165,768 research outputs found
Li-rich cathodes for rechargeable Li-based batteries: Reaction mechanisms and advanced characterization techniques
Full text linkDue to their high specific capacities beyond 250 mA h g-1, lithium-rich oxides have been considered as promising cathodes for the next generation power batteries, bridging the capacity gap between traditional layered-oxide based lithium-ion batteries and future lithium metal batteries such as lithium sulfur and lithium air batteries. However, the practical application of Li-rich oxides has been hindered by formidable challenges. To address these challenges, the understanding of their electrochemical behaviors becomes critical and is expected to offer effective guidance for both materials and cell development. This review aims to provide fundamental insights into the reaction mechanisms, electrochemical challenges and modification strategies of lithium-rich oxides. We first summarize the research history, the pristine structures, and the classification of lithium-rich oxides. Then we review the critical reaction mechanisms that are closely related to their electrochemical features and performances, such as lattice oxygen oxidation, oxygen vacancy formation, transition-metal migration, layered to spinel transitions, 'two-phase mechanism', and lattice evolution. These discussions are coupled with state-of-the-art characterization techniques. As a comparison, the anionic redox reactions of layered sodium transition metal oxides are also discussed. Finally, after a brief overview of the correlation among the aforementioned mechanisms, we provide perspectives on the rational design of lithium-rich oxides with high energy densities and long-term cycling stability. This journal i
Synthetic and structural investigations of some lithium thiolates and thiocarboxylates
Full text linkA series of closely related lithium aryl thiolates with pyridine as a donor ligand have been prepared. X-ray structure determination (Dr. W. Clegg) has shown that [PKSLi.(NC(_5)H(_5))] crystallises as an infinite chain polymer. Insertion of a methylene group between the phenyl ring and sulphur as in (PhCH(_2)SLi .NC(_5)H(_5). ] (_oo) produced an infinitely folded ladder polymer with Li-S rungs, while introduction of an 0-methyl group produces the monomeric complex [o-MeC(_6)H(_4)SLi .(NC(_5)H(_5))(_3)].The unusual symmetrical complex [Li(_14) (SCH(_2)Ph)(_12) S(TMEDA.)(_6)] has been prepared, in which a central sulphur atom is surrounded by a distorted cube of lithium atoms, each edge of which is bridged by a benzyl thiolate group such that the twelve S atoms form a cubo- octahedron: a further six Li atoms form a larger outer octahedron. When TMEDA is present in excess it appears that both PhSLi and PhCH(_2)SLi form dimeric compounds with a central Li(_2)S(_2) ring but structure determination of these complexes is incomplete.[PhOOSLi.TMEDA](_2)has been prepared and crystallises as a centrosymmetric dimer containing a chair shaped central eight membered (OOSLi)(_2) ring with the Li atoms out of the (COS)(-2), molecular plane. Lithiation of the related acids PhOOOH and PhCSSH has been carried out in the presence of TMEDA but crystal growth has so far been unsuccessful. Ab initio m.o. calculations on related model compounds are included. A preliminary study has been carried out on the lithiation of the thio-oxime (Ph(_2) C-NSH). Results were encouraging but detailed investigation is needed. The reaction of S(_4) N(_4) with BI(_3) produces, not the expected adduct, S(_4)N(_4) .BI(_3) , but an intractable polymer, empirical formula, S(_3)N(_3)BI. Other adducts of S(_4).N(_4) and (PhCN_2) S(_2))(_2), were prepared but were unsuitable for further reactions. The reaction of lithium borohydride and sulphur in THF to produce sulphurated lithium borohydride has been modified to give a controllable reaction. Further reaction with TMEDA gives clear orange crystals of a complex the composition of which is still unknown
Computational Methods in Economic Dynamics
Full text linkDawid H, Semmler W, eds. Computational Methods in Economic Dynamics. Berlin, Heidelberg: Springer; 2011
Molecular engineering of copolymers with donor-acceptor structure for bulk heterojunction photovoltaic cells toward high photovoltaic performance
No full textA series of donor-acceptor (D-A) conjugated copolymers with benzo[1,2-b:4,5-b-]dithiophene (BDT) as donor and two different electron-accepting groups bithiophenevinyl-2-pyran-4-ylidenemalononitrile (TVM) and benzothiadiazole (BT) moieties as acceptors is designed and synthesized. The optical and electrochemical properties show that the band gaps of the copolymers are in the range of 1.70-1.84 eV, and the HOMO and LUMO energy levels can be tuned effectively by controlling the varied ratios between TVM and BT because of the change of the ICT interaction between donor and acceptor, the electron delocalization degree, and the electron cloud density distribution of the copolymers. Bulk heterojunction photovoltaic devices are fabricated by using the copolymers as donors and (6,6)-phenyl-C61-butyric acid methyl ester (PC61BM) or (6,6)-phenyl-C71-butyric acid methyl ester (PC71BM) as acceptors. The optimized photovoltaic performances show that the open-circuit voltage (Voc) was gradually increased from 0.7 to 0.94 V when decreasing the HOMO energy levels of copolymers, and the short-circuit current density (Jsc) is greatly improved by increasing the absorption spectrum in the visible region, increasing the hole mobility and optimizing the morphologies of blend films between copolymers and PCBM. The optimized photovoltaic performance with a Voc of 0.78 V, J sc of 5.47 mA/cm2, fill factor (FF) of 0.40, and power conversion efficiency (PCE) of 1.67% under simulated AM 1.5 solar irradiation of 100 mW/cm2 is obtained by the copolymer PM50 (PM50:PC 61BM, 1:3 w/w, in CB solution). This is due to its high hole mobility and interpenetrating network morphology of PM50:PC61BM blend film. The photovoltaic device based on PM50:PC71BM shows a Jsc of 8.32 mA/cm2 and a PCE of 2.89%
C-H-activated aluminum hydroxide via molecular oxygen
No full textThe reaction of LAl[eta(2)-(C-2(SiMe3)(2))] (1; L = HC[(CMe)(NDipp)](2), Dipp = 2,6-iPr(2)C(6)H(3)) with dioxygen leads to the elimination of bis(trimethylsilyl)acetylene and the formation of the corresponding aluminum monohydroxide via the oxidation of one of the CHMe2 groups on the Dipp ring
Measurement of w-InN/h-BN Heterojunction Band Offsets by X-Ray Photoemission Spectroscopy
No full textX-ray photoelectron spectroscopy has been used to measure the valence band offset (VBO) of the w-InN/h-BN heterojunction. We find that it is a type-II heterojunction with the VBO being -0.30 +/- A 0.09 eV and the corresponding conduction band offset (CBO) being 4.99 +/- A 0.09 eV. The accurate determination of VBO and CBO is important for designing the w-InN/h-BN-based electronic devices
VCC-LF dataset
No full textThis is readme for VCC-LF dataset.
