Nanocomposite Electrolytes Research Articles

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.

Innovative Polymer Nanocomposite Electrolytes: Nanoscale Manipulation of Ion Channels by Functionalized Graphenes

The chemistry and structure of ion channels within the polymer electrolytes are of prime importance for studying the transport properties of electrolytes as well as for developing high-performance electrochemical devices. Despite intensive efforts on the synthesis of polymer electrolytes, few studies have demonstrated enhanced target ion conduction while suppressing unfavorable ion or mass transport because the undesirable transport occurs through an identical pathway. Herein, we report an innovative, chemical strategy for the synthesis of polymer electrolytes whose ion-conducting channels are physically and chemically modulated by the ionic (not electronic) conductive, functionalized graphenes and for a fundamental understanding of ion and mass transport occurring in nanoscale ionic clusters. The functionalized graphenes controlled the state of water by means of nanoscale manipulation of the physical geometry and chemical functionality of ionic channels. Furthermore, the confinement of bound water within the reorganized nanochannels of composite membranes was confirmed by the enhanced proton conductivity at high temperature and the low activation energy for ionic conduction through a Grotthus-type mechanism. The selectively facilitated transport behavior of composite membranes such as high proton conductivity and low methanol crossover was attributed to the confined bound water, resulting in high-performance fuel cells.

GDC - Y 2 O 3 Oxide Based Two Phase Nanocomposite Electrolyte

Oxide based two phase composite electrolyte (Ce0.9Gd0.1O2–Y2O3) was synthesized by coprecipitation method. The nanocomposite electrolyte showed the significant performance of power density 785 mW cm−2 and higher conductivities at relatively low temperature 550°C. Ionic conductivities were measured with ac impedance spectroscopy and four-probe dc method. The structural and morphological properties of the prepared electrolyte were investigated by scanning electron microscope (SEM). The thermal stability was determined with differential scanning calorimetry. The particle size that was calculated with Scherrer formula, 15–20 nm, is in a good agreement with the SEM and X- ray diffraction results. The purpose of this study is to introduce the functional nanocomposite materials for advanced fuel cell technology to meet the challenges of solid oxide fuel cell.

Preparation and characterization of Sm0.2Ce0.8O1.9/Na2CO3 nanocomposite electrolyte for low-temperature solid oxide fuel cells

Sm0.2Ce0.8O1.9 (SDC)/Na2CO3 nanocomposite synthesized by the co-precipitation process has been investigated for the potential electrolyte application in low-temperature solid oxide fuel cells (SOFCs). The conduction mechanism of the SDC/Na2CO3 nanocomposite has been studied. The performance of 20 mW cm−2 at 490 °C for fuel cell using Na2CO3 as electrolyte has been obtained and the proton conduction mechanism has been proposed. This communication demonstrates the feasibility of direct utilization of methanol in low-temperature SOFCs with the SDC/Na2CO3 nanocomposite electrolyte. A fairly high peak power density of 512 mW cm−2 at 550 °C for fuel cell fueled by methanol has been achieved. Thermodynamical equilibrium composition for the mixture of steam/methanol has been calculated, and no presence of C is predicted over the entire temperature range. The long-term stability test of open circuit voltage (OCV) indicates the SDC/Na2CO3 nanocomposite electrolyte can keep stable and no visual carbon deposition has been observed over the anode surface.

Dielectric and Ion Transport Studies in [PVA: LiC2H3O2]: Li2Fe5O8 Polymer Nanocomposite Electrolyte System

The present work deals with the findings on optical and ion transport behavior in a ferrite-doped polymer nanocomposite electrolyte system, namely, [(100 − x) PVA + xLiC2H3O2]: yLiFe5O8. This polymer electrolyte system has been characterized by SEM, DSC, IR and C-V measurements. The addition of filler seems to disturb the crystalline nature of the host matrix while the doping of salt shows a similar structure, but with a separate entity in SEM images. DSC studies reflect the interaction of the salt/filler with polymer with a change in morphology of the composite system. These results are well-corroborated by IR data. The effect of salt or filler in the enhancement of the a.c. conductivity of nanocomposite polymer electrolyte (NCPE) as well as dielectric relaxation behavior has been investigated with the help of impedance spectroscopy data. The a.c. conductivity of nanocomposite polymer electrolytes is seen to be best described by the universal power law.

