Characterization of PEO-PAN hybrid solid polymer electrolytes

Hybrid solid polymer electrolytes (HSPE) of high ionic conductivity were prepared using polyethylene oxide (PEO), polyacrylonitrile (PAN), propylene carbonate (PrC), ethylene carbonate (EC), and LiClO₄. These electrolyte films were dry, free standing, and dimensionally stable. The HSPE films were characterized by constructing symmetrical cells containing nonblocking lithium electrodes as well as blocking stainless steel electrodes. Studies were made on ionic conductivity, electrochemical reaction, interfacial stability, and morphology of the films using alternating current impedance spectroscopy, infrared spectroscopy, and scanning electron microscopy. The properties of HSPE were compared with the films prepared using (i) PEO, PrC, and LiClO₄; and (ii) PAN, PrC, EC, and LiClO₄. The specific conductivity of the HSPE films was marginally less. Nevertheless, the dimensional stability was much superior. The interfacial stability of lithium was similar in the three electrolyte films. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2191–2199, 1997     

Structural characterization of new poly(ethylene oxide)-based alkaline solid polymer electrolytes

A new class of alkaline solid polymer electrolytes (SPEs) based on poly(ethylene oxide) (PEO), potassium hydroxide (KOH), and water was investigated. The structure of the SPEs was studied by differential scanning calorimetry, thermogravimetric analysis (TGA), X-ray diffraction, and optical microscopy techniques. The existence of a crystalline complex between PEO, KOH, and H₂O was evidenced for some compositions, depending on the O/K ratio. A possible structure was proposed, and a schematic phase diagram was established for this PEO–KOH–H₂O system. The first conductivity measurements also revealed the great interest of these systems, with conductivity values up to 10^-3 S/cm. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:601–607, 1997     

Ionic conductivity of a novel solid polymer electrolyte

A novel kind of solid polymer electrolyte, the solvation unit of which is O?CNHR, has been studied. The effects of host polymer structure, ion species, salt concentration, and plasticizers on ionic conductivity are discussed in detail. The solvability of host polymers is a very important factor that affects the ionic conductivity of electrolytes and is fully decided by the structure of solvation units and their density in polymer chain. The latter two rest with monomers structure and copolymerization ratio. Effects of alkali metal salts and divalent metal salts on ionic conductivity are different because of their different leading factor of cation radius. Salt concentration dependence of ionic conductivity appears as a double‐peak shape when alkali metal salts are added because of the total contribution of two kinds of ionic conductance modes, and appears as similar shapes when divalent metal salts are added. Different influences of plasticizers on ionic conductivity result from their different action ways. Ethylene glycol acts well because of its effective action from three different modes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2176–2184, 2001     

Effect of surface modified porous inorganic-organic hybrid polyphosphazene nanotubes on the properties of polyethylene oxide based solid polymer electrolytes

2-(2-methyloxyethoxy)ethanol modified poly (cyclotriphosphazene-co-4,4′-sufonyldiphenol) (PZS) nanotubes were synthesized and solid composite polymer electrolytes based on the surface modified polyphosphazene nanotubes added to PEO/LiClO₄ model system were prepared. Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM) were used to investigate the characteristics of the composite polymer electrolytes (CPE). The ionic conductivity, lithium ion transference number and electrochemical stability window can be enhanced after the addition of surface modified PZS nanotubes. The electrochemical investigation shows that the solid composite polymer electrolytes incorporated with PZS nanotubes have higher ionic conductivity and lithium ion transference number than the filler SiO₂. Maximum ionic conductivity values of 4.95 × 10⁻⁵ S cm⁻¹ at ambient temperature and 1.64 × 10⁻³ S cm⁻¹ at 80 °C with 10 wt % content of surface modified PZS nanotubes were obtained and the lithium ion transference number was 0.41. The good chemical properties of the solid state composite polymer electrolytes suggested that the inorganic-organic hybrid polyphosphazene nanotubes had a promising use as fillers in solid composite polymer electrolytes and the PEO₁₀-LiClO₄-PZS nanotubes solid composite polymer electrolyte can be used as a candidate material for lithium polymer batteries.     

