the challenges and bring Li–S cells a step closer to commercialization, we obtained polar WS2 nanosheets deposited on carbon nanofibers (CNFs) using an efficient one-step hydrothermal reaction. Termed C@WS2, this is the first report of using this material as a composite electrode into Li–S batteries. In this flaky-structured C@WS2 composite electrode, dense WS2 nanosheets are wrapped around and anchored on the CNFs. Our experimental data was supported by a systematic simulation study, surveying WS2 with different binding strengths on Li2Sn species at different lithiation stages (n = 2, 3, 4, 6, 8). The nanoscale sulfur is firmly absorbed on the CNF surface not only through physical vdW forces, but also as a result of the WS2 polar functional groups. As a free-standing cathode material in Li–S batteries, the C@WS2 composite exhibits a high rate capability (≈1501 and 450 mA h g−1 are achieved at charge/discharge rates of 0.1 C and 3 C (1 C = 1675 mA h g−1), respectively) with outstanding Coulombic efficiencies (nearly 100%). The battery delivers Lithium–sulfur batteries, which exhibit a co-existence of high specific capacity (1675 mA h g−1) and energy density (2600 W h kg−1), have attracted increasing interest due to their low cost and environmentally friendly nature, both of which make them potentially applicable for electric vehicles (EVs) and large-scale stationary electric energy storage.[1,2] Unluckily, their implementation has been prevented by a series of reasons, including a weak cycle life and low capacities; these are caused by 1) the rapid dissolution of lithium polysulfide (Li2Sn) species into the electrolyte during the recharge, 2) the low electronic conductivity of both sulfur and lithium sulfide, and 3) the large volumetric expansion of sulfur (≈80%) upon lithiation.[3,4] Unquestionably, the poor performance of Li–S batteries is dominated by the issue of the soluble nature of the polysulfide (Sn) intermediates, which leads to their diffusion into the liquid electrolyte. This undesired phenomenon causes the mass transport of electroactive species, and it is termed the “polysulfide shuttle”.[4] To mitigate the detrimental effects of Sn solubility, over the past few decades, researchers have focused on two different aspects of the cell, following a logical train of thought. 1) For the electrolyte, some additives such as Li2S8 and LiNO3 have been added to slow down the polysulfide shuttle and improve Coulombic efficiency.[5] 2) In contrast, the majority of effort has been focused on the material used for the sulfur host; for example, conductive polymer matrices, such as polyaniline,[6] polypyrrole,[7] and poly(3,4-ethylenedioxythiophene),[8] have been shown to have a positive influence on increasing the cycle life of lithium–sulfur batteries. Although the above materials can relieve the effects of polysulfides shuttling, their ability to elongate the cell lifetime are yet far from perfect. To avoid corrosion on the current collector and reduce the production costs of the battery, aluminum was considered suitable for the current collector; it can be alternatively used in the place of Li–S electrodes. However, the role of a current collector can be for outstripping, transporting the current. Actually, 3D cathodes—such as sulfur–nickel foam (SNF)[9] and carbon nanotubes[10]—might be of interest for containing the active material and trapping the polysulfides during cycling,

Electrically conductive polymer composites for smart flexible strain sensors: a critical review

Abstract: The rapid development of wearable smart devices has contributed to the enormous demands for smart flexible strain sensors. However, to date, the poor stretchability and sensitivity of conventional metals or inorganic semiconductor-based strain sensors have restricted their application in this field to some extent, and hence many efforts have been devoted to find suitable candidates to overcome these limitations. Recently, novel resistive-type electrically conductive polymer composites (ECPCs)-based strain sensors have attracted attention based on their merits of light weight, flexibility, stretchability, and easy processing, thus showing great potential applications in the fields of human movement detection, artificial muscles, human–machine interfaces, soft robotic skin, etc. For ECPCs-based strain sensors, the conductive filler type and the phase morphology design have important influences on the sensing property. Meanwhile, to achieve a successful application toward wearable devices, several imperative features, including a self-healing capability, superhydrophobicity, and good light transmission, need to be considered. The aim of the present review is to critically review the progress of ECPCs-based strain sensors and to foresee their future development.

Transition metal nitrides for electrochemical energy applications.

Abstract: Transition metal nitrides (TMNs), by virtue of their unique electronic structure, high electrical conductivity, superior chemical stability, and excellent mechanical robustness, have triggered tremendous research interest over the past decade, and showed great potential for electrochemical energy conversion and storage. However, bulk TMNs usually suffer from limited numbers of active sites and sluggish ionic kinetics, and eventually ordinary electrochemical performance. Designing nanostructured TMNs with tailored morphology and good dispersity has proved an effective strategy to address these issues, which provides a larger specific surface area, more abundant active sites, and shorter ion and mass transport distances over the bulk counterparts. Herein, the most up-to-date progress on TMN-based nanomaterials is comprehensively reviewed, focusing on geometric-structure design, electronic-structure engineering, and applications in electrochemical energy conversion and storage, including electrocatalysis, supercapacitors, and rechargeable batteries. Finally, we outline the future challenges of TMN-based nanomaterials and their possible research directions beyond electrochemical energy applications.

Electromagnetic Interference Shielding Polymers and Nanocomposites - A Review

Abstract: Intrinsically conducting polymers (ICP) and conductive fillers incorporated conductive polymer-based composites (CPC) greatly facilitate the research in electromagnetic interference (EMI) s...

iPro54-PseKNC: a sequence-based predictor for identifying sigma-54 promoters in prokaryote with pseudo k-tuple nucleotide composition.

Abstract: The σ54 promoters are unique in prokaryotic genome and responsible for transcripting carbon and nitrogen-related genes. With the avalanche of genome sequences generated in the postgenomic age, it is highly desired to develop automated methods for rapidly and effectively identifying the σ54 promoters. Here, a predictor called ‘iPro54-PseKNC’ was developed. In the predictor, the samples of DNA sequences were formulated by a novel feature vector called ‘pseudo k-tuple nucleotide composition’, which was further optimized by the incremental feature selection procedure. The performance of iPro54-PseKNC was examined by the rigorous jackknife cross-validation tests on a stringent benchmark data set. As a user-friendly web-server, iPro54-PseKNC is freely accessible at http://lin.uestc.edu.cn/server/iPro54-PseKNC. For the convenience of the vast majority of experimental scientists, a step-by-step protocol guide was provided on how to use the web-server to get the desired results without the need to follow the complicated mathematics that were presented in this paper just for its integrity. Meanwhile, we also discovered through an in-depth statistical analysis that the distribution of distances between the transcription start sites and the translation initiation sites were governed by the gamma distribution, which may provide a fundamental physical principle for studying the σ54 promoters.