Nanocomposites based on borate esters as improved lithium-ion electrolytes

Borate esters with different lengths of ethyleneoxy units were investigated as electrolyte solvents for lithium salts such as lithium triflate, perchlorate, bis(trifluoromethanesulfonyl)imide, bis(pentafluoroethanesulfonyl)imide and bis(oxalato)borate. The ionic conductivity of the salt solutions was measured to be of the order of 10−3 to 10−4 S cm−1 at room temperature. Transference number measurements for the borate ester–lithium perchlorate system indicated roughly equal contributions of cations and anions to the total conductivity, while the borate ester–lithium bis(oxalato)borate showed predominant anionic conductivity. Nanocomposite electrolytes were prepared by heterogeneous doping of the borate esters with silica. Composites with 10 nm silica particles exhibited low-viscous electrolyte behavior with a clear but modest conductivity enhancement at very low volume fractions of silica and a depression of the conductivity value at higher volume fractions. In the case of fumed silica (7 nm) the nanocomposites had at a sufficiently high volume fraction and a jelly, transparent appearance with the favorable mechanical properties of a high-viscous semi-solid without noteworthy decrease in the Li ion conductivity. In particular the last material with its combination of favourable electrical, mechanical and optical properties, promises to be a viable candidate for various applications (Li-based batteries, solar cells).

Investigations of microstructure and ionic conductivity for (PEO)8-ZnO-LiClO4 polymer nanocomposite electrolytes

The effects of nanosized ZnO on the microstructure, the free volume and the ionic conductivity of poly ethylene oxide (PEO) nanocomposite electrolytes (PEO)8-ZnO-LiClO4 are systematically studied by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and positron annihilation lifetime spectroscopy (PALS), respectively. The experimental results show that the presence of the nanosized ZnO brings about a reduction in the crystallinity of the PEO phase and a very marked increase in ionic conductivity. PALS discrete analysis shows that the free volume size, the free volume concentration and the relative free volume fraction significantly increase with the increase of nano-ZnO. Specially, it is the first time to observe the occurrence of peaks of the free volume distribution split after nano-ZnO has been filled, which indicates that the ZnO added into (PEO)8-LiClO4 has an important effect on the microstructure for nanocomposites due to the interaction between the nano-ZnO and matrix. A direct correlation between the free volume fraction and the ionic conductivity is observed, and the ionic conductivity mechanism is discussed.

Electrochemical Characterization on SDC/Na2CO3 Nanocomposite Electrolyte for Low Temperature Solid Oxide Fuel Cells

Our previous work has demonstrated that novel core-shell SDC/Na2CO3 nanocomposite electrolyte possesses great potential for the development of low temperature (300-600 degrees C) solid oxide fuel cells. This work further characterizes the nanocomposite SDC/Na2CO3 electrochemical properties and conduction mechanism. The microstructure of the nanocomposite sintered at different temperatures was analyzed through scanning electron microscope (SEM) and X-ray diffraction (XRD). The electrical and electrochemical properties were studied. Significant conductivity enhancement was observed in the H2 atmosphere compared with that of air atmosphere. The ratiocination of proton conduction rather than electronic conduction has been proposed consequently based on the observation of fuel cell performance. The fuel cell performance with peak power density of 375 mW cm(-2) at 550 degrees C has been achieved. A.C. impedance for the fuel cell under open circuit voltage (OCV) conditions illustrates the electrode polarization process is predominant in rate determination.

