Influence of cathode materials on thermal characteristics of lithium-ion batteries.

In this work, the thermal stability of four types of 18,650 lithium-ion batteries with LiCoO2 (LCO), LiFePO4 (LFP), LiNi0.8Co0.1Mn0.1O2 (NCM811) and LiNi0.8Co0.15Al0.05O2 (NCA) materials as cathodes are experimentally investigated by the accelerating rate calorimeter (ARC) and the isothermal battery testing calorimeter (iso-BTC) under adiabatic and isothermal conditions, respectively. The thermal runaway danger level of these batteries can be ranked as LCO > NCA > NCM811 >> LFP by judging from the values of Tmax and HRmax, nominal. The higher the nickel and cobalt content, the higher the lithium-ion battery capacity, but the worse the thermal stability. The Qtotal of NCA is the largest in the complete standard charge and discharge process, due to that the capacity of NCA is significantly higher than that of the other three batteries, resulting in remarkable increase in Qirre proportioned to the square of the current. When the ambient temperature rises, the energy release decreases owing to the decrease in the internal resistance of the battery. These studies are expected to have important implications for the subsequent safe design of commercial lithium-ion batteries with different cathode materials.

Incorporating Ag@RF core-shell nanomaterials into the thin film nanocomposite membrane to improve permeability and long-term antibacterial properties for nanofiltration.

Ag@resorcinol-formaldehyde resin (Ag@RF) core-shell nanomaterials were prepared by Stöber method, and introduced into polyamide (PA) selective layer of thin-film nanocomposite (TFN) membranes through the interfacial polymerization (IP) process. Due to the abundant hydroxyl groups on the surface and suitable particle size, Ag@RF nanoparticles (Ag@RFs) could be uniformly dispersed in the piperazine aqueous solution and participate in the IP process to precisely regulate the microstructure of the PA selective layer. The resulting "crater structure" and irregular granular structure enlarged the permeable area and contributed to the surface hydrophilicity. For the nanofiltration application, the water flux of TFN membrane modified by Ag@RFs to Na2SO4 solution reached 150 L·m-2·h-1 which was 87.5% greater than TFC, and salt rejection was maintained. The antibacterial efficiency of the prepared TFN membrane on E. coli reached 99.6% in the antibacterial experiment. In addition, due to the special structure of Ag@RFs, the TFN membrane also showed an expected slow-release capability of Ag+, allowing for long-term anti-biofouling properties. This work demonstrates that Ag@RF core-shell nanoparticles with high compatibility of organic nanoparticles and antibacterial properties of Ag nanoparticles could be used as promising nanofillers for designing functional nanofiltration TFN membranes.

Enhanced flux performance of polyamide composite membranes prepared via interfacial polymerization assisted with ethyl formate.

A novel thin film composite (TFC) polyamide reverse osmosis membrane was prepared via the interfacial polymerization of m-phenylene diamine (MPD) in aqueous phase and 1,3,5-trimesoyl chloride (TMC) in organic phase on a polysulfone ultrafiltration support by assisting with ethyl formate as a co-solvent added in the organic phase. The ethyl formate added in the organic phase is intended to form a narrow miscibility zone, which leads to the thicker reaction zone. The multi-layered loose polyamide structure with larger pore size was formed due to the thicker reaction zone and lower content of MPD. The enhanced hydrophilicity of the membrane was proved by the decreased water contact angle. Water flux was measured at 1.6 MPa with 2,000 ppm NaCl aqueous solution. Compared to the TFC membrane prepared without ethyl formate, the water flux across the TFC membrane with ethyl formate in the organic phase increased with the increased ethyl formate content (from 23 to 45 L/(m2 h)) and the salt rejection remained at a high level (>90%). The ethyl formate can be used as a co-solvent to effectively enhance the performance of the TFC membrane.

Direct synthesis of hierarchical monolithic silica for high performance liquid chromatography.

The silica-based monolith exhibiting a hierarchical bimodal porous structure has been directly synthesized via lytropic mesophase. The hydrolysis and condensation of tetramethoxysilane (TMOS) in the presence of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (P123) and acetic acid results in silica monolith with MSU-type mesoporous structure embedded in the skeleton of the interconnected macropore. The silica monolith with bimodal porous structure can separate benzene and phenol with high flow rate and low back-pressure. Moreover, the chromatographic property of C18-grafted silica monolith is investigated in the separation of aromatic molecules. Our primary result shows that the silica monolith with interconnected macropore and MSU-type mesopore is a promising packing material as stationary phase for high performance liquid chromatography.

[Synthesis of periodic mesoporous ethanesilica and its application in high performance liquid chromatography].

