Ethylene Carbonate-propylene Carbonate Research Articles

Water as Dual-Function Plasticizer and Cosolvent in Gel Electrolytes for Dye-Sensitized Solar Cells.

This study presents a novel approach to developing eco-friendly dye-sensitized solar cells (DSSCs) using natural and renewable materials for gel polymer electrolytes (GPEs), reducing reliance on unsustainable solvents. Water is added to polar aprotic solvents, specifically ethylene carbonate/propylene carbonate (EC/PC), across various mass fractions (0:100 to 100:0). An amphiphilic hydroxypropyl cellulose (HPC) natural polymer is employed to formulate GPEs within this water-EC/PC cosolvent system, achieving successful gelation up to 50:50 mass fractions. Incorporating water reduced the gel strength and viscosity of the GPEs. Water acted as a plasticizer, enhancing the polymer chains mobility, and creating a more flexible and permeable structure. This increased ion diffusion coefficients and ion mobility, resulting in a maximum ionic conductivity of 18.17 mS cm-1. The highest efficiency achieved in DSSCs using these GPEs is 5.81%, with elevated short-circuit current density and reduced recombination losses. However, some compositions experienced syneresis, affecting their stability. The GPE with a 40:60 mass fraction exhibited superior long-term stability because it is free from syneresis, though it achieved a lower efficiency (4.83%), making it the best-performing sample. This work demonstrates the feasibility and benefits of using gel polymer electrolytes in an aqueous system, improving DSSC efficiency and sustainability.

Consolidation of ion promoters into quasi solid-state (QSS) polymer electrolytes for dye-sensitized solar cells (DSSCs)

Enhanced quasi solid-state (QSS) polymer electrolytes were developed by consolidating dissolved polyacrylonitrile (PAN) in a binary organic solvent of ethylene carbonate-propylene carbonate (EC-PC) with ion promoters such as 1-methyl-3-propylimidazolium iodide (MPII), sodium iodide (NaI) salt, and Iodine (I2). In this work, the concentration of I2 was varied to one-twentieth, one-fifteenth, one-tenth, one-fifth, and equal of the total weight of the NaI salt used. The purpose of this study is to investigate the dependence of dye-sensitized solar cells (DSSCs) performance on the concentration of I2. Fourier-transform infrared (FTIR) spectroscopy study confirmed that there is a complexation occurred between all materials used. The electrolyte consists of I2 with one-tenth of the weight of the NaI salt (I1/10 electrolyte) has achieved the highest ionic conductivity of 8.70 × 10–3 S cm-1 at ambient temperature. From the current density-voltage (J-V) study, DSSC based I1/10 electrolyte has achieved the best photovoltaic efficiency of 6.47%.

Sulfonylimide-Based Cation Exchange Membranes As Electrolyte for Lithium-Ion Batteries. Synthesis and Characterization