Electrochemical study of the composite electrolyte based on samaria-doped ceria and containing yttria as a second phase

The purpose of this study is to develop new oxide ionic conductors based on nanocomposite materials for an advanced fuel cell (NANOCOFC) approach. The novel two phase nanocomposite oxide ionic conductors, Ce 0.8Sm 0.2O 2 − δ (SDC)-Y 2O 3 were synthesized by a co-precipitation method. The structure and morphology of the prepared electrolyte were investigated by means of X-ray diffraction (XRD) and high resolution scanning electron microscopy (HRSEM). XRD results showed a two phase composite consisting of yttrium oxide and samaria doped ceria and SEM results exhibited a nanostructure form of the sample. The yttrium oxide was used on the SDC as a second phase. The interface between two constituent phases and the ionic conductivities were studied with electrochemical impedance spectroscopy (EIS). An electrochemical study showed high oxide ion mobility and conductivity of the Y 2O 3-SDC two phase nanocomposite electrolytes at a low temperature (300–600 °C). Maximum conductivity (about 1.0 S cm −1) was obtained for the optimized Y 2O 3-SDC composite electrolyte at 600 °C. It is found that the nanocomposite electrolytes show higher conductivities with the increased concentration of yttrium oxides but decreases after reaching a certain level. A high fuel cell performance, 0.75 W cm −2, was achieved at 580 °C.

α‐Al2O3 improves the properties of gel polyacrylonitrile nanocomposite electrolytes used as electrolyte materials in rechargeable lithium batteries

AbstractIn this investigation, a series of gel polyacrylonitrile (PAN)/α‐Al2O3 nanocomposite electrolyte materials that incorporate various fractions of PAN, α‐Al2O3 inorganic powders, propylene carbonate and ethylene carbonate as cosolvents, and LiClO4 were prepared. X‐ray diffraction revealed that the gel nanocomposite electrolyte materials contained amorphous PAN in which was uniformly dispersed α‐Al2O3. The gel PAN/α‐Al2O3 nanocomposite electrolytes had lower glass‐transition temperatures (as determined by dynamic mechanical analysis) and higher conductivity than a similar electrolyte prepared in the absence of α‐Al2O3. The conductivity of the PAN/α‐Al2O3 nanocomposite films was inversely proportional to the size of the α‐Al2O3 particles and directly proportional to (I) the amount of α‐Al2O3 (up to 7 wt %), (II) the F value [LiClO4/CH2CH(CN) ratio], and (III) the amount of plasticizer (propylene carbonate/ethylene carbonate = 1 : 1). Cyclic voltammetry revealed that adding α‐Al2O3 significantly increased the electrochemical stability of the composite electrolyte system. A rechargeable lithium battery prepared using this gel nanocomposite electrolyte system exhibited good cyclability and a stable capacity. The coulombic efficiency for the recharge/discharge process was approximately 75%, even after 100 cycles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of plasticizer on structural and electrical properties of nanocomposite solid polymer electrolytes

The solid polymer electrolyte films based on polyethylene oxide, NaClO4 with dodecyl amine modified montmorillonite as filler, and polyethylene glycol as plasticizer were prepared by a tape casting method. The effect of plasticization on structural, microstructural, and electrical properties of the materials has been investigated. A systematic change in the structural and microstructural properties of plasticized polymer nanocomposite electrolytes (PPNCEs) on addition of plasticizer was observed in our X-ray diffraction pattern and scanning electron microscopy micrographs. Complex impedance analysis technique was used to calculate the electrical properties of the nanocomposites. Addition of plasticizer has resulted in the lowering of the glass transition temperature, effective dissociation of the salt, and enhancement in the electrical conductivity. The maximum value of conductivity obtained was ∼4.4 × 10−6 S cm−1 (on addition of ∼20% plasticizer), which is an order of magnitude higher than that of pure polymer nanocomposite electrolyte films (2.82 × 10−7 S cm−1). The enhancement in conductivity on plasticization was well correlated with the change in other physical properties.

A quasi solid-state dye-sensitized solar cell made of polypyrrole counter electrodes

Quasi-solid state dye-sensitized solar cells have been constructed using nanocrystalline titania, a Ureasil-based nanocomposite gel electrolyte and polypyrrole-functionalized counter electrode. Polypyrrole was synthesized by potentiostatic electrodeposition using pyrrole monomer as precursor by a simple procedure in aqueous solution. The thus obtained polypyrrole films were very robust. They were characterized by FE-SEM microscopy and electrochemical impedance spectroscopy and they were used for the construction of solar cells. The employment of polypyrrole electrocatalyst was judged satisfactory for the present application since it was only 30% less efficient than the corresponding counter electrodes functionalized with Pt.

