Highest Bulk Conductivity Research Articles

Material Development of the Lgps Based Solid Electrolytes — Structure, Conductivity and Battery Characteristics

Lithium superionic conductors, which can be used as solid electrolytes, promise the potential to replace organic liquid electrolytes and thereby improve the safety of next-generation high-energy batteries. Although the advantages of non-flammable solid electrolytes are widely acknowledged, their low ionic conductivities and low chemical and electrochemical stabilities prevent them from being used in practical applications. The new lithium superionic conductor, Li10GeP2S12 (LGPS) exhibits an extremely high bulk conductivity of over 10-2 S cm-1 at room temperature (27 °C), and is a potential electrolyte candidate for an all solid-state battery [1]. In order to explore the material variety of the LGPS based electrolytes, solid solutions of the pseudo binary Li4GeS4 – Li3PS4 system were investigated. In addition, the new material systems were synthesized with the cation and/or anion substitutions (Si, Ge, Sn, O etc). The solid solution was synthesized for the LGPS parent phase in the binary system, and the conductivity varied with the lithium composition. The structures were determined by X-ray and neutron diffraction analyses, and the relationship between the ionic conduction and structures was clarified. The ionic conductivity and electrochemical stability varied with the compositions examined by the cation and/or anion substitutions. Battery performances using these LGPS systems were investigated. Based on the materials varieties and the battery performances using the LGPS electrolytes, the advantages of the all solid-state batteries will be discussed. Reference[1] N. Kamaya et al., Nat Mater, 10, 682-686 (2011).

Dependence of the conductivity of polycrystalline Li0.33BaxLa0.56–2/3xTiO3 on Ba loading

Abstract The dependence of lithium ion conductivity on barium loading was investigated for Li 0.33 Ba x La 0.56–2/3 x TiO 3 (LBLT, 0 ≤ x ≤ 0.1) ceramics. The highest bulk conductivity, σ dc , of 1.24 × 10 − 3 S cm − 1 obtained for 0.25 mol.% Ba loading was slightly improved compared to that of non-doped Li 0.33 La 0.56 TiO 3 (1.18 × 10 − 3 S cm − 1 ). The intensities of the XRD patterns in the independent cubic and tetragonal reflections, i.e. , I c(100) and I t(101) , were analyzed; a larger I c(100) / I t(101) ratio corresponded to a larger σ dc . A possible reason for the only slight enhancement of the σ dc by a small loading of Ba is an increased volume fraction of the more highly conductive LBLT cubic phase.

Microscopic Origin of the Ionic Transport Behaviors in Solid Electrolytes for Li Batteries

Recently Li-ion-conducting solid electrolytes have received intensive research interest, as they provide solutions for issues associated with the organic liquid electrolytes in conventional Li-ion batteries. However, despite the relatively high bulk conductivity achieved in many solid electrolytes, the grain-boundary conductivity is frequently low and limits the application. Detailed atomic structure and elemental distribution on the grain boundaries in these materials must be revealed in order to fundamentally understand the origin of large grain-boundary resistance. Such studies, however, are currently very rare. Here we present a detailed atomic scale study on the conduction behaviors of an extensively studied solid electrolyte (Li3x La2/3-x )TiO3 (LLTO). Using aberration-corrected scanning transmission electron microscopy (STEM) and the associated electron energy loss spectroscopy (EELS) analysis, we found that the large grain-boundary resistance of LLTO arose from the intrinsic local structural reconstruction, which is energetically not favorable for Li accommodation. Therefore, large flux of charge carriers was unlikely to occur both along and across the grain boundary, leading to the poor grain-boundary conductivity. The relationship among the processing condition, microstructure, and ionic conductivity was established. And the ionic transport behavior in LLTO is further compared to that in garnet-type Li7La3Zr2O12. These results paved the way for further improvement of the Li-ion-conducting solid electrolytes.

