Electrochemical characterizations and the effect of glycerol in biopolymer electrolytes based on methylcellulose-potato starch blend

ABSTRACT

Polymer electrolytes have been prepared by blending methylcellulose (MC)-potato starch, doped with lithium perchlorate (LiClO₄) and plasticized with glycerol. The blend of 60 wt% MC-40 wt% starch was found to be the most suitable ratio to serve as polymer host. Fourier transform infrared (FTIR) spectroscopy analysis proved the interaction among the components. X-ray diffraction (XRD) analysis indicated that the conductivity enhancement is due to the increase in amorphous content. The highest ionic conductivity obtained at room temperature was (4.25 ± 0.82) × 10^?4 S cm^?1 for MC-starch-LiClO₄-20 wt% glycerol. The highest conducting samples in both systems were found to obey Arrhenius rule. Dielectric study further strengthens the conductivity result.     

Flexible and high ion conducting solid polymer electrolytes prepared via ring-opening polymerization

Abstract

The chemical cross-linking of epoxy resin has been known as an imperative way to improve the mechanical strength and thermal stability of solid polymer electrolytes (SPEs). Herein, we prepare flexible epoxy-based SPEs with high ion conductivity for electrochemical devices via ring-opening polymerization. A diglycidyl ether of bisphenol-A (DGEBA) epoxy resin was selected as the mechanical supporting SPE matrix. The high flexibility of SPEs can be obtained by adding poly(ethylene glycol) diglycidyl ether (PEGDE) plasticizer to the epoxy resin. Furthermore, the incorporation of electrolyte mixture of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salts and 1-butyl-3 methylimidazolium bis(trifluorosulfonyl)imide (BMIM-TFSI) ionic liquids allows for boosting ionic conductivity of the epoxy-based SPEs. Consequently, the high room temperature ionic conductivity ～2.4?×?10^?3 S/cm was achieved in the SPE containing 30?wt% of the epoxy and 70?wt% of the electrolyte mixture.     

Structural,morphological, ionic conductivity,and thermal properties of pectin-based polymer electrolytes

New polymer electrolytes (PEs), potentially interesting for solid-state electrochemical devices applications, were synthesized by a solvent casting method using pectin and ionic liquid (IL) N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide ([N_{1 1 1 2(OH)}] [NTf₂]. The resulting electrolytes besides being moderately homogenous and thermally stable below 155°C, they also exhibited good mechanical properties. The SPE membranes were analyzed by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and complex impedance spectroscopy.     

The fabrication and properties of solid polymer electrolytes based on PEO/PVP blends

New solid polymer electrolytes were fabricated by the addition of lithium perchlorates in the blends of polyethylene oxide (PEO, MW = 5 × 10⁶) and poly-4-vinylpyridine (PVP, MW = 1.6 × 10⁶). Not only the coordinating bonding between ether units (-O-) of PEO and Li⁺ ions at about 1100 cm⁻¹ but also the existence of pyridine salts at about 3500 cm⁻¹ were definitely observed in the FT-IR spectra. The addition of PVP in the PEO matrix is to restrict mobility of ions through the coupling of PVP and ions. Therefore, the increase of PVP content is expected to decrease the self-discharge rate. In the case of PEO-PVP blends without LiClO₄, the melting temperature T_m and the degree of crystallinity were decreased by the increase of PVP content. On the contrary, those of PEO-PVP blends with LiClO₄ were increased with the increase of PVP content. The results can be explained lay ions, which reduced the crystallinity of PEO by steric hindrance, segregated from the PEO by the coupling of PVP and ions. The new solid polymer electrolytes based on PEO-PVP blends showed ionic conductivities of the order of 10⁻⁸ to 10⁻⁷ S/cm.     

Exploration on nano-composite fumed silica-based composite polymer electrolytes with doping of ionic liquid

Fumed silica (SiO₂)-based composite polymer electrolytes were prepared by means of solution casing technique. Horizontal attenuated total reflectance-Fourier Transform Infrared (HATR-FTIR) study shows the complexation between polymer matrix and SiO₂. The highest ionic conductivity of (4.11 ± 0.01) × 10^? 3 Scm^? 1 is achieved upon inclusion of 8 wt.% of SiO₂. Three different regions have been observed in the frequency dependence–ionic conductivity study. The conductivity rises sharply with frequency at low frequency regime. It is followed by a frequency independent plateau region and sharp decrease in the conductivity at high frequency range. The dielectric permittivity (ε^') and dielectric loss (ε^") are decreased with increasing the frequency. This phenomenon is mainly attributed to the electrode polarization effect. The formation of electrical double layer has been proven in these dielectric permittivity studies. This indicates the non-Debye properties of the nano-composite polymer electrolytes.     

