Synthesis and characterization of ε-VOPO_4 nanosheets for secondary lithium-ion battery cathode

Vanadium （III） phosphate monoclinic VPO4·H2O was synthesized hydrothermally. The ε-VOPO4 nanosheets, formed by the oxidative de-intercalation of protons from monoclinic VPO4·H2O, can reversibly react with more than 1 mol lithium atoms in two steps. Crystal XRD analysis revealed that the structure of the ε-VOPO4 nanosheets is monoclinic with lattice parameters of α=7.2588（4） A, b=6.8633（2） A and c=7.2667（4） A. The results show that the ε-VOPO4 nanosheets have a thickness of 200 nm and uniform crystallinity. Electrochemical characterization of the ε-VOPO4 monoclinic nanosheets reveals that they have good electrochemical properties at high current density, and deliver high initial capacity of 230.3 mA· h/g at a current density of 0.09 mA/cm2. Following the first charge cycle, reversible electrochemical lithium extraction/insertion at current density of 0.6 mA/cm2 affords a capacity retention rate of 73.6% （2.0？4.3 V window） that is stable for at least 1000 cycles.

Preparation and electrochemical performance of 2LiFe_(1-x)Co_xPO_4-Li_3V_2(PO_4)_3/C cathode material for lithium-ion batteries

2LiFe1-xCoxPO4-Li3V2（P04）3/C was synthesized using Fel-2xCo2xVO4 as precursor which was prepared by a simple co-precipitation method. 2LiFej-xCoxPO4-Li3V2（PO4）3/C samples were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical measurements. All 2LiFel-xCoxPOa-Li3V2（PO4）3/C composites are of the similar crystal structure. The XRD analysis and SEM images show that 2LiFe0.96Co0.04PO4-Li3V2（PO4）3/C sample has the best-ordered structure and the smallest particle size. The charge-discharge tests demonstrate that these powders have the best electrochemical properties with an initial discharge capacity of 144.1 mA.h/g and capacity retention of 95.6% after 100 cycles when cycled at a current density of 0.1C between 2.5 and 4.5 V.

BP化学开发顺酐新催化剂

BP化学公司使其基于钒/磷的新型催化剂推向工业化应用,该催化剂可提高固定床工艺丁烷转化为顺酐的转化率。该公司已将这种BP-5催化剂应用于其所有的固定床顺酐生产中。 BP-5的主要优点是开工时间较短,典型的为几天,而不是几星期,不仅可提高生产能力,而且可减少偏离规格的产品生成,从而限制了可能沾污流出物换热器的杂质。

Effect of Mg doping on electrochemical performance of Li_3V_2(PO_4)_3/C cathode material for lithium ion batteries

Li3Mg（2x）V（2-2x）（PO4）3/C（x=0,0.05,0.1,0.2） composites were synthesized by carbothermic reduction,using a self-made MgNH4PO4/MgHPO4 compound as Mg-doping agent.X-ray diffraction（XRD）,scanning electron microscope（SEM）,electrochemical performance tests were employed to investigate the effect of Mg doping on Li3V2（PO4）3/C samples.The results showed that a proper quantity of Mg doping was beneficial to the reduction of charge transfer resistance of Li3V2（PO4）3/C compound without changing the lattice structure,which led to larger charge/discharge capacity and better cycle performance especially at high current density.Li3Mg（2x）V（2-2x）（PO4）3/C sample with x=0.05 exhibited a better performance with initial charge/discharge capacity of146/128 mA·h/g and discharge capacity of 115 mA·h/g at 5C,while these two figures were 142/118 mA·h/g and 90 mA·h/g respectively for samples without Mg doping,indicating that a proper amount of doped Mg can improve the electrochemical performance of LVP sample.All of these proved that,as a trial Mg dopant,the synthesized MgNH4PO4/MgHPO4 compound exhibited well doping effect.

Synthesis and electrochemical performance of Li_(3-2x)Mg_xV_2(PO_4)_3/C composite cathode materials for lithium-ion batteries

The Li3 2xMgxV2（PO4）3/C （x-=0, 0.01, 0.03 and 0.05） composites were prepared by a sol-gel method and characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical measurements. The XRD results reveal that a small amount of Mg2＋ doping into Li sites does not significantly change the monoclinic structure of Li3V2（PO4）3, but Mg-doped Li3W2（PO4）3 has larger cell volume than the pristine Li3V2（PO4）3. All Mg-doped composites display better electrochemical performance than the pristine one, and Liz.94Mgo.03Vz（P04）3/C composite exhibits the highest capacity and the best cycle performance among all above-mentioned composites. The analysis of Li＋ diffusion coefficients in Li3V2（PO4）3/C and Li2.94Mgo.03V2（P04）3/C indicates that rapid Li＋ diffusion results from the doping of Mg2＋ and the rapid Li＋ diffusion is responsible for the better electrochemical performance of Mg-doped Li3V2（PO4）3/C composite cathode materials.

Mass Spectrometric Studies of Selective Oxidation of n-Butane over a Vanadium Phosphorus Oxide Catalyst

The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique. The reaction intermediates, buterie and furan, were found in the reaction effluent under near industrial feed condition (3% butane+15%O2), while dihydrofuran was detected at high butane concentration (12% butane, 5%O2). Some intermediates of MA decomposition were also identified. Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene, and butene further to form MA. Based on these observations, a modified scheme of reaction network is proposed. The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice, without a proceeding adsorption step. Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation. Adsorbed oxygen leads to deep oxidation, while lattice oxygen leads to selective oxidation.

