Showing papers on "Ion published in 2018"
TL;DR: In this paper, bimetallic sulfide (Co9S8/ZnS) nanocrystals embedded in hollow nitrogen-doped carbon nanosheets are demonstrated with a high sodium diffusion coefficient, pseudocapacitive effect, and excellent reversibility.
Abstract: Lithium-ion batteries (LIBs) have permeated energy storage market from portable electronics to electric vehicles in view of their high energy density and long cycle life.[1] Nevertheless, it is still expensive to scale up due to the limited Li sources.[2] In contrast, sodium-ion batteries (SIBs), with similar energy Sodium-ion batteries (SIBs) are promising next-generation alternatives due to the low cost and abundance of sodium sources. Yet developmental electrodes in SIBs such as transition metal sulfides have huge volume expansion, sluggish Na+ diffusion kinetics, and poor electrical conductivity. Here bimetallic sulfide (Co9S8/ZnS) nanocrystals embedded in hollow nitrogen-doped carbon nanosheets are demonstrated with a high sodium diffusion coefficient, pseudocapacitive effect, and excellent reversibility. Such a unique composite structure is designed and synthesized via a facile sulfidation of the CoZn-MOFs followed by calcination and is highly dependant on the reaction time and temperature. The optimized Co1Zn1-S(600) electrode exhibits excellent sodium storage performance, including a high capacity of 542 mA h g−1 at 0.1 A g−1, good rate capability at 10 A g−1, and excellent cyclic stability up to 500 cycles for half-cell. It also shows potential in full-cell configuration. Such capabilities will accelerate the adoption of sodium-ion batteries for electrical energy applications.
397 citations
TL;DR: A hybrid acceleration scheme based on the relativistic induced transparency mechanism using linearly polarised laser interaction with foil targets is demonstrated and its future implication in using high power lasers is explored.
Abstract: The range of potential applications of compact laser-plasma ion sources motivates the development of new acceleration schemes to increase achievable ion energies and conversion efficiencies. Whilst the evolving nature of laser-plasma interactions can limit the effectiveness of individual acceleration mechanisms, it can also enable the development of hybrid schemes, allowing additional degrees of control on the properties of the resulting ion beam. Here we report on an experimental demonstration of efficient proton acceleration to energies exceeding 94 MeV via a hybrid scheme of radiation pressure-sheath acceleration in an ultrathin foil irradiated by a linearly polarised laser pulse. This occurs via a double-peaked electrostatic field structure, which, at an optimum foil thickness, is significantly enhanced by relativistic transparency and an associated jet of super-thermal electrons. The range of parameters over which this hybrid scenario occurs is discussed and implications for ion acceleration driven by next-generation, multi-petawatt laser facilities are explored.
328 citations
TL;DR: Metal organic framework membranes, including ZIF-8 and UiO-66 membranes with uniform subnanometer pores consisting of angstrom-sized windows and nanometer-sized cavities for ultrafast selective transport of alkali metal ions are reported.
Abstract: Porous membranes with ultrafast ion permeation and high ion selectivity are highly desirable for efficient mineral separation, water purification, and energy conversion, but it is still a huge challenge to efficiently separate monatomic ions of the same valence and similar sizes using synthetic membranes. We report metal organic framework (MOF) membranes, including ZIF-8 and UiO-66 membranes with uniform subnanometer pores consisting of angstrom-sized windows and nanometer-sized cavities for ultrafast selective transport of alkali metal ions. The angstrom-sized windows acted as ion selectivity filters for selection of alkali metal ions, whereas the nanometer-sized cavities functioned as ion conductive pores for ultrafast ion transport. The ZIF-8 and UiO-66 membranes showed a LiCl/RbCl selectivity of ~4.6 and ~1.8, respectively, which are much greater than the LiCl/RbCl selectivity of 0.6 to 0.8 measured in traditional porous membranes. Molecular dynamics simulations suggested that ultrafast and selective ion transport in ZIF-8 was associated with partial dehydration effects. This study reveals ultrafast and selective transport of monovalent ions in subnanometer MOF pores and opens up a new avenue to develop unique MOF platforms for efficient ion separations in the future.
305 citations
TL;DR: This study examines the compositional dependence of the three determining factors for ionic conductivity, including ion mobility, ion transport pathways, and active ion concentration and finds that a higher content of LLZO leads to improved electrochemical stability of composite electrolytes.