Ceria-based nanocomposite with simultaneous proton and oxygen ion conductivity for low-temperature solid oxide fuel cells

The samarium doped ceria-carbonate (SDC/Na2CO3) nanocomposite systems have shown to be excellent electrolyte materials for low-temperature SOFCs, yet, the conduction mechanism is not well understood. In this study, a four-probe d.c. technique has been successfully employed to study the conduction behavior of proton and oxygen ion in SDC/Na2CO3 nanocomposite electrolyte. The results demonstrated that the SDC/Na2CO3 nanocomposite electrolyte possesses unique simultaneous proton and oxygen ion conduction property, with the proton conductivity 1–2 orders of magnitude higher than the oxygen ion conductivity in the temperature range of 200–600°C, indicating the proton conduction in the nanocomposite mainly accounts for the enhanced total ionic conductivity. It is suggested that the interface in composite electrolyte supplies high conductive path for proton, while oxygen ions are probably transported by the SDC grain interiors. An empirical “Swing Model” has been proposed as a possible mechanism of superior proton conduction.

Investigation of Advanced Hybrid PEM Based on Sulfonyl Fluoride PFSA and Grafted Inorganic Nanoparticles

Nano-composite polymer electrolyte membranes were prepared by melt processing of sulfonyl fluoride form of perfluorosulfonic acid (PFSA) ionomer and two families of inorganic nanofillers, spherical nanoparticles of silicon dioxide prepared by sol-gel, and clay sepiolite ungrafted and grafted with alkyl-sulfonic acid moieties. This approach produces hybrid electrolyte membranes with substantially better properties when compared to reference (neat polymer) and commercial Nafion. The melt-extruded nano-composite electrolytes showed very efficient dispersion of the inorganic fillers, an overall improvement in thermal and dimensional stability, and improved conductivities between 10-2 to 10-3 S.cm-1 at 80{degree sign}C over the entire humidity range from 100 to 30%.

Sulfonated Titanium Nanotubes Based Nanocomposite Blend Membranes for Fuel Cell Applications

New nano-composite electrolyte membranes with good electrical and mechanical properties have been developed using various blend compositions of poly(1-vinylimidazole) (PVIm), poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) and trifluoromethansulfonic acid (TA) with sulfonated nano-tubular titania (sTNT). Sulfonated nano-tubular titania and nanocomposite membranes have been successfully synthesized using in house acid-functionalised nano-tubular titania which was synthesized using hydrothermal method. Investigations of the synthesized membranes yield results of elevated conductivity and stability at temperatures in excess of 120°C. Conductivity values of 10-3 S/cm have been noted within these membranes and the morphology has also been found to improve with the addition of sulfonated nano-tubular titania. The nano-composite membranes also shows decrease in the water uptake with the addition of nano-tubular titania.

Electrical and electrochemical studies of poly(vinylidene fluoride)–clay nanocomposite gel polymer electrolytes for Li-ion batteries

A study is conducted on the electrical and electrochemical properties of nanocomposite polymer electrolytes based on intercalation of poly(vinylidene fluoride) (PVdF) polymer into the galleries of organically modified montmorillonite (MMT) clay. A solution intercalation technique is employed for nanocomposite formation with varying clay loading from 0 to 4 wt.%. X-ray diffraction results show the β phase formation of PVdF on intercalation. Transmission electron microscopy reveals the formation of partially exfoliated nanocomposites. The nanocomposites are soaked with 1 M LiClO 4 in a 1:1 (v/v) solution of propylene carbonate (PC) and diethyl carbonate (DEC) to obtain the required gel electrolytes. The structural conformation of the nanocomposite electrolytes is examined by Fourier transform infrared spectroscopy analysis. Examination with a.c. impedance spectroscopy reveals that the ionic conductivity of the nanocomposite gel polymer electrolytes increases with increase in clay loading and attains a maximum value of 2.3 × 10 −3 S cm −1 for a 4 wt.% clay loading at room temperature. The same composition exhibits enhancement in the electrochemical and interfacial properties as compared with that of a clay-free electrolyte system.

