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Sb@C coaxial nanotubes as a superior long-life and high-rate anode for sodium ion batteries
Liu, Zhiming,Yu, Xin-Yao,Lou, Xiong Wen (David),Paik, Ungyu Royal Society of Chemistry 2016 ENERGY AND ENVIRONMENTAL SCIENCE Vol.9 No.7
<P>Antimony (Sb) is an attractive anode material for sodium-ion batteries (SIBs) with a high theoretical capacity of 660 mAh g(-1). However, its practical application is greatly hindered by the rapid capacity fading which is largely due to the large volume expansion during sodiation. Tuning the morphology and structure at the nano-scale or using carbonaceous materials as the buffer layer is essential to address this issue. Here, a facile carbon-coating coupled with a thermal-reduction strategy has been developed to synthesize unique Sb@C coaxial nanotubes. With different annealing time, the hollow space and the amount of Sb inside the tube can be easily tuned by the partial evaporation of Sb. The as-obtained Sb@C nanotubes exhibit excellent sodium storage properties. The remarkable electrochemical performance results from the unique coaxial nanoarchitecture. Specifically, it delivers a high specific capacity of 407 mAh g(-1) at 100 mA g(-1) after 240 cycles. Furthermore, a stable capacity of 240 mAh g(-1) can be retained at 1.0 A g(-1) even after 2000 cycles. Most importantly, high capacities of 350 mAh g(-1) and 310 mAh g(-1) can be achieved at large current densities of 10 and 20 A g(-1), respectively, which represents the best rate performance among the reported Sb-based anode materials.</P>
Carbon coated porous nickel phosphides nanoplates for highly efficient oxygen evolution reaction
Yu, Xin-Yao,Feng, Yi,Guan, Buyuan,(David) Lou, Xiong Wen,Paik, Ungyu The Royal Society of Chemistry 2016 Energy & environmental science Vol.9 No.4
<P>Electrochemical splitting of water provides an attractive way to produce hydrogen fuel. Unfortunately, the efficient and large-scale H-2 production is still hindered by the sluggish kinetics of the oxygen evolution reaction (OER) at the anode side of a water electrolyzer. Starting from metal-organic frameworks (MOFs), we demonstrate a template-engaged strategy to transformNi-Ni Prussian blue analogue (PBA) nanoplates into porous carbon coated nickel phosphides nanoplates with mixed phases of Ni5P4 and Ni2P. For comparison, NiO and Ni(OH)(2) porous nanoplates with the similar morphology have also been synthesized from the same precursor. Benefitting from their structural merits and the in situ formed catalytically active oxidized nickel species, the as-derived nickel phosphides manifest excellent electrocatalytic activity for OER superior to NiO and Ni(OH)(2).</P>
W. Greg Miller,Gary L. Myers,Mary Lou Gantzer,Stephen E. Kahn,E. Ralf Schönbrunner,Linda M. Thienpont,David M. Bunk,Robert H. Christenson,John H. Eckfeldt,Stanley F. Lo,C. Micha Nübling,Catharine M. S 대한진단검사의학회 2012 Laboratory Medicine Online Vol.2 No.1
Results between different clinical laboratory measurement procedures (CLMP) should be equivalent, within clinically meaningful limits, to enable optimal use of clinical guidelines for disease diagnosis and patient management. When laboratory test results are neither standardized nor harmonized, a different numeric result may be obtained for the same clinical sample. Unfortunately, some guidelines are based on test results from a specific laboratory measurement procedure without consideration of the possibility or likelihood of differences between various procedures. When this happens, aggregation of data from different clinical research investigations and development of appropriate clinical practice guidelines will be flawed. A lack of recognition that results are neither standardized nor harmonized may lead to erroneous clinical, financial, regulatory, or technical decisions. Standardization of CLMPs has been accomplished for several measurands for which primary (pure substance) reference materials exist and/or reference measurement procedures (RMPs) have been developed. However, the harmonization of clinical laboratory procedures for measurands that do not have RMPs has been problematic owing to inadequate definition of the measurand, inadequate analytical specificity for the measurand,inadequate attention to the commutability of reference materials, and lack of a systematic approach for harmonization. To address these problems,an infrastructure must be developed to enable a systematic approach for identification and prioritization of measurands to be harmonized on the basis of clinical importance and technical feasibility, and for management of the technical implementation of a harmonization process for a specific measurand.
