Highest Room Temperature Conductivity Research Articles

Innovative Ionic Liquid Electrolytes, Based on the FSI Anion, for Highly Safe Lithium Batteries

There is a strong request to improve the safety of lithium battery systems, and researches towards novel generation solvents have been aimed. Among these, ionic liquids (ILs) are excellent candidates as electrolytes and/or electrolyte components in the place of volatile and hazardous alkyl carbonates, resulting in improved safety in case of overheating and thermal runaway of the lithium battery [1].ILs based on N-alkyl-N-ethylpyrrolidinium cations (PYR2A)+(the subscripts indicate the number of carbon atoms in the alkyl side chains) have been favorably used as electrolyte components for lithium batteries because of their sub-ambient melting point, high room temperature conductivity, and wide electrochemical stability [1].The feasibility to reversibly cycling lithium into graphite anodes [1] and LiCoO2cathodes [1] using IL electrolytes, based on the bis(fluorosulfonyl)imide (FSI) anion, was previously reported. The FSI anion was found able to form stable passive layer, preventing even the reduction of the unstable EMI cation [1] and allowing excellent lithium stripping/plating cycling behavior [1]. In addition, it is well known that FSI-based ILs display fast transport properties (due to their lower viscosity) [1] and low melting point.Therefore, we combined the PYR24 cation with the FSI anion to synthesize a novel IL (PYR24FSI), which was used for preparing PYR24FSI-LiFSI innovative electrolyte. The physicochemical properties of these mixtures as well as the electrode interfacial compatibility were investigated.The PYR24FSI-LiFSI electrolyte mixtures showed melting point close to -40 °C (Figure 1), resulting appealing for low temperature applications. It is worthy to note here that the crystallized PYR24FSI and PYR24FSI-LiFSI mixture (solid traces) do not show any shift of the endothermic melting peak with respect to not-crystallized corresponding samples. This behavior, previously observed in other pyrrolidinium FSI materials [1], clearly indicated that crystallization took place very quickly on cooling. Conductivity approaching 4´10-3 S cm-1 was achieved at ambient temperature (Figure 2A) whereas 1´10-2 S cm-1was matched at room-medium values. The conductivity trend shows a VTF behavior (Figure 2B), typical ion conduction in amorphous matrices and previously observed in different IL family electrolytes [1].Figure 1. DSC traces, obtained after quenching (dotted traces) and slow cooling/annealing (solid traces) from room temperature, of the PYR24FSI ionic liquid (panel A) and the (0.9)PYR24FSI-(0.1)LiFSI mixture (panel B).Figure 2.Ionic conductivity vs. temperature dependence (panel A) and VTF plot (panel B) of the PYR24FSI ionic liquid and the (0.9)PYR24FSI-(0.1)LiFSI mixture.AcknowledgementsJ.S.M. and G.B.A. thank the Italian Institute of Technology (IIT) for the financial support within the SEED Project “REALIST”. Y.D. and H.O. acknowledge the financial support from the Japan Society for the Promotion of Science (Grant No. 21225007).

Ion conduction in crystalline superionic solids and its applications

Superionic solids an area of multidisciplinary research activity, incorporates to study the physical, chemical and technological aspects of rapid ion movements within the bulk of the special class of ionic materials. It is an emerging area of materials science, as these solids show tremendous technological scopes to develop wide variety of solid state electrochemical devices such as batteries, fuel cells, supercapacitors, sensors, electrochromic displays (ECDs), memories, etc. These devices have wide range of applicabilities viz. power sources for IC microchips to transport vehicles, novel sensors for controlling atmospheric pollution, new kind of memories for computers, smart windows/display panels, etc. The field grew with a rapid pace since then, especially with regards to designing new materials as well as to explore their device potentialities. Amongst the known superionic solids, fast Ag+ ion conducting crystalline solid electrolytes are attracted special attention due to their relatively higher room temperature conductivity as well as ease of materials handling/synthesis. Ion conduction in these electrolytes is very much interesting part of today. In the present review article, the ion conducting phenomenon and some device applications of crystalline/polycrystalline superionic solid electrolytes have been reviewed in brief. Synthesis and characterization tools have also been discussed in the present review article.