Evaluation and investigation on the effect of ionic liquid onto PMMA-PVC gel polymer blend electrolytes

1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl imide), BmImTFSI based poly(methyl methacrylate)-poly (vinyl chloride), PMMA-PVC gel polymer electrolytes were prepared by solution casting technique. These ionic liquid-based gel polymer electrolytes exhibit Arrhenius type temperature dependence of ionic conductivity. The highest ionic conductivity of (8.08 ± 0.01) × 10^− 4 Scm⁻¹ was achieved at 80 °C upon addition of 60 wt.% of BmImTFSI. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies revealed the amorphous nature and morphology of these polymer electrolytes, respectively. The lower coherence length of the peak inferred the higher amorphous degree in these polymer matrices. Decreases in T_g and T_m indicate the flexibility of polymer backbone. The amorphous behavior of these ionic liquid-based gel polymer electrolytes are also enhanced as shown in differential scanning calorimetry (DSC) analysis. On the contrary, thermogravimetric analysis (TGA) divulges that the thermal stability of polymer electrolytes has been improved upon impregnation of BmImTFSI.     

Conductivity,thermal and infrared studies on plasticized polymer electrolytes with carbon nanotubes as filler

New composite polymer electrolytes (CPE) are prepared using solution-casting technique. The CPE are based on polyethylene oxide (PEO) and employ lithium hexafluorate (LiPF₆) as the doping salt, ethylene carbonate (EC) as the plasticizer and amorphous carbon nanotubes (αCNTs) as the filler. The crystallinity and ionic conductivity of the CPE are examined in this work. The conductivity increases from 10^?10 to 10^?5 S cm^?1 upon the addition of salt. The incorporation of EC and αCNTs into the salted polymer enhances the conductivity significantly to 10^?4 and 10^?3 S cm^?1. The Vogel–Tamman–Fulcher (VTF) plots suggest that the temperature dependence of conductivity is a thermally activated process. Differential Scanning Calorimetry (DSC) studies show that the melting transition temperature and crystallinity decrease upon the addition of salt, EC and αCNTs into the polymer electrolyte system. The complexation, nature and concentration of the various ionic species are examined using Fourier Transform Infrared Spectroscopy (FTIR). Scanning electron microscopy (SEM) images show the changes in morphologies of the composite polymer electrolytes. The application of CPE especially in batteries and the advantages of this composite are highly conductive and stable at elevated temperature.     

Preparation and the proton conductivity of chitosan/poly(vinyl phosphonic acid) complex polymer electrolytes

This study describes the preparation and proton conductivity of novel polymer complex electrolytes consisting of chitosan and poly(vinylphosphonic acid), PVPA. The materials were prepared via in situ polymerization of vinyl phosphonic acid in the presence of chitosan at various monomer feed ratios with respect to d-glucosamine repeat unit. Homogeneous materials were produced and they were extensively characterized for their compositions by elemental analysis (EA), thermal properties by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and the morphology by X-ray diffraction (XRD). The complexation of chitosan/PVPA via proton exchange reactions was confirmed by Fourier transform infrared (FT-IR). The methanol permeability of CHPVPA₅ was lower than Nafion^® 115. The water/methanol uptake was measured and the results showed that solvent absorption of the materials increased with increasing PVPA content in the matrix. The temperature dependence of the proton conductivity of the complex electrolytes follows VTF behavior at higher x. Proton conductivity of CHPVPA₅ was measured to be approximately 3 × 10⁻⁵ S/cm at 120 °C in the anhydrous state.     

Effect of ethylene carbonate in poly (methyl methacrylate)-lithium tetraborate based polymer electrolytes

Thin films composed of poly (methyl methacrylate) (PMMA), lithium tetraborate (Li₂B₄O₇) and ethylene carbonate (EC) were prepared by solution casting method. The highest ionic conductivity at room temperature was achieved for the composition PMMA:Li₂B₄O₇:EC (42:18:40) with the value 1.29 × 10⁻⁵ S cm⁻¹. The presence of plasticizer in the polymer complex is crucial in improving the ionic conductivity by increasing the concentration of free mobile ions through the structural conversion from crystalline to amorphous phase. This conversion lowers the viscosity of the polymer complex. Conductivity-temperature plots were found to obey Williams-Landel-Ferry (WLF) mechanism. Dielectric data was analyzed using the dielectric permittivity (ε′) and dielectric modulus (M′) of the samples. Fourier transform infrared (FTIR) studies confirmed that complexation occurs between PMMA, Li₂B₄O₇ and EC. Thermal stability of the polymer complex, which decreases with the addition of plasticizer (EC), was determined using thermal gravimetric analysis (TGA).     