Park, Hyunjung,Kwon, Jiseok,Choi, Heechae,Shin, Donghyeok,Song, Taeseup,Lou, Xiong Wen David American Chemical Society 2018 ACS NANO Vol.12 No.3
<P>A key issue with Na-ion batteries is the development of active materials with stable electrochemical reversibility through the understanding of their sodium storage mechanisms. We report a sodium storage mechanism and properties of a new anode material, digenite Cu<SUB>1.8</SUB>S, based on its crystallographic study. It is revealed that copper sulfides (Cu<SUB><I>x</I></SUB>S) can have metal-rich formulas (<I>x</I> ≥ 1.6), due to the unique oxidation state of +1 found in group 11 elements. These phases enable the unit cell to consist of all strong Cu-S bonds and no direct S-S bonds, which are vulnerable to external stress/strain that could result in bond cleavage as well as decomposition. Because of its structural rigidness, the Cu<SUB>1.8</SUB>S shows an intercalation/deintercalation reaction mechanism even in a low potential window of 0.1-2.2 V versus Na/Na<SUP>+</SUP> without irreversible phase transformation, which most of the metal sulfides experience through a conversion reaction mechanism. It uptakes, on average, 1.4 Na<SUP>+</SUP> ions per unit cell (∼250 mAh g<SUP>-1</SUP>) and exhibits ∼100% retention over 1000 cycles at 2C in a tuned voltage range of 0.5-2.2 V through an overall solid solution reaction with negligible phase separation.</P> [FIG OMISSION]</BR>
Zhang, Genqiang,Wu, Hao Bin,Song, Taeseup,Paik, Ungyu,Lou, Xiong Wen (David) WILEY‐VCH Verlag 2014 Angewandte Chemie Vol.126 No.46
<P><B>Abstract</B></P><P>While the synthesis of TiO<SUB>2</SUB> hollow structures is well‐established, in most cases it is particularly difficult to control the crystallization of TiO<SUB>2</SUB> in solution or by calcination. As a result, TiO<SUB>2</SUB> hollow structures do not really exhibit enhanced lithium storage properties. Herein, we report a simple and cost‐effective template‐assisted method to synthesize anatase TiO<SUB>2</SUB> hollow spheres composed of highly crystalline nanocrystals, in which carbonaceous (C) spheres are chosen as the removable template. The release of gaseous species from the combustion of C spheres may inhibit the growth of TiO<SUB>2</SUB> crystallites so that instead small TiO<SUB>2</SUB> nanocrystals are generated. The small size and high crystallinity of primary TiO<SUB>2</SUB> nanoparticles and the high structural integrity of the hollow spheres gives rise to significant improvements in the cycling stability and rate performance of the TiO<SUB>2</SUB> hollow spheres.</P>
Liang, Jin,Hu, Han,Park, Hyunjung,Xiao, Chunhui,Ding, Shujiang,Paik, Ungyu,Lou, Xiong Wen (David) The Royal Society of Chemistry 2015 ENERGY AND ENVIRONMENTAL SCIENCE Vol.8 No.6
<P>Bowl-like hybrid structures have been designed and fabricated by anchoring NiO nanosheets on flat carbon hollow particles. When evaluated as an anode material for lithium-ion batteries, these unique NiO/carbon hybrid particles exhibit superior lithium storage properties in terms of high capacity, long term cycling stability and excellent rate capability.</P> <P>Graphic Abstract</P><P>Bowl-like hybrid structures constructed by anchoring NiO nanosheets on flat carbon shells exhibit superior lithium storage properties. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5ee01125f'> </P>