This dataset provides light field mat files that capture by Lytro I.
The light field resolusion is [h,w,u,v,d].
If you use these data or our toolkit code, please cite our paper properly
@inproceedings{ lirsiggraphasia2019,
title={Hierarchical and View-invariant Light Field Segmentation by Maximizing Entropy Rate on 4D Ray Graphs},
author={Li, Rui and Heidrich, Wolfgang},
booktitle={ACM Transactions on Graphics (Proc. SIGGRAPH Asia)},
year={2019},
publisher={ACM}
Fig. 7. 1H–1H in Guaiane-type sesquiterpenoids from Cinnamomum migao H. W. Li: And their anti-inflammatory activities
No full textFig. 7. 1H–1H COSY and key HMBC correlations of compounds 9, 10, and 11.Published as part of Muhammad, Ishaq, Luo, Wei, Shoaib, Rana Muhammad, Li, Guang-li, Hassan, Syed Shams ul, Yang, Zhi-hua, Xiao, Xue, Tu, Guo-li, Yan, Shi-Kai, Ma, Xian-peng & Jin, Hui-Zi, 2021, Guaiane-type sesquiterpenoids from Cinnamomum migao H. W. Li: And their anti-inflammatory activities, pp. 1-10 in Phytochemistry (112850) 190 on page 7, DOI: 10.1016/j.phytochem.2021.112850, http://zenodo.org/record/825787
Advances and issues in developing intercalation graphite cathodes for aqueous batteries
No full textAqueous rechargeable batteries offer a safe alternative for electrochemical energy storage, integrating cost-efficiency and energy density to meet the demand for stationary applications. Recent efforts have focused on the improvement of electrode materials in aqueous electrolytes, particularly the cycle life and energy reliability of batteries. The anion intercalation chemistry in graphite could be an alternative cathode candidate, often requiring an upper cut-off potential above 4.5 V vs. Li+/Li. Such a potential readily exceeds the electrochemical stability windows of water-based electrolytes. Herein, we provide a progress report and critical comment on the reversible intercalation chemistry in graphite compounds, i.e., anion and halogen intercalations, for the development of economical, high-energy aqueous rechargeable batteries. In addition, this review focuses on the charge carrier species, their charge storage mechanisms and battery configurations, aiming to provide solutions to solve the remaining key challenges for aqueous batteries
Zawartosc pierwiastkow sladowych i makroelementow w wodach powierzchniowych w wybranych punktach wojewodztwa zachodniopomorskiego
No full textW pracy przedstawiono wartości stężeń Li, Sr, K, Na, Ca i Mg w wodach cieków wodnych i oczek śródpolnych w wybranych punktach województwa zachodniopomorskiego. Oznaczenia przeprowadzono w latach 2001-2002 na terenach użytkowanych rolniczo w bezpośrednim sąsiedztwie dróg komunikacyjnych. Badane wody zawierały niskie stężenia pierwiastków śladowych i mogą być wykorzystywane do nawadniania pól i pojenia bydła. Największe stężenia Li, Sr, Na, Ca i Mg występowały w wodach rzeki Bielicy, przepływającej pod drogą krajową E65, a najniższe poza sodem w wodach oczka śródpolnego koło Krąpieli. Najwyższy poziom koncentracji K stwierdzono w wodach oczek śródpolnych.Paper presents the data on concentrations of Li, Sr, K, Na, Ca i Mg in water of water-courses and midfield ponds at selected points of Western Pomerania. The analyses were carried out in 2001-2002 in an agricultural area adjacent to the roads. Tested water contained low concentrations of Li and Sr and night be used for irrigation and as drink water for cattle. The contents of Li, Sr, Na, Ca and Mg were the highest in Bielica river, which runs under E65 while the lowest, beside Na were in the midfield pond. Higtest K concentrations were found in the water of midfield ponds
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