Abstract: Composite electrolytes are widely studied for their potential in realizing improved ionic conductivity and electrochemical stability. Understanding the complex mechanisms of ion transport within composites is critical for effectively designing high-performance solid electrolytes. This study examines the compositional dependence of the three determining factors for ionic conductivity, including ion mobility, ion transport pathways, and active ion concentration. The results show that with increase in the fraction of ceramic Li7La3Zr2O12 (LLZO) phase in the LLZO–poly(ethylene oxide) composites, ion mobility decreases, ion transport pathways transit from polymer to ceramic routes, and the active ion concentration increases. These changes in ion mobility, transport pathways, and concentration collectively explain the observed trend of ionic conductivity in composite electrolytes. Liquid additives alter ion transport pathways and increase ion mobility, thus enhancing ionic conductivity significantly. It is also...
279 citations
TL;DR: In this article, a method based on Kelvin probe force microscopy was developed to map charge redistribution in an operating device upon a voltage- or light pulse with sub-millisecond resolution.
Abstract: In this study, we discuss the underlying mechanism of the current–voltage hysteresis in a hybrid lead-halide perovskite solar cell. We have developed a method based on Kelvin probe force microscopy that enables mapping charge redistribution in an operating device upon a voltage- or light pulse with sub-millisecond resolution. We observed the formation of a localized interfacial charge at the anode interface, which screened most of the electric field in the cell. The formation of this charge happened within 10 ms after applying a forward voltage to the device. After switching off the forward voltage, however, these interfacial charges were stable for over 500 ms and created a reverse electric field in the cell. This reverse electric field directly explains higher photocurrents during reverse bias scans by electric field-assisted charge carrier extraction. Although we found evidence for the presence of mobile ions in the perovskite layer during the voltage pulse, the corresponding ionic field contributed only less than 10% to the screening. Our observation of a time-dependent ion concentration in the perovskite layer suggests that iodide ions adsorbed and became neutralized at the hole-selective spiro-OMeTAD electrode. We thereby show that instead of the slow migration of mobile ions, the formation and the release of interfacial charges is the dominating factor for current–voltage hysteresis.
278 citations
TL;DR: A comprehensive review including characterization methods, the effects of chemical composition of the ionic liquids on the thermal, electrochemical, and radiolytic stabilities of ions, respectively, and the thermal stability of some special types of ionic fluids are discussed.
Abstract: Research on ionic liquids has achieved rapid progress in the last several decades. Stability is a prerequisite for the application of ionic liquids. Ionic liquids may be used at elevated temperature, as electrolytes, or under irradiation. Therefore, the thermal, electrochemical, and radiolytic stabilities of ionic liquids are important and need to be known before their usage. Many research papers and some reviews on the stabilities of ionic liquids have been published. However, new results are continuously being published and a comprehensive review and perspective on this topic are still urgently needed. In this perspective, we intend to provide a comprehensive review including characterization methods, the effects of chemical composition of the ionic liquids on the thermal, electrochemical, and radiolytic stabilities of ionic liquids, respectively. Moreover, the thermal stability of some special types of ionic liquids such as poly(ionic liquids) and mixed ionic liquids, and the thermal and electrochemical stabilities of protic ionic liquids are discussed too. For thermal stability, the interactions between ions are less important than the individual anions and cations. The decomposition temperature is mainly determined by the less-stable ion, usually the anion. For electrochemical stability, the electrochemical window is determined by both the cation and anion. The less stable ion could influence the stability by interaction between the generated species from the decomposition with the more stable ion (opposite ion). This perspective is helpful for people to avoid using unstable ionic liquids and choose suitable ionic liquids.
232 citations
TL;DR: In this article, the influence of near-surface denuded zones and implanted ion effects is analyzed, including diffusional broadening effects, at high ion irradiation energies, which can lead to enhanced defect production or recovery.
225 citations
198 citations
TL;DR: Nanoporous polymeric membranes with a high density of 0.5 nm pores are fabricated with an excellent balance between selectivity and permeability of ions and demonstrate their exceptional performance for ion sieving.
