Nanocomposite Electrolytes Research Articles

Effect of silicone dioxide and poly(ethylene glycol) on the conductivity and relaxation dynamics of poly(ethylene oxide)–silver triflate solid polymer electrolyte

AbstractThe conducting and relaxation dynamics of Ag+ ions in poly(ethylene oxide) (PEO)–silver triflate (AgCF3SO3) solid polymer electrolytes (SPEs) containing nanosize SiO2 filler and poly(ethylene glycol) (PEG) as a plasticizer were studied in the frequency range 10 Hz to 10 MHz and in the temperature range 303–328 K. The comparatively lower conductivity of the plasticized (PEG) PEO–AgCF3SO3–SiO2 nanocomposite electrolyte system was examined by analysis of the Fourier transform infrared (FTIR) spectroscopy and conductivity data. The electric modulus (M″) properties of the SPE systems were investigated. A shift of the M″ peak spectra with frequency was found to depend on the translation ion dynamics and the conductivity relaxation of the mobile ions. The value of the conductivity relaxation time was observed to be lower for the PEO–AgCF3SO3 system only with nanofiller SiO2. The scaling behavior of the M″ spectra showed that the dynamical relaxation processes was temperature‐independent in the PEO–AgCF3SO3 and PEO–AgCF3SO3–SiO2–PEG polymer systems, whereas they were temperature‐dependent for the PEO–AgCF3SO3–SiO2 system. However, the relaxation processes of all of theses systems were found to be dependent on their respective compositions. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Study of Ceria-Carbonate Nanocomposite Electrolytes for Low-Temperature Solid Oxide Fuel Cells

Composite and nanocomposite samarium doped ceria-carbonates powders were prepared by solid-state reaction, citric acid-nitrate combustion and modified nanocomposite approaches and used as electrolytes for low temperature solid oxide fuel cells. X-ray Diffraction, Scanning Electron Microscope, low-temperature Nitrogen Adsorption/desorption Experiments, Electrochemical Impedance Spectroscopy and fuel cell performance test were employed in characterization of these materials. All powders are nano-size particles with slight aggregation and carbonates are amorphous in composites. Nanocomposite electrolyte exhibits much lower impedance resistance and higher ionic conductivity than those of the other electrolytes at lower temperature. Fuel cell using the electrolyte prepared by modified nanocomposite approach exhibits the best performance in the whole operation temperature range and achieves a maximum power density of 839 mW cm(-2) at 600 degrees C with H2 as fuel. The excellent physical and electrochemical performances of nanocomposite electrolyte make it a promising candidate for low-temperature solid oxide fuel cells.

A quasi solid state dye-sensitized solar cell based on poly(vinylidenefluoride-co-hexafluoropropylene)/SBA-15 nanocomposite membrane

Poly(vinylidenefluoride-co-hexafluoropropylene)/SBA-15 molecular sieves (designated as P(VDF-HFP)/SBA-15) nanocomposite membranes were prepared by a solution casting method. Prior to blending, the SBA-15 molecular sieves were impregnated with dimethylpropylimidazolium iodide (DMPII) ionic liquid. The P(VDF-HFP)/SBA-15 nanocomposite membranes were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and AC impedance spectroscopy. The room temperature ionic conductivity of the P(VDF-HFP)/SBA-15A nanocomposite polymer electrolyte was of the order of around 10−3Scm−1. The quasi-solid-state dye-sensitized solar cells (DSSCs) were assembled by using photo-electrodes of TiO2 films on FTO/glass and the counter electrode based on the pulsed-plated Pt films. P(VDF-HFP)/I-SBA-15 nanocomposite electrolyte membrane containing dimethylpropylimidazolium iodide (DMPII) provides the best energy conversion efficiency of ca. 5.29%. This result indicates that the P(VDF-HFP)/I-SBA-15 nanocomposite membrane is a good candidate for a quasi-solid-state DSSC applications.

