Ionic Conduction Mechanism Research Articles

Synthesis, Vibrational Analysis, Optical, Ionic Conductivity and Conduction Mechanism of γ-NaCoPO4 Compound

The specific features of the crystallization kinetics of the ternary Al-Ni-Fe system due to the order of the introduction of the alloying elements are explained in terms of the cluster structure of the melts of binary metal systems Al-Ni and Al-Fe.

Macroscopic conductivity of aqueous electrolyte solutions scales with ultrafast microscopic ion motions

Despite the widespread use of aqueous electrolytes as conductors, the molecular mechanism of ionic conductivity at moderate to high electrolyte concentrations remains largely unresolved. Using a combination of dielectric spectroscopy and molecular dynamics simulations, we show that the absorption of electrolytes at ~0.3 THz sensitively reports on the local environment of ions. The magnitude of these high-frequency ionic motions scales linearly with conductivity for a wide range of ions and concentrations. This scaling is rationalized within a harmonic oscillator model based on the potential of mean force extracted from simulations. Our results thus suggest that long-ranged ionic transport is intimately related to the local energy landscape and to the friction for short-ranged ion dynamics: a high macroscopic electrolyte conductivity is thereby shown to be related to large-amplitude motions at a molecular scale.

Multiarm Aniline Oligomers: Molecular Architecture, Self-Assembly, and Electrochromic Performance

Solution-processable aniline oligomers with a benzene ring as the core and para, meta, and triple substituted amino/carboxyl-capped tetraaniline (NH2-(Ani)4-COOH) as arms, named as Bi(p)-(Ani)4-COOH, Bi(m)-(Ani)4-COOH, and Tri-(Ani)4-COOH, were synthesized and characterized. It was found that aniline oligomers with increased arms presented a more regular porous breathing structure revealed by atomic force microscopy. An electrochemical quartz crystal microbalance was used to study their long-term stability by recording the mass change of electrochromic films during redox and analyze the mechanism of ion conduction in the electrochromic process. The results suggested that the porous breathing structure was conducive to H+ conduction, which contributed to their improved performance in switching time, coloration efficiency, and cycling stability. Tri-(Ani)4-COOH had the shortest switching time (tb = 1.45 s, tc = 1.82 s), highest coloration efficiency (190.7 cm2/C), and best cycling stability. Especially on the conductive glass, in 0.5 mol/L sulfuric acid electrolyte, it reached the charge retention of 96.8% after 3000 cycles, implying that the multiarm star-shaped aniline oligomer will be a promising material in electrochromic area with good processability, short switching time, and high cycling stability.

Conductive Metal-Organic Frameworks: Mechanisms, Design Strategies and Recent Advances.

Metal-organic frameworks (MOFs), constructed from metal ions and organic ligands through coordination assembly, exhibit considerable conductivity, which originates from the ionic or electronic transport pathway between the host architecture and guest species. In recent decades, the study of conductive MOFs has accelerated deservedly due to their importance in the electronic information industry. In this review, we first briefly describe the different mechanisms of ionic and electronic conduction. The design strategies of constructing intrinsic and doping MOFs are then summarized and generalized into three major categories (host-based-, guest-based- and host-guest-related systems) in terms of promoting conductive performance. In the next section we provide an overview of recent progress in research on conductive MOFs, providing details according to the various carriers of transporting electrons, protons and other ions. We conclude with a discussion on the practicability and emerging applications of conductive MOFs and a section on the existing challenges and development prospects. Conduction mechanisms, design strategies, recent progresses and emerging applications of conductive MOFs.

A glimpse on all-solid-state Li-ion battery (ASSLIB) performance based on novel solid polymer electrolytes: a topical review

All-solid-state batteries are swiftly gaining the attention of the research community owing to their widespread applications in electric vehicles, digital electronics, portable appliances, etc. A battery comprises three components: cathode, anode and electrolyte. An electrolyte is the heart of the battery and plays a crucial role in the overall performance of the battery. In order to make the review more focused, all-solid-state Li-ion batteries (ASSLIBs) have been considered. This review covers the architecture of ASSLIBs, advantages, and characteristics of the solid polymer electrolytes. The important preparation methods are summarized, followed by the characterizations for testing the suitability of electrolytes for solid-state batteries. The discussion is focused on the ‘state of the art’ in the field of solid-state batteries, device fabrication, and comparison in terms of capacity, energy density, and cyclic stability. In the last section, the ion conduction mechanism in different solid polymer electrolytes is discussed. Finally, it is tried to give a possible outlook for developing future hybrid and multifunctional electrolytes which can act as a bridge for developing solid-state batteries covering a broad range of applications.

