Ion Transport Properties Research Articles

Effect of Al2O3 on Nanostructure and Ion Transport Properties of PVA/PEG/SSA Polymer Electrolyte Membrane.

Polymer electrolyte membrane (PEM) fuel cells have the potential to reduce our energy consumption, pollutant emissions, and dependence on fossil fuels. To achieve a wide range of commercial PEMs, many efforts have been made to create novel polymer-based materials that can transport protons under anhydrous conditions. In this study, cross-linked poly(vinyl) alcohol (PVA)/poly(ethylene) glycol (PEG) membranes with varying alumina (Al2O3) content were synthesized using the solvent solution method. Wide-angle X-ray diffraction (XRD), water uptake, ion exchange capacity (IEC), and proton conductivity were then used to characterize the membranes. XRD results showed that the concentration of Al2O3 affected the degree of crystallinity of the membranes, with 0.7 wt.% Al2O3 providing the lowest crystallinity. Water uptake was discovered to be dependent not only on the Al2O3 group concentration (SSA content) but also on SSA, which influenced the hole volume size in the membranes. The ionic conductivity measurements provided that the samples were increased by SSA to a high value (0.13 S/m) at 0.7 wt.% Al2O3. Furthermore, the ionic conductivity of polymers devoid of SSA tended to increase as the Al2O3 concentration increased. The positron annihilation lifetimes revealed that as the Al2O3 concentration increased, the hole volume content of the polymer without SSA also increased. However, it was densified with SSA for the membrane. According to the findings of the study, PVA/PEG/SSA/0.7 wt.% Al2O3 might be employed as a PEM with high proton conductivity for fuel cell applications.

Improved self-consistency and oxygen reduction activity of CaFe2O4 for protonic ceramic fuel cell by porous NiO-foam support

Considerable efforts have been made in the past several decades to search the cheap metal-oxides electrocatalysts with superior electrical properties including ionic and electronic for electrochemical energy devices. In this work, simple orthorhombic structured CaFe2O4 nano-particles were embedded on a porous Ni-foam by spin coating method for the application of air electrode for protonic ceramic fuel cells (PCFCs), which provides high oxygen reduction activity than using traditional processes. CaFe2O4 coated Ni-foam cathode shows very small area-specific-resistance (ASR) of ≤0.2 Ωcm2and fuel cell device assembled by CaFe2O4 coated Ni-foam cathode over ceramic BaZr0.8Y0.2O3 (BZY) electrolyte exhibited a peak power density (PPD) of 612 mW cm−2 when operating at 500°C. The porous Ni-foam support superficially improves the electrical and gas diffusion capabilities along with ionic transport properties of CaFe2O4 by narrowing the bandgap to effectively facilitating small polaron hopping energy of valence electrons. However, various spectroscopic measurements such as electrochemical impedance, X-ray photoelectron, thermogravimetric analysis, and Density Functional Theory (DFT) calculations were employed to understand the improved ORR electrocatalyst function of CaFe2O4 with Ni-foam support as three-dimensional heterostructure composite cathode. The results can further help to develop functional cobalt-free electro-catalysts for low temperature-PCFCs and other related applications.

Chloride Ion Transport Properties in Lightweight Ultra-High-Performance Concrete with Different Lightweight Aggregate Particle Sizes.

In this paper, the microstructure and resistance to chloride ion penetration of ultra-high-performance concrete (UHPC) prepared from lightweight aggregate (LWA) were studied through simulation and experiment. The effects of LWA with different particle sizes on the chloride ion transport properties of lightweight ultra-high-performance concrete (L-UHPC) were discussed through simulation test results. The random delivery model of LWA in L-UHPC was established by MATLAB, and the model was introduced into COMSOL. Through the comparative analysis of experimental data and simulation results, the repeatability of the proposed model and the simulation accuracy were verified. The results show that when the LWA particle size changes from 0.15–4.75 mm to 0.15–1.18 mm, the width of interfacial transition zone (ITZ) and the overall porosity of L-UHPC decrease. This is because the large particle size LWA has more open pores with larger pore diameters and related interconnections, which are potential channels for chloride ion transport. Therefore, the chloride ion transport properties in L-UHPC are inhibited, which is manifested by the “tortuosity effect” of the LWA.

