最新刊期
卷 ， 期 11 ， 2015
- 摘要：This manuscript reviews the latest progress to characterize the uniformity of lamellar thickness,the tensile behavior and the uniformity of cavitation during stretching of the casting film,and further to predict the pore size distribution and thickness distribution of the final separator.Five -PP precursor films,which had similar crystallinity and extremely high contents of -crystals,but different lamellar thickness distribution,were prepared through crystallizing at different temperatures.In the tensile test,we first discovered a peculiar double yield phenomenon in -PP under tensile loading.Based on the detailed characterization of morphological evolution during stretching,we concluded that the second yield point corresponds to the transition point where the lamellae began to transform into amorphous phase.Meanwhile,a narrower -lamellar thickness distribution would result in a homogeneous deformation,delayed occurrence of second yield point and a more uniform pore size distribution in the porous membrane.In addition,the stress-strain behaviors of -PP after annealing treatments also verified the trend above.Therefore,the uniaxial tensile testing can be used to evaluate the lamellar thickness distribution of -PP cast films efficiently.关键词：-Nucleated polypropylene;Double yielding behavior;Lamellar thickness distribution;Pore size distribution
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发布时间：2021-03-19
Feature Articles
- 摘要：In recent years,lithium batteries have attracted extensive interest owing to their recent application in large scale energy storage systems such as electric vehicles (EVs) and smart grids.However,the conventional microporous polyolefin separators suffer from a poor thermal shrinkage at relatively high temperatures above 90 ℃,which has raised serious concern over their ability to prevent internal electrical short circuit at high temperature conditions.As a kind of thermosetting polymer material,cellulose is one of the most abundant,renewable resources on the Earth and possesses outstanding properties such as biocompatibility,desired chemical stability and high decomposition temperature of above 270 ℃.The abundance,renewable and superior thermal stability could qualify cellulose a very promising material for battery application instead of fossil-based chemicals.Herein,the recent progress of cellulose-based composite separators for high power lithium ion batteries in literatures is briefly reviewed.The perspective and research frontiers in this fascinating field are presented as well.关键词：Lithium ion batteries;Separator;Cellulose;Composite
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发布时间：2021-03-19 - 摘要：Lithium-Sulfur (Li-S)batteries are considered to be one of the most promising new types of high performance batteries because of their high theoretical capacity and energy density,which have the advantages of rich raw materials,good environmental protection and low cost.Li-S batteries are mainly composed of the cathode material,anode material,electrolyte and separator.And separator is one of the important parts of Li-S batteries,whose performance has great effect on the overall performance of batteries.In this paper,the developments of high quality separator materials of Li-S batteries are reviewed,including polyolefin,polyethylene oxide (PEO),polyvinylidene fluoride (PVDF),various blending polymer and nanofiber separators,and the development trends of separator materials for Li-S batteries are also prospected.Research results showed that the properties of Li-S batteries,including charge discharge capacity,cycle performance,ionic conductivity and coulomb efficiency could be improved and promoted by the preparation and modification of the separators.The separators prepared by electrospinning method were studied primarily as the Li-S battery separators because of the excellent pore structure.We believe that the nanofiber porous membranes will become a hotspot in the application and research of separator materials for lithium sulfur batteries because of their excellent pore structure and gelation characteristics.关键词：Lithium-Sulfur batteries;Separator materials;Modification;Nanofiber
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发布时间：2021-03-19 - 摘要：With the rapid development of science and technology nowadays,Li-ion battery,as one kind of green batteries,has been an important approach for energy storage and indispensible for mobile information and daily life as well.eparator is a necessary component of Li-ion battery.It is a physical barrier between the positive and negative electrodes preventing electrical short circuits,the transport of ions making the charging and discharging cycles available.Therefore,the separator has critical effect on the performance and safety of Li-ion batteries.In order to understand the tendency of technology for separator preparation all over the world and in China,the relevant patents (2005 to 2014) from the Derwent Innovations Index and the Patent Search and Service System of SIPO are reviewed.关键词：Li-ion battery;Separator;Patents
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发布时间：2021-03-19
Reviews