The use of cation-exchange membranes as electrolytes in lithium-ion batteries is considered to be one of their highly promising applications. Polystyrene-based membranes containing sulfonylimide functional groups are the promising materials for these application due to the low crystallinity of polymer, high dissociation degree of functional groups, as well as thermal and electrochemical stability of obtained electrolytes. There are two different approaches for the synthesis of sulfonylimide based polymers: polymerization of functional monomer [1], and functionalization of the polymer [2]. The aim of this work was to synthesize membranes based on polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) containing functional sulfo R–SO3Li and sulfonylimide groups [R–SO2NSO2–X]Li, where X= –CF3, –CCl3, –CH3, –C6H5, –p-NO2C6H4 and –p-CF3C6H4, and investigation of Li+ conductivity of polyelectrolytes solvated by mixtures of ethylene carbonate/dimethylacetamide (EC-DMA) and ethylene carbonate/propylene carbonate (EC-PC). Membranes were synthesized according to the Scheme.To prepare plasticized polymer electrolytes, the synthesized dry SSEBS and SSEBS-X membranes in the Li+ form were transferred to a dry argon box (humidity level <10 ppm) and placed in the solutions containing equal volumes of EC-DMA or EC-PC for 24 h. Solvation degrees (n) of the membranes with EC-DMA and EC-PC mixtures were calculated as a ratio of the number of solvent molecules to the total number of membrane functional groups.The acid-base titration was used to determine full ion-exchange capacity (IEC) of the SSEBS membrane containing functional sulfo groups, as well as the residual amount of R–SO3 - functional groups in the SSEBS-NH2 membrane after the amination.The structure of SEBS, SSEBS and SSEBS-X were proven by ATR IR spectroscopy, using Nicolet iS5 IR in the frequency range 4000-500cm-1, and CHNS analysis, using EuroVector ЕА3000 equipment.Ionic conductivity of the obtained polymer electrolytes in the Li+ form plasticized by EC-PC and EC-DMA mixtures was investigated by impedance spectroscopy in the temperature range 0...+50 °С under the argon atmosphere, using the alternating current bridge Elins Z-1500J (frequency range from 2 MHz to 10 kHz) on symmetrical cells carbon/membrane/carbon. Resistance was determined from the intercept with the axis of active resistances in Nyquist plot.Optimal concentrations and equivalent excesses required for complete transformation of R–SO2NH2 groups into sulfonylimide functional groups [R–SO2NSO2–X]M by the Hinsberg reaction were found using phenylsulfonyl chloride. In particular, 1.5М is the minimal concentration of sulfonyl chloride in the mixture, and minimal excesses of sulfonyl chloride and triethylamine with respect to the amount of R–SO2NH2 groups are 10 and 3, respectively.IEC of the obtained membranes SSEBS-X are 1.54-1.68 mmol∙g-1. Solvation of the membranes with the EC-PC solvent mixture, which is the most common solvent in lithium-ion batteries, is not efficient for this purpose due to low solvation capability of organic carbonates and a high viscosity of the mixture. The solvation number of the membranes with this mixture does not exceed 1.7 solvent molecules per functional group, and Li+ conductivity is equal to or below 2∙10-3 mS∙cm-1 at 25°С. The use of amide-containing solvents leads to an increase of ionic conductivity of the sulfonylimide-based membranes due to specific interactions that determine their high solvation capability. In particular, when the EC-DMA mixture is used the solvation degree and ionic conductivity of the SSEBS-CF3 membranes at 25°С increase to 14.1 and 1 mS∙cm-1, respectively.The lowest solvation degree (1.9 solvent molecules per sulfonic group) and conductivity (0.1 mS∙cm-1 at 25°С) was found for the SSEBS membrane and the largest values were found for the SSEBS-CF3 polymer that contains trifluoromethanesulfonylimide functional groups (14.1 solvent molecules per 1 sulfonic group and 1.1 mS∙cm-1 at 25°С)According to acidity of [R–SO2NHSO2X] groups negative charge delocalization degree decreases along the following sequence X=CF3>CCl3>p-CF3Ph>Ph, whereas the sulfonic group should be placed at the end of the sequence having the lowest acidity. Such consistency of measured ionic conductivity and calculated acidity.This work was financially supported by the Russian Science Foundation (project No 17-79-30054) Bouchet, S. Maria, R. Meziane, A. Aboulaich, L. Lienafa, J.-P. Bonnet, T.N.T. Phan, D. Bertin, D. Gigmes, D. Devaux, R. Denoyel, M. Armand. Single-ion BAB triblock copolymers as highly efficient electrolytes for lithium-metal batteries // Nat. Mater. 2013. V. 12. P. 452-457. Rohan, Y. Sun, W. Cai, Y. Zhang, K. Pareek, G. Xu, H. Cheng. Functionalized polystyrene based single ion conducting gel polymer electrolyte for lithium batteries // Solid State Ionics 2014. V. 268. P. 294-299. Figure 1

Iron-Doped Sodium Vanadium Oxyflurophosphate Cathodes for Sodium-Ion Batteries-Electrochemical Characterization and In Situ Measurements of Heat Generation.