Ca3(PO4)2‐incorporated poly(ethylene oxide)‐based nanocomposite electrolytes for lithium batteries. Part II. Interfacial properties investigated by XPS and a.c. impedance studies

AbstractThe surface layer and elemental composition of a lithium‐metal electrode before and after in contact with nanocomposite polymer electrolytes (NCPEs) comprising poly(ethylene oxide)/Ca3(PO4)2/LiX (X = N(CF3SO2)2, ClO4) were analyzed by X‐ray photoelectron spectroscopy. The presence of Li2CO3/LiOH in the outer layer of the native film was identified. The formation of LiF was detected on lithium surface when in contact with NCPE containing LiN(CF3SO2)2 and is attributed to the reaction between the native film and impurities. Li/NCPE/Li symmetric cells were assembled, and the thickness of the solid electrolyte interface as a function of time was analyzed at 60°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

SDC/Na2CO3 nanocomposite: New freeze drying based synthesis and application as electrolyte in low-temperature solid oxide fuel cells

A key issue to develop low-temperature solid oxide fuel cells (LTSOFCs) is to develop new electrolyte materials with enhanced ionic conductivity. Recently, SDC/Na2CO3 nanocomposite, as a proton and oxide co-ion conductor, has been developed as promising electrolyte candidates for LTSOFCs, where Na2CO3 as the secondary phase performs several crucial functions. However, it’s difficult to control the homogeneity of Na2CO3 phase in the composite by the current methods for composite fabrication. In this study, we report a new freeze drying technique to fabricate SDC/Na2CO3 nanocomposites with different content of Na2CO3. Structural and morphological study confirmed that the homogeneity of both SDC and Na2CO3 phases in the nanocomposite is well controlled by the freeze drying technique. The effect of Na2CO3 content on proton and oxygen ion conductivities of SDC-carbonate samples were investigated by the four-probe d.c. measurement. Proton conductivity transformation around 350 °C has been observed for all the SDC/Na2CO3 nanocomposites due to the glass transition of amorphous Na2CO3 phase, and the proton conductivity is dependent on Na2CO3 content. While oxygen ion conductivity deceases with the increasing of Na2CO3 volume fraction in the nanocomposite. Finally, SOFCs were fabricated using SDC/Na2CO3 nanocomposite samples and tested for electrochemical performances. The excellent performance of SOFCs using SDC/Na2CO3 nanocomposite electrolyte verifies that nanocomposite approach is an effective way to fabricate electrolyte with enhanced ionic conductivity for LTSOFCs.

Polyoctahedral Silsesquioxane-Nanoparticle Electrolytes for Lithium Batteries: POSS-Lithium Salts and POSS-PEGs

Nanocomposite electrolytes have been prepared from mixtures of two polyoctahedral silsesquioxanes (POSS) nanomaterials, each with a SiO1.5 core and eight side groups. POSS-PEG8 has eight polyethylene glycol side chains that have low glass transition (Tg) and melt (Tm) temperatures and POSS-benzyl7(BF3Li)3 is a Janus-like POSS with hydrophobic phenyl groups and −Si–O–BF3Li ionic groups clustered on one side of the SiO1.5 cube. The electron-withdrawing POSS cage and BF3 groups enable easy dissociation of the Li+. In the presence of polar POSS-PEG8, the hydrophobic phenyl rings of POSS-benzyl7(BF3Li)3 aggregate and crystallize, forming a biphasic morphology, in which the phenyl rings form the structural phase and the POSS-PEG8 forms the conductive phase. The −Si–O–BF3– Li+ groups of POSS-benzyl7(BF3Li)3 are oriented toward the polar POSS-PEG8 phase and dissociate so that the Li+ cations are solvated by the POSS-PEG8. The nonvolatile nanocomposite electrolytes are viscous liquids that do not flow under their ...

Electrochemical study on co-doped ceria–carbonate composite electrolyte

A co-doped ceria–carbonate (Ce 0.8Sm 0.2− x Ca x O 2− δ –Na 2CO 3) has been synthesized by a co-precipitation method. The detailed electrochemical characterizations (e.g. impedance spectra, polarization curve and IV curves) of this composite material are reported and discussed. The two phase nanocomposite electrolytes with carbonate coated on the co-doped ceria displays dual (H +/O 2−) ion conduction at low temperature (300–600 °C) in solid oxide fuel cell. The observed remarkable temperature-dependent of conductivity is attributed to the softening/melting of carbonate phase as the physical state of carbonate phase transforms from solid to molten state. Coexistence of various charge carriers, oxide phase composition, and the oxide–carbonate interfacial area are investigated by Raman spectra. The enhancement of conductivity is also discussed by the general mixing rule/percolation theory of composite interfaces. The co-doping with 2nd phase gives a good approach to realize challenges for solid oxide fuel cell.