Fluoropolymers and Their Nanohybrids As Energy Materials: Application to Fuel Cells and Energy Harvesting.

The current review article provides deep insight into the fluoropolymers and their applications in energy technology, especially in the field of energy harvesting and the development of fuel cell electrolyte polymeric membranes. Fluoropolymers have gained wide attention in the field of energy applications due to their versatile properties. The incorporation of nanofillers within the fluoropolymer to develop the nanohybrid results in an enhancement in the properties, like thermal, mechanical, gas permeation, different fuel cross-over phenomena through the membrane, hydrophilic/hydrophobic nature, ion transport, and piezo-electric properties for fabricating energy devices. The properties of nanohybrid materials/membranes are influenced by several factors, such as type of filler, their size, amount of filler, level of dispersion, surface acidity, shape, and formation of networking within the polymer matrix. Fluoropolymer-based nanohybrids have replaced several commercial materials due to their chemical inertness, better efficacy, and durability. The addition of certain electroactive fillers in the polymer matrix enhances the polar phase, which enhances the applicability of the hybrid for fuel cell and energy-harvesting applications. Poly(vinylidene fluoride) is one of the remarkable fluoropolymers in the field of energy applications such as fuel cell and piezoelectric energy harvesting. In the present review, a detailed discussion of the different kinds of nanofillers and their role in energy harvesting and fuel cell electrolyte membranes is projected.

Ion conduction in Na＋ containing ionogels based on the UiO-66 metal organic framework

▪ conducting materials are critical to the development of solid-state sodium batteries which may enable the use of sodium metal anodes. Ionogels are hybrid liquid–solid electrolytes that are made by embedding an ionic liquid into a suitable solid framework. In this study, ionogels based on the UiO-66 type metal organic framework (MOF) porous structure were prepared. Three isostructural MOFs were synthesized and used: (i) the UiO-66 material, (ii) an amine functionalized MOF (UiO-66- ▪ ) and iii) a hydroxyl functionalized MOF (UiO-66- ▪ ). A mixture of sodium bis(fluorosulfonyl)imide (NaFSI) and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI) was embedded in the pores of the MOFs. FTIR and conductivity spectroscopy were used to asses the interaction of the mobile species with the MOF structure as well as ion transport and electric relaxation properties of the materials. We found that the conductivity of the ionogels is strongly influenced by the functionalized linker used. The UiO-66- ▪ -based ionogels present an encouraging conductivity increase trend when sodium ions are present, whereas the UiO-66- ▪ -based ionogels present the highest conductivity in the order of 0.3 mScm−1 at 293 K, albeit this is very likely due to highly mobile protons. While further studies are needed to understand which species are dominating the ion conduction, this investigation offers an insight into the behavior of MOF-based ionogels and may guide further work in the field.

Self‐assembly of covalent porphyrin compound and its enhanced electrochemiluminescence performance

AbstractA novel Zn‐coordination covalent porphyrin assembly (TCPP‐BZA‐Zn) is designed. The assembly structure is synthesized through the amidation reaction between the porphyrin terminal carboxyl group and the amino group of benzylamine (BZA), and further assembled through π–π stacking. In particular, the inherently ordered structure of TCPP‐BZA‐Zn with Zn as the catalytic active center endows the porphyrin assembly structure with several obvious advantages, such as high ion transport properties and high electrocatalytic performance. In the presence of hydrogen peroxide as a co‐reaction reagent, TCPP‐BZA‐Zn/GCE showed excellent ECL behavior. The amplification phenomenon of ECL was further studied by cyclic voltammetry and the corresponding mechanism was proposed. Based on TCPP‐BZA‐Zn, an electrochemiluminescence sensor was constructed for copper ion detection. The ECL intensity of the sensor shows a good linear relationship with the concentration of copper ion in the range of 10 nM–1 mM, and the detection limit is 1.3 nM.