Probing the Dynamics of Li+ Ions on the Crystal Surface: A Solid-State NMR Study.

Polyethylene oxide-based solid polymer electrolytes (SPEs) are of research interest because of their potential applications in all-solid-state Li+ batteries. However, despite their advantages in terms of compatibility with the electrodes and easy processing, polyethylene oxide (PEO)/Li+ complexes often suffer from low conductivity at room temperature. Understanding the conduction mechanism and, in turn, developing strategies to improve the conductivity have long been the main objectives underlying research into PEO/Li+ complex electrolytes. Here, we prepared several special PEO/Li+ complex samples where the PEO/Li+ complex structures were located on the surfaces of PEO crystals and consisted of high content chain ends. We found two different Li+ species in the PEO/Li+ complex structures via solid-state nuclear magnetic resonance (NMR). The 2D 7Li exchange NMR showed the exchange process between the different Li+ species. The exchange dynamics of the Li+ ions provide a molecular mechanism of the Li+ transportation in the surface of PEO crystal lamella, which is further correlated with the ionic conduction mechanism of the PEO/Li+ complex structure.

The Mechanism of ION Conduction and Selectivity in the Eukaryotic NaVPaS Channel

The Mechanism of ION Conduction and Selectivity in the Eukaryotic NaVPaS Channel

Investigation of the Ionic Conduction Mechanism of Polyether/Li7La3Zr2O12 Composite Solid Electrolytes by Electrochemical Impedance Spectroscopy

Polyether-based polymer/cubic Li7La3Zr2O12 (LLZO) composite solid electrolytes were prepared by dispersing LLZO powder in a lithium (Li) conductive polyether-based solid polymer electrolyte. [SUS ∣ electrolyte ∣ SUS] (SUS: stainless steel) and [Li ∣ electrolyte ∣ Li] symmetrical cells were fabricated, and the ionic conductivity, Li/electrolyte interfacial resistance, and Li-cation transport number of the electrolytes were evaluated by electrochemical impedance spectroscopy. The polyether-based polymer/LLZO composite solid electrolytes showed relatively high ionic conductivity of over 10−4 S cm−1 at 333.15 K, along with high electrochemical stability and low interfacial resistance to Li metal electrodes. Remarkable changes of Cole-Cole plots were observed with the variation of LLZO content, which was attributed to the formation of local percolation pathways between LLZO grains in the polymer matrix. Li-ion conduction was faster in the LLZO phase than in the polymer phase. The Li-cation transport number of the polymer/LLZO composite solid electrolytes was almost constant value regardless of LLZO content because of the rate-limiting ionic transport in the polymer phase with a low Li-cation transport number.

Synthesis and ion conduction mechanism of a new sodium ion conducting solid polymer electrolytes

Synthesis and ion conduction studies of a new Na+ ion conducting Solid Polymer Electrolytes (SPEs): (1-x) PEO: x NaCl, where 0 ≤ x ≤ 50 wt% have been reported. SPE films have been casted by a novel hot- press/dry technique in place of traditional solution cast method. The conductivity measurements as a function of salt complexation revealed SPE film: [70PEO:30NaCl] as the Optimum Conducting Composition (OCC) with σ ∼ 4.5 × 10-6 S/cm at 27 °C. A conductivity enhancement of approximately three orders of magnitude from that of pure polymeric host has been resulted in SPE OCC due to salt complexation in PEO. Ion conduction mechanism have been explained with the help of some basic ionic parameters viz. ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n), ionic transference number (tion) and various theoretical models proposed for polymeric electrolyte materials. The temperature dependent conductivity studies have also been done to compute the activation energy (Ea) values from ‘log σ-1/T’ Arrhenius plots.

Ionic conduction mechanism of a lithium superionic argyrodite in the Li–Al–Si–S–O system

Unique interstitial Li+ and O2−/S2− site disorder lower the percolation threshold for 3D Li-ion diffusion in lithium argyrodite Li6.15Al0.15Si1.35S6−xOx (LASSO).