Effect of melt compounding temperature on dielectric relaxation and ionic conduction in PEO–NaClO4–MMT nanocomposite electrolytes

Polymer nanocomposite electrolytes (PNCEs) of poly(ethylene oxide) and sodium perchlorate monohydrate complexes with montmorillonite (MMT) clay up to 20 wt.% MMT concentration of poly(ethylene oxide) (PEO) are synthesized by melt compounding technique at melting temperature of PEO (∼70 °C) and NaClO4 monohydrate (∼140 °C). Complex dielectric function, electric modulus, alternating current (ac) electrical conductivity, and impedance properties of these PNCEs films are investigated in the frequency range 20 Hz to 1 MHz at ambient temperature. The direct current conductivity of these materials was determined by fitting the frequency-dependent ac conductivity spectra to the Jonscher power law. The PNCEs films synthesized at melting temperature of NaClO4 monohydrate have conductivity values lower than that of synthesized at PEO melting temperature. The complex impedance plane plots of these PNCEs films have a semicircular arc in upper frequency region corresponding to the bulk material properties and are followed by a spike in the lower frequency range owing to the electrode polarization phenomena. Relaxation times of electrode polarization and ionic conduction relaxation processes are determined from the frequency values corresponding to peaks in loss tangent and electric modulus loss spectra, respectively. A correlation is observed between the ionic conductivity and dielectric relaxation processes in the investigated PNCEs materials of varying MMT clay concentration. The scaled ac conductivity spectra of these PNCEs materials also obey the ac universality law.

Electrical and electrochemical properties of magnesium ion conducting composite gel polymer electrolytes

The effect of micro- and nano-sized MgO and nano-sized SiO2 dispersion on the electrical and electrochemical properties of poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) based Mg2+ ion conducting gel polymer electrolyte has been investigated. The gel electrolytes have been characterized using electrical conductivity, cationic transport number (t+) measurements and cyclic voltammetry. A two-maxima feature has been observed in the ‘conductivity versus composition’ curve at ∼3 wt% and 10–15 wt% of the filler contents. The highest conductivity has been obtained for the SiO2 dispersed gel electrolyte of ∼1 × 10−2 S cm−1 for 3 wt% and ∼9 × 10−3 S cm−1 at 15 wt% content. The value of ‘t+’ is found to be enhanced substantially with increasing amount of MgO (both micro- and nanoparticles), whereas in the case of SiO2 dispersion the value does not increase substantially. The highest ‘t+’ value of ∼0.44 has been obtained for the addition of 10 wt% MgO nanoparticles. The enhancement in ‘t+’ is explained on the basis of the formation of space-charge regions due to the presence of MgO : Mg2+-like species, which supports Mg2+ ion motion. A substantial increase in the amount of anodic and cathodic peak currents is observed due to the addition of nano-sized MgO particles in the gel polymer electrolyte, whereas in the cases of micrometre-sized MgO and nano-sized SiO2 the enhancement is not significant. The enhancement in conductivity in SiO2 dispersed nanocomposite gel electrolyte is predominantly due to anionic motion.

Interfacial Properties of Ca3(PO4)2-Incorporated Poly(ethylene oxide)-Based Nanocomposite Electrolytes Investigated by XPS and FTIR Studies

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Nanocrystalline filler induced changes in electrical and stability properties of a polymer nanocomposite electrolyte based on amorphous matrix

An ion conducting polymer nanocomposite electrolyte (PNCE) series of film based on an amorphous polymer host (PMMA)–lithium salt (LiClO4) complex dispersed with nanocrystalline yttria stabilized zirconia (n-YSZ) is reported. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis have confirmed feasibility of interaction among composite components (i.e. polymer–ion–filler). Ions in the PNCE matrix are present in the form of both free cations/anions as well as contact ion pairs and their concentration depends on filler loading in the matrix. Electrical conductivity enhancement on n-YSZ dispersion occurs by ~2 orders of magnitude at 30 °C and by ~5 orders of magnitude at 100 °C when compared with room temperature conductivity of the undispersed polymer salt (PS) film. The highest achieved conductivity value is ~1.3 × 10−4 S cm−1 at 100 °C for 2 wt% n-YSZ. An excellent correlation between variation of d.c. conductivity and free mobile charge carriers versus filler loading has been observed. This correlation has been attributed to filler-induced polymer–ion–filler interaction. These evidences have formed the basis to propose a mechanism for ion transport.