Electrical Properties of Carboxyl Methylcellulose/Chitosan Dual-Blend Green Polymer Doped with Ammonium Bromide

This present work discusses dual-blend green polymer electrolyte (GPE)–based natural polymers, composed of carboxyl methylcellulose (CMC) and chitosan (CS), created by introducing various compositions of ammonium bromide (NH4Br) as a dopant in the system. These GPEs were successfully prepared by the solution casting technique and characterized using electrical impedance spectroscopy (EIS). From EIS measurement, the highest room-temperature conductivity is 1.21 × 10−5 Scm−1 for the sample containing 20 wt.% of NH4Br. Plot of the temperature dependence of the GPEs revealed that the system obeys the Arrhenius rule and was thermally assisted. Besides that, dielectric studies were also conducted and the data were analyzed using complex permittivity, ϵ*, and complex electrical modulus, M*, to determine the sample with the highest conductivity value. Thus, this study confirmed non-Debye behavior in the sample.

Charge-transfer complexes: new perspectives on an old class of compounds

The discovery of the organic metal TTF–TCNQ in 1973 led to an explosion of research conducted on organic charge-transfer complexes. While these materials have been studied intensely for several decades, the research was mostly aimed at the discovery of materials with high room-temperature conductivity or high-temperature superconductivity. Recently, attention has turned to technologically-relevant properties of charge-transfer complexes, such as ambipolar transport, metallicity, photoconductivity, ferroelectricity or magnetoresistance. This manuscript reviews the growth, structure and properties of charge-transfer complexes and underlines recent progress in their application in organic devices. Their prospects in future applications are discussed, as well as the challenges yet to be overcome to understand the fundamental parameters governing their operation.

Search for the Major Chlorine-Related Defects in CdTe:Cl

ABSTRACTUnderstanding the effect of chlorine-related defects on the CdTe electric properties is important both for obtaining high resistivity CdTe-based detectors and for high efficiency CdTe-based thin-film solar cells. The actual mechanism of the effect of Cl on electric properties of CdTe is not clear and different sometimes contradictory hypotheses appear. For example ClTeVCd shallow acceptor complex defect was proposed both as a reason of increased carrier concentration in CdTe thin film and also as a reason of high resistivity of CdTe:Cl thin films. In the present work we are trying to clarify the effect of Cl on CdTe electric properties and to find the reason of high resistivity of CdTe:Cl crystals using first principles calculations and defect chemistry modeling. For the first time we are trying to develop a model capable to describe experimental data on both high temperature and room temperature conductivity of CdTe:Cl.

A new metal–organic hybrid material with intrinsic resistance-based bistability: monitoring in situ room temperature switching behavior

Two new silver containing materials with TCNQ derivatives were prepared by electrocrystallization. Synchrotron radiation diffraction studies were conducted to determine the structures of the new phases which exhibit unprecedented high room temperature conductivity. The I–V characteristics reveal a room-temperature switching behaviour and memory effect based on intrinsic negative differential resistance (NDR). EPR spectroscopic measurements performed under an applied electric field indicate a g-tensor shift that is correlated to the amplitude of current.

Conductivity and Dielectric Studies of Methylcellulose/Chitosan-NH<sub>4</sub>CF<sub>3</sub>SO<sub>3</sub> Polymer Electrolyte

Films of methyl cellulose (MC) /chitosan blends were prepared via solution casting technique and their properties with different amount of ammonium trilate, NH4CF3SO3 were compared. Measurements of conductivity as a function of frequency at room temperature on these films were carried out using HIOKI 3532-50 LCR Hi-Tester where the frequency was set between 50 Hz to 1 MHz. Samples having 40 wt% of NH4CF3SO3 exhibit the highest room temperature conductivity of (4.99±4.18) x 10-6 Scm-1. Dielectric data were analyzed using complex permittivity and complex electrical modulus for the sample with the highest ionic conductivity.

Investigation on the Effect of TiO<sub>2</sub> Nanofiller to the Structural and Conductivity Characteristics of Poly(vinylidene fluoride-co-hexafluoropropylene)/Poly(ethyl methacrylate) Based Polymer Electrolytes System

In this study, Poly (vinylidene fluoride-co-hexafluoropropylene)/Poly (ethyl methacrylate (PEMA) nanocomposite polymer electrolytes was prepared by solution casting technique. The effects of TiO2 nanofiller on the structural, thermal and conductivity characteristics were examined using x-ray diffraction, scanning electron microscopy, differential scanning calorimetry and impedance spectroscopy. The crystallinity and conductivity of the salted system are found to increase with the addition of TiO2. The system containing 5 wt % of TiO2 exhibited the highest room temperature conductivity of 1.32 × 10-3 S cm-1.

