15500-04-6Relevant articles and documents
Ionic-liquid-assisted synthesis of nanostructured and carbon-coated Li 3V2(PO4)3 for high-power electrochemical storage devices
Zhang, Xiaofei,Boeckenfeld, Nils,Berkemeier, Frank,Balducci, Andrea
, p. 1710 - 1718 (2014)
Carbon-coated Li3V2(PO4)3 (LVP) displaying nanostructured morphology can be easily prepared by using ionic-liquid-assisted sol-gel synthesis. The selection of highly viscous and thermally stable ionic liquids might promote the formation of nanostructures during the sol-gel synthesis. The presence of these structures shortens the diffusion paths and enlarges the contact area between the active material and the electrolyte; this leads to a significant improvement in lithium-ion diffusion. At the same time, the use of ionic liquids has a positive influence on the coating of the LVP particles, which improves the electronic conductivity of this material; this leads to enhanced charge-transfer properties. At a high current density of 40 C, the LVP/N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide material delivered a reversible capacity of approximately 100 mA h g-1, and approximately 99 % of the initial capacity value was retained even after 100 cycles at 50 C. The excellent high rate and cycling stability performance make Li3V2(PO 4)3 prepared by ionic-liquid-assisted sol-gel synthesis a very promising cathode material for high-power electrochemical storage devices. Storage solutions: Carbon-coated Li3V2(PO 4)3 displaying nanostructured morphology is easily prepared by using ionic-liquid-assisted sol-gel synthesis. This material displays improved lithium-ion diffusion and electronic conductivity and thus enhanced charge-transfer properties. Li3V2(PO 4)3 prepared by this sol-gel route is a very promising cathode material for high-power electrochemical storage devices.
Layered hybrid phase Li2NaV2(PO4)3/carbon dot nanocomposite cathodes for Li+/Na+ mixed-ion batteries
Wang, Jichao,Zhang, Xudong,He, Wen,Yue, Yuanzheng,Wang, Yaoyao,Zhang, Chuanjiang
, p. 2658 - 2666 (2017)
Hybrid phase Li2NaV2(PO4)3 (H-LNVP) is one of the most promising cathode materials for Li+/Na+ mixed-ion batteries. Here we have successfully synthesized layered hybrid phase Li2NaV2(PO4)3/carbon dot (H-LNVP/CD) nanocomposites via a simple sol-gel and carbon thermal reduction method and its inserted-extracted mechanism is investigated. As a novel composite cathode, H-LNVP/CD nanocomposite cathode delivers 158 mA h g-1 of reversible capacity at 0.1C in a Li+/Na+ mixed-ion cell with the electrochemically active redox reactions of V3+/V4+ and V4+/V5+, which is far higher than single phase contrastive samples. The cell exhibits one main high voltage plateau with well-defined discharge voltage near 3.7 V, and a coulombic efficiency of approximate 100 percent at 10C. Because the carbon dots on the surface of layered H-LNVP nanoparticles can remarkably enhance their electronic conductivity, the cell still exhibits a higher specific capacity of about 89.4 mA h g-1 at 10C. These results are attributed to the nanocomposite structure of H-LNVP and CDs. This work will contribute to the development of Li+/Na+ mixed-ion batteries.
Structural dynamics of molybdenum vanadium oxide (MoVOx): Influence of activation condition
Suppiah, Durga Devi,Komar, Anna,Hamid, Sharifah Bee Abd
, p. 1367 - 1376 (2017)
Molybdenum and vanadium oxides were known to be an effective catalyst for light olefin (propane) activation for conversion to value-added chemicals. However, it is difficult to control the selectivity to desired product whereby subsequent reaction can lead to coking and rapid catalyst deactivation. One of the key ways to improve on the above limitation is to optimise and control the molybdenum phase structure, particularly during catalyst precursor activation stage. This paper demonstrates the combination of optimal in situ activation under different condition and thermal analysis for structural control that can help to guide and gain an insight into the structure–activity relationship of the nanostructured catalyst system. In situ XRD analysis reveals the crystallization of molybdenum vanadium oxide was highly influenced by the activation condition hence exhibiting different structural properties. Activation under Air at 300?°C forms highly crystalline hexagonal phase and transforms to thermodynamically stable orthorhombic (o-MoO3) phase at 450?°C. Activation under inert (helium) reveals the precursor remains amorphous until nanostructuring occurs at 450?°C. The precursor further transforms to the thermodynamically stable crystallized tetragonal phase (Mo5O14) at 500?°C. The obtained structural transition information is important in order to control and identify the catalytic active phase that is suitable for a particular reaction.