Palladium nanocrystals supported on photo-transformed C60 nanorods: Effect of crystal morphology and electron mobility on the electrocatalytic activity towards ethanol oxidation

We report on the synthesis and decoration of high-aspect-ratio crystalline C60 nanorods (NRs) by functionalized palladium nanoparticles with an average size of 4.78±0.66nm. In their pristine form, C60 NRs suffer from partial damage in the solution-based decoration process resulting in poor crystallinity. However, by modifying the NR surface via in situ photochemical transformation in the liquid state, we are able to prepare highly stable NRs that retain their crystalline structure during the decoration process. Our method thus opens up for the synthesis of highly crystalline nanocomposite hybrids comprising Pd nanoparticles and C60 NRs. Bys measuring the electron mobility of different C60 NRs, we relate both the effect of electron mobility and crystallinity to the final electrocatalytic performance of the synthesized hybrid structures. We show that the photo-transformed C60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity. These findings give important information in the search for efficient catalyst support.

Low temperature reduction of free-standing graphene oxide papers with metal iodides for ultrahigh bulk conductivity

Here we report a green and facile route for highly efficient reduction of free-standing graphene oxide (GO) papers with metal iodide aqueous solutions at low cost. The metal iodides (MgI2, AlI3, ZnI2, FeI2) were synthesized directly from metal and iodine powder with water as a catalyzer. An extremely high bulk conductivity of 55088 S/m for reduced graphene oxide (rGO) papers were obtained with FeI2 solution of which pH = 0 at 95°C for 6 hours. The catalytic effect of strong Lewis acid for the promotion of the nucleophilic substitution reaction is responsible for the greatly improved bulk conductivity. Furthermore, it was found that the layer-to-layer distance (dL) and the crystallinity of the rGO papers are regarded as two main factors affecting the bulk conductivity rather than C/O ratio and defect concentration.Electronic supplementary materialThe online version of this article (doi:10.1038/srep03965) contains supplementary material, which is available to authorized users.

Re-examination of effects of alumina on bulk and grain boundary conductivities of CGO solid electrolytes

Identification of secondary phases and their dependence on composition and firing conditions were used as guidelines to re-examine effects of alumina on bulk and grain boundary properties of ceria-gadolinia electrolytes. Solubility of alumina may contribute to enhance bulk properties of samples with low contents of gadolinia, probably by enhancing the concentration of oxygen vacancies as prevailing charge carriers. This gain is slightly reverted for excessive addition of Al, probably combining effects of depletion of Gd in the fluorite phase, due to onset of GdAlO 3 , and microstructural changes. For samples with intermediate contents of Gd one found that alumina affects mainly the grain boundary properties, as a consequence of depletion of Gd, even for relatively low additions of Al, possibly due to heterogeneities induced by preferential location of secondary phases at grain boundaries. Additions of Al may exert a slight positive effect on bulk conductivity of samples with relatively high contents of Gd, i.e., above the composition with highest bulk conductivity. In this case, precipitation of GdAlO 3 may contribute to optimize the final composition of the fluorite phase. • Effect of alumina on bulk and grain boundary properties of ceria-gadolinia materials. • A freeze drying method was used to prepare nanopowders of ceria-gadolinia materials. • Alumina contributes to bulk conductivity for samples with low contents of Gd. • Grain boundary properties are mostly affected for intermediate contents of Gd.

Highly stretchable electric circuits from a composite material of silver nanoparticles and elastomeric fibres

Conductive electrodes and electric circuits that can remain active and electrically stable under large mechanical deformations are highly desirable for applications such as flexible displays, field-effect transistors, energy-related devices, smart clothing and actuators. However, high conductivity and stretchability seem to be mutually exclusive parameters. The most promising solution to this problem has been to use one-dimensional nanostructures such as carbon nanotubes and metal nanowires coated on a stretchable fabric, metal stripes with a wavy geometry, composite elastomers embedding conductive fillers and interpenetrating networks of a liquid metal and rubber. At present, the conductivity values at large strains remain too low to satisfy requirements for practical applications. Moreover, the ability to make arbitrary patterns over large areas is also desirable. Here, we introduce a conductive composite mat of silver nanoparticles and rubber fibres that allows the formation of highly stretchable circuits through a fabrication process that is compatible with any substrate and scalable for large-area applications. A silver nanoparticle precursor is absorbed in electrospun poly (styrene-block-butadiene-block-styrene) (SBS) rubber fibres and then converted into silver nanoparticles directly in the fibre mat. Percolation of the silver nanoparticles inside the fibres leads to a high bulk conductivity, which is preserved at large deformations (σ≈2,200Scm(-1) at 100% strain for a 150-µm-thick mat). We design electric circuits directly on the electrospun fibre mat by nozzle printing, inkjet printing and spray printing of the precursor solution and fabricate a highly stretchable antenna, a strain sensor and a highly stretchable light-emitting diode as examples of applications.

