Ionic conductivity and spectroscopic characterisation of γ-LiAlO2-filled polymer electrolytes

Spectroscopic characterisation of γ-LiAlO₂ composite polymeric electrolytes based on poly-(ethylene oxide)(PEO)/perfluorinated polyphosphazene blends and LiPF₆ as electrolyte was studied by means of FTIR and X-ray spectroscopy. Ionic conductivity was analysed by using complex impedance. A parallel study was made on samples containing propylene carbonate as plasticizer instead of γ-LiAlO₂. The results obtained indicate, in a first approximation, that there is a drastic change in PEO morphology resulting from the co-ordination with the lithium salt and, at the same time, that the morphology of the composite polymer electrolytes is dependent on the nature of the polymer host. Complex impedance data show that the incorporation of γ-LiAlO₂ enhances the ionic conductivity of the composite polymer electrolyte, a reverse behaviour is found for the composite systems plasticized with PC.     

Preparation of γ-LiAlO2 green bodies through the gel-casting process

An aqueous gel-casting process using methacrylamide (MAM) as monomer and N,N′-methylenebisacrylamide (MBAM) as crosslinker was developed for γ-LiAlO₂ ceramics. The precursor γ-LiAlO₂ powder with mean particle size of 3.4 μm was synthesized via solid-state reaction process. The zeta potential of the γ-LiAlO₂ powders in deionized water and viscosity of the slurries with different solid loadings were measured. It was found that the solid loading of the γ-LiAlO₂ slurry that met the requirement of gel-casting could reach 56 vol.%. The effects of pH values and the kind of initiator on the copolymerization of MAM/MBAM were investigated. The green bodies with the binder content of 5.3 wt% exhibited a compressive strength of 12.6 MPa and a yield point as high as 6.4 MPa. SEM results revealed homogeneous and compact morphology of the green bodies. In addition, the compressive strength of the sintered γ-LiAlO₂ bodies were studied simultaneously.     

Morphological characterization of γ-LiAlO2-filled composite polymer electrolytes containing LiPF6

Morphological properties of composite polymer electrolytes based on blends of polyethylene oxide (PEO) and a perfluorinated polyphosphazene (PPz) containing LiPF₆ as lithium salt and a finely divided ceramic filler, γ-LiAlO₂, were studied by using polarizing optical microscopy and differential scanning calorimetry (DSC). A parallel study was performed on propylene carbonate plasticized composite polymer electrolytes. Results indicate that both the morphology and the thermal properties depend upon the composition of the polymer host, a result not observed in composite polymer electrolytes having the same polymer composition containing LiCF₃SO₃ as lithium salt. The incorporation of the ceramic filler at the lower concentration tested (10% by wt) has practically no effect on the thermal behavior of the samples; whereas, differences were clearly distinguished at a concentration of ceramic material of 20 wt %. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1023–1030, 1999     

Rheology and chemorheology of aqueous γ-LiAlO2 slurries for gel-casting

The rheological and chemorheological properties of aqueous γ-LiAlO₂ slurries for gel-casting as well as their precursor solutions of methacrylamide and N,N′-methylenebisacrylamide (MAM/MBAM) were studied in the present work. The influences of mean particle size of γ-LiAlO₂ powder, the dispersant content and solid loading, mechanical stirring time on the rheology of γ-LiAlO₂ slurries were investigated systematically. It was demonstrated that the slurries exhibited shear-thinning behaviors with relatively low viscosity which could satisfy the gel-casting process. A rotary rheometer was used to study the chemorheology of the copolymerization of MAM/MBAM solution and the gelation process of γ-LiAlO₂ slurries. The activation energy calculated from the idle time for MAM/MBAM solutions and γ-LiAlO₂ slurries were 27.5 ± 0.4 kJ/mol and 25.3 ± 0.4 kJ/mol, respectively, which revealed the catalytic effect of the γ-LiAlO₂ particles on the copolymerization process.     

An aqueous gel-casting process for γ-LiAlO2 ceramics

Methyl cellulose (MC) was used as the gelation agent in the gel-casting of γ-LiAlO₂ because it could form strong gels during heating. The thermal gelation behavior of the MC solution was studied based on the measurement of its apparent viscosity as a function of temperature. The effects of MC solution concentration and solid loading on the rheological properties of the γ-LiAlO₂ slurries were studied systematically. It was found that all the slurries exhibited a shear-thinning behavior, which was considered to be favorable for the casting process. The compressive strength and relative density of the dried γ-LiAlO₂ green bodies were measured, and the microstructure of the green and sintered bodies was investigated.     