The role of inorganic nanoparticle on ion conduction of epoxy-based solid polymer electrolytes for lithium-ion batteries

Abstract

Recently, extensive efforts have focused on the development of solid polymer electrolytes (SPEs) requiring high mechanical performance without sacrificing ion conductivity. To develop such a SPE, we incorporate robust silica mesoporous particles (SMP) into the epoxy-based SPEs, and increasing the SMP content raises the glass transition temperature of the SPEs. This enables to increase the mechanical properties of the SPEs, supported by the microstructural investigation showing a highly compact structure. Ionic conductivities of these SPEs follow Vogel temperature dependence, and increasing the silica nanoparticle content leads to a slight decrease in the conductivity, consistent with the dielectric response investigation.     

Synthesis and characterizations of nano sized MgO and its nano composite with poly(vinyl alcohol)

Magnesium oxide (MgO) nano particle was synthesized by ultrasound assisted one pot method and thus synthesized nano MgO was mixed with poly(vinyl alcohol) (PVA) to prepare the polymer nano composite. The influence of the nano sized MgO on the structural modification of PVA was evaluated. The particle size and morphology of MgO was confirmed by High Resolution Transmission Electron Microscopy (HRTEM). The properties of PVA/MgO nano composite materials were characterized by Fourier Transform Infrared analysis (FTIR), Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC) like analytical tools.     

Thermal,vibrational and Ac impedance studies on proton conducting polymer electrolytes based on poly(vinyl acetate)

Proton conducting polymer electrolytes based on poly(vinyl acetate) (PVAc) and perchloric acid (HClO₄) have been prepared by solution casting technique with various compositions. The X-ray diffraction analysis confirms the polymer–HClO₄ complex formation. FTIR spectra analysis reveals the interaction between proton and ester oxygen of poly(vinyl acetate) (PVAc). The shift in T_g towards the lower temperature indicates that the polymer salt interaction takes places in the amorphous phase of the polymer matrix. Ac impedance spectroscopy reveals that 75 mol% PVAc:25 mol% HClO₄ exhibits maximum conductivity, 3.75 × 10^? 3 S cm^? 1 at room temperature (303 K). The increase in conductivity with increase in dopant concentration and temperature may be attributed to the enhanced mobility of the polymer chains, number of charge carriers and rotations of side chains. The temperature dependence of conductivity shows non-Arrhenius behavior at higher temperatures.     

Conductivity and dielectric properties of polymer electrolytes PEO:LiN(CF3SO2)2 near glass transition

Results of measurements of PEO:LiN(CF₃SO₂)₂ polymer electrolytes of composition between 12:1 and 1.5:1 EO:Li, performed by impedance spectroscopy, impedance spectroscopy simultaneous with microscope observation, differential scanning calorimetry and X-ray diffraction were analyzed focusing on electrical properties of semicrystalline and rapidly cooled amorphous samples. In the loss spectra measured at low temperature, the occurrence of two dielectric relaxations was evidenced: local (β) and segmental (α). For each of the investigated electrolytes, the temperature dependence of the ionic conductivity and the frequency of α relaxation could be described by the VTF function with the same value of parameter T₀, which indicated close coupling of both phenomena. The local (β) relaxation exhibited an Arrhenius type temperature dependence. With increasing amount of salt, two effects were observed for amorphous samples: an increase of the glass transition temperature T_g affecting the α relaxation and changes of structure of PEO:LiN(CF₃SO₂)₂ complexes reflected in shift of the β relaxation frequency. Crystallization caused decrease of both the ionic conductivity and the strength of dielectric relaxations. The presence of crystalline phase was also reflected in a shift of the T_g of amorphous phase remaining in the system with respect to the T_g of amorphous electrolyte obtained by rapid cooling.     

Preparation and characterizations of bulk GaN crystals

The growth conditions and mechanism of hexagonal GaN platelet crystals by Li flux were studied. The experimental results confirmed that these crystals crystallized from Li–Ga–N liquid phase. Photoluminescence (PL) spectra and Raman scattering spectrum of the crystals were obtained, which show that GaN crystals obtained by this method possess good crystalline quality.     