Sodium-ion batteries (NaIBs) are increasingly being envisioned for grid-scale energy-storage systems because of cost advantages. However, implementation of this vision has been challenged by the low-energy densities delivered by most NaIB cathodes. Toward addressing this challenge, the authors report the synthesis and characterization of a new iron-doped Na3Fe0.3V1.7O(PO4)2F2 cathode using a novel facile hydrothermal route. The synthesized material was characterized using scanning electron microscopy, X-ray diffraction, and Mössbauer spectroscopy techniques. The obtained discharge capacity in the half-cell configuration lies from 119 to 125 to 130 mA h/g at C/10 while tested using three different electrolyte formulations, dimethyl carbonate-ethylene carbonate (EC)-propylene carbonate (PC), diethyl carbonate-EC, and EC-PC, respectively. The synthesized cathodes were also evaluated in full-cell configurations, which delivered an initial discharge capacity of 80 mA h/g with NaTi2(PO4)3MWCNT as the anode. Ionic diffusivity and interfacial charge transfer kinetics were also evaluated as a function of temperature and sodium concentration, which revealed that electrochemical rate performances in this material were limited by charge-transfer kinetics. To understand the heat generation mechanism of the Na/Na3Fe0.3V1.7O(PO4)2F2 half-cell during charge and discharge processes, an electrochemical isothermal calorimetry measurement was carried out at different current rates for two different temperatures (25 and 45 °C). The results showed that the amount of heat generated was strongly affected by the operating charge/discharge state, C-rate, and temperature. Overall, this work provides a new synthesis route for the development of iron-doped Na3Fe0.3V1.7O(PO4)2F2-based high-performance sodium cathode materials aimed at providing a viable pathway for the development and deployment of large-scale energy-storage based on sodium battery systems.

Polymer Electrolytes for LIBs Based on Perfluorinated Sulfocationic Nepem-117 Membrane and Aprotic Solvents.

Polymer electrolytes have been obtained by using Nepem-117 membranes in a Li+ form intercalated by polar aprotic solvents, such as dimethylformamide, dimethyl sulfoxide (DMSO), and dimethylacetamide (DMA), and solvent mixtures, such as ethylene carbonate-propylene carbonate (EC-PC), EC-DMA, EC-PC-DMA, and EC-PC-DMA-tetrahydrofuran. The obtained electrolytes have been characterized by IR impedance and 7Li pulsed field gradient NMR spectroscopy. Ion mobility was observed to increase with higher degrees of solvation of the membranes. A method is demonstrated to determine the solvent uptake corresponding to the percolation threshold. With comparable solvent uptake, materials containing a solvent with a higher permittivity and a lower viscosity have higher values of ionic conductivity. The membranes containing the three-component mixture of EC-PC-DMA show the highest ionic conductivity values (8.1 and 2.1 mS/cm at 25 and -20 °C, respectively). Such values exceed the conductivity of electrolytes on the basis of the Nafion membranes solvated with aprotic solvents.

Monochromatic "Photoinitibitor"-Mediated Holographic Photopolymer Electrolytes for Lithium-Ion Batteries.

A new polymer electrolyte based on holographic photopolymer is designed and fabricated. Ethylene carbonate (EC) and propylene carbonate (PC) are introduced as the photoinert substances. Upon laser‐interference‐pattern illumination, photopolymerization occurs within the constructive regions which subsequently results in a phase separation between the photogenerated polymer and unreacted EC–PC, affording holographic photopolymer electrolytes (HPEs) with a pitch of ≈740 nm. Interestingly, both diffraction efficiency and ionic conductivity increase with an augmentation of the EC–PC content. With 50 wt% of EC–PC, the diffraction efficiency and ionic conductivity are ≈60% and 2.13 × 10−4 S cm−1 at 30 °C, respectively, which are 60 times and 5 orders of magnitude larger than the electrolyte without EC–PC. Notably, the HPEs afford better anisotropy and more stable electrochemical properties when incorporating N,N‐dimethylacrylamide. The HPEs exhibit good toughness under bending, excellent optical transparency under ambient conditions, and astonishing capabilities of reconstructing colored images. The HPEs here open a door to design flexible and transparent electronics with good mechanical, electrical, and optical functions.