Studies of solvent effect on the conductivity of 2‐mercaptopyridine‐doped solid polymer blend electrolytes and its application in dye‐sensitized solar cells

Solvents and electrolytes play an important role in the fabrication of dye‐sensitized solar cells (DSSCs). We have studied the poly(ethylene oxide)‐poly(methyl methacrylate)‐KI‐I₂ (PEO‐PMMA‐KI‐I₂) polymer blend electrolytes prepared with different wt % of the 2‐mercaptopyridine by solution casting method. The polymer electrolyte films were characterized by the FTIR, X‐ray diffraction, electrochemical impedance and dielectric studies. FTIR spectra revealed complex formation between the PEO‐PMMA‐KI‐I₂ and 2‐mercaptopyrindine. Ionic conductivity data revealed that 30% 2‐mercaptopyridine‐doped PEO‐PMMA‐KI‐I₂ electrolyte can show higher conductivity (1.55 × 10^?5 S cm^?1) than the other compositions (20, 40, and 50%). The effect of solvent on the conductivity and dielectric of solid polymer electrolytes was studied for the best composition (30% 2‐mercaptopyridine‐doped PEO‐PMMA‐KI‐I₂) electrolyte using various organic solvents such as acetonitrile, N,N‐dimethylformamide, 2‐butanone, chlorobenzene, dimethylsulfoxide, and isopropanol. We found that ac‐conductivity and dielectric constant are higher for the polymer electrolytes processed from N,N‐dimethylformamide. This observation revealed that the conductivity of the solid polymer electrolytes is dependent on the solvent used for processing and the dielectric constant of the film. The photo‐conversion efficiency of dye‐sensitized solar cells fabricated using the optimized polymer electrolytes was 3.0% under an illumination of 100 mW cm^?2. The study suggests that N,N‐dimethylformamide is a good solvent for the polymer electrolyte processing due to higher ac‐conductivity beneficial for the electrochemical device applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42489.     

Conductivity studies of solid polymer electrolytes based on polyethers and polyphosphazene blends

In this work, electrical characteristics of several polymer electrolytes based on polyether and polyphosphazene blends are reported by means of complex impedance spectroscopy. In addition, a statistical analysis was conducted applying a mathematical model to a previously designed pattern to the purpose of gaining insight into the effect exerted on the conductivity of the electrolyte by the portion of each component in the blend. Evidence was obtained to prove that the dependence of conductivity on blend composition adjusts to a reduced cubic model, whose regression coefficients are determined in this work. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2181–2186, 1998     

PEO-based polymer electrolytes

Like a liquid solvent, poly(ethylene oxide) dissolves a wide variety of inorganic salts. Ionic conductivity occurs in the amorphous region of the polymer and typically both anions and cations are mobile to some extent. This paper discusses the preparation, thermal behaviour and ionic transport of thin cast films of PEO-based electrolytes containing monovalent and divalent cations. The techniques that shed light on the structure-conductivity relationship are emphasized. The temperature and composition dependence of conductivity is also considered. Finally, attention has been paid to the possible uses of these polymeric electrolytes in solid-state electrochemical devices such as primary and secondary batteries, electrochromic displays and sensors.     

Crystallinity,thermal properties,morphology and conductivity of quaternary plasticized PEO‐based polymer electrolytes

Quaternary plasticized solid polymer electrolyte (SPE) films composed of poly(ethylene oxide), LiClO₄, Li_1.3Al_0.3Ti_1.7(PO₄)₃, and either ethylene carbonate or propylene carbonate as plasticizer (over a range of 10–40 wt%) were prepared by a solution‐cast technique. X‐ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) indicated that components such as LiClO₄ and Li_1.3Al_0.3Ti_1.7(PO₄)₃ and the plasticizers exerted important effects on the plasticized quaternary SPE systems. XRD analysis revealed the influence from each component on the crystalline phase. DSC results demonstrated the greater flexibility of the polymer chains, which favored ionic conduction. SEM examination revealed the smooth and homogeneous surface morphology of the plasticized polymer electrolyte films. EIS suggested that the temperature dependence of the films' ionic conductivity obeyed the Vogel–Tamman–Fulcher (VTF) relation, and that the segmental movement of the polymer chains was closely related to ionic conduction with increasing temperature. The pre‐exponential factor and pseudo activation energy both increased with increasing plasticizer content and were maximized at 40 wt% plasticizer content. The charge transport in all polymer electrolyte films was predominantly reliant on lithium ions. All transference numbers were less than 0.5. Copyright © 2006 Society of Chemical Industry     

Partial crystallisation in liquid polymer electrolytes based on co-polymers of ethylene oxide/propylene oxide

Solutions of lithium perchlorate in a low molecular weight ethylene oxide/propylene oxide (EO/PO) co-polymer were studied by differential scanning calorimetry. The pure co-polymer was found to crystallise partially, while addition of the salt impaired crystallisation first by slowing crystal growth then by slowing nucleation. At high salt concentrations (～1·0 molal) no crystallisation occurred. The solvation of Li⁺-ions and the introduction of ‘transient crosslinking’ between cations and anions effectively suppresses the separation of the polymer into microregions of EO and PO. The crystallisation phenomena are relevant to the use of these copolymers as ‘model’ polymer electrolyte systems.     