Enhanced ionic conductivity in calcium doped ceria – Carbonate electrolyte: A composite effect

Recently, ceria-based nanocomposites, as a proton and oxygen ion conductor, has been developed as promising electrolyte candidates for low-temperature solid oxide fuel cells (LTSOFCs). Up to now, samarium doped ceria (SDC) was studied as a main oxide for nanocomposite electrolyte; while calcium doped ceria (CDC) is considered as a good alternative from both material performance and economical aspects. Yet the conduction behavior of CDC-based composite has not been reported. In the present study, calcium doped ceria was prepared by oxalate co-precipitation method, and used for the fabrication of CDC/Na 2 CO 3 composite. The thermal decomposition process, structure and morphology of the samples were characterized by TGA, XRD, SEM, etc. The oxygen ion conductivity of single phase CDC sample was measured by electrochemical impedance spectroscopy (EIS), while the proton and oxygen ion conductivity of CDC/Na 2 CO 3 nanocomposite sample were determined by four-probe d.c. measurements. The CDC/Na 2 CO 3 samples show significantly enhanced overall ionic conductivity compared to that of single phase CDC samples, demonstrating pronounced composite effect. This confirms that the use of nanocomposite as electrolyte can effectively lower the operation temperature of SOFC due to improved ionic conductivity.

Effect of different anions of lithium salt and MMT nanofiller on ion conduction in melt-compounded PEO–LiX–MMT electrolytes

Polymer nanocomposite electrolyte (PNCE) films composed of poly(ethylene oxide) (PEO), lithium salt (\( {\text{LiX}};\;{\text{X}} = ClO_4^{ - },\;BF_4^{ - },\;C{F_3}SO_3^{ - } \)) and montmorillonite (MMT) clay as nanofiller were prepared by melt-compounded hot-pressed technique at 70 °C under 3 tons of pressure. The ionic conductivity and relaxation behaviour of the films were investigated by dielectric relaxation spectroscopy in the frequency range of 20 Hz to 1 MHz at ambient temperature. The results revealed that the ionic conductivity of the PNCE films having 20:1 stoichiometric ratio of ethylene oxide monomer units to the lithium cation are governed by the size of different anions and the dissociation constant of salt, and also MMT concentration. It was found that PEO–LiBF4 film has comparative high dc ionic conductivity, whereas both the LiBF4 and LiClO4 containing PNCE films exhibit anomalous conductivity behaviour with varying MMT concentration. The PEO–LiCF3SO3 film has two orders of magnitude low value of dc ionic conductivity as compared to that of the other salts electrolyte films, but its conductivity enhances by one order of magnitude when 2 wt.% MMT is added as filler. A correlation between the values of ionic conductivity, conductivity relaxation time and the real part of permittivity at 1 MHz were found and the same was discussed in relation to the transient ion-dipolar type cross-linked structural behaviour of the polymeric nanocomposite electrolytes.

A novel core–shell nanocomposite electrolyte for low temperature fuel cells

We report a rapid and cost-effective method to coat SDC nano-particles with a thin LiZn-oxide nanocomposite layer. This composite is determined to have a structure with two phases consisting of Li 2O and ZnO and examined to distribute over the surfaces of SDC nano-particles uniformly by using energy dispersive X-ray (EDX) and high-resolution TEM (HRTEM). The measurments of electrical property demonstrate that such a thin layer enables the ionic conductivity of SDC to be significantly increased (higher than 0.1 S cm −1 at the temperature of 300 °C) equivalent to the conductivity of pure SDC at 800 °C or YSZ at 1000 °C. This superionic conductivity is caused by the two-phase interfaces formed between nano-particles.

Novel Solid‐State Li/LiFePO4 Battery Configuration with a Ternary Nanocomposite Electrolyte for Practical Applications

A novel ternary nanocomposite electrolyte based on an ionic liquid electrolyte immobilized in a mesoporous SiO2 matrix is demonstrated in a solid-state Li/TNCE/LiFePO4 battery configuration (see figure) to give solid-state lithium ion batteries viable for practical applications. This specific solid-state battery has the advantages of high energy/power density, good safety, low cost, flexible design, and environmental benignity.

Investigation on ion conduction behaviour in Zn-ferrite based polymer nanocomposite electrolyte

Present paper deals with, improvement in ion transport property and dielectric relaxation of polyethylene oxide (PEO)-based polymer electrolytes subsequent to dispersal of nanosized Zn-ferrite filler particles. The nanocomposite polymer electrolyte (NCPE) system [93PEO:7NH4SCN]: x% Zn-ferrite was prepared by solution cast technique through dispersal of sol gel derived Zn-ferrite nano powder in the pristine polymer electrolyte solution. The structural and morphological behavior of NCPEs have been studied by XRD, SEM, IR and DSC measurements. Electrical conductivity (both a.c. & d.c.) measurement on nanocomposite polymer electrolyte sample have been carried out using impedance spectroscopic technique. Dielectric relaxation studies were extracted by impedance data. The hopping ion transport mechanism in NCPEs has been concluded with the help of dielectric and modulus formalism.