Abstract: The great potential of nanoporous membranes for water filtration and chemical separation has been challenged by the trade-off between selectivity and permeability. Here we report on nanoporous polymer membranes with an excellent balance between selectivity and permeability of ions. Our membranes are fabricated by irradiating 2-μm-thick polyethylene terephthalate Lumirror® films with GeV heavy ions followed by ultraviolet exposure. These membranes show a high transport rate of K+ ions of up to 14 mol h−1 m−2 and a selectivity of alkali metal ions over heavy metal ions of >500. Combining transport experiments and molecular dynamics simulations with a polymeric nanopore model, we demonstrate that the high permeability is attributable to the presence of nanopores with a radius of ~0.5 nm and a density of up to 5 × 1010 cm−2, and the selectivity is ascribed to the interaction between the partially dehydrated ions and the negatively charged nanopore wall.
185 citations
TL;DR: This work suggests that anomalously high diffusion rates for specific hydration numbers of ions are generally determined by the degree of symmetry match between the hydrates and the surface lattice.
Abstract: Ion hydration and transport at interfaces are relevant to a wide range of applied fields and natural processes1–5. Interfacial effects are particularly profound in confined geometries such as nanometre-sized channels6–8, where the mechanisms of ion transport in bulk solutions may not apply9,10. To correlate atomic structure with the transport properties of hydrated ions, both the interfacial inhomogeneity and the complex competing interactions among ions, water and surfaces require detailed molecular-level characterization. Here we constructed individual sodium ion (Na+) hydrates on a NaCl(001) surface by progressively attaching single water molecules (one to five) to the Na+ ion using a combined scanning tunnelling microscopy and noncontact atomic force microscopy system. We found that the Na+ ion hydrated with three water molecules diffuses orders of magnitude more quickly than other ion hydrates. Ab initio calculations revealed that such high ion mobility arises from the existence of a metastable state, in which the three water molecules around the Na+ ion can rotate collectively with a rather small energy barrier. This scenario would apply even at room temperature according to our classical molecular dynamics simulations. Our work suggests that anomalously high diffusion rates for specific hydration numbers of ions are generally determined by the degree of symmetry match between the hydrates and the surface lattice. A sodium ion hydrated with three (rather than one, two, four or five) water molecules diffuses orders of magnitude more quickly than the other ion hydrates owing to the interfacial symmetry mismatch.
175 citations
TL;DR: The tunable nanoconfinement in layered graphene-based nanoporous membranes is exploited to show that sub-2 nm confined ion diffusion can be strongly modulated by the surface potential-induced EDL, which suggests an anomalously enhanced diffusion that cannot be explained by conventional theoretical predictions.
Abstract: Ion transport in nanoconfinement differs from that in bulk and has been extensively researched across scientific and engineering disciplines1–4. For many energy and water applications of nanoporous materials, concentration-driven ion diffusion is simultaneously subjected to a local electric field arising from surface charge or an externally applied potential. Due to the uniquely crowded intermolecular forces under severe nanoconfinement (<2 nm), the transport behaviours of ions can be influenced by the interfacial electrical double layer (EDL) induced by a surface potential, with complex implications, engendering unusual ion dynamics5–7. However, it remains an experimental challenge to investigate how such a surface potential and its coupling with nanoconfinement manipulate ion diffusion. Here, we exploit the tunable nanoconfinement in layered graphene-based nanoporous membranes to show that sub-2 nm confined ion diffusion can be strongly modulated by the surface potential-induced EDL. Depending on the potential sign, the combination and concentration of ion pairs, diffusion rates can be reversibly modulated and anomalously enhanced by 4~7 times within 0.5 volts, across a salt concentration gradient up to seawater salinity. Modelling suggests that this anomalously enhanced diffusion is related to the strong ion–ion correlations under severe nanoconfinement, and cannot be explained by conventional theoretical predictions.
TL;DR: A simple and effective strategy is reported to weaken and degrade this process by engineering the intensified surface and near-surface reactions, which is realized by making use of a sandwich-type nanoarchitecture composed of graphene as electron channels and few-layered MoS2 with expanded interlayer spacing.