A multifunctional separator based on dilithium tetraaminophthalocyanine self-assembled on rGO with improved cathode and anode performance in Li–S batteries

Li–S batteries are strong candidates for next-generation energy-storage applications. However, practical cells face critical challenges including the dissolution and shuttling of polysulfides on the cathode as well as the uncontrolled dendrite growth and degradation of the anode. Herein, we demonstrate a multifunctional separator based on dilithium tetraaminophthalocyanine (Li2TaPc) self-assembled on rGO that exhibits a comprehensive regulation effect on important ion transport properties to address the above issues in one configuration. Li2TaPc presents strong sulfiphilic/lithiophilic binding sites for the confinement of polysulfides within the cathode region to improve sulfur utilization. Charge transfers from the central cavity of the TaPc ligand to the rGO promotes the dissociation of Li+ cations to produce additional charge carriers. The negatively-charged TaPc ligand exhibits strong electrostatic repulsions to the salt anions and hinders their migration across the separator. The apparently increased Li+ transference number (0.41–0.89) suppresses dendrite formation and improves the reversibility of the Li anode. Meanwhile, the strong coordination effects of Li+ with Li2TaPc enable a high retention of Li + conductivity. The comprehensive functionalities of the separator result in significantly improved electrochemical performance of Li–S full cells. Pouch cells with a high areal sulfur loading and limited electrolyte addition are also demonstrated.

Measurement of ion transport properties in ion exchange membranes for photoelectrochemical water splitting

Photoelectrochemical (PEC) water-splitting systems have the unique ability to produce renewable hydrogen directly from sunlight, independent of the electrical grid. These systems are therefore appealing technological options for resilient long-term energy storage. Ion selective membranes, such as monopolar and bipolar membranes, are a vital component of PEC water-splitting systems. These membranes allow for ionic conduction between the cathode and anode chambers, separation of products, and improved catalyst environments for reactions. In order to measure key properties and to study the performance of these ion exchange membranes, it is imperative to develop a robust testing protocol that can be used across the field. This paper introduces two standard electrochemical cells designed to directly measure ion transport properties in monopolar and bipolar membranes. The first electrochemical cell uses commercially available Pt disk electrodes to preform electrochemical impedance spectroscopy (EIS) and reliably measure through-plane conductivity of monopolar membranes. The second electrochemical cell uses four-point measurements with Luggin capillaries and a series of membrane configurations to perform current density-voltage and Faradaic efficiency (FE) measurements for water dissociation (WD) reactions on bipolar membranes. The cell designs and techniques laid out below allow for accurate measurement of ion transport parameters in ion exchange membranes, direct comparison of membranes being developed across the field, and in turn, greater advancements in ion exchange membranes and PEC water-splitting systems.

Gaseous transport properties of the ground and excited Cr, Co, and Ni cations in He: Ab initio study of electronic state chromatography.

The electronic state chromatography (ESC) effect allows the differentiation of ions in their ground and metastable states by their gaseous mobilities in the limit of low electrostatic fields. It is investigated here by means of accurate transport calculations with ab initio ion-atom potentials for the Cr, Co, and Ni cations in He buffer gas near room temperature. The values for the open-shell ions in degenerate states are shown to be well approximated by using the single isotropic interaction potential. Minimalistic implementation of the multireference configuration interaction (MRCI) method is enough to describe the zero-field transport properties of metastable ions in the 3dm-14s configuration, such as Cr+(a6D), Co+(a5F), and Ni+(4F), due to their weak and almost isotropic interaction with He atom and the low sensitivity of the measured mobilities to the potential well region. By contrast, interactions involving the ions in the ground 3dm states, such as Cr+(a6S), Co+(a3F), and Ni+(2D), are strong and anisotropic; the MRCI potentials poorly describe their transport coefficients. Even the coupled cluster with singles, doubles, and non-iterative triples approach taking into account vectorial spin-orbit coupling may not be accurate enough, as shown here for Ni+(2D). The sensitivity of ion mobility and the ESC effect to interaction potentials, similarities in ion-He interactions of the studied ions in distinct configurations, accuracy and possible improvements of the ab initio schemes, and control of the ESC effect by macroscopic parameters are discussed. Extensive sets of improved interaction potentials and transport data are generated.