Studies on poly(vinylidene fluoride-co-hexafluoropropylene) based gel electrolyte nanocomposite for sodium–sulfur batteries

Experimental investigations on a sodium ion conducting gel polymer electrolyte nanocomposite based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), dispersed with silica nanoparticles are reported. The gel nanocomposites have been obtained in the form of dimensionally stable, transparent and free-standing thick films. Physical characterization by X-ray diffraction (XRD), Fourier transform Infra-red (FTIR) spectroscopy and Scanning electron microscopy (SEM) have been performed to study the structural changes and the ion–filler–polymer interactions due to the dispersion of SiO 2 nanoparticles in gel electrolytes. The highest ionic conductivity of the electrolyte has been observed to be 4.1 × 10 −3 S cm − 1 at room temperature with ~ 3 wt.% of SiO 2 particles. The temperature dependence of the ionic conductivity has been found to be consistent with Vogel-Tammen-Fulcher (VTF) relationship in the temperature range from 40 to 70 °C. The sodium ion conduction in the gel electrolyte film is confirmed from the cyclic voltammetry, impedance analysis and transport number measurements. The value of sodium ion transport number (t Na+) of the gel electrolyte is significantly enhanced to a maximum value of 0.52 on the 15 wt.% SiO 2 dispersion. The physical and electrochemical analyses indicate the suitability of the gel electrolyte films in the sodium batteries. A prototype sodium–sulfur battery, fabricated using optimized gel electrolyte, offers the first discharge capacity of ~165 mAh g − 1 of sulfur.

Ionic transport studies in hyperbranched polyurethane/clay nanocomposite gel polymer electrolytes

In the present work, we report a novel nanocomposite gel electrolytes based on intercalation of hyperbranched polyurethane (HBPU) into organically modified montmorillonite for application in Li-ion batteries. The nanocomposites have been prepared by solution intercalation technique with varying clay loading. The formation of partially exfoliated nanocomposites has been confirmed by X-ray diffraction. Nanocomposites were soaked with 1 M LiCO4 in 1:1 (v/v) solution of propylene carbonate and diethyl carbonate to get the required gel electrolytes. AC impedance analysis shows that ionic conductivity increases with the increase of clay loading and attains the highest value of 8.3 × 10−3 S/cm for 5 wt.% clay concentration. Surface morphology of the nanocomposite electrolytes has been examined by SEM analysis. Improvement of electrochemical properties, viz., electrochemical potential window and interfacial stability, is also observed in the clay-loaded HBPU samples.

Enhancement in electrical and stability properties of amorphous polymer based nanocomposite electrolyte

A novel combination of dispersed phase polymer nanocomposite electrolyte (PNCE) series based on an amorphous polymer host (PMMA) 4–LiClO 4 complex dispersed with nanocrystalline CeO 2 is reported. XRD analysis has confirmed the dispersed phase nanocomposite formation. Effect of nano CeO 2 dispersion on ion–ion and ion–polymer interactions has been analyzed. A drastic enhancement in electrical conductivity, by 2 orders of magnitude at 30 °C and 5 orders of magnitude at 100 °C, has occurred on nano CeO 2 dispersion when compared with room temperature conductivity of undispersed PS film. An excellent correlation between variation of d.c. conductivity and free mobile charge carriers has been observed. An ion conduction model is proposed. Strength of the model lies in the experimental evidences from FTIR, conductivity and TEM analyses. Thermal analysis indicates a strong dependence of thermodynamical parameters, e.g., glass transition temperature (T g), crystalline melting temperature (T m), enthalpy etc. on filler addition. Substantial improvement in voltage stability (~ 4.4 V), thermal stability and ion transport properties has been noticed on nano CeO 2 dispersion.

Effects of TiO2 on conductivity performance of cellulose acetate based polymer gel electrolytes for proton batteries

An experimental investigation is performed on proton conducting polymer gel electrolyte nanocomposites based on cellulose acetate dispersed with nanosized titanium dioxide particles. The nanocomposite polymer gel electrolyte systems are in the form of a highly viscous gel. The optimised material, with 7·0 wt-%TiO2, offers the highest electrical conductivity of 1·37×10−2 S cm−1 at room temperature (30°C) and also possesses the lowest activation energy. A discharge capacity of 60·1 and 54·1 mA h is observed when the cells are discharged at a constant current of 0·5 and 1·0 mA, respectively. Both electrical and electrochemical studies demonstrate promising characteristics for these composite polymer gel electrolytes, making them suitable as electrolytes in proton batteries.