Abstract: To achieve the high-power sodium-ion batteries, the solid-state ion diffusion in the electrode materials is a highly concerned issue and needs to be solved. In this study, a simple and effective strategy is reported to weaken and degrade this process by engineering the intensified surface and near-surface reactions, which is realized by making use of a sandwich-type nanoarchitecture composed of graphene as electron channels and few-layered MoS2 with expanded interlayer spacing. The unique 2D sheet-shaped hierarchical structure is capable of shortening the ion diffusion length, while the few-layered MoS2 with expanded interlayer spacing has more accessible surface area and the decreased ion diffusion resistance, evidenced by the smaller energy barriers revealed by the density functional theory calculations. Benefiting from the shortened ion diffusion distance and enhanced electron transfer capability, a high ratio of surface or near-surface reactions is dominated at a high discharge/charge rate. As such, the composites exhibit the high capacities of 152 and 93 mA h g-1 at 30 and 50 A g-1 , respectively. Moreover, a high reversible capacity of 684 mA h g-1 and an excellent cycling stability up to 4500 cycles can be delivered. The outstanding performance is attributed to the engineered structure with increased contribution of surface or near-surface reactions.
TL;DR: By combining inelastic neutron scattering measurements with density functional theory, fast lithium conductors were shown to have low lithium vibration frequency or low center of lithium phonon density of states as discussed by the authors.
Abstract: Lithium ion conductivity in many structural families can be tuned by many orders of magnitude, with some rivaling that of liquid electrolytes at room temperature. Unfortunately, fast lithium conductors exhibit poor stability against lithium battery electrodes. In this article, we report a fundamentally new approach to alter ion mobility and stability against oxidation of lithium ion conductors using lattice dynamics. By combining inelastic neutron scattering measurements with density functional theory, fast lithium conductors were shown to have low lithium vibration frequency or low center of lithium phonon density of states. On the other hand, lowering anion phonon densities of states reduces the stability against electrochemical oxidation. Olivines with low lithium band centers but high anion band centers are promising lithium ion conductors with high ion conductivity and stability. Such findings highlight new strategies in controlling lattice dynamics to discover new lithium ion conductors with enhanced conductivity and stability.
TL;DR: The radical modification of the pseudocapacitive properties of an oxide material, ZnxCo1−xO, via atomic-level structure engineering is reported, which changes its dominant charge storage mechanism from surface redox reactions to ion intercalation into bulk material.
Abstract: Atomic-level structure engineering can substantially change the chemical and physical properties of materials. However, the effects of structure engineering on the capacitive properties of electrode materials at the atomic scale are poorly understood. Fast transport of ions and electrons to all active sites of electrode materials remains a grand challenge. Here, we report the radical modification of the pseudocapacitive properties of an oxide material, Zn x Co1-x O, via atomic-level structure engineering, which changes its dominant charge storage mechanism from surface redox reactions to ion intercalation into bulk material. Fast ion and electron transports are simultaneously achieved in this mixed oxide, increasing its capacity almost to the theoretical limit. The resultant Zn x Co1-x O exhibits high-rate performance with capacitance up to 450 F g-1 at a scan rate of 1 V s-1, competing with the state-of-the-art transition metal carbides. A symmetric device assembled with Zn x Co1-x O achieves an energy density of 67.3 watt-hour kg-1 at a power density of 1.67 kW kg-1, which is the highest value ever reported for symmetric pseudocapacitors. Our finding suggests that the rational design of electrode materials at the atomic scale opens a new opportunity for achieving high power/energy density electrode materials for advanced energy storage devices.
TL;DR: In this article, the authors investigate the mechanism of ion selectivity through atomistic simulations and free-energy calculations, and show that both rapid permeation of K+ and ion selectivities are ultimately based on a single principle: the direct knock-on of completely desolvated ions in the channels' selectivity filter.
Abstract: The seeming contradiction that K+ channels conduct K+ ions at maximal throughput rates while not permeating slightly smaller Na+ ions has perplexed scientists for decades Although numerous models have addressed selective permeation in K+ channels, the combination of conduction efficiency and ion selectivity has not yet been linked through a unified functional model Here, we investigate the mechanism of ion selectivity through atomistic simulations totalling more than 400 μs in length, which include over 7,000 permeation events Together with free-energy calculations, our simulations show that both rapid permeation of K+ and ion selectivity are ultimately based on a single principle: the direct knock-on of completely desolvated ions in the channels’ selectivity filter Herein, the strong interactions between multiple ‘naked’ ions in the four filter binding sites give rise to a natural exclusion of any competing ions Our results are in excellent agreement with experimental selectivity data, measured ion interaction energies and recent two-dimensional infrared spectra of filter ion configurations That K+ channels conduct K+ ions at near-diffusion limited rates, but block the passage of smaller Na+ ions, creates an apparent contradiction Now, atomistic simulations and free-energy calculations are used to show that both K+ permeation and ion selectivity are governed by the direct knock-on of completely desolvated ions in the channels’ selectivity filter
TL;DR: In this paper, a phase gradient outer layer with a layered coexisting phase spinel structure accompanied by decreasing nickel content is self-induced and formed successfully, which endows fast ion diffusion channels, suppressed voltage decay, and good cyclic stability for Li-rich-layered cathode materials.