Biodegradable and highly conductive polymeric blend based on the latex of Calotropis gigantea as solid electrolyte in energy storage applications

A blend polymer based on the latex of the South-Asian giant milkweed Calotropis gigantea (CGL) combined with poly (vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) at a mass ratio of 1:1 without the addition of doping salts was synthesized via solution casting to prepare an ionic conductive film. The morphology, crystalline state, vibrational and thermal properties of the film were investigated by Scanning electron microscopy, X-ray diffraction, Fourier Transform infrared spectroscopy (FTIR), Thermal gravimetric analysis (TGA) and Differential scanning calorimetry (DSC). The ionic conductivity and transport properties were investigated by using electrochemical impedance spectroscopy (EIS) Technique. Due the highest ionic conductivity at room temperature (2.7 x 10−2 S/cm), all-solid-state electrolyte was assembled using the prepared polymer film and a comparative study was conducted with respect to 1M H2SO4 liquid electrolyte, regarding the specific capacitance and the electrical properties. The results demonstrate that the fabricated all-solid-state supercapacitor using PVDF-HFP/CGL blend polymer film as electrolyte matches the performance of the liquid electrolyte.

A cation-dipole-reinforced elastic polymer electrolyte enabling long-cycling quasi-solid-state lithium metal batteries

The application of ionic liquids (IL) in polymer electrolytes represents a safer alternative to the currently used organic solvents in lithium batteries due to their nonflammability and thermal stability. However, as a plasticizer, it is generally agreed that the introduction of ionic liquid usually leads to a trade-off between ion transport and mechanical properties of polymer electrolyte. Here we report the synthesis of an IL-embedded polymer electrolyte with both high ionic conductivity (2.77 × 10−4 S cm−1 at room temperature) and excellent mechanical properties (high tensile strength up to 11.4 MPa and excellent stretchability of 387% elongation at break) achieved by strong ion–dipole interactions between polymer electrolyte components, which was unveiled by the DFT calculation. Moreover, this polymer electrolyte also exhibits nonflammability, good thermal stability and the ability to recover reversibly from applied stress, i.e., excellent elasticity. This highly viscoelastic polymer electrolyte enables tight interfacial contact and good adaptability with electrodes for stable lithium stripping/plating for 2000 h under a current density of 0.1 mA cm−2. By coupling with this polymer electrolyte, the LiFePO4/Li cells exhibit outstanding cycling stability at room temperature as well as the reliability under extreme environmental temperature or being abused.

Engineering Bio-inspired Self-assembled Nanochannels for Smart Ion Transport.

Highly efficient biological ion channels with sophisticated transport characteristics in living organisms have inspired the design of artificial channels that are functionally comparable to those of their natural counterparts and applicable on a much larger scale. Self-assembly currently offers a facile approach for producing nanoconfined ion channels that exhibit smart ion-transport properties, including ion selectivity, gating, and rectification, and have shown great potential for various applications. In this Minireview, we give an overview of strategies for engineering bio-inspired self-assembled ion channels. We focus on emerging channel assemblies based on different fabrication processes such as supramolecular assembly, nanosystem-based fabrication, and polymer-based integration. The applications of these bio-inspired channels in the exploration of physiological events, detection of molecules/ions, ion separation, and energy conversion are concisely presented. Finally, future developments and challenges of this booming research field are proposed.

