Development of electrospun PVdF–PAN membrane-based polymer electrolytes for lithium batteries

Electrospun fibrous membranes of composites of polyvinylidene fluoride and polyacrylonitrile (PVdF–PAN–ESFMs) are prepared with different proportions of PAN (25, 50 and 75%, w/w). The morphology of the ESFMs is examined by field emission scanning electron microscopy (FESEM). FESEM image of PVdF–ESFM reveals that the fibers have uniform diameters and smooth surfaces. However, the fibers of PVdF–PAN–ESFMs are interconnected with large number of voids and cavities of different sizes. These voids are effectively utilized for the preparation of polymer electrolytes by loading lithium perchlorate dissolved in propylene carbonate. PVdF–PAN–ESFM with 25% PAN (designated as PVdF–PAN(25)–ESFM) could load a high amount of lithium salt with electrolyte uptake of more than 300%. PVdF–PAN(25)–ESFM electrolyte exhibits a high conductivity of 7.8 mS cm⁻¹ at 25 °C and electrochemically stable up to 5.1 V. Also, the addition of PAN into PVdF decreases the interfacial resistance with lithium electrode. PVdF–PAN–ESFM electrolytes have complementary advantageous characteristics of PVdF and PAN. The promising results reported here clearly indicate that polymer electrolytes based on PVdF–PAN–ESFMs are most suited for lithium batteries.     

Plastic–polymer composite electrolytes: Novel soft matter electrolytes for rechargeable lithium batteries

We present here a soft matter solid composite electrolyte obtained by inclusion of a polymer in a semi-solid organic plastic lithium salt electrolyte. Compared to lithium bis-trifluoromethanesulfonimide-succinonitrile (LiTFSI-SN), the (100 − x)%-[LiTFSI-SN]: x%-P (P: polyacrylonitrile (PAN), polyethylene oxide (PEO), polyethylene glycol dimethyl ether (PEG)) composites possess higher ambient temperature ionic conductivity, higher mechanical strength and wider electrochemical window. At 25 °C, ionic conductivity of 95%-[0.4 M LiTFSI-SN]: 5%-PAN was 1.3 × 10⁻³ Ω⁻¹ cm⁻¹ which was twice that of LiTFSI-SN. The Young’s modulus (Y) increased from Y → 0 for LiTFSI-SN to a maximum ∼1.0 MPa for (100 − x)%-[0.4 M LiTFSI-SN]: x%-PAN samples. The electrochemical voltage window for composites was approximately 5 V (Li/Li⁺). Excellent galvanostatic charge/discharge cycling performance was obtained with composite electrolytes in Li|LiFePO₄ cells without any separator.     

Reasons for the effect of the amount of electrolyte on the performance of lithium–sulfur cells

As is known, the depth of the electrochemical reduction of sulfur and lithium polysulfides, the reduction rate, and the cycle life of lithium–sulfur cells decrease with the electrolyte content. The present paper studies the reasons for the effect of the amount of electrolyte on the depth of sulfur reduction and the cycle life of lithium–sulfur cells. The main reason for the effect of the amount of electrolyte on the depth of the electrochemical reduction of sulfur was shown to be the generation of solvate complexes of lithium polysulfides. The minimum amount of electrolyte required for complete reduction of sulfur during the discharge of lithium–sulfur cells is determined by the composition of the generated solvate complexes of lithium polysulfides. The solvate numbers of the lithium ion in the solvate complexes of lithium polysulfides generted in sulfolane electrolyte systems were evaluated from the experimental data. An analysis of the results shows that the minimum solvate number of lithium ions in the solvate complexes of lithium polysulfides with sulfolane is 1.     

Influence of the synthesis parameters on the thermal behavior of some ZnO–starch composites

Ten ZnO–starch composites were synthesized using a simple precipitation methodology. The IR spectroscopy and XRD investigations reveal the presence of amorphous starch and crystalline ZnO. The obtained composites present a spherical morphology, 5–8 spheres being interconnected into aggregates. The thermal analysis demonstrates that starch decomposition and ZnO thermally induced nucleation and crystal growth depending on the synthesis parameters such as starch processing (dissolution or gelatinization), reaction temperature (80, 90, and 100 °C), reaction time (15 min or 6 h), and applied treatments (heating or ultrasound irradiation).     