Processing and microstructure of γ-LiAlO2 ceramics

γ-LiAlO₂ ceramics with different grain sizes were prepared by controlling the sintering process and regulating the size and shape of the precursor powders. It was found that a size gradation of powders promoted the growth of γ-LiAlO₂ grains. Ceramics with an average grain size of 10 μm were prepared from the size-graded powders. It was demonstrated that the shape of the precursor powders greatly affected the grain growth of the ceramics whereas the granulation of the powders restrained the abnormal grain growth. Furthermore nano-sized precursor powders obtained by a sol–gel route made it possible to prepare nano-structured γ-LiAlO₂ ceramics.     

Rheological behavior of aqueous polymer-plasticized γ-LiAlO2 pastes for plastic forming

The rheological properties of aqueous methylcellulose (MC) plasticized γ-LiAlO₂ pastes with high solid loading were investigated.     

Solid polymer electrolytes of blends of polyurethane and polyether modified polysiloxane and their ionic conductivity

Polymer electrolytes based on thermoplastic polyurethane (TPU) and polyether modified polysiloxane (PEMPS) blend with lithium salts were developed via an in-situ polymerization of TPU with the presence of PEMPS and salts. Morphological study of TPU/PEMPS electrolytes showed that TPU and PEMPS were immiscible and TPU/PEMPS electrolytes had a multiphase morphology. The lithium salt enhanced the interfacial compatibilization between TPU and PEMPS via the interaction of lithium ions with different phases. Three lithium salts with different interaction strengths with TPU and PEMPS were used to prepare TPU/PEMPS electrolytes with different levels of phase compatibilization: LiCl, LiClO₄, and LiN(SO₂CF₃)₂ (LiTFSI). The effect of PEMPS on ionic conductivity, dimensional stability and thermal stability of TPU/PEMPS electrolytes and their relationship with the blend morphology were investigated. TPU/PEMPS electrolytes showed good dimensional stability and thermal stability. The addition of PEMPS to TPU increased the ionic conductivity of TPU/PEMPS electrolytes. The room temperature ionic conductivity of TPU/PEMPS electrolytes with LiTFSI can reach up to 2.49 × 10⁻⁵ S/cm.     

Preparation and characterization of gel polymer electrolyte based on PVA-K2CO3

ABSTRACT

In this study, electrolyte materials were synthesized by mixing a highly conducting salt (K₂CO₃) with the poly(vinyl alcohol) (PVA) in different proportions (from 10 to 50 wt.%). The synthesized electrolyte was characterized using Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) for their functional groups, morphology, thermal stability, glass transition temperature (T_g ), ionic conductivity, and potential window, respectively. Characterization results show that the complex formation between PVA and K₂CO₃ salt has been established by FTIR spectroscopic study, which indicates the detailed interaction between PVA and the salts in PVA-K₂CO₃ composites while the amorphous nature of the electrolyte after incorporation of the salts has been confirmed by FESEM analysis. Similarly, TGA and DSC analysis revealed that both decomposition temperature and T_g of the synthesized electrolytes decrease with the addition of K₂CO₃ due to the strong plasticizing effect of the salt. The results confirm that the electrolytes have sufficient thermal stability for supercapacitor operation, as well as an amorphous phase to effectively deliver high ionic conductivity. The highest ionic conductivity of 4.53 × 10^?3 S cm^?1 at 373 K and potential window of 2.7 V was exhibited by PK30 (30 wt.% K₂CO₃), which can be considered as high value for solid-state electrolytes which are superior to those electrolytes from PVA salts earlier reported. The results similarly show that the prepared electrolyte is temperature-dependent as conductivity increase with increase in temperature. Based on these properties, it can be imply that the PVA-K₂CO₃ gel polymer electrolyte (GPE) could be a promising electrolyte candidate for EDLC applications. The results indicate that the PVA-K₂CO₃ as a new electrolyte material has great potential in practical applications of portable energy-storage devices.     