Effect of the iron content on the structure and electrical properties of sodium borosilicate glasses: XRD, TEM, Mössbauer, FTIR and DIS spectroscopy study

The iron-bearing sodium borosilicate glasses with different contents of iron were prepared by the charge melting method and studied by XRD, TEM, FTIR, Mössbauer and Dynamic Impedance Spectroscopy techniques. An analysis and the transmittance spectra of two-phase sodium borosilicate glasses with different contents of iron oxide were carried out. A usage of the Mössbauer spectroscopy revealed differences between two-phase and porous glasses. In both cases Fe2+ and Fe3+ ions in octahedral and tetrahedral coordination were found, while in the two-phase glasses the significant contribution of magnetite was additionally detected. The activation energy associated with the relaxation processes determined from the electric modulus spectra was found to be in a range between 0.986 eV and 0.729 eV, which is close to the activation energy for dc conductivity. Two different conduction mechanisms were observed and their physical origin was explained. The hopping between two valence states of iron and the sodium ion conduction mechanism was additionally discussed.

Polymer-in-salt solid electrolytes for lithium-ion batteries

Solid-state polymer lithium-ion batteries with better safety and higher energy density are one of the most promising batteries, which are expected to power future electric vehicles and smart grids. However, the low ionic conductivity at room temperature of solid polymer electrolytes (SPEs) decelerates the entry of such batteries into the market. Creating polymer-in-salt solid electrolytes (PISSEs) where the lithium salt contents exceed 50[Formula: see text]wt.% is a viable technology to enhance ionic conductivity at room temperature of SPEs, which is also suitable for scalable production. In this review, we first clarify the structure and ionic conductivity mechanism of PISSEs by analyzing the interactions between lithium salt and polymer matrix. Then, the recent advances on polyacrylonitrile (PAN)-based PISSEs and polycarbonate derivative-based PISSEs will be reviewed. Finally, we propose possible directions and opportunities to accelerate the commercializing of PISSEs for solid polymer Li-ion batteries.

Electrical Conduction and Impedance Behavior of Sr0.97Ti0.6Fe0.4O3-δ Electrode Containing YSZ for Various Applications

Sr0.97Ti0.6Fe0.4O3-δ (STF) and 8 mol% Y2O3 stabilized ZrO2 (YSZ) composites were prepared by mixing them in different weight fractions. The composites were compacted into discs, sintered and evaluated for phase stability, microstructure and mixed ionic-electronic conductivity. Phase analysis by XRD showed no clearly detectable secondary phases. Chemical analysis by energy dispersive spectroscopy (EDS) also showed the diffusion of elements (especially Y and Zr from YSZ). The electrical conductivity measurement on the STF-YSZ composites showed a decrease in total electrical and ionic conductivities with YSZ amount increasing. And the ionic conduction mechanism was concerned by impedance behavior analysis.

Ion conduction and relaxation mechanism in ionogels embedded with imidazolium based ionic liquids

The impact of physicochemical properties of imidazolium based different ionic liquids such as BDMIMBF4, BMIMBF, and EMIMBF4 on the ion conduction and relaxation mechanisms in ionogels is investigated using broadband dielectric spectroscopy. The complex conductivity isotherms of these ionogels are analyzed using a universal power law coupled with a modified Poisson-Nernst-Planck model for the contribution of electrode polarization dominated in the low frequency region. The effect of electrode polarization is analyzed by using the Macdonald-Coelho model to determine free-ion diffusivity and number density in these ionogels. The relaxation process of ions is also systematically studied using electric modulus spectroscopy over wide frequency and temperature ranges. The temperature dependence of the ionic conductivity, free-ion diffusivity, and relaxation times follows the Vogel-Tammann-Fulcher relationship, indicating existence of coupling between the ion transport and segmental dynamics in these ionogels. The EMIMBF4 ionic liquid doped ionogel shows the highest ionic conductivity, lowest relaxation time, highest free-ion diffusivity and highest number density due to the smallest size of cations, highest static dielectric constant, and lowest viscosity of the EMIMBF4 ionic liquid. It is observed that the stretched exponents for different ionogels obtained from Havriliak-Negami and Kohlrausch-Williams-Watts fits of electric modulus are lower than unity, indicating highly nonexponential relaxation in the investigated ionogels.

