Ionic conductivity and physical stability study of gel nework polymer electrolytes

Gel polymer electrolytes (GPE) were prepared by a crosslinking reaction between poly(ethylene glycol) and a crosslinking agent with three isocyanate groups in the presence of propylene carbonate (PC) and ethylene carbonate (EC) or their mixture, and their ionic conducting behavior was carefully investigated. When the plasticizer amount was fixed, the ionic conductivity was greatly influenced by the nature of plasticizers. It was found that the conductivity data followed the Arrhenius equation in the GPE. Whatever plasticizer was used, a maximum ambient conductivity was found at a salt concentration near [Li⁺]/[EO] equal to 0.20. The physical stability of GPE was studied qualitatively by weight loss of GPE under pressure. It was shown that the stability was greatly affected by the network structure of the GPE and the most stable one in our research was the GPE containing the PEO₁₀₀₀ segment, which has a strong interaction between network and plasticizers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2957–2962, 2000     

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     

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     

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.     

Sulfonate based ionic liquid incorporated polymer electrolytes for Magnesium secondary battery

The polymer electrolytes comprising of PVdF-HFP/PVAc/Mg(ClO₄)₂ as salt based polymer blend electrolytes derived from the addition of varying amounts of 1-ethyl – 3-methylimidazolium trifluoromethane sulfonate [EMITF], as dopant were synthesized in the form of films by solution-casting method. The XRD and FTIR patterns confirm the formation of an amorphous phase and also that complex formation between the polymers, salt and ionic liquid. The SEM images show that the polymer electrolyte exhibit a enormous pores, remarkably, the maximum ionic conductivity is obtained in the case of the typical polymer system I₃ is found to be 9.122 × 10^?4 Scm^?1at 303 K.     

超级电容器电解质的研究进展

综述了超级电容器电解质的研究现状,重点介绍了适用于新型电极材料的水系电解质以及目前已实现商业化的有机电解质,对离子液体电解质、固体和凝胶电解质的产业化提出了展望。     

Effect of solvent on thermal transitions and conductivity of poly (vinylidene fluoride) gel electrolytes

ABSTRACT

The melting (T_m) and crystallization (T_c) temperature increased with increasing solvent phenyl propanol (PhP) concentration in the mixture of solvent propylene carbonate and phenyl propanol (PC/PhP). It is also a little enhances of Tm and Tc with adding ethylene carbonate (EC) to propylene carbonate (PC). The melting (T_m) and softening temperature (T_soft) follows the following order of solvents PC<EC:PC<PhP:PC. There was a small change of modulus was observed with the addition of PhP. The conductivity falls with increasing PhP concentration and viscosity and re-calculate free ion concentration. The adding EC to PC raises temperatures slightly, but conductivity much the same. The overall, adding poorer solvent PhP increases the melting and crystallization temperatures at the expense of conductivity, but a little changes was observed in storage modulus, much better gel network, thereby securing the continuity of the complex leads to more flexible ductile and crystalline phase serves better mechanical properties. The crystallinity of PVDF gel electrolyte is about 50%, which facilitate to changes gel network structure slightly with PhP concentration. The formation of fully interconnected three dimensional frame work structure uniformly distributed pores with large surface area can function as efficient channels for ion conduction.     

用于锂离子电池的改性凝胶聚合物电解质

综述了凝胶聚合物电解质的性能影响因素和改性方法;着重介绍了无机纳米粒子掺杂改性;论述了近年来离子液体在聚合物电解质方面的应用;展望了凝胶聚合物电解质的发展及应用前景。     

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     

Effect of Prolonged Duration of Gelatinization in Starch and Incorporation with Potassium Iodide on the Enhancement of Ionic Conductivity

Three systems of starch-based crust electrolytes were prepared using various gelatinization times, various weight percentages (wt%) of starch, and various wt% of starch incorporated into potassium iodide. All the samples were subjected to electrochemical impedance spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and transference number measurements. Electrochemical impedance spectroscopy shows that 1.7?wt% of starch has maximized the room temperature conductivity of the electrolyte to 1.4587?×?10^?4?S?cm^?1. The conductivity was enhanced to 4.5278?×?10^?4?S?cm^?1 on the increment of starch’s wt% from 1.7 to 3.2. This conductivity was further enhanced to 3.4609?×?10^?3?S?cm^?1 on the addition of 0.3?wt% of potassium iodide. The conductivity enhancement was found due to the formation of glucosyl carboxonium ions. The effect of longer heating time in gelatinization is attributed to the formation of glucosyl carboxonium ions. X-ray diffraction spectroscopy affirms the reduction in crystallinity of starch. Scanning electron microscopy analysis shows the porous morphology of starch electrolyte, and addition of potassium iodide shows the morphology of bean nuts like particles seated on the pores. Fourier transform infrared confirms the degradation of starch. Transference number measurements of the crust electrolyte shows that ions are the dominant conducting species. All the results are authenticating that the conductivity enhancement in starch-based crust electrolyte is due to starch and the addition of inorganic salts.     