Abstract: A phase‐gradient outer layer with “layered‐coexisting phase‐spinel” structure accompanied by decreasing nickel content is self‐induced and formed successfully, which endows fast ion diffusion channels, suppressed voltage decay, and good cyclic stability for Li‐rich–layered cathode materials. This finding sheds light on a universal principle for simultaneously tailoring structure and composition of electrode materials.
TL;DR: This work evaluates the performance of a new chemical ionization source called Vocus, consisting of a discharge reagent-ion source and focusing ion-molecule reactor (FIMR) for use in proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF) measurements of volatile organic compounds (VOCs) in air.
Abstract: We evaluate the performance of a new chemical ionization source called Vocus, consisting of a discharge reagent-ion source and focusing ion–molecule reactor (FIMR) for use in proton-transfer-reacti...
TL;DR: In this article, the effect of fission-energy ion irradiation on the electronic structure at the surface of bulk and thin film samples of CeO2 as a simulant for UO2 nuclear fuel was considered.
TL;DR: The experimental and simulation results indicate that water structure-breaking chaotropic anion salts with a high propensity to form ion networks in aqueous solutions would be excellent candidates for water-based LIB electrolytes.
Abstract: Lithium-ion batteries (LIBs) have been deployed in a wide range of energy-storage applications and helped to revolutionize technological development. Recently, a lithium ion battery that uses superconcentrated salt water as its electrolyte has been developed. However, the role of water in facilitating fast ion transport in such highly concentrated electrolyte solutions is not fully understood yet. Here, femtosecond IR spectroscopy and molecular dynamics simulations are used to show that bulk-like water coexists with interfacial water on ion aggregates. We found that dissolved ions form intricate three-dimensional ion–ion networks that are spontaneously intertwined with nanometric water hydrogen-bonding networks. Then, hydrated lithium ions move through bulk-like water channels acting like conducting wires for lithium ion transport. Our experimental and simulation results indicate that water structure-breaking chaotropic anion salts with a high propensity to form ion networks in aqueous solutions would be ...
TL;DR: In this article, the authors investigated the capacity of N2/3Ni1/3Mn 2/3O2 with a P2 phase as a cathod material for sodium ion batteries.
TL;DR: It is found that K and Cl ions coexisting in g-C3N4 could function as a dual channel for electron and hole transfer, respectively, and could present a new design concept to effectively steer the efficiency of photocatalysts.
Abstract: Limited by relatively fast charge carrier recombination, the performance of g-C3N4 photocatalysts is still far below what is expected. Herein, we tackle this challenge by introducing K and Cl ions into the interlayer of graphitic carbon nitride (KCl-doped g-C3N4). It is found that K and Cl ions coexisting in g-C3N4 could function as a dual channel for electron and hole transfer, respectively. As-prepared KCl-doped g-C3N4 shows a narrow bandgap, positive-shifted valence band edge and lower barriers for charge transfer between layers. Under visible light irradiation, the electrons created in the g-C3N4 layer are transferred by K ions, while the holes are transferred via Cl ions to induce photocatalysis. As expected, the enhanced visible light absorption, strong oxidization ability of the valence band holes and the prolonged lifetime of the charge carriers benefiting from the dual electronic channel endow KCl-doped g-C3N4 with a superior photocatalytic performance for NOx removal, exceeding the performances of both bare g-C3N4 and K doped g-C3N4. An in situ DRIFTS investigation reveals the reaction mechanism of the photocatalytic NO oxidation. The perspective of the dual channel for charge transfer could present a new design concept to effectively steer the efficiency of photocatalysts.