Flexible battery-type pressure sensor enhanced with locked water by calcium ion in graphene oxide solid electrolyte

Wearable pressure sensors have received recent attention due to their contributions to artificial intelligence, electronic skin, and the Internet of Things. However, this traditional sensor is faced with the integration dilemma caused by the need for external energy supply devices. Targeting this obstacle, here, we report a scheme that improves the battery as a pressure sensor. Benefiting by the redox potential conversion mechanism and the water-retention characteristics of calcium ion, this scheme can encode pressure signals into electrical signals, thus converting the battery into a pressure sensor. Proposed battery-type sensors exhibit notable sensing performance and have a high total power density of 1.93 mW cm −2 due to the improvement of conductivity to 1.08 × 10 −3 S/cm, which is ∼4,000 times higher than that of the sensor prepared by unmodified GO solid electrolyte. Therefore, this study provides a general platform for manufacturing high-performance one-body electronic skin in passive mode. • Hydrated GO [Ca] has excellent ion transport properties • The sensor can meet the requirements of self-powered and stable output signals • The sensor has high total power density due to the improvement of conductivity • The battery can be used as a pressure sensor Lei et al. present a scheme that combines battery and pressure sensor in one device. Benefiting by the redox potential conversion mechanism and the water-retention characteristics of calcium ion, this scheme can encode pressure signals into electrical signals, thus converting the battery into a pressure sensor.

Effects of S doping and S/N co-doping on electronic structure and ion diffusion of LiFePO4

First-principle calculations were performed to investigate the electronic structure and dynamics properties of S single doped and S/N co-doped LiFePO4. The un-doped LiFePO4 was a semiconductor with large band gap, while doping made the band gap of LiFePO4 become smaller. With the increase of S-doping concentration, the band gap decreased gradually and sulfur atoms formed covalent bond with its adjacent iron atoms and the covalency of Fe-S bond was enhanced. The configuration of the Li8Fe8P8O29S3 had the least diffusion energy barrier (0.31049 eV), which improved its ion transport properties. For sulfur and nitrogen co-doped LiFePO4 systems, the configuration of Li8Fe8P8O29NS2 had the least band gaps (0.095 eV), showing the best electronic conductive properties. And co-doping could also improve the diffusion of lithium ions.

PBC@cellulose-filter paper separator design with efficient ion transport properties toward stabilized zinc-ion battery

The uneven pore structure and sluggish transport kinetics of the separator will accelerate the growth of dendrites and directly deteriorate the performance of zinc metal battery. Herein, we present a simple and unique interface engineering strategy to anchor persimmon branch carbon (PBC) material onto a cellulose-filter (CF) paper separator to address these issues. The novel PBC material demonstrates a hierarchical pore structure, uniform distribution of carbon dots, and rich N, and O functional groups, and an efficient ion transport modulator PBC@CF separator is designed to serve the dual function of promoting ions transfer and suppressing dendrite growth. Owing to the anchoring of PBC on CF and uniform filling of the surface interspace, the PBC modified separator not only greatly facilitates Zn2+ transport between the fiber-electrolyte interface, but also evenly redistributes the ion transport on the anode interface. As a result, highly reversible Zn plating/stripping is achieved in the symmetric Zn-Zn cell with the PBC@CF separator. Meanwhile, the modified Zn-LiFePO4 dual ion full battery can retain a specific capacity of 109.4 mAh g−1 after 200 cycles at 1 C with an excellent capacity retention of 86 %. The unique PBC material and facile separator engineering provide a new perspective to designing advanced separators for high-performance aqueous Zn dual ion full battery.

Effective Ion Mobility and Long‐Term Dark Current of Metal Halide Perovskites with Different Crystallinities and Compositions