Synthesis and electrical properties of a new fluorite-like anionic conductor in the Nd2O3–MoO3 system (43–47 mol% Nd2O3)

This work addresses phase relations in the Nd2O3–MoO3 system (25–50mol% Nd2O3) and properties of a fluorite-like compound existing in this system in the composition range of 43–47mol% Nd2O3. We describe for the first time the crystal growth of this compound. The composition of the crystals is Nd10Mo6O33 (Nd2O3:MoO3=5:6, 45.5mol% Nd2O3), which falls within the above composition range. Dielectric spectroscopy data for polycrystalline Nd14Mo8O45 (within the homogeneity range of the fluorite-like compound) suggest a phase transition at 650–700°C. The exact mechanism of the transition remains to be clarified. Nd14Mo8O45 has rather high bulk conductivity, approaching 10−2S/cm at 800°C. The low activation energy and key structural features of the compound in question indicate that it is an anionic conductor.

Conductive Behaviour and Self-Conductance Characteristic of Carbon Nanotubes/Functionalized Graphene Hybrid Films

Multi-walled carbon nanotubes (MWCNTs)/Functionalized graphite (FG) hybrid films were fabricated by a simple solution-casting method. The films showed a layered, well-entangled and interconnected porous structure at nanometer scale. Such the nanostructures resulted in the films having the relatively high bulk conductivity and self-conductance characteristics. With increasing MWCNT mass fraction, the conductivity rapidly increased from approximately 10(-9) S/m of the host FG to over 10(-1) S/m. The percolation threshold was found to be about 29.6 wt% of MWCNTs. For the film with 83 wt% MWCNTs the specific capacitance was about 1 F/cm3. The hybrid films are of much higher power factor compared to conventional dielectric capacitors. The energy density of the film with 50 wt% MWCNTs was found to be 0.1 Wh/m3 and the charge-discharge period was very short about 8 seconds. It is believed that the MWCNTs/FG hybrid films have great potential as electrode materials for applications to energy storage.

Base metal alloys with self-healing native conductive oxides for electrical contact materials

Base metals for electrical contacts exhibit high bulk conductivities but form low-conductivity native oxide scales in air, leading to unacceptably high contact resistances. Here we show that alloying base metals can lead to higher conductivity native scales by: doping to enhance carrier concentration; inducing mixed oxidation states to give electron/polaron hopping; and/or phase separation for conducting pathways. Data from Cu–La, Fe–V, and Ni–Ru alloys demonstrate the viability of these approaches, yielding contact resistances up to 106 times lower than that for oxidized Cu.

Effects of Sintering Temperature on the Structure and Conductivity of LiSn<sub>2</sub>P<sub>3</sub>O<sub>12</sub> Prepared by Mechanical Milling Method

LiSn2P3O12 has been prepared using mechanochemical milling method and sintered at 700 °C, 800 °C, 900 °C and 1000 °C for 8 hours. All samples sintered up to 900 °C show a rhombohedral structure. However, the sample sintered at 1000 °C possessed a monoclinic structure. This is attributed to the rotation of skeleton LiSn2P3O12 as indicated by the change in the a and c parameters of the sample. The sample sintered at 700 °C shows the highest bulk conductivity of 1.65 × 10-6 S cm-1 and the lowest bulk activation energy of 0.09 eV. The grain boundary activation energy of the samples decreases with increase in sintering temperature due to enhancement in grain contacts.

