Enhanced Electrochemical Performances of LiFePO4/C via V and F Co-doping for Lithium-Ion Batteries

Based on the method of in situ polymerization synthesis combined with two-step sinter-ing process, LiFe_1-xV_x(PO₄)_(3-y)/₃F_y/C was prepared. The e ects of V and F co-doping on the structure, morphology, and electrochemical performances of LiFePO₄/C were in-vestigated by X-ray di raction, Fourier transform infrared spectra, scanning electron mi-croscope, charge/discharge tests, and electrochemical impedance spectroscopy, respectively. The results indicated that the V and F co-doping did not destroy the olivine structure of LiFePO₄/C, but it can stabilize the crystal structure, decrease charge transfer resistance, enhance Li ion di usion velocity, further improve its cycling and high-rate capabilities of LiFePO₄/C.     

A metal-free C–C/C–O bond formation for the synthesis of 2-amino-5-oxo-4-aryl-4H,5H-pyrano[3,2-c]chromene-3-carboxamide catalyzed by polystyrene-supported p-toluenesulfonic acid (PS-PTSA)

An efficient and eco-friendly procedure for the synthesis of 2-amino-5-oxo-4-aryl-4H,5H-pyrano[3,2-c]chromene-3-carboxamide has been developed through a one-pot three-component condensation of 4-hydroxycoumarin with aldehydes and cyanoacetamide, in the presence of catalytic amount of polystyrene-supported p-toluenesulfonic acid (PS-PTSA) as a highly active and reusable heterogeneous acid catalyst in EtOH at 80?°C conditions. This new procedure offers several advantages such as shorter reaction times, excellent yields, a wide range of functional group tolerance, easy experimental work-up procedure, operationally simple under metal-free reaction conditions and C-C/C-O bond formation. The catalyst can be recovered and reused for at least four runs without any significant impact on the product yields.     

Physicochemical properties of sodium succinate sulfate and effects on BaSO4 suspension

Sodium succinate sulfate (MAPEG1500-OSO₃Na) was prepared using maleic anhydride (MA) and polyethylene glycols (PEG1500) as raw materials. The structure was characterized by Fourier transform infrared spectrometry (FTIR) and ¹H-nuclear magnetic resonance (¹H NMR). Its physicochemical properties, such as surface activity, adsorption behavior, spreading performance, and rheological property, were investigated by static/dynamic surface tension (DST) measurements, contact angle techniques, and rheological techniques at 25°C. Surface tension measurement for this surfactant is about 17?mN/m. The DST results indicated that the adsorption process is mixed diffusion-kinetic adsorption mechanism. The spreading measurement demonstrated that MAPEG1500-OSO₃Na possessed an excellent spreading ability. Besides, the dispersion performances of MAPEG1500-OSO₃Na on barium sulfate (BaSO₄) particles under different conditions have been studied by the weighing method and transmission electron microscope (TEM). These results showed that there exist optimum pH value and added amount of MAPEG1500-OSO₃Na corresponding to the highest dispersion rate.     

Synthesis of Single‐Crystalline Spinel LiMn2O4 Nanorods for Lithium‐Ion Batteries with High Rate Capability and Long Cycle Life

The long‐standing challenge associated with capacity fading of spinel LiMn₂O₄ cathode material for lithium‐ion batteries is investigated. Single‐crystalline spinel LiMn₂O₄ nanorods were successfully synthesized by a template‐engaged method. Porous Mn₃O₄ nanorods were used as self‐sacrificial templates, into which LiOH was infiltrated by a vacuum‐assisted impregnation route. When used as cathode materials for lithium‐ion batteries, the spinel LiMn₂O₄ nanorods exhibited superior long cycle life owing to the one‐dimensional nanorod structure, single‐crystallinity, and Li‐rich effect. LiMn₂O₄ nanorods retained 95.6 % of the initial capacity after 1000 cycles at 3C rate. In particular, the nanorod morphology of the spinel LiMn₂O₄ was well‐preserved after a long‐term cycling, suggesting the ultrahigh structural stability of the single crystalline spinel LiMn₂O₄ nanorods. This result shows the promising applications of single‐crystalline spinel LiMn₂O₄ nanorods as cathode materials for lithium‐ion batteries with high rate capability and long cycle life.     

Preparation of Nano Silica Supported Sodium Hydrogen Sulfate: As an Efficient Catalyst for the Trimethyl,Triethyl and t‐Butyldimethyl Silylations of Aliphatic and Aromatic Alcohols in Solution and under Solvent‐free Conditions

Nano silica supported sodium hydrogen sulfate has been prepared by mixing NaHSO₄ with activated Nano silicagel. We wish to report a new method for the synthesis of trimethyl (TMS), triethyl (TES) and t‐butyldimethyl silyl (TBS) ethers from benzylic, allylic, propargylic alcohols, phenols, naphtholes and some of phenolic drugs in the solution and under solvent‐free conditions.     

Synthesis of arylidene derivatives of N-unsubstituted pyrrolin-2-ones

5-Alkyl(aryl)-3-arylidene-3H-pyrrolin-2-ones were synthesized by ammonolysis of their O-heteroanalogs or by the reactions of 5-alkyl(aryl)-3H-pyrrolin-2-ones with aromatic aldehydes. The structures of the compounds obtained were confirmed by ¹H NMR spectra.     

Preparation of activated carbons and their adsorption properties for greenhouse gases: CH4 and CO2

Three kinds of activated carbons were prepared using coconut-shells as carbon precursors and characterized by XRD, FT-IR and texture property test. The results indicate that the prepared activated carbons were mainly amorphous and only a few impurity groups were adsorbed on their surfaces. The texture property test reveals that the activated carbons displayed different texture properties, especially the micropore size distribution. The adsorption capacities of the activated carbons were investigated by adsorbing CH4, CO2, N2 and O2 at 25 ?C in the pressure range of 0-200 kPa. The results reveal that all the activated carbons had high CO2 adsorption capacity, one of which had the highest CO2 adsorption value of 2.55 mmol/g at 200 kPa. And the highest adsorption capacity for CH4 of the activated carbons can reach 1.93 mmol/g at 200 kPa. In the pressure range of 0-200 kPa, the adsorption capacities for N2 and O2 were increased linearly with the change of pressure and K-AC is an excellent adsorbent towards the adsorption separation of greenhouse gases.     

A novel Prins-alkynylation reaction for the synthesis of 4-phenacyl tetrahydropyrans

Aldehyde, homoallylic alcohol, and alkyne undergo smooth Prins-type cyclization in the presence of BF₃·OEt₂/CuCl (10 mol % each) in dichloromethane under mild reaction conditions to afford 4-phenacyl tetrahydropyran derivatives in good yields. This method is highly stereoselective, affording cis-tetrahydropyrans exclusively. The salient features of this method are high conversions, mild reaction conditions, short reaction times, high selectivity, and operational simplicity.