TL;DR: This study creates sub-nanometer vacancies in suspended single-layer molybdenum disulfide (MoS2) via Ga+ ion irradiation, producing membranes containing membranes containing ∼300 to 1200 pores with average and maximum diameters of ∼0.5 and ∼1 nm, respectively.
Abstract: Atomic-defect engineering in thin membranes provides opportunities for ionic and molecular filtration and analysis. While molecular-dynamics (MD) calculations have been used to model conductance through atomic vacancies, corresponding experiments are lacking. We create sub-nanometer vacancies in suspended single-layer molybdenum disulfide (MoS2) via Ga+ ion irradiation, producing membranes containing ∼300 to 1200 pores with average and maximum diameters of ∼0.5 and ∼1 nm, respectively. Vacancies exhibit missing Mo and S atoms, as shown by aberration-corrected scanning transmission electron microscopy (AC-STEM). The longitudinal acoustic band and defect-related photoluminescence were observed in Raman and photoluminescence spectroscopy, respectively. As the irradiation dose is increased, the median vacancy area remains roughly constant, while the number of vacancies (pores) increases. Ionic current versus voltage is nonlinear and conductance is comparable to that of ∼1 nm diameter single MoS2 pores, provin...
TL;DR: In this paper, the authors presented a new framework for extracting single ion diffusion coefficients in ion exchange membranes from experimental ion sorption, salt permeability, and ionic conductivity data.
Abstract: This study presents a new framework for extracting single ion diffusion coefficients in ion exchange membranes from experimental ion sorption, salt permeability, and ionic conductivity data. The framework was used to calculate cation and anion diffusion coefficients in a series of commercial ion exchange membranes contacted by aqueous NaCl solutions. Counterion diffusion coefficients were greater than co-ion diffusion coefficients for all membranes after accounting for inherent differences due to ion size. A model for ion diffusion coefficients in ion exchange membranes, incorporating ideas from counterion condensation theory, was proposed to interpret the experimental results. The model predicted co-ion diffusion coefficients reasonably well with no adjustable parameters, while a single adjustable parameter was required to accurately describe counterion diffusion coefficients. The results suggest that for cross-linked ion exchange membranes in which counterion condensation occurs condensed counterions mi...
TL;DR: In this paper, the superionic conductor Na11 Sn2 PS12, which possesses a room temperature Na+ conductivity close to 4'mS'cm-1, is presented.
Abstract: Highly conductive solid electrolytes are crucial to the development of efficient all-solid-state batteries. Meanwhile, the ion conductivities of lithium solid electrolytes match those of liquid electrolytes used in commercial Li+ ion batteries. However, concerns about the future availability and the price of lithium made Na+ ion conductors come into the spotlight in recent years. Here we present the superionic conductor Na11 Sn2 PS12 , which possesses a room temperature Na+ conductivity close to 4 mS cm-1 , thus the highest value known to date for sulfide-based solids. Structure determination based on synchrotron X-ray powder diffraction data proves the existence of Na+ vacancies. As confirmed by bond valence site energy calculations, the vacancies interconnect ion migration pathways in a 3D manner, hence enabling high Na+ conductivity. The results indicate that sodium electrolytes are about to equal the performance of their lithium counterparts.
TL;DR: In this paper, high-valence Mo-doped Na3V2(PO4)3/C (0 < x < 0.04) was introduced into NASICON-structure, and the crystal structure, electrochemical performances, sodium ion diffusion kinetics and ion transfer mechanism of high-value Mo6+ ion was investigated, which showed that Na2.9V1.98Mo0.02 exhibited a performance of 90 mA h g−1 at 10C and preserved 83.5% of original capacity after 500 cycles.
Abstract: NASICON-structure Na3V2(PO4)3 (NVP) is a potential cathode material for sodium ion battery, which is still confronted with low rate performance because of its poor conductivity. To address this problem, high-valance Mo6+ ion was introduced into NVP. The crystal structure, electrochemical performances, sodium ion diffusion kinetics and ion transfer mechanism of high valence Mo-doped Na3−5xV2−xMox(PO4)3/C (0 < x < 0.04) were investigated. X-ray diffraction, electron microscopy and XPS data confirmed high purity NASICON phosphate phases. The Na ion diffusion process was identified through CV measurement, which clearly shows rapid sodium ion transportation in the Mo-doped NASICON materials. Moreover, DFT calculations proved that Na ion diffusion is promoted by Mo doping. Benefiting from the superior Na ion kinetics, Na2.9V1.98Mo0.02(PO4)3 exhibited a performance of 90 mA h g−1 at 10C and preserved 83.5% of the original capacity after 500 cycles. Our studies demonstrate that high-valence Mo doped Na3V2(PO4)3/C is a promising cathode material for sodium ion batteries with super-high rate capability and stable cycle life.