- 摘要：Poly(vinylidene fluoride) (PVDF)/poly(vinylidene fluoridehexafluoropylene) (PVDF-HFP) monolayer nanofibrous membrane and PVDF/PVDF-HFP/Al2O3 multilayer composite nanofibrous membranes were successfully prepared by the electrospinning method.The surface morphology,crystallinity,dimensional thermal stability,and electrochemical properties of the composite nanofibrous membranes were characterized by scanning electron microscopy (SEM),differential scanning calorimetry (DSC),thermal shrinkage and alternating current (AC) impedance.The smooth surface and uniform distribution fibers morphology were obtained for the PVDF/PVDF-HFP monolayer nanofibrous membrane.This membrane are made of fibers of 2 m diameter.The coarse surface and thinner fiber diameter were observed for the composite membrane.Moreover,the composite membrane exhibits lower crystallinity and higher electrolyte uptake than PVDF/PVDF-HFP monolayer nanofibrous membrane.The dimensional shrinkage of PVDF/PVDF-HFP/Al2O3 bilayer composite membrane is 3% at 170 ℃ for 1 h.Polymer electrolytes were prepared by immobilizing 1 mol/L LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC)/diethyl carbonate(DEC) in the membranes.The PVDF/PVDF-HFP/Al2O3 bilayer composite membranes exhibit a high electrolyte uptake of 497 wt%.The ion conductivity of the bilayer composite polymer electrolyte is 5.0410-3 S/cm at 25 ℃.Meanwhile,it has electrochemical stability at potentials higher than 4.6 V versus Li/Li+.The three types of membranes were assembled with lithium iron phosphate (LiFePO4)/Li coin cells.The cell based on the PVDF/PVDF-HFP/Al2O3 bilayer composite electrolyte presents good rate capabilities over various discharge current densities.The PVDF/PVDF-HFP/Al2O3 bilayer composite electrolyte has better compatibility and interface stability with lithium metal.关键词：Electrospinning;Composite nanofibrous membrane;Lithium ion battery;Interface stability
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发布时间：2021-03-19 - 摘要：A series of sulfonated poly(ether ether ketone) (SPEEK) and graphene oxide (GO) blend membranes were prepared with various mixing mass ratios.The water uptake,ion exchange capacity,proton conductivity,vanadium ion permeability,mechanical properties and chemical stability were measured.The blend membranes were characterized by FTIR,SEM and TG.The blend membranes exhibit higher water uptake and ion exchange capacity and lower vanadium ion permeability than Nafion115 membranes,the ion exchange capacity decreases with the increase of GO content.The VO2+ permeability of the blend membranes decreased,while mechanical properties increased with increasing GO content.Random embedding of GO in the membranes can block the transport of vanadium ions effectively,resulting in vanadium ion permeability of the blend membranes decreased obviously.In VRB single cell test,the blend membranes showed higher energy efficiency (EE) compared with Nafion115 membrane,the EE of S/GO-2 (GO,2 wt%) blend membrane was 80% which increased by 9% compared to that with Nafion115.The S/GO blend membranes showed stable performance up to 100 cycles test.The experimental results indicate that the S/GO blend membranes show favorable development prospects for VRB.关键词：Sulfonated poly(ether ether ketone);Graphene oxide;Vanadium redox flow battery;Vanadium ion permeability;Battery efficiency
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发布时间：2021-03-19 - 摘要：Seven kinds of polypropylene (PP) composite separators were prepared by coating PP separators with inorganic particles such as aluminum oxide (Al2O3),barium sulfate (BaSO4),lead zirconate titanate (PZT),titanium dioxide (TiO2),fumed silica R202 (RSiO2),A380 (ASiO2) and precipitated silica (PSSiO2).The morphology study showed that uniform coating layers were formed on the PP separators.Compared with the bare PP separator,the permeability of the composite separators decreased a little,while the thermal stability improved greatly.The effects of coating layer on the electrochemical stability of the electrolyte were also investigated by linear sweep voltammetry (LSV) and it was found that the coating material didn't deteriorated the performance of the electrolyte.The cycling performance of the cells showed that the capacity of cells increased by more than 20 mAh/g for almost all kinds of composite separators and could retain the advantage at a high discharge rates of 2 C (except for ASiO2).However,for the cells with ASiO2 composite separators,the capacity decayed very rapidly at the rate of 2 C.We attributed the rapid capacity decay to the too large specific surface area and lots of silicon hydroxyls on the surface of ASiO2,which increased the transport resistance of the lithium ion.关键词：Lithium-ion battery;Inorganic coating;Composite separator