Synergism of surface group transfer and in-situ growth of silica-aerogel induced high-performance modified polyacrylonitrile separator for lithium/sodium-ion batteries

As the pivotal component, separators play the important role in electrochemical performance and even determine the safety of batteries to a great extent. Here, a kind of modified polyacrylonitrile/silica-aerogel (M-PSA) as high-safety separator for lithium/sodium-ion battery is reported, which is obtained as follows: the polyacrylonitrile (PAN) nonwoven prepared through electrospinning, is modified by hydrolysis of its nitrile group and then, in-situ growth of silica-aerogel on it. The as-synthesized M-PSA can enhance the chemical stability in conventional electrolytes, such as ethylene carbonate/propylene carbonate (EC/PC), ethylene carbonate/methyl-carbonate (EC/DMC) and diglyme. It shows high porosity and excellent affinity to these conventional electrolytes. More importantly, the M-PSA separator could hold its structural integrity at 250 °C and no severe shrinkage at 350 °C (80.06% of separator area retention) indicating excellent thermal stability. Electrochemical measurements of the M-PSA separator are tested in lithium battery and sodium battery (half cells and full cells), respectively, exhibiting good cycle performance and fast kinetics. The M-PSA separator is promising as high-safety separator for advanced lithium/sodium-ion batteries for widely applications.

Deciphering the Ethylene Carbonate-Propylene Carbonate Mystery in Li-Ion Batteries.

As one of the landmark technologies, Li-ion batteries (LIBs) have reshaped our life in the 21stcentury, but molecular-level understanding about the mechanism underneath this young chemistry is still insufficient. Despite their deceptively simple appearances with just three active components (cathode and anode separated by electrolyte), the actual processes in LIBs involve complexities at all length-scales, from Li+ migration within electrode lattices or across crystalline boundaries and interfaces to the Li+ accommodation and dislocation at potentials far away from the thermodynamic equilibria of electrolytes. Among all, the interphases situated between electrodes and electrolytes remain the most elusive component in LIBs. Interphases form because no electrolyte component (salt anion, solvent molecules) could remain thermodynamically stable at the extreme potentials where electrodes in modern LIBs operate, and their chemical ingredients come from the sacrificial decompositions of electrolyte components. The presence of an interphase on electrodes ensures reversibility of Li+ intercalation chemistry in anode and cathode at extreme potentials and defines the cycle life, power and energy densities, and even safety of the eventual LIBs device. Despite such importance and numerous investigations dedicated in the past two decades, we still cannot explain why, nor predict whether, certain electrolyte solvents can form a protective interphase to support the reversible Li+ intercalation chemistries while others destroy the electrode structure. The most representative example is the long-standing "EC-PC Disparity" and the two interphasial extremities induced therefrom: differing by only one methyl substituent, ethylene carbonate (EC) forms almost ideal interphases on the graphitic anode, thus becoming the indispensable solvent in all LIBs manufactured today, while propylene carbonate (PC) does not form any protective interphase, leading to catastrophic exfoliation of the graphitic structure. With one after another hypotheses proposed but none satisfactorily rationalizing this disparity on the molecular level, this mystery has been puzzling the battery and electrochemistry community for decades. In this Account, we attempted to decipher this mystery by reviewing the key factors that govern the interaction between the graphitic structure and the solvated Li+ right before interphase formation. Combining DFT calculation and experiments, we identified the partial desolvation of the solvated Li+ at graphite edge sites as a critical step, in which the competitive solvation of Li+ by anion and solvent molecules dictates whether an electrolyte is destined to form a protective interphase. Applying this model to the knowledge of relative Li+ solvation energy and frontier molecular orbital energy gap, it becomes theoretically possible now to predict whether a new solvent or anion would form a complex with Li+ leading to desirable interphases. Such molecular-level understanding of interphasial processes provides guiding principles to the effort of tailor-designing new electrolyte systems for more aggressive battery chemistries beyond Li-ion.

Design of ionic liquid-based hybrid electrolytes with additive for lithium insertion in graphite effectively and their effects on interfacial properties

To address the challenge of the IL-based electrolyte cannot be effectively intercalated in graphite anode, and especially the urgent needs for the compatibility between high performance and high security, the IL-based hybrid electrolyte systems with ethylene carbonate/propylene carbonate (EC/PC) as a co-solvent and vinylene carbonate (VC) as an additive were designed. The high dielectric constant of EC/PC significantly increased the ionic conductivity and lithium ion migration of the electrolyte system. Meanwhile, the presence of VC can form SEI preventing EC and PYR14+ reductive decomposition on the electrode interface, and at the same moment, the SEI promotes effective Li cation insertion into the graphene interlayer. The Li/C half-cells showed high reversible capacity, cycling efficiency, and good cycle stability with the IL-based hybrid electrolyte. It is worth to highlight the better performance, in terms of the excellent thermal stability and high safety. Thus, the IL-based hybrid electrolyte combined with good electrochemical performance holds substantial promise for lithium-ion battery, and should have broad application prospects in the high energy density, especially high-security requirements, of the new lithium-ion battery.