The periodic mesoporous ethanesilica (PME) was synthesized in acidic medium by the condensation of 1,2- bis (trimethoxysily) ethane (BTME) using triblock copolymer EO20PO70EO20 (P123) as template, cetyltrimethylammonium bromide (CTAB) as co-surfactant and ethanol as co-solvent. The results of nitrogen-sorption measurement, powder X-ray diffraction (XRD), and scanning electron microscopy (SEM) show that the PME has high surface area (1152 m2/g), narrow pore-size distribution, ordered pore structure, and spherical morphology. The spherical PME without further chemical modification was used as the stationary phase in reversed-phase high performance liquid chromatography. Highly efficient and rapid separation of the mixture of polycyclic aromatic hydrocarbons (benzene, naphthalene, biphenyl, phenanthrene and pyrene) was obtained on the column packed with the PME.

Phase transformation of the periodic mesoporous organosilicas assisted by organotrialkoxysilane.

A phase transformation of mesoporous organosilicas from 2D-hexagonal P6mm to cubic Pm3n phase can be induced by the organotrialkoxysilane with hydrophilic pendant group with the aid of methanol during the co-condensation of 1,2-bis(trimethoxysilyl)ethane (BTME) and (EtO)(3)Si-R (R = L-prolinamide, trans-(1R,2R)-diaminocyclohexane, and gamma-aminopropyl) using the cationic surfactant, octadecyltrimethylammonium chloride (C(18)TMACl), as template in basic medium. Under similar synthesis conditions, no cubic Pm3n phase could be formed in the absence of (EtO)(3)Si-R. Depending on the type of the pendant group, different amounts of methanol were needed for the formation of the cubic Pm3n phase. N-[(triethoxysilyl)propyl]-L-prolinamide (M(L-Pro)) could easily induce the phase changing from 2D-hexagonal P6mm to cubic Pm3n phase probably because L-proline could result in a decreasing of the surfactant packing factor (g) through formation of large architecture on the outer boundary of the surfactant micelles. The organotrialkoxysilane can also help the formation of spherical morphology of the resultant materials.

trans-(1R,2R)-Diaminocyclohexane-functionalized mesoporous organosilica spheres as chiral stationary phase.

The bifunctionalized mesoporous organosilica spheres with trans-(1R,2R)-diaminocyclohexane (DACH) in the pore were synthesized and their application as chiral stationary phase in high-performance liquid chromatography (HPLC) was demonstrated. Bifunctionalized mesoporous organosilica spheres with narrow particle size distribution of 5-7 microm were prepared by the co-condensation of N-[3-(triethoxysilyl)propyl]-trans-(1R,2R)-diaminocyclohexane (M(propyl)) with 1,2-bis(trimethoxysilyl)ethane (BTME) in basic medium using octadecyltrimethylammonium chloride (C(18)TACl) as structural directing agent and ethanol as co-solvent. The morphologies of the bifunctionalized mesoporous organosilicas were sensitive to the molar fraction of M(propyl). At higher M(propyl)/BTME molar ratio, the bifunctionalized organosilica spheres with ordered mesoporous structure can be formed in a wide range of synthetic conditions. When the molar percent of M(propyl)/(M(propyl)+BTME) is less than 20, the formation of spheres could be hardly observed. The structural order of the materials mainly depends on the base concentration and M(propyl)/BTME molar ratio in the initial sol mixture. A column packed with the bifunctionalized mesoporous organosilica spheres exhibits higher selectivity and resolution for racemic amino acids than that packed with DACH-SiO(2) prepared by conventional post-synthesis grafting method.

Synthesis of bifunctionalized mesoporous organosilica spheres for high-performance liquid chromatography.

Phenyl-functionalized mesoporous ethane-silicas with spherical morphology were synthesized by one-step co-condensation of phenyltrimethoxysilane (PTMS) and 1,2-bis(trimethoxysily)ethane (BTME) using a triblock copolymer EO(20)PO(70)EO(20) (P123) as template with the aid of a co-surfactant (cetyltrimethylammonium bromide, CTAB) and a co-solvent (ethanol) in acidic medium. Powder X-ray diffraction (XRD), nitrogen sorption measurement and scanning electron microscopy (SEM) show that phenyl-functionalized ethane-silica has wormhole-like mesostructure and perfect spherical morphology. The chemical stability of phenyl-functionalized mesoporous ethane-silica in basic medium is greatly improved owing to the ethane groups bridged in the mesoporous framework. This work also demonstrates that the phenyl-functionalized mesoporous ethane-silica spheres are excellent packing materials for potential application in the reversed-phase high-performance liquid chromatography (HPLC).