Preparation of solid-state composite electrolytes based on organic/inorganic hybrid star-shaped polymer and PEG-functionalized POSS for all-solid-state lithium battery applications

A series of composite electrolytes (CEs) consisting of organic/inorganic hybrid star-shaped polymer (SPP13), plasticizer (PEG-functionalized POSS derivatives), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were prepared to investigate the effects of the composite compositions and PEG chain length of PEs on the properties of CEs. SPP13 was prepared via ATRP from poly(ethylene glycol) methyl ether methacrylate (PEGMA) and methacryl-cyclohexyl-POSS (MA-POSS) using an octafunctional initiator, and the PEG-functionalized POSS derivatives were synthesized by the hydrosilylation reaction of octakis(dimethylsilyloxy)silsesquioxane (OHPS) and allyl-PEG. The CEs were found to be dimensionally-stable enough to separate the electrodes in batteries, but they still possessed high mobility of ion-conducting P(PEGMA) segments, as estimated by the low glass transition temperatures (T_g). The CEs having solid-state show quite high ionic conductivity (4.5 × 10⁻⁵ S cm⁻¹ at 30 °C) which is about three times of magnitude larger than that of the matrix polymer (SPP13) electrolyte (1.5 × 10⁻⁵ S cm⁻¹ at 30 °C). The CEs were electrochemically stable up to +4.2 V without the decomposition of electrolytes. An all-solid-state lithium battery prepared from the CEs exhibited larger discharge capacity than that prepared from the SPP13 electrolyte at 60 °C.     

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     

Preparation and characterization of PVP-based polymer electrolytes for solid-state battery applications

Sodium ion conducting polymer electrolyte films based on poly(vinyl pyrrolidone) (PVP) were prepared using solution casting technique. Structural characterization was performed using X-ray diffraction (XRD) technique. Increase in amorphous phase with the increase of dopant concentration was observed. Temperature dependence of electrical conductivity was performed using AC impedance analyzing technique in the frequency range of 0.1?KHz to 1?MHz. Activation energy values were evaluated, as well. Optical absorption studies were carried out in the wavelength range 200?C600?nm. Absorption edge, direct band gap, and indirect band gap values were also evaluated. Optical absorption edge and optical band gap (both direct and indirect) showed decreasing trend with increasing the concentration of the dopant. Dominant conducting species in the present electrolyte system was determined using Wagner polarization technique and dominant conducting species were found to be ions rather than electrons. Solid-state batteries were developed using the present solid polymer electrolyte system and discharge characteristics over the load of 100?k??. Cell parameters, e.g., open circuit voltage, short circuit current, current density, power density were evaluated, too. Among these cells, the cell made up of PVP/NaI (70/30) ratio for electrolyte was found to be more stable than the other two cells PVP/NaI (90/10) and (80/20) ratios and the obtained results were comparable with the results achieved by other studies.     

Single-ion conducting polymer-silicate nanocomposite electrolytes for lithium battery applications

Solid-state polymer-silicate nanocomposite electrolytes based on an amorphous polymer poly[(oxyethylene)₈ methacrylate], POEM, and lithium montmorillonite clay were fabricated and characterized to investigate the feasibility of their use as ‘salt-free’ electrolytes in lithium polymer batteries. X-ray scattering and transmission electron microscopy studies indicate the formation of an intercalated morphology in the nanocomposites due to favorable interactions between the polymer matrix and the clay. The morphology of the nanocomposite is intricately linked to the amount of silicate in the system. At low clay contents, dynamic rheological testing verifies that silicate incorporation enhances the mechanical properties of POEM, while impedance spectroscopy shows an improvement in electrical properties. With clay content ≥15 wt.%, mechanical properties are further improved but the formation of an apparent superlattice structure correlates with a loss in the electrical properties of the nanocomposite. The use of suitably modified clays in nanocomposites with high clay contents eliminates this superstructure formation, yielding materials with enhanced performance.     