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发布时间：2021-03-19 - 摘要：Organic/PP composite separators were prepared by coating polymers (PVDF,PTFE,PEK-C,PES and PPSU),which are of high temperature resistance,onto uniaxially stretched PP separators.The porous coating layers of PVDF,PEK-C,PES and PPSU were obtained by phase inversion method.And PTFE coating layer were formed by coating a suspension of PTFE nanoparticles.It could be found by SEM that pores were formed in the inter-particle area when the PTFE deposited on surface of the bare PP separator.The permeability and thermal stability of the composite separators were studied.It could be found that although the permeability of the organic composite separators decreased slightly,the thermal shrinkage properties could improve obviously,which meant that organic coating layers were helpful for improving the thermal stability of the composite separators.Linear sweep voltammetry was measured and showed that the composite separators were stable in the electrochemical window for lithium-ion batteries.The organic/PP composite separators were also used to assemble cells and evaluated by the charge and discharge performance.Cycle performance showed that the cells with composite separators had higher discharge capacity and better rate discharge performance than those cells with bare PP separator.We attributed the improvement of discharge capacity and rate discharge performance to the better wetting ability of the electrolyte to the composite separators.关键词：Organic composite separator;Lithium-ion battery;Polypropylene separator
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发布时间：2021-03-19 - 摘要：For the purpose of improving the safety of lithium-ion batteries,polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) porous layers were coated onto both sides of polyethylene (PE) separators by immersion-precipitation process.The effect of differences in solubility parameters () between solvent and composite non-solvent on the structure of the coating layer was studied by varying the strong non-solvent/weak non-solvent ratio in order to prepare a coating layer with porous structure,which is beneficial to reduce thermal shrinkage of composite separator and to improve electrochemical properties of the lithium-ion batteries.As between the solvent (DMAc) and composite non-solvent (ethanol/water composite non-solvent,different in ratio between ethanol and water) increases,the microporous structure of coating layer becomes more developed.Taking the conceptual image of phase diagram into consideration,this is suggested to be caused by different phase separation mechanisms.Ethanol,a weak non-solvent which is against the phase separation process,just develops a dense structure.As the content of strong non-solvent (water) increases,solid-liquid phase separation takes place and it finally develops a porous layer with spherical PVDF-HFP crystallites of roughly identical size.Obvious differences in thermal shrinkage and electrochemical properties of the composite separators were observed with different structures in the coating layers.Sandwiched separators with reduced thermal shrinkage,increased conductivity,enhanced cycle and C-rate performance were prepared by this immersion-precipitation process with ethanol/water ratios 3:2 and 2:3.关键词：Composite separator;Polyvinylidene fluoride-co-hexafluoropropylene;Thermal shrinkage;Lithium-ion battery
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发布时间：2021-03-19 - 摘要：A water-based silica (SiO2) dispersion was prepared with SiO2 as ceramic particle and polyvinyl alcohol (PVA) as binder,and the composite separator for lithium-ion batteries was prepared by the introduction of SiO2 layer on both sides of polypropylene (PP) separator surface through a dip-coating process.The surface and cross-section morphology of SiO2/PVA layer were investigated,and the porous structure of pristine and composite separators was quantitatively analyzed by the porosity and the Gurley value.The contact angles of water and water-based SiO2 dispersion with and without the surfactant on PP surface were measured,and the influence of the coated layers on thermal stability,wettability,electrolyte uptake,ionic conductivity,C-rate capability and cyclability was researched.The test results showed that the coated layer had porous network structure and its thickness was only 800 nm.Owing to the introduction of the porous thin layer on PP separator surface,the porosity of the composite separator increased to 62.9% and the Gurley value of composite separator decreased to 515 s.Compared to the pristine separator,the composite separator showed not only lower thermal shrinkage but also better wettability with liquid electrolyte and higher electrolyte uptake.Furthermore,the composite separator exhibited higher ionic conductivity and better cell performance such as C-rate capability and cycle performance.关键词：Ceramic coated layers;Water-based dispersion;Porous network structure;Polypropylene separator
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发布时间：2021-03-19 - 摘要：In order to investigate the explicit self-assembly variations of the photoluminescent polymers under different micro-environments,two pH-responsive blue light emitting polymer molecular brushes (P2 and P3) were successfully synthesized through Suzuki coupling reaction and atom transfer radical polymerization.The molecular structures of polymers P2 and P3 were fully characterized by 1H-NMR,13C-NMR,elemental analysis and gel-permeation chromatograph,respectively.The Fourier transform infrared spectra of polymers P2 and P3 in thin solid films further verified the successful synthesis of polymer molecular brushes through atom transfer radical polymerization.The photophysical properties and self-assembly behaviors of polymers P2 and P3 were examined through UV-Vis absorption,photoluminescent emission spectra,dynamic laser light scattering and transmission electron microscopy