A Silatrane:Molecule‐Based Crystal Composite Solid‐State Electrolyte for All‐Solid‐State Lithium Batteries

AbstractAll‐solid‐state batteries (ASSBs) are promoted as a promising option towards higher energies and power densities as well as drastically reduced safety risks as compared to conventional lithium‐ion batteries (LIBs). Herein, a composite solid‐state electrolyte (SSE) based on two crystalline materials with two distinctly different ion conduction mechanisms, percolation and ion hopping, is reported. By combining a silatrane (SA; here ethoxysilatrane) with a molecule‐based crystal (MBC; here LiTFSI‐TMEDA) the resulting SA : MBC 2 : 1 crystalline composite shows an appreciable ion conductivity of 10−5 S cm−1 at room temperature, and low apparent activation energy, 836 K, for the ion transport. Studies of the overall and local structure show that in the composite the Li+ and TFSI ions are dissociated, and this seems to be mediated by the SA part of the matrix. As a proof‐of‐concept, an ASSB based on this SSE can operate at 50 °C providing up to 105 mAh g−1 during 20 cycles.

Paradigms of Structural, Chemical, and Dynamical Frustration in Superionic Conductors

Rationally motivated computational discovery and optimization of solid electrolytes require the development of reliable descriptors for fast ionic conductivity. However, many of the fundamental motivations for superionic behavior in solids remain enigmatic, which has generally slowed progress in screening electrolyte candidates, as well as in tuning existing materials to maximize ionic conductivity. I will discuss our efforts using first-principles molecular dynamics simulations to unravel various mechanisms of ionic conductivity in model classes of solid electrolytes. Using computational “experiments”, our simulations systematically isolate factors such as stoichiometry, strain, composition, and crystal structure in the determination of ionic conductivity. Collectively, the results point to the importance of a frustrated energy landscape in promoting ultrafast diffusion. Different types of frustration in model superionic conductors will be discussed, arising from factors such as off-stoichiometry, competition between interstitial site occupancies, symmetry incompatibilities between local bonding character and lattice geometry, and dynamical frustration coupled to anharmonic processes. Physicochemical origins of the relevance of these factors for cation mobility will be explored, with a view towards developing design rules for engineering faster ionic conductors. Our findings suggest that the relative contributions of the different frustration paradigms depend chiefly on the fundamental nature of the lattice-forming ions, suggesting there may be no single universal descriptor for ionic conductivity, but rather classes of superionic conductors with similar underlying motivations. Specific examples will be drawn from our recent results on superionic materials based on oxides, halides, and polyatomic anions. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Improving the Ionic Conductivity of Li15P4S16Cl3 By Doping

All-solid-state Li-ion batteries are a next generation electrochemical energy storage technology and an emerging alternative to conventional Li-ion batteries owing to higher energy density, wider operation temperature range and better safety properties1. Solid state ionic conductor as the solid electrolyte (SEs) is the key component in all-solid-state Li-ion batteries. Among existing SEs, sulfides SEs attract extensive attentions due to high room temperature ionic conductivity and favorable mechanical properties. However, currently known sulfide SEs only present a few limited types of crystal structures, which limits the materials design and hinders our understanding of ionic conduction mechanisms. Exploring new compound and new crystal structures beyond known groups is much desired in order to expand the ionic conductor database and advances the knowledge about ionic conduction. Recently, our group successfully synthesized and identified a new lithium chloro-thiophosphate in Li2S-P2S5-LiCl system, namely Li15P4S16Cl3 2. This compound shows a low ionic conductivity of ~10-7 S/cm at room temperature. However, this crystal structure provides abundant choices for composition and unit cell size tuning, which may trigger high ionic conductivity. We successfully substituted P in Li15P4S16Cl3 with aliovalent cations to tune the Li content and the interstitial site occupancy. As a result, high room temperature conductivity of ~10-5 S/cm was achieved. The structure of the doped compounds was examined with using synchrotron X-ray and neutron diffractions. The Li+ diffusion pathway was also theoretically investigated with using ab initio molecular dynamics (AIMD) method and experimentally examined with using 7Li solid state nuclear magnetic resonance (NMR) techniques. Auvergniot, J.; Cassel, A.; Ledeuil, J.-B.; Viallet, V.; Seznec, V.; Dedryvère, R., Interface Stability of Argyrodite Li6PS5Cl toward LiCoO2, LiNi1/3Co1/3Mn1/3O2, and LiMn2O4 in Bulk All-Solid-State Batteries. Chemistry of Materials 2017, 29 (9), 3883-3890.Liu, ZT.; Zinkevich, T.; He, XF.; Indris, S.; Xiong, S.; Liu, J.; Xu, W.; Bai, J.; Mo, Yifei; Chen, HL., Li15P4S16Cl3, a new lithium chloro-thiophosphate as a solid state ionic conductor. Submitted.