Transparent and conducting intrinsic ZnO thin films prepared at high growth-rate with c-axis orientation and pyramidal surface texture

The growth of ZnO thin films has been optimized by adjusting the intrinsic ion vacancies, by controlling the RF power applied to the plasma in magnetron sputtering. Preferred c-axis oriented intrinsic ZnO films with largest grain size and a hexagonal wurtzite structure, exhibiting high room temperature conductivity, σ∼1.37S/cm, high transparency, ∼80–90% within 450–800nm and ∼90–96% within 800–1900nm, low reflectance (<5% in the visible range) was obtained at a very high deposition rate ∼214nm/min, at 300°C, by maintaining higher concentration of Zn interstitials or singly ionized oxygen vacancy, corresponding to an optimized RF power of 200W. Films have lowest internal stress, smallest dissipation factor defined as ɛ2/ɛ1, and the specific pyramidal surface texture creates enough surface roughness that helps to improve the light scattering from the surface and makes it suitable for efficient use in thin-film silicon solar cells. With increasing RF power beyond 200W, the Zn–O bond length reduces promptly and the internal stress increases monotonically approaching toward a virtual saturation. The preferred crystallographic alignment shifts from (002) to (103), i.e., from c to a-axis orientation, as the surface energy of ZnO crystal changes due to the increase in the Zn-to-ZnO ion ratio in the plasma caused by the plausible de-oxygenation of ZnO at elevated RF powers. Oxygen deficient ZnO films having the flower-like surface texture prepared with a very high deposition rate ∼554nm/min at 500W could indeed make the material suitable for gas and chemical sensing applications.

Nanoporous Polymer‐Ceramic Composite Electrolytes for Lithium Metal Batteries

A nanoporous composite material that offers the unique combination of high room-temperature ionic conductivity and high mechanical modulus is reported. When used as the separator/electrolyte in lithium batteries employing metallic lithium as anode, the material displays unprecedented cycling stability and excellent ability to prevent premature cell failure by dendrite-induced short circuits

Conductivity study of solid polyelectrolytes based on hydroiodide salt of poly(4-vinyl pyridine-co-butylmethacrylate), poly(4-vinyl pyridine-co-butylacrylate)

The chain flexibility of poly(4-vinylpyridine) was tried to increase by lowering its glass transition temperature ( T g ) and by increasing its amorphous region by copolymerizing with butyl methacrylate and butylacrylate which act as internal plasticizer. The copolymers were prepared in five different feed molar ratios to optimize the required properties such as higher room temperature conductivity and better film-forming capacity. The conductivity and conduction behaviour of the copolymers, as well as their hydroiodide salts have been reported. There was about 103–104-fold increase in room temperature conductivity of these plasticized polyelectrolytes.

Effect of Rb and Ta Doping on the Ionic Conductivity and Stability of the Garnet Li7+2x–y(La3–xRbx)(Zr2–yTay)O12 (0 ≤ x ≤ 0.375, 0 ≤ y ≤ 1) Superionic Conductor: A First Principles Investigation

In this work, we investigated the effect of Rb and Ta doping on the ionic conductivity and stability of the garnet Li7+2x–y(La3–xRbx)(Zr2–yTay)O12 (0 ≤ x ≤ 0.375, 0 ≤ y ≤ 1) superionic conductor using first principles calculations. Our results indicate that doping does not greatly alter the topology of the migration pathway, but instead acts primarily to change the lithium concentration. The structure with the lowest activation energy and highest room temperature conductivity is Li6.75La3Zr1.75Ta0.25O12 (Ea = 19 meV, σ300K = 1 × 10–2 S cm–1). All Ta-doped structures have significantly higher ionic conductivity than the undoped cubic Li7La3Zr2O12 (c-LLZO, Ea = 24 meV, σ300K = 2 × 10–3 S cm–1). The Rb-doped structure with composition Li7.25La2.875Rb0.125Zr2O12 has a lower activation energy than c-LLZO, but further Rb doping leads to a dramatic decrease in performance. We also examined the effect of changing the lattice parameter at fixed lithium concentration and found that a decrease in the lattice parameter leads to a rapid decline in Li+ conductivity, whereas an expanded lattice offers only marginal improvement. This result suggests that doping with larger cations will not provide a significant enhancement in performance. Our results find higher conductivity and lower activation energy than is typically reported in the experimental literature, which suggests that there is room for improving the total conductivity in these promising materials.