The effect of lithium salt type on ionic conductivity of poly(vinylidene difluoride)-based solid polymer electrolytes

Abstract

Recently, research on solid polymer electrolytes (SPEs) for lithium-ion batteries (LIBs) has been actively carried out as an alternative to conventional liquid electrolytes that present safety issues such as flammability and explosion. However, the SPEs show relatively low ion conductivity, compared to the liquid electrolytes. In this study, a poly(vinylidene difluoride) (PVDF)-based SPE was prepared by introducing two different electrolytes; one is weak-binding lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt mixture with solvating plastic crystal succinonitrile (SN) and the other is lithium bis(fluorosulfonyl)imide (LiFSI) salts. Among the SPEs studied, the PVDF/LiFSI-containing SPE membrane exhibited the highest room temperature ion conductivity of 1 x 10^?3 S/cm, characterized by electrochemical impedance spectroscopy (EIS).     

Electrical characterizations of silver chalcogenide glasses

We present a study of the electrical properties of silver chalcogenide glasses ‘40AgI’–30Ag₂S–30GeS₂, 45AgI–27.5Ag₂S–27.5GeS₂ and 50AgI–25Ag₂S–25GeS₂ in the 77–400 K temperature and the 20 Hz to 1 MHz frequency ranges. In our temperature range, a large variation of the real permittivity is observed, in relation with an electrodes polarization effect. As the amount of silver iodide increases in the Ag₂S–GeS₂ matrix, the glass transition temperature and the activation energies decrease, the electrical conductivity increases and reaches 4 Ω⁻¹ m⁻¹ at room temperature for the glass with 50% AgI. The study of the conductivity shows a behavior due to a high ionic conductivity, thermally activated with E_dc = 0.21 eV, E₁ = 0.075 eV (40AgI–30Ag₂S–30GeS₂, 45AgI–27.5Ag₂S–27.5GeS₂), E_dc = 0.17 eV, E₁ = 0.055 eV for 50AgI–25Ag₂S–25GeS₂. For these glasses, we have seen three conductivity regimes. The first two terms are thermally activated. The third term cannot be actually clearly identified because either it is thermally activated with a very low activation energy and frequency dependent, or it is almost non-thermally activated and frequency dependent.     

Synthesis and structural characterization of amorphous nano-sized SiBONC ceramic powders via polymer pyrolysis

SiBONC ceramic powders have been prepared via a polymer pyrolysis route using silicon tetrachloride (SiCl₄), benzaldehyde (PhCHO), boron trichloride (BCl₃) and aniline (PhNH₂) as starting materials. Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were performed to investigate the structural characteristics of the polymer precursor and the ceramic powders. The SiBONC ceramic powders in spherical shape with a mean diameter of 50 nm are amorphous and composed of B-N, Si-O, Si-C, and SiON_x groups. The SiBONC ceramic powders were sintered at 1700 °C to a dense material which still remained amorphous.     

Synthesis and structural properties of a 1-D copper(I) coordination polymer

A coordination polymer catena-chloro(4-pyridinecarboxylic acid)copper(I): [Cu(C₆H₅ O₂N)Cl]_n (1) has been prepared directly by reacting Cu^IICl₂ 2H₂O and 4-cyanopyridine in the presence of disodium maleate under hydrothermal conditions at 140°C. Crystal data for 1 are as follows: monoclinic, P2₁/n, a = 16.4623(9) Å, b = 3.7795(2) Å, c = 24.7612(11) Å, = 101.534(1)°, V = 1509.5(1) ų, Z = 4, D _calc. = 1.955 g cm^–3, R1 = 0.0511, wR2 = 0.1060 for all 2666 reflections. In this 1-D stair-polymer, two [Cu–Cl–Cu]_n zigzag chains are held together by weak interchain Cu–Cl bonds. The 4-pyridinecarboxylic acid ligands derived from the 4-CNpy molecules coordinate to the approximately tetrahedral Cu(I) centers through pyridyl-N atoms. The carboxyl ends of 4-pyridinecarboxylic acid participate in interchain hydrogen-bonding interactions to form a 2-D supramolecular network.     

Synthesis and structure of a HgI2 coordination polymer with novel rigid N-donor ligand

Solution reaction of mercury iodide with organic multifunctional ligand 2, 3-di (4-pyridyl)-2, 3-butanediol (dpb) generated a 1D polymer [(HgI₂)₂(dpb)₂(DMSO)₂] _n 1, and the crystal structure has been determined (C₁₈H₂₈HgI₂N₂O₄S₂), M _r=854.93, a=10.821(2), b=25.196(5), c=10.039(2)?, space group Pnma, Z=4, and V=2737.0(9)?³. In 1 the rigidity of HgI₂ and dpb make it a zigzag structure.