Synthesis of biocarbon coated Li3V2(PO4)3/C cathode material for lithium ion batteries using recycled tea
Wei, Chuanliang,He, Wen,Zhang, Xudong,Liu, Shujiang,Jin, Chao,Liu, Shikun,Huang, Zhen
, p. 28662 - 28669 (2015)
A biocarbon coated Li3V2(PO4)3/C (LVP-C) cathode material was synthesized by a facile sol-gel method using recycled tea as both the structural template and biocarbon source. X-ray diffraction (XRD) patterns show that LVP has a monoclinic structure with space group P21/n. High-resolution transmission electron microscopy (HRTEM) images show that the LVP nanoparticles are surrounded by amorphous biocarbon, and the thickness of the biocarbon shell is about 10-20 nm. Electrochemical measurements demonstrate that the LVP-C nanocomposite shows a significantly better rate capability and cycling performance than pure LVP. In the potential range of 3.0-4.3 V, the LVP-C nanocomposite delivers a high initial discharge capacity of 132 mA h g-1 at 0.5 C, and maintains an initial discharge capacity of 110 mA h g-1 at 10 C. After 80 cycles at 10 C, it still retains a discharge capacity of 110 mA h g-1. Electrochemical impedance spectroscopy (EIS) measurements have disclosed that the LVP-C sample exhibits enhanced electrode reaction kinetics and improved electrochemical performance. The good electrochemical performance of the LVP-C nanocomposite is mainly related to the presence of the conductive biocarbon, thus leading to an improvement in the electron and lithium ion diffusivity. These results indicate that the biocarbon coated LVP-C material is a promising candidate for large capacity and high power cathode materials in next generation lithium-ion batteries for electric vehicles.
The synthesis and structure of a single-phase, nanocrystalline MoVW mixed-oxide catalyst of the Mo5O14 type
Knobl,Zenkovets,Kryukova,Ovsitser,Niemeyer,Schloegl,Mestl
, p. 177 - 187 (2003)
The different preparation steps are characterized for the single-phase, crystalline, ternary oxide (MoVW)5O14, which is important for catalytic, mild selective oxidation reactions. For the synthesis of this oxide, solutions of ammonium heptamolybdate, ammonium metatungstate, and vanadyl oxalate were spray-dried followed by different thermal treatments. The structures of the materials formed at each preparation step, starting from the precursor to the final product, were studied using scanning and transmission electron microscopy, X-ray powder diffraction, thermal analysis, and Raman spectroscopy. Raman spectroscopy was also applied to shed some light into the aqueous chemistry of the mixed precursor solutions. Raman data indicate that a molecular structure which seems to be closely related to that of the final crystalline Mo5O14-type oxide is already formed in solution. X-ray diffraction revealed that the thermal treatment steps strongly affect the degree of crystallinity of the ternary Mo5O14 oxide. Transmission electron microscopy with energy-dispersive microanalysis confirmed the presence of V and W in the molybdenum oxide particles and gave evidence for the (010) plane as the most developed face of the crystals of this phase. Details of the structural transformation of this system at the different preparation and calcination steps are discussed in relation to their performance in the selective partial oxidation of acrolein to acrylic acid.
Structural and electrochemical properties of Al3+ doped V 2O5 nanoparticles prepared by an oxalic acid assisted soft-chemical method
Zhan, Shiying,Wei, Yingjin,Bie, Xiaofei,Wang, Chunzhong,Du, Fei,Chen, Gang,Hu, Fang
, p. 92 - 96 (2010)
V2O5 and Al0.2V2O5 nanoparticles were prepared by an oxalic acid assisted soft-chemical method. X-ray photoelectron spectroscopy confirmed the V5+ oxidation state of V2O5, whereas an intermediate state between V 5+ and V4+ of Al0.2V2O5. Raman scattering showed that the Al3+ ions existed in an [AlO 6] octahedral environment. The doping of Al3+ increased the cohesion between the V2O5 slabs, which enhanced the structural stability of the material. The chemical diffusion coefficients of the Al0.2V2O5 nanoparticles were a little bit smaller than those of V2O5. Charge-discharge cycling showed that the Al0.2V2O5 nanoparticles exhibited much better capacity retention than the un-doped V2O 5, which was attributed to the enhanced structural stability of the material.
Electrochemical performances of Li3V2-(4/3)xTix(PO4)3/C as cathode material for Li-ion batteries synthesized by an ultrasound-assisted sol-gel method
Li, Lingfang,Fan, Changling,Zeng, Taotao,Zhang, Xiang,Zhang, Weihua,Han, Shaochang
, p. 136 - 142 (2015)
Cathode materials Li3V2-(4/3)xTix (PO4)3 (x = 0,0.03, 0.06, 0.09, 0.12) using Polyvinylidene Fluoride (PVDF) as carbon source are synthesized via an ultrasound-assisted sol-gel method. Ultrasound helps to a uniform dispersion of the water insoluble PVDF. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that samples exhibit pure monoclinic structure and have similar morphology. Electrochemical galvanostatic charging/discharging results show that the capacities at low current density (less than 2C) of all samples are not that different. However, the discharge capacities and cyclic performance are improved at higher current density by a proper amount of Ti4+ doping (x = 0.03-0.06). The electrochemical performances become a bit worse when x is higher than 0.06. This may be attributed to the uniform lattice distortion caused by the overmuch dopant.