Ac conductivity and relaxation in CdO doped poly ethylene oxide-LiI nanocomposite electrolyte

We have studied the ac conductivity and relaxation in PEO-LiI electrolytes in which different concentrations of CdO nanoparticles (ranging from 0.05 to 0.2 wt. %) have been introduced. The ac conductivity data have been discussed in the framework of power law and electric modulus formalisms. The hopping frequency obtained from the power law analysis obeys the Vogel–Tamman–Fulcher relation and the sample possessing the highest hopping frequency shows the highest dc conductivity. Furthermore, the frequency exponent decreases with the increase of temperature, suggesting a weaker correlation among the Li+ ions. Scaling of the conductivity spectra has also been performed in order to obtain insight into the relaxation mechanisms. We have observed that the imaginary modulus spectra are much broader than the Debye peak-width, but are asymmetric and skewed toward the high frequency sides of the maxima. The modulus data have been fitted to the non-exponential Kohlrausch–Williams–Watts function and the value of the stretched exponent is fairly low, suggesting a wide distribution of relaxation times and cooperative motion of the ions in the nanocomposites.

Heterogeneously doped polyethylene glycol as nano-composite soft matter electrolyte

We have applied the concept of heterogeneous doping [1] to prepare and examine composite electrolytes, consisting of silica particles, low molecular weight polyethylene glycol solvents and lithium perchlorate salt. These “soggy sand” electrolytes combine high ionic conductivities (on the order of mS cm −1) and high Li transference numbers (typically 60–80%) with improved mechanical properties. They were characterized using differential scanning calorimetry, dc-polarization and ac-impedance spectroscopy, zeta potential measurements and viscosimetry. Oxide, size and concentration as well as solvent molecular weight were varied to better understand the influence of ceramic oxide fillers on the ion conduction in these systems. As regarding the filler content, we observe that both conductivity and transference number of Li + start increasing already at low volume fractions of oxide particles, reach a maximum and subsequently decrease to low values. The percolating network is – after initial partial coarsening – found to be stable within the time periods of the measurements.

Low-cost quasi-solid-state dye-sensitized solar cells based on a metal-free organic dye and a carbon aerogel counter electrode

Low-cost quasi-solid-state dye-sensitized solar cells (DSSCs) are designed and fabricated by using a metal-free organic dye and a mesoporous carbon aerogel instead of expensive ruthenium-based sensitizers and Pt electrode. The electrospun TiO2 nanorods are added into a polyvinylidene fluoride (PVDF) solution to form a 3D network nanocomposite gel electrolyte. The presence of TiO2 nanorods in the gel electrolyte obviously increases the ionic conductivity and decreases charge-transfer resistance of the DSSC. The effects of the gel electrolyte and the carbon aerogel counter electrode on electrochemical and photovoltaic properties have been investigated in detail. Particularly, an optimized DSSC with a nanocomposite gel electrolyte and a carbon aerogel counter electrode affords a power conversion efficiency (PCE) of 6.20% at a light intensity of 100 mW cm−2.

Dielectric spectroscopy and confirmation of ion conduction mechanism in direct melt compounded hot-press polymer nanocomposite electrolytes

Solid-type polymer nanocomposite electrolyte (PNCE) comprising poly(ethylene oxide) (PEO), lithium perchlorate (LiClO4) and montmorillonite (MMT) nano-platelets were synthesized by direct melt compounded hot-press technique at 70 °C under 3 tons of pressure. The spectra of complex dielectric function, electric modulus and alternating current (ac) electrical conductivity, and complex impedance plane plots of these materials were investigated in the frequency range 20 Hz to 1 MHz at ambient temperature. The variation of electrode polarization and ionic conduction relaxation times with MMT concentration up to 20 wt.% confirms their strong correlation with direct current ionic conductivity. The predominance of exfoliated MMT structures in PEO matrix and their effect on cation conduction mechanism and ion pairing were discussed by considering a supramolecular transient cross-linked structure. The normalized ac conductivity as a function of scaled frequency of these PNCE materials obey the universal time–concentration superposition behaviour alike the disordered solid ionic conductors.