Synthesis and characterization of Ag+ion conducting glassy electrolytes

Synthesis and characterization of new Ag + ion conducting glassy systems: x [0.75AgI:0.25AgC1]: (1 – x )[Ag 2 O:P 2 O 5 ], where 0.1 1 in molar weight fraction, are reported. The present glassy electrolytes have been synthesized by melt-quench technique using a high-speed twin roller-quencher. An alternate host salt: “quenched [0.75AgI:0.25AgC1] mixed system/solid solution”, has been used in place of the traditional host AgI. The compositional dependence conductivity studies on the glassy systems: x [0.75AgI:0.25AgC1]:(1 – x )[Ag 2 O:P 2 O 5 ] as well as x AgI:(1 – x )[Ag 2 O:P 2 O 5 ] prepared identically, indicated that the composition at x = 0.75 exhibited the highest room temperature conductivity ( σ ~ 5.5 x 10 −3 S cm −1 ). The composition: 0.75[0.75AgI:0.25AgC1]:0.25[Ag 2 O:P 2 O 5 ] has been referred to as optimum conducting composition (OCC). The some basic ion transport parameters viz. ionic conductivity ( σ ), ionic mobility ( μ ), mobile ion concentration ( n ), ionic drift velocity ( v d ), ion transference number ( t ion ) and activation energy ( E a ) values have been characterized with the help of various experimental techniques. A solid state battery was fabricated and its basic cell parameters calculated.

A New High-Temperature Lithium Para-Toluene Sulfonate (LIPTSA) Salt for Rechargeable Batteries

Lithium para-toluene sulfonate [LIPTSA] was used for lithium rechargeable batteries, with poly(methyl methacrylate) [PMMA] as the base material. Tri block copolymer of PEO-PPO-PEO was used to increase the solubility of lithium salts in PMMA matrix. FTIR, TGA, XRD, impedance spectroscopy, and SEM were used for characterizations and morphological studies. LIPTSA salt is stable up to 375°C. The highest room temperature conductivity obtained was around 5 × 10−4 Scm−1. The SEM picture shows clearly the heterogeneous morphology (salt-rich phases) distributed throughout the PMMA matrix. The XRD picture indicates the presence of crystalline, which increases with an increase in salt concentration.

Proton conducting zeolite films for low-voltage oxide-based electric-double-layer thin-film transistors and logic gates

Three-dimensional nanoporous zeolite films with Linde Type A (LTA) structure prepared by a seeding-free synthesis strategy exhibited high room-temperature proton conductivity and large electric-double-layer (EDL) capacitance. In-plane-gate indium-zinc-oxide thin-film transistors gated by such proton conducting zeolite LTA films were fabricated by a simple self-assembled method. Due to the strong EDL capacitive coupling triggered by mobile protons in zeolite LTA, such transistors showed a low-voltage operation of 1.5 V and a high performance with a large field-effect mobility of 13 cm2 V−1 s−1 and a small subthreshold swing of 95 mV per decade. Furthermore, AND logic operation was also experimentally demonstrated on the dual in-plane-gate EDL transistors. Our results strongly indicate that zeolite LTA films are promising gate dielectric candidates for application in low-voltage and low-cost electronics, which greatly expands the application areas of zeolites.

A highly conducting organic metal derived from an organic-transistor material: benzothienobenzothiophene

BTBT ([1]benzothieno[3,2-b][1]benzothiophene) is an organic semiconductor that realizes high mobility in organic transistors. Here we report that the charge-transfer (CT) salt, (BTBT)2PF6, shows a high room-temperature conductivity of 1500 S cm(-1). This compound exhibits a resistivity jump around 150 K, but when it is covered with Apiezon N grease the resistivity jump is suppressed, and the metallic conductivity is maintained down to 60 K. Owing to the very high conductivity, the ESR signal shows a significantly asymmetric Dysonian lineshape (A/B ≅ 3) even at room temperature. Since most organic conductors are based on strong electron donors, it is remarkable that such a weak electron donor as BTBT realizes a stable and highly conducting organic metal.