under different experimental conditions.The self-assembly variations of polymers P2 and P3 in different solvents or temperatures were studied to illustrate the correlation between the morphologies of the formed vesicles and the chemical structures of the polymers.The size and morphologies of the formed vesicles from polymers P2 and P3 can be effectively tuned in a range of 2100 nm to 300 nm with the shape of sphere,spindle,hollow and nuclear-shell structure.The water solubility of polymer P3 is worse than that of polymer P2,which makes polymer P3 easier to form sphere-shaped vesicles in the mixture solvent of tetrahydrofuran and water with more water proporation.This work can serve as an excellent exploratory example for the fine self-assembly control in the blue-light emitting polymer molecular brushes with different amphipathic side chains.关键词：Blue-light;Polymer molecular brushes;Self-assemble;Vesicle;Morphologies
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发布时间：2021-03-19 - 摘要：Two kinds of substituted acetylene monomers were synthesized using propargylamine with Boc-L-alanine and acrylic acid.These two kinds of monomers were separately named as chiral monomers 1 and achiral monomers 2.Then chiral monomers 1 and achiral monomers 2 were polymerized using (nbd)Rh+[6-C6H5B-- (C6H5)3] as catalyst to obtain copolymers with Mn=2.0104,yield 60%.CD and UV-Vis spectroscopic data indicated the copolymers and homopolymers exhibited high optical activity and formed stable single helical conformation.And the achiral monomers did not affect the helical structure of the copolymers,but the optical activities and CD intensity of the copolymers were slightly lower than those of the homopolymers.The copolymer 2 was prepared in the condition of TFA/CH2Cl2,and then it was grafted to the chemical modified silica nanoparticles by the condensation reaction.The surface grafting density of the silica nanoparticles was 2.4 mol/m2,which was estimated from the thermo-gravimetric curve.Finally,the chiral fluorescent polymeric microspheres were prepared by the distillation-precipitation polymerization of N-vinylcarbazole.TEM and SEM were used to observe the surface morphology and particle size of polymeric microspheres.UV-Vis and fluorescence spectra showed the chiral fluorescent polymeric microspheres had certain fluorescence properties.They will play an important role in the field of drug delivery and biomarkers.关键词：Chiral;Polyacetylene;Helical conformation;Fluorescence;Nanoparticles
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发布时间：2021-03-19 - 摘要：A series of fluorine-containing polyurethanes (FUs) were polymerized by radical polymerization with 2,3,4,5,5,5-hexafluoro-2,4-bis(trifluoromethyl)pentyl methacrylate (FDPMA) and double bond capped polyurethane oligomer (DCU) which was synthesized by stepwise polymerization.During the polymerization process,the self-assembly behavior of FU was observed,which is attributed to the conversion of solubility of FDPMA caused by polymerization.The phenomenon in the process of FU polymerization was similar to that of typical emulsion polymerization.The blue-light effect appeared in the primary stage of polymerization,and stable emulsion formed later.The transformation of self-assembled particles during polymerization was evaluated by dynamic light scattering (DLS).It was confirmed by scanning electron microscope (SEM) that the self-assembled particles presented in FU polymerization.Moreover,the self-assembled structure was affected greatly by component contents,and could deform or re-assemble in the process of solvent extraction to various forms,such as sun-flower shape or nanowire.By transmission electron microscope (TEM),it is certified that these self-assembled particles had unambiguous core-shell structure,and could keep boundaries clearly while in mutual extrusion.The stereoscopic morphology of self-assembled structure was characterized by atomic force microscopy (AFM),showing that the ellipsoid shape appeared after the solvent extraction.The surface performance of FU was detected by contact angle tester (CA) and X-ray photoelectron spectroscopy (XPS),it was shown that FU had good hydrophobic and oleophobic performance due to the fluorine enrichment on surface.All the results above indicated that the solubility conversion of FDPMA caused by polymerization is available as an effective means to prepare and control the self-assembled structure of FU,and the product FU has good surface performance and application prospect.关键词：Fluorine-containing polyurethanes;Copolymer;Polymerization-introduced self-assembly