Trimethyl-1,4-Benzoquinone Synthesis via 2,3,6-Trimethylphenol Catalytic Oxidation by Oxygen in the Presence of Non-Keggin-Type Mo-V-Phosphoric Heteropoly Acid Solutions

In the present study, the modified （non-Keggin-type） aqueous solutions of Mo-V-phosphoric heteropoly acids HaPzMoyVx,Oh （HPA-x＇） were applied as homogeneous catalysts for the two-stage oxidation of TMP （2,3,6-trimethylphenol） by oxygen into TMQ （2,3,5-trimethyl-l,4-benzoquinone）, the latter being the key intermediate in the synthesis of vitamin E. The TMQ yield was analyzed regarding solvent type, reaction temperature, molar HPA-x ＇：TMP ratio, and the concentration of vanadium （V） in the HPA-x＇ solution. The TMQ yield was found to depend strongly on the catalyst redox potential and the rate of electron transfer. The results obtained enabled to establish the optimal reaction conditions as well as to suggest the reaction mechanism. In the target reaction, which proceeds in the two-phase system, the TMQ yield is higher than 99%. After phase separation, the catalyst is rapidly regenerated by oxygen and reused.

Vanadium extraction and dephosphorization from V-bearing hot metal with fluxes containing CaO

Extracting vanadium and removing phosphorus simultaneously by adding CaO containing materials to V-bearing hot metal were investigated under the condition of simulating the process of vanadium extraction with insufficiently supplying oxygen in converter. Through preliminary experiments, 3 h and 1375 °C were chosen as the optimum holding time and reaction temperature for formal experiments, respectively. The results of the formal experiments suggest that making basic slag can extract vanadium and remove phosphorus simultaneously. The vanadium extraction rate(ηV) and phosphorus removal rate(ηP) both increase with an increase in the basicity of the original slag materials and the Fe2O3 contents. The vanadium distribution ratio)(V L′is about an order of magnitude greater than the phosphorus distribution ratio),(P L′but the latter is more sensitive to slag basicity than the former. The phosphorus distribution ratio is beyond 6 when the basicity of the original slag materials is beyond 1, which indicates a much better performance of phosphorus removal compared to the phosphorus removal in the current process. Therefore, it is very feasible to properly raise slag basicity to remove phosphorus with consideration of the grade of vanadium slag. The relations between ηV and ηP, and between L′V and L′P are linear under the experimental conditions.

Ammoxidation of 3-Picoline over V-Mo-P Oxide Catalyst Prepared from 11-Molybdo-l-Vanado Phosphoric Acid

V-Mo-P oxide catalyst system was directly prepared from ll-molybdo-l-vanado phosphoric acid by thermal decomposition. Supported V-Mo-P oxide catalysts were prepared by wet impregnation method. Catalysts were characterized by FTIR （Fourier transform infrared）, XRD （X-ray diffraction） and TPD （temperature programmed desorption）. The catalytic activity of V-Mo-P oxide catalysts were investigated for vapour phase ammoxidation of 3-picoline. The unsupported catalyst showed 92.1% yield where as V-Mo-P oxide/HZSM-5 showed the highest yield （80.4%） amongst the supported catalysts.

First-principles investigation of cohesive energy and electronic structure in vanadium phosphides

First-principles calculations based on the density-functional theory were employed to study the crystal structure of vanadium phosphide compounds,such as V3P,V2P,VP,VP2 and VP4. Cohesive energy of five types of vanadium phosphide compounds was calculated to assess their structural stability. The charge density distribution and densities of states of vanadium phosphides were discussed to study further their electronic structures. The results show that the structure of metal-rich compounds is considerably more stable than the phosphorus-rich compositions,and covalent bond exists between the V and P atoms of V3P,V2P,VP,VP2 and VP4.

Structural Studies of [V_2S_6O_2(CuPPh_3)_4(CuMeCN)_2]·2CH_2Cl_2·2PrOH

The title V-Cu-S heterometallic cluster compound C84 H86Cl4Cu6N2O4P4S6V2, crystallizes in the monoclinic space group P21/n with a=16.381(5), b=17.114(3),c=16.749(6) A,β=107. 04(3)°,V=4490(2)A3, Mr=2128.84,Z=2,Dc=1. 57 g/cm3,μ= 19. 6 cm-1,F(000)=2160. Final R=0.074(Rw=0.082) for 2662 unique reflections with I≥3σ(I). The V atom in the compound retains the tetrahedral geometry of the VS3O with S-V-S or S-V-O angles of 108.6(6)～110.3 (6)°.The cluster core [V2Cu6S6O2] of the compound can be regarded as two cluster cores [VCu3S3O] bonded by bondings of the Cu-Cu'(distances of 2.774(3)～2.707(5) A) and Cu-S (distances of 2.463(7)～2.396(9) A) with centrosymmetric. Atoms of the cluster core V2Cu6 form a distorted cube with the Cu Cu'or the V-Cu distances of 2. 774(3)～2. 707(5) A.