New polymer electrolytes based on polyethylene glycol diacrylate–LiBF4–1-ethyl-3-methylimidazolium tetrafluoroborate with the introduction of alkylene carbonates

Russian Chemical Bulletin - Polymer gel electrolytes based on polyethylene glycol diacrylate (PEG DA), salt LiBF4, and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) were synthesized and...     

Investigation of double-diffusive mixed convection effect on the particles dissolution in the shear flow using coupled SPM–LBM

Journal of Thermal Analysis and Calorimetry - In the present study, double-diffusive mixed convection related to the heat and mass transfer of the solid particles dissolution in a shear flow was...     

Solid polymer electrolytes X: Preparation and characterizations of polyether–siloxane,organic–inorganic,hybrid nanocomposites complexed with lithium perchlorate

Organic–inorganic hybrid nanocomposites of poly(ethylene glycol)/siloxane were obtained via the sol–gel approach. In these composites, nanometric siloxane heterogeneity was embedded into a polymer matrix with a covalent bond at the interfaces. The ²⁹Si magic-angle spinning (MAS) spectrum exhibited a high degree of condensation through the relative abundance of T⁰ [RSi(OR)₃], T¹ [RSi(OR)₂(OSi)], T² [RSi(OR)(OSi)₂], and T³ [RSi(OSi)₃] silicone nuclei. The effect of lithium salt concentration on ionic interaction, conductivity, and thermal properties of these composite electrolytes were investigated by Fourier transform infrared spectroscopy, DSC, thermogravimetric analysis, alternating current impedance, and solid-state ⁷Li MAS NMR measurements. These observations indicated that the different types of complexes by the interactions of Li⁺ and ClO ions are formed within a hybrid host, and the formation of transient crosslinks between Li⁺ ions and the ether oxygens results in an increased glass-transition temperature of the polyether segment and decomposed rate of composite electrolyte. ⁷Li MAS NMR measurements revealed the changes in line shape of lithium resonances with different LiClO₄ contents, suggesting that a significant degree of ionic association is present in the polymer-salt complexes. The behavior of ion transport in these composite electrolytes was correlated with the interactions between ions and polymer host. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1928–1937, 2004     

Investigation of scale inhibition mechanisms based on the effect of scale inhibitor on calcium carbonate crystal forms

To probe the scale inhibition mechanisms,calcium carbonate scale occurring before and after the ad- dition of scale inhibitors was collected.The results from scale SEM confirm that,without scale inhibitor, calcium carbonate scale shows rhombohedron and hexagon,which are the characteristic feathers of calcite.After addition of inhibitors,morphology of scale is changed,and the more efficient the scale inhibitor is,the more greatly the morphology is modified.To elucidate the scale constitute,they were further analyzed by FT-IR,XRD.Besides calcite,vaterite and aragonite occur in calcium carbonate scale after addition of inhibitors,and the higher scale inhibition efficiency is,the more vaterite presents in scale.It can be concluded that the alteration of morphology is ascribed to the change of crystal form. There are three stages in the crystallizing process including occurrence and disappearing of unstable phase,occurrence and disappearing of metastable phase,development of stable phase.Without scale inhibitors,metastable phases usually transform into stable phase,thus the main constitute of formed scale is calcite.When scale inhibitors are added,both formation and transformation of metastable phases are inhibited,which results in the occurrence of aragonite and vaterite.From the fact that more vaterite presents in scale with a more efficient scale inhibitor added,we can see that the function of scale inhibitor is realized mainly by controlling the crystallizing process at the second stage.     

Investigation of the effect of finite-sized ions on the nanowire field-effect transistor in electrolyte concentration using a modified Poisson–Boltzmann model

One-dimensional (1D) nanowire field-effect transistors (FETs) have recently played a major role in sensing applications. Due to charging of the surface functional chemical groups with protonation and deprotonation, the transport properties of these nanowire transistors affect the aqueous environment, altering the electrical double layer (EDL) potential drops and charge distributions in the electrolyte concentration. In this work, we have implemented the simple modified Poisson–Boltzmann (MPB) theory in a 1D silicon nanowire FET, and the effect of the various finite sizes of ions in z:z symmetric electrolyte concentration was investigated. For a given ionic concentration and surface charge, the EDL potential drop, accumulation of charges and the charge distributions of NaCl and CsCl ions were studied. From the MPB model results with the nanowire FET, it was observed that the potential drop of the EDL depends on the size of the ions in the electrolyte. The study of various electrostatic investigations of finite-sized ions was successfully done by implementing the MPB model on a silicon nanowire FET. It can be used in both chemical and biological sensors.     