The performance over the frequency range 140GHz–220GHz of thick-film CPW lines fabricated from nano-particle silver

Coplanar waveguide lines fabricated using thick-films of pure silver paste (Ag) and also pastes containing silver nano-particles (nAg) were measured in the high frequency range 110GHz–220GHz. Suitable feed lines and pads were designed and fabricated using photoimageable silver ink, to allow measurements to be performed using a wafer-probing station with 75μm pitch CPW probes. Silver nano-particle materials have a particular benefit in the higher frequency ranges due to the high bulk conductivity, resulting in lower bulk loss. Different lengths of CPW lines were fabricated, to allow subtraction of the mismatches between the feeding pads and the coplanar lines under test. The CPW lines were fabricated on various alumina substrates, with purities of 96%. The pastes were prepared at Warsaw University of Technology (Poland), and tested at the University of Surrey (UK).

Study of bulk and grain-boundary conductivity of Ln2+xHf2−xO7−δ (Ln = Sm-Gd; x = 0, 0.096) pyrochlores

The electrical conductivity of new solid electrolytes Eu2.096Hf1.904O6.952 and Gd2Hf2O7 have been compared with those for different pyrochlores including titanates and zirconates Ln2+xМ2−xO7−δ (Ln = Sm-Lu; M = Ti, Zr; x = 0−0.81). Impedance spectroscopy data demonstrate that Eu2.096Hf1.904O6.952 and Gd2Hf2O7 synthesized from mechanically activated oxides have high ionic conductivity, comparable to that of their zirconate analogues. The bulk and grain-boundary components of conductivity in Sm2.096Hf1.904O6.952 (Тsynth = 1600oС), Eu2.096Hf1.904O6.952 and Gd2Hf2O7 (Тsynth = 1670oС) have been determined. The highest bulk conductivity is offered by the disordered pyrochlores prepared at 1600oC and 1670oC: ~1.5 × 10−4 S/cm for Sm2.096Hf1.904O6.952, 5 × 10−3 S/cm for Eu2.096Hf1.904O6.952 and 3 × 10−3 S/cm for Gd2Hf2O7 at 780oС, respectively. The conductivity of the fluorite-like phases at the phase boundaries of the Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x ~ 0.286) solid solutions, as well as that of the high-temperature fluorite-like phases Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x = 0−0.286), is lower than the conductivity of the disordered pyrochlores Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x = 0−0.096).

AC impedance analysis of polyaniline–montmorillonite nanocomposites

Investigation of the electrical properties of polymer–clay nanocomposites is important in the development of nanoelectronic devices. These nanocomposites may be prepared by intercalating suitable monomers within interlayer spaces of expanding layered clay materials, followed by in situ polymerization. We made use of this approach to prepare montmorillonite–polyaniline nanocomposites by ion-exchanging the intergallery cations for anilinium ions and subsequently polymerizing the anilinium ions by peroxydisulphate in the acidic medium to yield emeraldine salt form of polyaniline intercalated in montmorillonite (ES1-MMT). The emeraldine salt form of polyaniline contains one positive charge per three monomer units, and hence, polymerization of anilinium ions reduces the number of cations present within the interlayer. Charge compensation thus requires uptake of required amount of cations from the solution. Further, the emeraldine salt form of polyaniline can be neutralized by treating with excess base such as ammonia. Thus, the neutralization of emeraldine salt results in an uptake of ammonium ions for charge balance. We have, therefore, neutralized ES1-MMT using aqueous ammonium hydroxide, and the cations inserted into the interlayer were again exchanged for anilinium ions. The latter was polymerized in acidic medium to yield more polyaniline in its emeraldine salt form (ES2-MMT). By repeating this procedure we have also prepared ES3-MMT. X-ray diffraction (XRD) spectra recorded at 150 °C reveal the enhancement of d-spacing upon increased amounts of polymer formation, and the Fourier transform infrared (FTIR) analysis also supports this by showing enhanced absorption due to bands typical of emeraldine salt (for example, B–NH+ = Q, where B and Q stand for benzanoid and quinoid, respectively). Careful analyses of FTIR spectra reveal that the polymer is present within the interlayers, as well as adsorbed onto the external surfaces and is bound to clay layers through hydrogen bonding. In this publication, we report the electrical properties of such ES-MMT nanocomposites. Alternating current (AC) impedance analysis shows that the nanocomposites are highly conducting materials, and their bulk conductivity enhances in the order ES1-MMT < ES2-MMT < ES3-MMT. The materials are pure electronic conductors as revealed by the direct current polarization studies. Further, their conductivities decrease with increasing temperature as of pure electronic conductors. By treating kaolinite with anilinium ions in acidic medium followed by peroxydisulphate ions, emeraldine salt–kaolinite (ES-KAL) composites have also been prepared. Because kaolinite is a non-expanding clay, the ion exchange is not possible, and hence, the polymer cannot be incorporated into the interlayer. This is indeed shown in the XRD analysis. The polymer can only reside out of the kaolinite particles. FTIR spectra reveal the hydrogen bonding between the polymer and kaolinite outer surfaces. AC impedance spectra of ES-KAL do not show high bulk conductivity. Thus, the comparison of AC impedance spectra of ES-KAL with ES-MMT systems clearly indicates that the bulk conductivity of the latter systems is predominantly due to intercalated polyaniline.