Improved performance of solid polymer electrolytes for structural batteries utilizing plasticizing co‐solvents

This study describes the formulation, curing, and characterization of solid polymer electrolytes (SPE) based on plasticized poly(ethylene glycol)‐methacrylate, intended for use in structural batteries that utilizes carbon fibers as electrodes. The effect of crosslink density, salt concentration, and amount of plasticizer has been investigated. Adding a plasticizing solvent increases the overall performance of the SPE. Increased ionic conductivity and mechanical performance can be attained compared to similar systems without plasticizer. At ambient temperature, ionic conductivity (σ) of 3.3 × 10^?5 S cm^?1, with a corresponding storage modulus (E ′) of 20 MPa are reached. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44917.     

Ionic conductivity of solid polymer electrolytes for dye‐sensitized solar cells

We developed an ionic conductivity model of solid polymer electrolytes for dye‐sensitized solar cells (DSSCs) based on the Nernst–Einstein equation in which the diffusion coefficient is derived from the molecular thermodynamic model. We introduced concentration‐dependence of the diffusion coefficient into the model, and the diffusion coefficient was expressed by differentiating the chemical potential by concentration. The ionic conductivities of polymer electrolytes (PEO/LiI/I₂ system) were investigated at various temperatures and compositions. We prepared a set of PEO in which an EO : LiI mole ratio of 10 : 1 was kept constant for PEO·LiI·(I₂)_n compositions with n = 0.02, 0.05, 0.1, 0.15, 0.2, and 0.3 (mole ratio of LiI : I₂). The ionic conductivities of the electrolytes were measured using a stainless steel/polymer‐electrolyte/stainless steel sandwich‐type electrode structure using alternating current impedance analysis. The values calculated using the proposed model agree well with experimental data. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Reply to comments on the need to reconsider traditional free volume theory for polymer electrolytes

New aspects of the defect diffusion model (DDM) are presented. First, it is shown that if the correlation volume exhibits two dimensional scaling, e.g. grows in two dimensions more rapidly than in a third orthogonal direction, the standard Vogel relation is obtained. Second, it is pointed out that, independent of the dimensionality, ∂ ln σ/∂P should be proportional to ∂ ln σ/∂ ln T where the proportionality constant is −∂ ln T_c/∂P. It is shown that both of these results are consistent with the temperature and pressure variation of the electrical conductivity for 20:1 PPG:LiCF₃SO₃ below about 1.3 times the glass transition temperature, T_g. Finally, the DDM is compared with the free volume theory (FVT) of Dlubek et al. who have reconsidered “traditional” FVT and presented a formalism where the free volume is not proportional to the macroscopic volume. One aspect of the new FVT, which is difficult to understand is that the compressibility of the occupied volume is larger than the compressibility of the free volume.     

Composite polymer electrolytes based on the low crosslinked copolymer of linear and hyperbranched polyurethanes

Low crosslinked copolymer of linear and hyperbranched polyurethane (CHPU) was prepared, and the ionic conductivities and thermal properties of the composite polymer electrolytes composed of CHPU and LiClO₄ were investigated. The FTIR and Raman spectra analysis indicated that the polyurethane copolymer could dissolve more lithium salt than the corresponding polymer electrolytes of the non crosslinked hyperbranched polyurethane, and showed higher conductivities. At salt concentration EO/Li = 4, the electrolyte CHPU30‐LiClO₄ reached its maximum conductivity, 1.51 × 10^?5 S cm^?1 at 25°C. DSC measurement was also used for the analysis of the thermal properties of polymer electrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3607–3613, 2007     

Nanocomposite polymer electrolytes for solid-state lithium-ion batteries with enhanced electrochemical properties

Solid-state polymer electrolytes (SPEs) have attracted significant attention owing to their improvement in high energy density and high safety performance. However, the low lithium-ion conductivity of SPEs at room temperature restricts their further application in lithium-ion batteries (LIBs). Herein, we propose a novel poly (ethylene oxide) (PEO)-based nanocomposite polymer electrolytes by blending boron-containing nanoparticles (BNs) in the PEO matrix (abbreviated as: PEO/BNs NPEs). The boron atom of BNs is sp²-hybridized and contains an empty p-orbital that can interact with the anion of lithium salt, promoting the dissociation of the lithium salts. In addition, the introduction of the BNs could reduce the crystallinity of PEO. And thus, the ionic conductivity of PEO/BNs NPEs could reach as high as 1.19 × 10⁻³ S cm⁻¹ at 60°C. Compared to the pure PEO solid polymer electrolyte (PEO SPEs), the PEO/BNs NPEs showed a wider electrochemical window (5.5 V) and larger lithium-ion migration number (0.43). In addition, the cells assembled with PEO/BNs NPEs exhibited good cycle performance with an initial discharge capacity of 142.5 mA h g⁻¹ and capacity retention of 87.7% after 200 cycles at 2 C (60°C).     