On the continuity of the diffusion behaviour at amorphous polymer–polymer interfaces on both sides of the bulk glass transition temperature

The diffusion behaviour at amorphous polystyrene (PS)–PS interfaces has been investigated over an interval of temperatures (T) from below to above the bulk glass transition temperature (T _g ^bulk) using the Arrhenius and Vogel-Fulcher approaches. No discontinuity in the variation of the logarithm of the diffusion coefficient versus 1/T has been observed when going through the PS T _g ^bulk over a broad interval of T, from T _g ^bulk???50 °C to T _g ^bulk?+?50 °C. The molecular mechanism of interdiffusion has been discussed.     

‘‘Soggy sand＇＇ polymer composite nanofber membrane electrolytes for lithium ion batteries

A kind of octanol-modifded silica nanoparticle was fabricated and employed as a framework to form‘‘soggy sand’’electrolyte along with 1-butyl-3-methylimidazolium tetrafluoroborate.‘‘Soggy sand’’and poly（vinylidene fluoride-hexafluoropropylene）composite electrolyte membranes were electrospun for the frst time.The properties of this membrane electrolyte have been evaluated by the mechanical test and electrochemical test.The Young’s modulus increased by 275%from 6.8 MPa to 25.5 MPa and the electrical conductivity increased to 7.6 10à5S/cm at 290.15 K when compared to pristine P（VdF-HFP）membrane electrolyte.The conductivity is 3.1 10à4S/cm at 323.15 K.     

Investigation of the effect of cobalt on the Ni–Al2O3 catalyst prepared by the mechanochemical method for CO2 methanation

Research on Chemical Intermediates - Various Ni–Co catalysts supported on alumina were produced by the mechanochemical technique and applied to CO2 Methanation. X-ray diffraction,...     

Dimethyl carbonate (DMC) electrolytes – the effect of solvent purity on Li–ion intercalation into graphite anodes

Graphite electrodes cycled in single solvent electrolytes based on dimethyl carbonate (DMC) exhibit surprising and unfamiliar behavior. The electrochemical performance of graphite anodes cycled vs. Li metal in DMC electrolytes, containing 1 M LiPF₆ is strongly dependent on the solvent purity. The behavior of the graphite anodes in electrolytes containing “pure” DMC is dependent mainly on the identity of the contamination present in the native solvent. It was found that methanol is causing deterioration in the electrochemical performance of the cycled graphite electrode, while carbon dioxide and mainly carbonochloridic acid methyl ester are enhancing the performance. It was established that it is essential to investigate and understand the processes and materials used during the production of battery grade solvents, in order to clarify the roll of traces of chemical compounds responsible for the variation and modification in the electrochemical behavior of the cycled electrodes.     

Beneficial effect of phase transition on kinetics of deintercalation/intercalation process in lithium–manganese spinel

Journal of Solid State Electrochemistry - In this work, a detailed characterization of LixMn2O4 spinel oxides is shown to demonstrate the correlation between the anomalous thermoelectric properties...     

Influence of polymer structure on the rheological behavior of hydroxypropylmethylcellulose–sodium carboxymethylcellulose dispersions

Aqueous dispersions of mixtures of hydroxypropylmethylcellulose (HPMC) and sodium carboxymethylcellulose (NaCMC) were prepared in accordance with a two-component simplex lattice design, using polymer varieties with different molecular weights and substitution characteristics. The resulting systems were characterized rheologically by capillary viscometry, flow rheometry, and oscillatory shear techniques, for the determination of kinematic viscosity, index of consistency, index of fluidity, elastic modulus, and viscous modulus. The values obtained for these parameters were fitted with appropriate canonical models, which revealed synergistic effects for some polymer proportions. Maximum synergy was observed when polymer proportions were optimal for the establishment of between-polymer interactions. The synergistic effects on viscosity and elasticity are attributable to the establishment of hydrophobic interactions and hydrogen bonds between HPMC and NaCMC chains, as revealed by IR spectroscopy and modifications in the cloud-point temperature. The observed among-mixture differences in the polymer proportions at which maximum synergy occurs, and the degree of this synergy, are explained by differences in molecular weights and substitution characteristics, and indeed the degree of synergy (as measured by interaction parameters from the fitted canonical models) showed strong dependence on these variables. Microviscosity values, derived from theophylline diffusion data for some of the mixtures, show that the crossover and chain expansion of the polymers in the mixtures (i.e. increased viscosity and elasticity) give rise to a three-dimensional network with greater mesh size and a more hydrophilic microenvironment, favoring solute mobility. Received: 17 July 2000 Accepted: 20 November 2000     