Silk-Ion Jelly: a novel ion conducting polymeric material with high conductivity and excellent mechanical stability

In this work, a thin, flexible and mechanically stable polymer conducting material (Silk-Ion Jelly) was developed though application of Ion Jelly on to silk fabrics. Ion Jelly was prepared through jellification of a room temperature ionic liquid, 1-butyl-3-methyl-imidazolium dicyanamide ([bmim][dca]) using gelatin and water and applied to silk fabrics using two different processes: impregnation and in-situ. Various parameters influencing ionic conductivity such as Ion Jelly composition (ratio of [bmim][dca], water and gelatin) and incorporation as well as the type of application process were thoroughly investigated. It was observed that the Ion Jelly compositions containing lower gelatin and water ratio as well as application through in-situ process at high temperature (200 °C) led to considerable improvement in conductivity, mainly due to increased [bmim][dca] concentration, structural flexibility and reduced silk crystallinity. Silk-Ion Jelly prepared using optimized conditions showed excellent mechanical stability and possessed high room temperature conductivity (2.9 × 10−3 S. cm−1), similar to [bmim][dca], and therefore, this novel ion conducting material may find potential applications in electrochemical devices due to its eco-friendly preparation route using biomaterials and green solvents. Copyright © 2012 John Wiley & Sons, Ltd.

Experimental studies on high-performance supercapacitor based on nanogel polymer electrolyte with treated activated charcoal

Electrochemical capacitors, based on the double-layer capacitance of high specific surface area carbon materials, are attracting major fundamental and technological interest as highly reversible, electrical-charge storage and delivery devices, capable of being operated at high power densities. In the present paper, studies have been carried out on nanocomposite gel polymer electrolyte comprising poly(vinylidene fluoride-co-hexafluoropropylene)-propylene carbonate-magnesium perchlorate-nanofumed silica with a view to use them as electrolyte in electrochemical double-layer capacitors (EDLCs) based on chemically treated activated charcoal as electrodes. The optimized composition of nanogel polymer electrolyte exhibits high room-temperature ionic conductivity of 5.4 × 10−3 S cm−1 with good mechanical and dimensional stability which is suitable for their application as electrolyte in EDLCs. Detailed chemical and microstructural characterization of chemically treated and untreated activated charcoal was conducted using scanning electron microscopy and Brunauer–Emmett–Teller (BET). BET studies reveal that the effective surface area of treated activated charcoal powder (1,515 m2 g−1) increases by more than double-fold compared with untreated one (721 m2 g−1). Performance characteristics of EDLCs have been tested using cyclic voltammetry, impedance spectroscopy, prolonged cyclic test, and charge–discharge techniques. Analysis shows that the treated activated charcoal electrodes have almost five times more capacitance values as compared with the untreated one. The maximum capacitance of 324 mF cm−2, equivalent to single electrode specific capacitance of 216 F g−1 was achieved. It corresponds to an energy density of 20 Wh kg−1 and a power density of 2.2 kW kg−1.

Ionic Transport in PMMA-NaCF&lt;sub&gt;3&lt;/sub&gt;SO&lt;sub&gt;3&lt;/sub&gt; Gel Polymer Electrolyte

In this work, the polymethylmethacrylate (PMMA) based gel polymer electrolyte samples have been prepared by the solution casting technique. The composition range of the salt was from 3 wt% to 35 wt%. The ionic conductivity of the samples was measured using a.c. impedance technique. The highest room temperature conductivity was obtained from the sample containing 30 wt% of NaCF3SO3 salt, i.e. 5.31 x 10-3 S cm-1. The increase in the ionic conductivity with increasing salt concentrations is due to the increase in both concentration and mobility of charge carriers. The decrease in ionic conductivity at higher salt concentrations can be explained by aggregation of the ions, leading to the formation of ion-pair, thus decreasing the number of charge carriers and hence the ionic mobility. The conductivity-temperature dependence obeys the Arrhenius rule from which the activation energy was evaluated. The ionic transference number estimated by dc polarization method revealed that the conducting species are predominantly ions.

Ionic Conductivity of PVC-NH4I-EC Proton Conducting Polymer Electrolytes

Poly(vinyl) chloride (PVC)-NH4I-EC films have been prepared by solution cast technique. The sample containing 30 wt. % NH4I exhibited highest room temperature conductivity of 4.60 × 10-7S cm-1. The conductivity increased to 1.08 × 10-6Scm-1when 15 wt. % of ethylene carbonate (EC) was added to 70 wt. % PVC - 30 wt. % NH4I. Fourier Transform Infrared (FTIR) showed evidence of polymer–salt complexation while DSC showed increase in glass transition temperature (Tg) of PVC -NH4I - EC polymer electrolytes. The conductivity behavior of the studied system could be accounted by the changes in Tgvalues.