Conductivity of Nafion-117 membranes intercalated by polar aprotonic solvents

The Nafion-117 membranes in the Li+ form with pore-intercalated aprotonic organic solvents were prepared. The prepared materials were characterized by IR, impedance, and 7Li NMR spectroscopy. The solvent uptake of the membranes is shown to be controlled by the composition of organic solvents and their mixtures as well as by the conditions of the preliminary treatment of the initial membranes. For the Nafion-117 membrane, the degree of solvation can be improved by the preliminary treatment with alcohols, especially by the thermal treatment in methanol. Conductivity of the membranes is shown to increase with increasing content of the sorbed solvents. The best conductivity at 25 °C (2.5 × 10−3 and 1.6 × 10−3 S cm−1) was attained for the electrolytes based on the Nafion-117 membrane in lithium form with sorbed ethylene carbonate-propylene carbonate and ethylene carbonate-dimethoxyethane mixtures, respectively.

Role of solvents on the oxygen reduction and evolution of rechargeable Li-O2 battery

Abstract The choice of electrolyte solvent is expected to play a key role in influencing the lithium-oxygen battery performance. The electrochemical performances of three electrolytes composed of lithium bis (trifluoromethane sulfonyl) imide (LiTFSI) salt and different solvents namely, ethylene carbonate/propylene carbonate (EC/PC), tetra ethylene glycol dimethyl ether (TEGDME) and dimethyl sulfoxide (DMSO) are investigated by assembling lithium oxygen cells. The electrolyte composition significantly varied the specific capacity of the battery. The choice of electrolyte also influences the overpotential, cycle life, and rechargeability of the battery. Electrochemical impedance spectra, cyclic voltammetry, and chronoamperometry were utilized to determine the reversible reactions associated with the air cathode.

Cell Chemistry of Sodium–Oxygen Batteries with Various Nonaqueous Electrolytes

Development of the nonaqueous Na–O2 battery with a high electrical energy efficiency requires the electrolyte stable against attack of highly oxidative species such as nucleophilic anion O2•–. A combined evaluation method was used to investigate the Na–O2 cell chemistry with various solvents, including ethylene carbonate/propylene carbonate (EC/PC)-, N-methyl-N-propylpiperidinium bis(trifluoromethansulfonyl) imide (PP13TFSI)-, and tetraethylene glycol dimethyl ether (TEGDME)-based electrolytes. It is found that the TEGDME-based electrolytes have the best stability with the predominant yield of NaO2 upon discharge and the largest electrical energy efficiency (approaching 90%). Both EC/PC- and PP13TFSI-based electrolytes severely decompose during discharge, forming a large amount of side products. Analysis of the acid dissociation constant (pKa) of these electrolyte solvents reveals that the TEGDME has the relatively large value of pKa, which correlates with good stability of the electrolyte and high round-...

Carbide derived carbon electrode with natural graphite addition in magnesium electrolyte based cell for supercapacitor enhancements

Herein, we have presented a supercapacitor based on carbide derived carbon (CDC) electrode with natural graphite (NG) addition. The capacitor was analyzed at 22 °C by cyclic voltammetry, galvanostatic charge-discharge and impedance techniques using a 0.5 mol/L of magnesium (II) bis (trifluoro methanesulfonyl) imide (MgTFSI) in ethylene carbonate-propylene carbonate (EC: PC = 1: 1, v/v) as electrolyte. The results conclude that the CDC cell enhancements have been proven by the composite electrode (5%–30% NG to CDC) especially on the cell efficiency and voltage i.e., the CDC cell around 2.5 V limit was improved. An obtainable specific capacitance, real power and energy density are 15 F·g−1, 1.2 kW·kg−1 and 15 Wh·kg−1, respectively.