Investigation of the effect of berberines alkaloids in Coptis chinensis Franch on Bacillus shigae growthby microcalorimetry

The inhibitory effects of five berberines alkaloids (BAs) from rhizoma of Coptis chinensis Franch, a traditional Chinese medicinal (TCM) herb, on Bacillus shigae (B. shigae) growth were investigated by microcalorimetry. The power-time curves of B. shigae with and without BAs were acquired; meanwhile, the extent and duration of inhibitory effects on the metabolism were evaluated by growth rate constants (k1, k2), half inhibitory ratio (IC50), maximum heat output (Pmax), and peak time (tp). The values of k1 and k2 of B. shigae in the presence of the five BAs decreased with the increasing concentrations of BAs. Moreover, Pmax was reduced, and the value of tp increased with increasing concentrations of the five drugs. The inhibitory activity varied with different drugs. IC50 of the five BAs was respectively 75 μg/mL for berberine, 90 μg/mL for coptisine, 115 μg/mL for palmatine, 220 μg/mL for epiberberine, and 400 μg/mL for jatrorrhizine. The sequence of antimicrobial activity of the five BAs: berberine > coptisine > palmatine > epiberberine > jatrorrhizine. The functional groups methylenedioxy at C2 and C3 on phenyl ring improve antimicrobial activity more strongly than methoxyl at C2 and C3 on phenyl ring. However, the effect of bacteriostasis is not significant with methylenedioxy or methoxyl at C9 and C10 on phenyl ring.     

The effect of gypsum on the hydration of alite–belite–ferrite phase system

Journal of Thermal Analysis and Calorimetry - Thermal analysis is a very effective method for the study of the hydration process of cement. This paper focuses on the interactions between the...     

Effects of heat–moisture treatment on organic cassava starch

Organic foods and crops are produced throughout the world under strict controls on growing conditions, so that synthetic chemicals, irradiation or genetic modifications are avoided. Organic starch is extracted following the same rules. Heat–moisture treatment (HMT) on starch is a physical method considered to be natural: it consists of heating starch at a temperature above its gelatinisation point with insufficient moisture (<35 %) to cause gelatinisation. Samples of organic cassava starch (with 12.8 % moisture) were dried in an oven with forced air circulation at 50 °C for 48 h and, immediately, distilled water was added to each sample until it reached the ratios of 10, 20, and 30 %, respectively. The samples were transferred into 100 mL pressure flasks, sealed tightly with a cap, and maintained in an autoclave for 60 min at 120 °C. The flasks were opened and the samples were kept in a desiccator containing anhydrous calcium chloride up to constant mass. The effects of HMT were studied using the following techniques: thermogravimetry and derivative thermogravimetry (TG/DTG), differential scanning calorimetry (DSC), rapid viscoamylographic analysis (RVA), reflectance photocolorimetry, atomic force microscopy (NC-AFM) and X-ray diffractometry (XRD). Rheological properties such as the pasting temperature (RVA) and the peak temperature (DSC) increased, while gelatinisation enthalpy ?H (DSC) decreased. The average diameters of the granules showed no significant changes, while the degree of relative crystallinity decreased.     

Investigation of interface compatibility in stiff polymer/metal–organic frameworks

Polymers with excellent comprehensive performance toward enhanced stability and mechanical strength are attractive for matrix loading of tunable porous and inherently brittle metal?organic frameworks (MOFs). Polyethersulfone (PES) with high mechanical strength (elastic modulus = ~2.6 GPa) is one of the best polymeric materials widely applied in gas and liquid separations but hindered by its ability to adhere to MOFs surface. The combination of the interface width, porosity, atomic density, and hydrogen bonding number and strength strongly influences MOFs/PES compatibility. ZIF-8 is one of the most frequently investigated MOFs, and exhibits excellent interface compatibility with PES, which is confirmed by both computational and experimental analyses. The desired porosity and adsorption properties of ZIF-8 are retained in ZIF-8/PES composites. This study sheds light on the theoretical understanding and characterization of hybrid material systems with diverse differences between brittle MOFs and stiff polymers.