Soap-free emulsion polymerization of n-butyl acrylate: Copolymerization with 1,1-(dimethyl)-1- (3-methacryloxyethyl)-1-(sulfopropyl)ammonium betaine

Emulsifier-free emulsion polymerization of n-butyl acrylate has been performed in the presence of a polymerizable sulfobetaine monomer, 1,1-(dimethyl)-1-(3-methacryloxyethyl)-1-(sulfopropyl)ammonium betaine (SPE). An investigation of the effect of various salts (NaCl, NaHCO₃, Na₂CO₃, and NaH₂PO₄) on the emulsifier-free emulsion polymerization of n-butyl acrylate revealed that the type and quantity of salt is important in determining the size and size distribution of the final latex particles. In the case of the copolymerizations, control of the monomer feeding protocol (batch vs. semicontinuous and unseeded vs. seeded reactions) and of the ionic strength of the reaction mixture via addition of electrolytes allowed the preparation of stable latexes at 10% solids content with controllable particle size distributions. The results indicate that the amphiphilic sulfobetaine is able to stabilize the latex in much the same way as a polymerizable surfactant or an ionic comonomer. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 227–236, 1998     

Synthesis of γ-Bi2O3/YSZ composite powders using a facile precipitation method

Low melting point and high ionic conductivity of γ-Bi₂O₃ make it a promising additive to decrease the sintering and operation temperatures of yttria stabilized zirconia (YSZ)-based electrolyte for solid oxide fuel cell application. Herein, γ-Bi₂O₃/YSZ composite powders with good uniformity and precise control of morphology and phase were successfully synthesized via a low cost chemical precipitation method. Both the concentration of NaOH solution and the reactant adding sequence affect the morphology and synthesis of γ-Bi₂O₃/YSZ composite powders. When the concentration of NaOH was in the range of 1.25–1.875 M, tetrahedron γ-Bi₂O₃/YSZ powders were synthesized. While, cubic structural γ-Bi₂O₃/YSZ powders were obtained when adding Bi³⁺ and YSZ suspension into 1.5 M NaOH solution. The addition of YSZ facilitates the fabrication of γ-Bi₂O₃ and widens its process window to a higher NaOH concentration. Thus synthesized γ-Bi₂O₃/YSZ composite powders effectively decrease the sintering temperature of YSZ to 1050°C due to the uniform distribution of γ-Bi₂O₃ inside YSZ powders. This work provides a facile method to fabricate γ-Bi₂O₃/YSZ composite powder with controlled morphology and phase, which will promote the mass production of low cost YSZ-based electrolyte for SOFC applications.     

Composite alkaline polymer electrolytes and its application to nickel-metal hydride batteries

In order to enhance the ionic conductivity of polyethylene oxide (PEO)-KOH based alkaline polymer electrolytes, three types of nano-powders, i.e., TiO₂, β-Al₂O₃ and SiO₂ were added to PEO-KOH complex, respectively, and the corresponding composite alkaline polymer electrolytes were prepared. The experimental results showed that the prepared polymer electrolytes exhibited higher ionic conductivities at room temperature, typically 10⁻³ S cm⁻¹ as measured by ac impedance method, and good electrochemical stability. The electrochemical stability window of ca. 1.6 V was determined by cyclic voltammetry with stainless steel blocking electrodes. The influence of the film composition such as KOH, H₂O and nano-additives on ion conductivity was investigated and explained. The temperature dependence of conductivity was also determined. In addition, polyvinyl alcohol (PVA)-sodium carboxymethyl cellulose (CMC)-KOH alkaline polymer electrolytes were obtained using solvent casting method. The properties of the polymer electrolytes were characterized by ac impedance, cyclic voltammetry and differential thermal analysis methods. The ionic conductivity of the prepared PVA-CMC-KOH-H₂O electrolytes can reach the order of 10⁻² S cm⁻¹. The effect of CMC addition on the alkaline polymer electrolytes was also explained. The experimental results demonstrated that the PVA-CMC-KOH-H₂O polymer electrolyte could be used in Ni/MH battery.     