TL;DR: In this paper, a low defect density monocrystalline MAPbBr3 (MA = methylammonium) solar cells free of a hole transport layer (HTL) suppresses the effect of electronic current.
Abstract: Lead halide perovskites are mixed electronic–ionic semiconductors that have recently revolutionized the photovoltaics field. The physical characterization of the ionic conductivity has been rather elusive because of the high intermixing of ionic and electronic current. In this work, the synthesis of low defect density monocrystalline MAPbBr3 (MA = methylammonium) solar cells free of a hole transport layer (HTL) suppresses the effect of electronic current. Impedance spectroscopy reveals the characteristic signature of ionic diffusion (the Warburg element and transmission line equivalent circuit) and ion accumulation at the interface of MAPbBr3 with the external contacts. Diffusion coefficients are calculated based on a good correlation between thickness of MAPbBr3 and characteristic diffusion transition frequency. In addition, reactive external interfaces are studied by comparison of polycrystalline MAPbBr3 devices prepared either with or without a HTL. The low-frequency response in impedance spectroscopy ...
TL;DR: In this article, the effect of the salt concentration on transport properties and ion dynamics of blend solid polymer electrolyte (PEO-PAN) prepared by solution cast technique was studied.
Abstract: In the present article, we have studied the effect of the salt concentration (LiPF6) on transport properties and ion dynamics of blend solid polymer electrolyte (PEO–PAN) prepared by solution cast technique. Fourier transform infrared (FTIR) spectroscopy confirms the presence of microscopic interactions such as polymer–ion and ion–ion interaction evidenced by a change in peak area of anion stretching mode. The fraction of free anions and ion pairs obtained from the analysis of FTIR implies that both influence the ionic conductivity with different salt concentration. The complex dielectric permittivity, dielectric loss, complex conductivity have been analyzed and fitted in the entire frequency range (1 Hz–1 MHz) at room temperature. The addition of salt augments the enhancement of dielectric constant and shift of relaxation peak in loss tangent plot toward high frequency indicates a decrease of relaxation time. We have implemented the Sigma representation (σ″ vs. σ′) for solid lithium ion conducting films which provide better insight regarding the dispersion region in Cole–Cole plot (e″ vs. e′) in lower frequency window. The dielectric strength, relaxation time and hopping frequency are in correlation with the conductivity which reveals the authenticity of results. Finally, the ion transport mechanism was proposed for getting the better understanding of the ion migration in the polymer matrix.
TL;DR: In this paper, a simple, fast, reliable technique for measuring ionic conductivity based on direct contact between the membrane and electrodes was proposed, which was used to measure ionic values for a series of commercial ion exchange membranes as a function of external solution NaCl concentration.
TL;DR: The results present a general method to investigate the kinetics of the solid-state ion migration, and the gained insights on ion diffusion can provide guidelines for rationally designing perovskite heterostructures that could lead to new properties for fundamental studies and technological applications.
Abstract: The facile chemical transformation of metal halide perovskites via ion exchange has been attributed to their “soft” crystal lattices that enable fast ion migration Kinetic studies of such processes could provide mechanistic insights on the ion migration dynamics Herein, by using aligned single-crystal nanowires of cesium lead bromide (CsPbBr3) perovskite on epitaxial substrates as platforms, we visualize and investigate the cation or anion interdiffusion kinetics via spatially resolved photoluminescence measurement on heterostructures fabricated by stacking CsPbCl3, MAPbI3, or MAPbBr3 microplates on top of CsPbBr3 nanowires Time-dependent confocal photoluminescence microscopy and energy-dispersive X-ray spectroscopy showed the solid-state anion interdiffusion readily occurs to result in halide concentration gradients along CsPbBr3–3xCl3x (x = 0–1) nanowires Quantitative analysis of such composition profiles using Fick’s law allowed us, for the first time, to extract interdiffusion coefficients of the