Effect of hard segment and concentration of NaClO4 on poly(ethylene oxide)–urethane/NaClO4 complex

Solid poly(ethylene oxide)–urethane electrolytes were prepared from blends of polyurethane and NaClO₄. The samples were characterized by FTIR, DSC, atomic force microscopy, and complex impedance analysis. The effect of the concentration of NaClO₄ on the poly(ethylene oxide)–urethane/NaClO₄ complex were studied. The results showed that the concentration of NaClO₄ had an important effect on the ion–polymer interaction, ion–ion interaction, glass‐transition temperature, morphologic structure, and ionic conductivity of the complex. We also prepared a model compound of hard segments and found that the conductivity of the complex decreased when the model compound was blended into the complex. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2502–2510, 2001     

Nanocomposite polymer electrolytes containing silica nanoparticles: Comparison between poly(ethylene glycol) and poly(ethylene oxide) dimethyl ether

Nanocomposite polymer electrolytes consisting of low molecular weight poly(ethylene oxide) (PEO), iodine salt MI (M = K⁺, imidazolium⁺), and fumed silica nanoparticles have been prepared and characterized. The effect of terminal group in PEO, i.e., hydroxyl (? OH) and methyl (CH₃) using poly(ethylene glycol) (PEG) and PEO dimethyl ether (PEODME), respectively, was investigated on the interactions, structures, and ionic conductivities of polymer electrolytes. Wide angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), and complex viscositymeasurements clearly showed that the gelation of PEG electrolytes occurred more effectively than that of PEODME electrolytes. It was attributed to the fact that the hydroxyl groups of PEG participated in the hydrogen‐bonding interaction between silica nanoparticles, and consequently helped to accelerate the gelation reaction, as confirmed by FTIR spectroscopy. Because of its interaction, the ionic conductivities of PEG electrolytes (maximum value ～ 6.9 × 10^?4 S/cm) were lower than that of PEODME electrolytes (2.3 × 10^?3 S/cm). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

碳酸乙烯酯催化水解合成乙二醇

对二步法合成乙二醇(EG)过程的碳酸乙烯酯(EC)催化水解反应进行了研究,考察了水/EC摩尔比、反应温度、催化剂用量(以EC质量计)和反应压力对反应的影响,确定了EC催化水解反应的较佳工艺条件:反应温度160～180℃,水/EC摩尔比2.0～4.0,催化剂质量分数约2.0%,反应压力范围3.0～4.0MPa.在以上工艺条件下,原料含有EG时(EG/EC摩尔比O.5～1.0),反应2h,EC也可完全水解,EG选择性高于98%.     

Effect of purification of 2-methyltetrahydrofuran/ethylene carbonate mixed solvent electrolytes on cyclability of lithium metal anodes for rechargeable cells

The effects of the purification of LiAsF₆–2-methyl tetrahydrofuran (2MeTHF)/ethylene carbonate (EC) mixed solvent organic electrolytes on the charge–discharge cyclability of lithium metal anodes has been investigated by using an accelerated method for evaluating lithium cycling efficiency. This method involves cycle tests on coin cells with an amorphous V₂O₅–P₂O₅ (95:5 molar ratio) cathode and an anode containing a small amount of lithium. Using this method, the cycle life of the cell was determined over a short period simply from the lithium cycling efficiency. The lithium cycling efficiency in LiAsF₆–2MeTHF/EC was improved by removing both water and organic impurities such as peroxides. An electrolyte containing less than 14ppm of water and 20ppm of organic impurities had a high lithium cycling efficiency of 97.2%.     

碳酸乙烯酯酯交换合成碳酸二苯酯

为利用碳酸乙烯酯固定的CO2,拓展碳酸二苯酯的合成方法,对碳酸乙烯酯酯交换合成碳酸二苯酯的反应进行了热力学分析,并考察了催化剂、反应温度、催化剂质量分数和反应时间对合成碳酸二苯酯的影响。结果表明:碳酸乙烯酯与苯酚的酯交换反应在热力学上是不可行的,而将苯酚乙酰化后可以实现由碳酸乙烯酯经酯交换合成碳酸二苯酯;不同催化剂催化酯交换反应时,n-Bu2SnO显示了最高的酯交换选择性。当反应温度为190℃,碳酸乙烯酯与乙酸苯酯的摩尔比为1∶2,n-Bu2SnO质量分数8%,反应时间10 h时,碳酸乙烯酯的转化率为15.1%,酯交换选择性64.2%,碳酸二苯酯的收率7.5%。