Salt‐Induced Modulation of the Krafft Temperature and Critical Micelle Concentration of Benzyldimethylhexadecylammonium Chloride

In this work, the effect of some sodium salts on the Krafft temperature (T_K) and critical micelle concentration (CMC) of benzyldimethylhexadecylammonium chloride (C16Cl) in aqueous solution has been studied. It was observed that the T_K can be modulated to lower and higher values and the CMC can be depressed significantly upon the addition of the electrolytes. More chaotropic Br^? and I^? raise the T_K with an increase of the concentration of the ions. On the other hand, less chaotropic NO₃^? initially lowers and then raises the T_K. Kosmotropic F^?, SO₄^2? and CO₃^2? gradually lower the T_K with increasing concentration of the electrolytes. The more chaotropic ions form contact ion pairs with the surfactant and decrease the solubility with a consequent increase in the T_K. On the other hand, kosmotropic ions, being extensively hydrated in the bulk, remain separated from the surfactant by hydrated layers of water molecules. As a result, a significant electrostatic repulsion exists between the charged headgroups of the surfactant, resulting in a decrease in the T_K. The CMC of the surfactant decreases significantly in the presence of these ions. The surface tension at the CMC (γ_CMC) also decreases in the presence of all the salts except for F^?. The electrostatic repulsion between the charged headgroups is significantly reduced because of screening of the surface charge of both micelles and adsorbed monolayers by the associated counterions, resulting in a decrease in both the CMC and γ_CMC.     

FT-IR studies on interactions of AlCl3 with PEO-NaSCN polymer electrolytes

Solid polymer electrolytes are potentially useful electrolytes to be applied in high-energy batteries. In the present work, a novel polymer electrolyte, polyethylene oxide (PEO)-NaSCN-AlCl₃, was prepared and investigated by FT-IR spectroscopic techniques. Based on the FT-IR data, the bands in the CN stretching envelope have been assigned and the effect of AlCl₃ on ion-ion and ion-polymer interactions in the polymer electrolyte has been examined. It is shown that the Lewis acid-base interaction of AlCl₃ with SCN¹⁻ leads to the formation of the complex anions AlCl₃SCN⁻ and Al₂Cl₆SCN⁻, depending on the content of AlCl₃ and/or NaSCN in PEO; the preferential interactions of AlCl₃ with crystal complex P(EO)₃NaSCN occur in PEO-NaSCN-AlCl₃ electrolytes; the AlCl₃-NaSCN complex anions can play a plasticization role in PEO-NaSCN-AlCl₃ electrolyte, and are expected to be a important factor to improve the conductivity and to enhance the cation transference number. In addition, the interactions between AlCl₃ and ether oxygen of PEO were analyzed, and their effect on ionic association was also discussed.     

Effect of γ-LiAlO2 powder on ionic conductivity of coexisting single alkali carbonates

The electrical conductivity of alkali molten carbonates coexisting with γ-LiAlO₂ powders have been measured by ac impedance method. The temperature and composition dependence of the electrical conductivity are investigated. The effects of the solid phase upon the ionic species are discussed. The electrical conductivity varies with the liquid content and drastically increases at ca. 30 vol.%. The Arrhenius plot shows an increase of the electrical conductivity with increasing temperature. A significant value of the electrical conductivity below the salt melting point is observed. This indicates the existence of a non-frozen phase assuming conduction within the system. The activation energy increases with a decrease of apparent average thickness of the liquid layer. The influence of the solid system is conspicuous in Na₂CO₃ mixtures rather than in K₂CO₃ or Li₂CO₃ one. This shows that the order of magnitude of perturbations by the solid phase depends also on the cationic species associated within the system.     

A nickel tetra-coordinated complex as catalyst in heterogeneous hydrogenation

The [NiCl₂(NH₂(CH₂)₁₂CH₃)₂] complex supported on γ-Al₂O₃ produces a catalyst which is considerably more active and sulfur-resistant for the hydrogenation of cyclohexene carried out in mild conditions than a conventional catalyst obtained from acid solutions of NiCl₂ and even than the same complex unsupported. As determined by XPS, the active species is the complex itself, which is stable under the reaction conditions. The higher sulfur-resistance is attributed to electronic and geometrical effects. The catalyst system is considerably more resistant to poisoning with thiophene than with tetrahydrothiophene. © 1998 SCI     

One-step aromatic acids assisted synthesis of γ-Fe2O3 nanoparticles with large surface area by thermal decomposition of ferric nitrate