Salt concentration dependence of the compensated Arrhenius equation for alcohol-based electrolytes

It has been previously shown that the temperature-dependent conductivity of dilute, organic liquid electrolytes is non-Arrhenius due to the temperature dependence of the dielectric constant contained in the exponential prefactor. Scaling the temperature-dependent conductivities to conductivities at a reference temperature removes the dielectric constant dependence; the log of the scaled conductivities is then linearly dependent on the inverse temperature. Previous applications of this analysis focused on 0.0055 M solutions of tetrabutylammonium triflate (TbaTf) dissolved in linear alcohols and linear ketones. This work expands the scope of this analysis to a range of salt concentrations and different salts in propanol solutions. The energy of activation in TbaTf-propanol solutions obtained by the analysis described above varied in a smooth but nonlinear fashion from 32.6 ± 0.3 kJ mol⁻¹ at 4.30 × 10⁻⁵ M to 39.4 ± 0.3 kJ mol⁻¹ at 5.50 × 10⁻³ M. An examination of the temperature dependence of six salts in propanol suggests that choice of the cation has a larger effect on the activation energy than the choice of the anion.     

Morphology and ionic conductivity of thermoplastic polyurethane electrolytes

Thermoplastic polyurethane (TPU) with a mixture of soft segments [poly(ethylene glycol) (PEG) and poly(tetramethylene glycol) (PTMG)], denoted TPU‐M, was prepared as an ion‐conducting polymer electrolyte. TPUs with PEG and PTMG as soft segments were also synthesized individually as polymer electrolytes. The changes in the morphology and ion conductivity of the phase‐segregated TPU‐based polymer electrolytes as a function of the lithium perchlorate concentration were determined with differential scanning calorimetry, Fourier transform infrared spectroscopy, alternating‐current impedance, and linear sweep voltammetry measurements. Both solid and gelatinous polymer electrolytes were characterized in this study. The effect of temperature on conductivity was studied. The conductivity changes revealed the combined influence of PTMG and PEG units in TPU‐M. The swelling characteristics in a liquid electrolyte and the dimensional stability were evaluated for the three TPUs. Because of its dimensional stability and ionic conductivity, the TPU system containing both PEG and PTMG as soft segments was found to be more suitable for electrolyte applications. A room‐temperature conductivity of approximately 1 × 10^?4 was found for TPU‐M containing 50 wt % liquid electrolyte. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1154–1167, 2004     

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.     

Agar-based films for application as polymer electrolytes

New types of polymer electrolytes based on agar have been prepared and characterized by impedance spectroscopy, X-ray diffraction measurements, UV-vis spectroscopy and scanning electronic microscopy (SEM). The best ionic conductivity has been obtained for the samples containing a concentration of 50 wt.% of acetic acid. As a function of the temperature the ionic conductivity exhibits an Arrhenius behavior increasing from 1.1 × 10⁻⁴ S/cm at room temperature to 9.6 × 10⁻⁴ S/cm at 80 °C. All the samples showed more than 70% of transparency in the visible region of the electromagnetic spectrum, a very homogeneous surface and a predominantly amorphous structure. All these characteristics imply that these polymer electrolytes can be applied in electrochromic devices.     

聚合物及离子液体电解质在锂二次电池中的应用

系统地介绍了锂离子二次电池电解质,特别是聚合物电解质及离子液体电解质的应用研究现状。开发具有高能量密度、稳定的充放电性能、循环寿命长、可塑性、高安全性与低成本的锂离子电池是当前的研究热点。离子液体具有较高的离子电导率、宽电化窗口,且无蒸汽压,而聚合物具有良好的机械加工性能。二者的结合将为锂离子电池电解质的研究提供了新的开发思路。     

离子液体电解质在锂二次电池中的应用

锂二次电池作为动力电池,被寄予厚望。但锂二次电池面临的安全隐患也是不容忽视的,是当前亟需解决的问题,而这与电解质的性质有着紧密的联系。离子液体由于具有较宽电化学窗口、良好的导电性、高热稳定性、几乎无挥发及不燃烧等优良的特性,正在作为一种新型绿色替代溶剂被电化学领域所关注。离子液体的不燃烧特性,对于替代传统有机电解质具有十分重要的意义。本文阐述了新型溶剂“离子液体”作为电解质在锂二次电池中的应用,其中重点阐述了在碳、硅、钛酸锂(Li₄Ti₅O₁₂)、磷酸亚铁锂(LiFePO₄)、钴酸锂LiCoO₂、镍锰酸锂(LiNi_xMn_yO_z),镍钴锰锂(LiNi_xCo_yMn_zO_w)及在锂硫(Li-S)电池中的应用。