High lithium ion conductivity glass-ceramics in Li 2O–Al 2O 3–TiO 2–P 2O 5 from nanoscaled glassy powders by mechanical milling

Mechanical milling (MM) has been used to prepare the nanosized Li 1.4Al 0.4Ti 1.6(PO 4) 3 (denoted LATP) glassy powders, which was converted into glass-ceramics through thermal treating at 700–1000 °C. The XRD, TEM, FESEM and ac impedance techniques were used to characterize the products. The results showed that completely amorphous products were prepared by MM for 40 h, and single-phase LiTi 2(PO 4) 3-type structured glass-ceramics were obtained by further heat treatment. The lithium ion conductivity of the glass-ceramics increased with the growth of the crystalline phase and decrease of the grain size. The highest bulk conductivity ( σ b) of 1.09 × 10 − 3 S cm − 1 with an energy of activation as low as 0.28 eV was obtained at room temperature for the specimen treated at 900 °C for 6 h. The high conductivity, easy fabrication and low cost make the LATP glass-ceramics promising to be used as inorganic solid electrolyte for all-solid-state Li-ion rechargeable batteries.

Lithium ion conductivity of the B-site substitution in Li3xLa0.67−xRE y III Ti1−2yPyO3 system (REIII=Sc3+, Y3+, Nd3+, Sm3+, Eu3+, Yb3+)

The B-site substituted perovskite solid solution systems Li3xLa0.67−xREyTi1−2yPyO3 (RE=Sc, Y, Nd, Sm, Eu, Yb) have been investigated. Perovskite solid solutions formed in the range of x=0.10, y<0.10 for RE=Sc3+, Y3+, Yb3+, x=0.10, y≤0.05 for RE=Nd3+, Sm3+, Eu3+. Li0.3La0.57Nd0.05Ti0.9P0.05O3 has the highest bulk conductivity of 4.31×10−4 S·cm−1 and the highest total conductivity of 2.52×10−4 S·cm−1 at room temperature in all prepared compositions. The compositions have low activation energies of about 24–30 kJ/mol in the temperature ranges of 298–523 K. SEM studies showed that the sample made by solid-state reaction has a sphere-like morphology and a rough particle with particle size of about 50 µm. The research results also indicated that the reaction temperature decreases and the electrochemical stabilities of the titanate-based perovskite-type solid solutions are improved by using RE3+ and P5+ replaced Ti4+ on B-site in the Li3xLa0.67−xTiO3 parent.