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发布时间：2021-03-19 - 摘要：Quaternized chitosan/alginate/CaCO3 composite microcapsules were prepared by the coacervation effect of quaternized chitosan and alginate,and in situ precipitation of CaCO3 particles.The composite microcapsules were formed in a microfluidic device based on gas-liquid shearing interaction.The effects of gas flow rate,liquid flow rate,the composition of liquid phase on the size and size distribution of the microcapsules were studied in detail.The morphology and average particle size were characterized and analyzed by 3D video microscopy and SEM.Swelling behavior of the composite microcapsules was studied in aqueous solutions with different pH values and ionic strengths.The encapsulation and release of the microcapsules for model drug were evaluated by ultraviolet spectrophotometry.The optimal conditions to preparing uniform composite microcapsules were the gas rate at 0.7 L/min,the liquid phase rate at 3 mL/h,the alginate concentration at 1.75 wt%,the quaternized chitosan concentration at 0.8 wt%,the Na2CO3 concentration at 0.8 wt% and the CaCl2 concentration at 1.75 wt%.The composite microcapsules swelled in alkaline solutions,but scarcely swelled in acidic solutions and natural water.The microcapsules presented a more efficient drug release rate in alkaline solutions and at 37 ℃.When the alginate amount during preparation of the composite microcapsules increased,the relaese rate of the microcapsules for drug decreased.关键词：Microcapsule;Gas-liquid Shearing;Natural polymer;CaCO3 particles;Swelling;Drug release
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发布时间：2021-03-19 - 摘要：Simultaneous reduction and surface functionalization of graphene oxide (GO) were realized by simple refluxing of GO with polyetheramine (Huntsman Jeffamine M-2005,abbreviation:JM-2005) without the addition of any reducing agents.The JM-2005-reduced GO sample (JM-2005-rGO) prepared via the epoxide aminolysis reaction in this work were characterized by FTIR spectroscopy,X-Ray photoelectron spectroscopy (XPS),X-ray diffraction analysis (XRD) and Raman spectroscopy.All of the above results confirmed that JM-2005 not only covalently bonded to the GO,as a functionalization moiety,but also partly restored the conjugate structure of GO,as a reducing agent.Transmission electron microscopy (TEM) revealed that JM-2005-rGO sheets were slightly wrinkled and folded on the ultrathin carbon membrane.The well-defined diffraction spots of the selected area electron diffraction (SAED) pattern confirmed the crystalline structure of JM-2005-rGO.The evolution of surface functionality during reaction made the hydrophilic GO hydrophobic,as evidenced by the good dispersion of JM-2005-rGO in toluene solvent without noticeable precipitation.Furthermore,the various amounts of JM-2005-rGO were added to the epoxy resin,producing the JM-2005-rGO/epoxy nanocomposites.The flame retardancy and thermal stability of JM-2005-rGO/epoxy nanocomposites containing various weight fractions of JM-2005-rGO were investigated by the limiting oxygen index (LOI) test and thermogravimetric analysis (TGA) in nitrogen.Significant increases in the char yield and LOI were achieved with the addition of 10 wt% JM-2005-rGO in epoxy,giving improvements of 137% and 30%,respectively.This report demonstrates a cost-effective approach to construct the functionalized graphene/epoxy nanocomposites,with reinforced properties and indicates further application in research and industrial areas.关键词：Graphene;Polyetheramine;Covalent graft;Epoxy nanocomposite;Flame-retardant
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发布时间：2021-03-19 - 摘要：A great deal of polymerizable double bond was chemically introduced onto crosslinked polyvinyl akohol (CPVA) microspheres via molecular design,and then monomer sodium p-styrenesulfonate was graft-polymerized on the surfaces of CPVA microspheres by grafting through method,resulting in the grafted microspheres CPVA-g-PSSS,which have anionic polyelectrolyte brush structure.These grafted microspheres were characterized by FTIR and scanning electron microscopy (SEM),and their zeta potential curves were determined.The grafted microspheres CPVA-g-PSSS were used for the adsorption of two basic proteins,trypsin (TRY) and lysozyme (LZM).The effects of main factors on the adsorption properties were examined,the adsorption mechanism was explored,and the adsorption thermodynamics was investigated.The results show that by using the method in this work,the graft-polymerization of SSS on the surfaces of CPVA microspheres can be realized smoothly.The anionic polyelectrolyte brush CPVA-g-PSSS possesses very strong adsorption ability for TRY and LZM by the driving of strong electrostatic interaction.The pH value of the medium affects the adsorption property greatly.The adsorption capacities of TRY and LZM on CPVA-g-PSSS first increases and then declines with the increase of pH value,and there are maximum adsorption capacities (82 mg/g for TRY and 78 mg/g for LZM) as the pH value of the medium is equal to their isoelectric points.The ion strength also affects the property of CPVA-g-PSSS microspheres for the two basic proteins.On both sides of the isoelectric point,the effects of ion strength on the adsorption capacity are opposite.The adsorption capacities of TRY and LZM decrease with the increase of the electrolyte NaCl as pH value isoelectric point,and the adsorption capacities of TRY and LZM increase with the increase of the electrolyte NaCl as pH value isoelectric point.As pH value is equal to the isoelectric point,the ion strength does not affect the adsorption capacities.During the adsorption process,the entropy of the system increases and the process is exothermic.关键词：Crosslinked vinyl alcohol;Sodium p-styrenesulfonate;Polyelectrolyte brush;Basic protein;Adsorption mechanism
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发布时间：2021-03-19
Research Article
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