Enhanced ionic conductivity in borate ester plasticized Polyacrylonitrile electrolytes for lithium battery application

The effect of low molecular weight borate ester on the ionic conductivity of polyacrylonitrile (PAN) was systematically investigated by means of measuring conductivity using the impedance technique. Gel polymer electrolyte (SPE) films consisting of PAN as host polymer, LiCF3SO3 and LiBF4 as ionic salts, and poly (ethylene glycol) borate ester (PEGB), ethylene carbonate/propylene carbonate (EC/PC) as plasticizers were prepared by physical blending method. All measurements were performed on electrolyte samples with various contents. Fourier transform infrared spectroscopy (FT-IR) gave evidence of the interactions among PAN, plasticizers and lithium salt. The surface morphology of the electrolytes was investigated by scanning electron microscopy (SEM). Thermal properties of these materials were searched with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Conductivity studies of these blend polymer electrolytes were carried out in the temperature range 20–100°C. The maximum ionic conductivity values of 1.8×10−3 and 1.4×10−4Scm−1 were measured for the film containing 4PAN-10EC/PC-4LiBF4 and 4PAN-10PEGB-4LiCF3SO3, respectively, at room temperature. These films have a good conductivity, better dimensional stability and wide electrochemical stability window. These unique properties make the composite gel membranes suitable for application as electrolyte in rechargeable Li-ion batteries.

AC ionic conductivity and DC polarization method of lithium ion transport in PMMA–LiBF4 gel polymer electrolytes

Polymethylmethacrylate (PMMA)-based gel polymer electrolytes comprising ethylene carbonate–propylene carbonate (EC/PC) mixed solvent plasticizer and various concentrations of lithium tetrafluoroborate (LiBF4) salt are prepared using a solvent casting technique. Electrical conductivity and transference number measurements were carried out to investigate conductivity and charge transport in the gel polymer electrolytes. The conductivity results show that the ionic conductivity of the samples increases when the amount of salt is increased, however decreases after reaching the optimum value. This result is consistent with the transference number measurements. The conductivity–frequency dependence plots show two distinct regions; i.e. at lower frequencies the conductivity increases with increasing frequency and the frequency independent plateau region at higher frequencies. The temperature-dependence conductivity of the films seems to obey the Arrhenius rule.

Cathodic and Thermal Stabilities of the P(VdF-HFP)-Based Ionic Liquid Composite Polymer Electrolyte

以聚偏氟乙烯-六氟丙烯P(VdF-HFP)聚合物为基体, 制备了含离子液体1-甲基-3-乙基咪唑六氟磷酸盐(EMIPF6)、用于锂离子电池的离子液体复合聚合物电解质[P(VdF-HFP)/LiPF 6 /EMIPF 6 /EC(碳酸乙烯酯)-PC(碳酸丙烯酯)]. 采用热重分析法以及燃烧实验测试了复合聚合物电解质的热稳定性. 离子电导率测试表明, 离子液体的存在显著改善了复合聚合物电解质的离子传输; 循环伏安测试表明, 添加剂EC和PC的加入提高了复合电解质的阴极稳定性, 制得的离子液体复合聚合物电解质在0.3-4.3 V 电压范围内稳定存在. Li 4 Ti 5 O 12 和LiCoO 2 为电极材料、P(VdF-HFP)/LiPF 6 /EMIPF 6 /EC-PC 为电解质的半电池表现出优良的循环性能, 0.1C充放电倍率下, Li/LiCoO 2 和Li/Li 4 Ti 5 O 12 半电池的可逆容量分别为130和144 mAh·g -1 . 但EC、PC在一定程度上降低了离子液体复合聚合物电解质的热稳定性.