Evidence for microbial enhanced electrical conductivity in hydrocarbon‐contaminated sediments

Bulk electrical conductivity of sediments during microbial mineralization of diesel was investigated in a mesoscale laboratory experiment consisting of biotic contaminated and uncontaminated columns. Population numbers of oil degrading microorganisms increased with a clear pattern of depth zonation within the contaminated column not observed in the uncontaminated column. Microbial community structure determined from ribosomal DNA intergenic spacer analysis showed a highly specialized microbial community in the contaminated column. The contaminated column showed temporal increases in bulk conductivity, dissolved inorganic carbon, and calcium, suggesting that the high bulk conductivity is due to enhanced mineral weathering from microbial activity. The greatest change in bulk conductivity occurred in sediments above the water table saturated with diesel. Variations in electrical conductivity magnitude and microbial populations and their depth distribution in the contaminated column are similar to field observations. The results of this study suggest that geophysical methodologies may potentially be used to investigate microbial activity.

Analysis of thermal conduction in carbon foams

Carbon foams are a new class of porous organic materials that are being developed for use as insulation, heat spreaders, and compact heat exchanger cores. The thermal conductivity of carbon foams is difficult to determine analytically, particularly for the case of high porosity, graphitic foams that show moderate to high bulk conductivity. Models that predict thermal conductivity of foams often use an empirical parameter to account for the effect of pore shape and material microstructure on the conduction process. A finite element (FEM) analysis has been developed to calculate the thermal conductivity of carbon foams for the complete range of porosity. The results are interpreted in terms of analytical and semi-empirical solutions. It is shown that the FEM solution matches the theoretical solution that is valid for low porosity, but differs significantly from semi-empirical solutions of high porosity foams.

In‐situ apparent conductivity measurements and microbial population distribution at a hydrocarbon‐contaminated site

We investigated the bulk electrical conductivity and microbial population distribution in sediments at a site contaminated with light nonaqueous‐phase liquid (LNAPL). The bulk conductivity was measured using in‐situ vertical resistivity probes; the most probable number method was used to characterize the spatial distribution of aerobic heterotrophic and oil‐degrading microbial populations. The purpose of this study was to assess if high conductivity observed at aged LNAPL‐impacted sites may be related to microbial degradation of LNAPL. The results show higher bulk conductivity coincident with LNAPL‐impacted zones, in contrast to geoelectrical models that predict lower conductivity in such zones. The highest bulk conductivity was observed to be associated with zones impacted by residual and free LNAPL. Data from bacteria enumeration from sediments close to the resistivity probes show that oil‐degrading microbes make up a larger percentage (5–55%) of the heterotrophic microbial community at depths coincident with the higher conductivity compared to ∼5% at the uncontaminated location. The coincidence of a higher percentage of oil‐degrading microbial populations in zones of higher bulk conductivity suggests that the higher conductivity in these zones may result from increased fluid conductivity related to microbial degradation of LNAPL, consistent with geochemical studies that suggest that intrinsic biodegradation is occurring at the site. The findings from this study point to the fact that biogeochemical processes accompanying biodegradation of contaminants can potentially alter geoelectrical properties of the subsurface impacted media.

The effect of plasticizers on transport and electrochemical properties of PEO-based electrolytes for lithium rechargeable batteries

The effect of plasticizers (or solvent additives) on the transport and electrochemical properties of polymer electrolytes has been examined. First, the mobility of cations and anions of LiN(CF 3SO 2) 2 (LiTFSI) was increased by doping the PEO-based electrolytes with ethylene carbonate and poly(ethylene glycol dimethyl) ether. However, the cation mobility in PEO-based electrolytes doped with propylene carbonate was suppressed resulting in a lower cation transference number. Nevertheless, all the plasticized electrolytes have higher bulk conductivity than the non-plasticized, even in the case the cation transference number decreased. This is due to increased ion mobilities and/or higher degree of ion dissociation upon the introduction of plasticizers. A study of the electrochemical stability of the electrolytes, by linear sweep voltammetry, shows that the plasticizers have a negligible effect on the electrolyte stability windows. Finally, the electrolyte/lithium metal electrode interfacial impedance was monitored by A.C. impedance as a function of storage time. The formation and growth rate of the passivation layer was diminished in the presence of the plasticizers.