Ionic conduction mechanism of a nanostructured BCY electrolyte for low-temperature SOFC

A solid oxide fuel cell with 1.2 mm thick nanocrystalline BCY (BaCe0.9Y0.1O3) electrolyte was prepared by the copressing method, and its electrochemical performance was tested in H2/air conditions. The maximum power density of the nanocrystalline electrolyte cell prepared with BCY powders calcined at 1000 °C and operated at 550 °C in H2 is 405.2 mW cm−2. The carriers of nanocrystalline BCY electrolyte were studied by using double-layer electrolyte cells with pure oxygen ion conductor GDC (Gd0.1Ce0.9O2) and proton conductor SCY (SrCe0.95Y0.05O3), sintered at high temperatures as proton and oxygen ion filters. It is found that nanocrystalline BCY is a mixed conductor of oxygen ions and protons. The results of hydrogen and oxygen concentration cells show that the transference number of oxygen ions in the nanocrystalline BCY prepared in this study is higher than that of protons. XPS and HRTEM results of BCY particles before and after performance testing showed that an amorphous layer containing a high concentration of oxygen vacancies and suspected carbonate was formed on the surface of BCY particles after fuel cell performance testing. We believe that the amorphous layer should be a high-speed ion conduction channel for nanocrystalline BCY electrolyte during performance testing.

Variations of chemical bonds in silver halides under high pressures

ABSTRACTRocksalt structured AgI (rs-AgI), which appears under pressures between 0.4 and 11.3 GPa, shows high ionic conductivity as high as that in α-AgI, especially at high temperatures. Microscopic origins of ion conduction mechanisms have not been clarified until now and are therefore investigated using the discrete variational Xα (DV-Xα) cluster method. Comparable studies for AgCl and AgBr, which are known as high ionic conductors just below melting temperatures and form the rocksalt structure, are also done. Ionic interactions between a mobile Ag ion and remaining ions are almost the same between those under different pressures, while covalent interactions between the mobile Ag ion and the remaining Ag ions change drastically when the mobile Ag ion is migrating. Similar results are also obtained for AgCl and AgBr. The covalent interactions between the mobile Ag ion and the remaining Ag ions, which should affect the Ag ion migration, play important roles in not only rs-AgI but AgBr and AgCl.

Ion transport mechanism and dielectric relaxation behavior of PVA-imidazolium ionic liquid-based polymer electrolytes

Solid polymer electrolytes based on poly(vinyl alcohol) (PVA) with different wt% ionic liquid (IL), 1-Butyl-2, 3-dimethylimidazolium tetraflouroborate [BDMITFB] were prepared using the solution cast technique. Prepared samples were characterized using the AC impedance spectroscopic technique. AC conductivity spectra of a PVA-IL-based system at different concentrations/temperatures have been discussed. The fitted AC conductivity spectra using Jonscher’s power law (JPL) exhibits the correlated barrier hopping (CBH) type conduction mechanism. The scaled AC conductivity spectra of PVA-IL-based films with temperature/concentrations collapsed into a single master curve indicating the ion conduction mechanism have the same origin. For higher IL loaded samples (20 and 25 wt%) mobility, μ dc conductivity, σdc as well as total number density of charge carriers, N increases with increasing IL content in PVA. Dielectric permittivity (ε′ and ε″) and electric modulus (M′ and M″) study of prepared samples has been done. Temperature-dependent dc conductivity for prepared polymeric films follows the Arrhenius type thermally activated process.