Impedance and FTIR studies on plasticized PMMA–LiN(CF3SO2)2 nanocomposite polymer electrolytes

Plasticized polymer electrolytes composed of poly(methyl methacrylate) (PMMA) as the host polymer and lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 as a salt were prepared by solution casting technique at different ratios. The ionic conductivity varied slightly and exhibited a maximum value of 3.65 × 10−5 S cm−1 at 85% PMMA and 15% LiN(CF3SO2)2. The complexation effect of salt was investigated using FTIR. It showed some simple overlapping and shift in peaks between PMMA and LiN(CF3SO2)2 salt in the polymer electrolyte. Ethylene carbonate (EC) and propylene carbonate (PC) were added to the PMMA–LiN(CF3SO2)2 polymer electrolyte as plasticizer to enhance the conductivity. The highest conductivities obtained were 1.28 × 10−4 S cm−1 and 2.00 × 10−4 S cm−1 for EC and PC mixture system, respectively. In addition, to improve the handling of films, 1% to 5% fumed silica was added to the PMMA–LiN(CF3SO2)2–EC–PC solid polymer electrolyte which showed a maximum value at 6.11 × 10−5 S cm−1 for 2% SiO2.

PREPARATION OF STAR NETWORK PEG-BASED GEL POLYMER ELECTROLYTES FOR ELECTROCHROMIC DEVICES

An amorphous, colorless, and highly transparent star network polymer with a pentaerythritol core linking four PEG-block polymeric arms was synthesized from the poly(ethylene glycol) (PEG), pentaerythritol, and dichloromethane by Williamson reaction. FTIR and 1 H-NMR measurement demonstrated that the polymer repeating units were C(CH2―OCH2O―(CH2CH2O)m―CH2O―(CH2CH2O)n―CH2O)4. The polymer host held well mechanical properties for pentaerythritol cross-linking. The gel polymer electrolytes based on Lithium perchlorate (LiClO4) and ethylene carbonate/propylene carbonate (EC/PC) were prepared and characterized by AC impedance spectroscopy and thermogravimetry (TG), the results showed thermal stability up to at least 150°C and ionic conductivity reaching 8.83 × 10 −4 S·cm −1 at room temperature. The gel polymer electrolytes were further evaluated in electrochromic devices (ECD) fabricated by transparent PET-ITO and electrochromic active viologen derivative films, and its excellent performance promised the usage of the gel polymer electrolytes as ionic conductor material in ECD.

Application of polyacrylonitrile-based polymer electrolytes in rechargeable lithium batteries

Polyacrylonitrile (PAN)-based polymer electrolytes have obtained considerable attention due to their fascinating characteristics such as appreciable ionic conductivity at ambient temperatures and mechanical stability. This study is based on the system PAN–ethylene carbonate (EC)–propylene carbonate (PC)–lithium trifluoromethanesulfonate (LiCF3SO3). The composition 15 mol% PAN–42 mol% EC–36 mol% PC–7 mol% LiCF3SO3 has shown a maximum room temperature conductivity of 1.2 × 10−3 S cm−1. Also, it was possible to make a thin, transparent film out of that composition. Cells of the form, Li/PAN–EC–PC–LiCF3SO3/polypyrrole (PPy)–alkylsulfonate (AS) were investigated using cyclic voltammetry and continuous charge–discharge tests. When cycled at low scan rates, a higher capacity could be obtained and well-defined peaks were present. The appearance of peaks elucidates the fact that redox reactions occur completely. This well proves the reason for higher capacity. The average specific capacity was about 43 Ah kg−1. Cells exhibited a charge factor close to unity during continuous charging and discharging, indicating the absence of parasitic reactions.

Preparation and proton conductivity of poly(vinylidene fluoride)/layered double hydroxide nanocomposite gel electrolytes

Layered double hydroxide (LDH) was synthesized in the presence of sodium dodecyl sulfate. X-ray diffraction (XRD) and infrared spectrum revealed that dodecyl sulfate (DS) anions were successfully intercalated into the interlayers of LDH. Poly(vinylidene fluoride)/LDH nanocomposite membranes were prepared by mixing the DS intercalated LDH with poly(vinylidene fluoride) (PVDF) in N,N’′-dimethylformamide solution followed by the solvent evaporation. The nanocomposite membranes were further swollen with a H3PO4 solution in ethylene carbonate-propylene carbonate to obtain the proton conducting nanocomposite gel electrolytes. XRD and transmission electron microscope results showed that LDH particles were well-dispersed in the polymer matrix and partially intercalated by polymer chains. The proton conductivity was highly enhanced in the nanocomposite gel electrolyte systems. In the case of the nanocomposite gel electrolyte containing 7.40 wt.% LDH, the proton conductivity increased by about 2.5 times compared to pure PVDF gel electrolyte.