Maghemite (γ-Fe₂O₃) has attracted much attention due to its variety of applications in many areas. However, the current preparation methods of γ-Fe₂O₃ still involve complicated processes and a high cost, thereby needing improvement. In this study, a novel and facile one-step solid-state method for the preparation of γ-Fe₂O₃ nanoparticles (NPs) is performed through the thermal decomposition of ferric nitrate (Fe(NO₃)₃?9H₂O) and the addition of aromatic acids. Three aromatic acids that have different numbers of carboxyl groups (i.e., benzoic acid, phthalic acid, and trimesic acid) are used as additives and their effects on the formation of γ-Fe₂O₃ NPs are investigated. Furthermore, the influence of the aromatic acid/Fe(NO₃)₃?9H₂O mass ratio and calcination temperature on the structural properties of the products are investigated. The structural properties, morphology, and magnetic properties of the products are analyzed through X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption/desorption measurements, and magnetic measurements. The results show that the addition of aromatic acids to Fe(NO₃)₃?9H₂O leads to the formation of γ-Fe₂O₃ NPs, and has a significant influence on the morphology of γ-Fe₂O₃ NPs. When the aromatic acid/Fe(NO₃)₃?9H₂O mass ratio is greater than 0.5, the addition of the three aromatic acids leads to the formation of pure γ-Fe₂O₃. The γ-Fe₂O₃ NPs obtained from benzoic acid/Fe(NO₃)₃?9H₂O and phthalic acid/Fe(NO₃)₃?9H₂O systems do not show a well-defined morphology. In contrast, the γ-Fe₂O₃ NPs obtained from the trimesic acid/Fe(NO₃)₃?9H₂O system are composed of a porous three-dimensional hierarchical structure and have the largest Brunauer?Emmett?Teller surface area (100.0 m² g^?1).     

Influence of Barium Titanate on poly(vinyl pyrrolidone)‐based composite polymer blend electrolytes for lithium battery applications

Nanocomposite polymer blend electrolytes based on poly (ethylene oxide), poly (vinyl pyrrolidone) that contained lithium perchlorate as a dopant, propylene carbonate (PC) as a plasticizer and Barium Titanate (BaTiO₃) as a filler were prepared for various concentrations of BaTiO₃ using solvent casting technique. The structural and complex formations of the composite electrolyte membranes were confirmed by X‐ray diffraction and FTIR analysis. The addition of BaTiO₃ nanofillers improved the ionic conductivity of the polymer electrolytes to some extent when the content of the BaTiO₃ is 10 wt%. The addition of BaTiO₃ also enhanced the thermal stability of the electrolyte. The surface morphology of the sample having a maximum ionic conductivity was studied by AFM. Molecular motion in the polymeric media was supported by fluorescence studies. The charge transfer arises between the polymer blend and Li‐ions were confirmed by UV‐Vis analysis. POLYM. COMPOS., 36:302–311, 2015. © 2014 Society of Plastics Engineers     

Effect of reaction kinetics of polymer electrolyte on the ion‐conductive behavior for poly(oligo oxyethylene methacrylate)–LiTFSI mixtures

The effect of the reaction kinetics on the ionic conductivity for a comblike‐type polyether (MEO) electrolyte with lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) was characterized by DSC, complex impedance measurements, and ¹H pulse NMR spectroscopy. The ionic conductivity of these electrolytes was affected by the reaction condition of the methacrylate monomer and revealed by the glass transition temperature (T_g), spin–spin relaxation time (T₂), steric effects of the terminal groups, and the number of charge carriers indicated by the VTF kinetic parameter. In this system, the electrolytes prepared by the reaction heating rate of 10°C/min of MEO–H and 15°C/min of MEO–CH₃ showed maximum ionic conductivity, σ_i, two to three times higher in magnitude than that of the σ_i of the others at room temperature. As experimental results, the reaction kinetic rate affected the degree of conversion, the ionic conductivity, and the relaxation behaviors of polyether electrolytes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2149–2156, 2003     

Carbon nanotubes embedding organic ionic plastic crystals electrolytes for high performance solid-state dye-sensitized solar cells

Carbon nanotubes (CNTs) embedding organic ionic plastic crystals electrolytes were prepared and characterized by thermal analysis and scanning electron microscopy to investigate the influence of CNTs contents on the thermal properties and surface morphology. The investigation showed the addition of CNTs had little effect on the melting points and solid–solid phase transition properties of the plastic crystals electrolytes. However, with CNTs increasing, the solid-state electrolytes produced more defected/amorphous regions, resulting in better ionic conductivity and diffusion coefficients of I⁻ and I₃⁻. Furthermore, based on these solid-state electrolytes, the resulting solid-state dye-sensitized solar cell exhibited maximal power conversion efficiency of 5.60%, and displayed much more excellent long-term stability than that of referenced ionic liquids-based device. These results offer us a feasible method to develop more excellent plastic crystals electrolytes for high performance solid-state dye-sensitized solar cells.