Ion transport properties in metal halide perovskite still constitute a subject of intense research because of the evident connection between mobile defects and device performance and operation degradation. In the case of X‐ray detectors, dark current level and instability are regarded to be connected to the ion migration upon bias application. Two compositions (MAPbBr3 and MAPbI3) and structures (single‐ and microcrystalline) are checked by the analysis of long‐term dark current evolution. Electronic current increases with time before reaching a steady‐state value within a response time (from 104 down to 10 s) that strongly depends on the applied bias. A coupling between electronic transport and ion kinetics exists that ultimately establishes the time scale of electronic current. Effective ion mobility is extracted for a range of applied electric field ξ. While ion mobility results field‐independent in the case of MAPbI3, a clear field enhancement is observed for MAPbBr3 (), irrespective of the crystallinity. Both perovskite compounds present effective ion mobility in the range of ≈ 10−7–10−6 cm−2 V−1 s−1, in accordance with previous analyses. The ξ‐dependence of the ion mobility is related to the lower ionic concentration of the bromide compound. Slower migrating defect drift is suppressed in the case of MAPbBr3, in opposition to that observed here for MAPbI3.

Moisture and ion transport properties in blended pastes and their relation to the refined pore structure

This paper presents a study of the moisture transport properties in blended pastes measured by a new procedure and setup. The dependence of moisture transport coefficient on relative humidity (RH) is confirmed. The differences in the moisture dependency may be due to discrepancies in the critical RH for the percolation of liquid. Fly ash and slag increase the percentage of mesopores or “ink-bottle” pores with a mesoscale neck and they strongly reduce the pore connectivity in pastes. These effects cause the evident reduction in the moisture and chloride diffusivity. The additional replacement with limestone filler has little effect on the pore connectivity. The formation factor controls the moisture transport at the high RH interval, but the volume of small pores (middle capillary and mesopores) is the major determinant at a low RH interval. The relationship between water-binder ratio, pore structure and moisture transport or chloride migration coefficient is discussed.

Ultrasonic-assisted fungi modification of lignocellulose-derived hierarchical porous carbon for efficient desalination

Biomass materials have received increasing attention due to their eco-friendly, high availability and low costs. However, these biomass materials have stubborn structural characteristics, which require specific pretreatment methods to promote practical value. Herein, we reported a novel strategy of ultrasonic-fungi pretreatment of lignocellulose to obtain biomass-based hierarchical porous carbon (LSC-FU). The structure of LSC-FU enables the fabricated electrode to exhibit high conductivity and rapid ion transport properties, with capacitance retention of 99.7 % after 5000 consecutive cycles. And it shows a high adsorption capacity (500 mg·L−1) of 29.39 mg·g−1 with a 94.6 % adsorption capacity retention rate in the electrosorption test. The lignocellulose-based porous carbon electrodes obtained by this effective pretreatment method have great potential for the practical application of CDI. This work provides original outlooks to prepare high-performance carbon electrodes. It emphasizes the significance of sustainable development and green environmental protection by using natural biomass materials to prepare porous carbon materials.

Brain Wave-Like Signal Modulator by Ionic Nanochannel Rectifier Bridges.

Smart modulation of bioelectric signals is of great significance for the development of brain-computer interfaces, bio-computers, and other technologies. The regulation and transmission of bioelectrical signals are realized through the synergistic action of various ion channels in organisms. The bionic nanochannels, which have similar physiological working environment and ion rectification as their biological counterparts, can be used to construct ion rectifier bridges to modulate the bioelectric signals. Here, the artificial smart ionic rectifier bridge with light response is constructed by anodic aluminum oxide (AAO)/poly (spiropyran acrylate) (PSP) nanochannels. The output ion current of the rectifier bridge can be switched between "ON" and "OFF" states by irradiation with UV and visible (Vis) light, and the conversion efficiency (η) of the system in "ON" state is ≈70.5%. The controllable modulation of brain wave-like signal can be realized by ionic rectifier bridge. The ion transport properties and processes of ion rectifier bridges are explained using theoretical calculations based on Poisson-Nernst-Planck (PNP) equations. These findings have significant implications for the understanding of the intelligent ionic circuit and combination of artificial smart ionic channels to organisms, which provide new avenues for development of intelligent ion devices.

Tuning the Electronic, Ion Transport, and Stability Properties of Li-rich Manganese-based Oxide Materials with Oxide Perovskite Coatings: A First-Principles Computational Study.

Lithium-rich manganese-based oxides (LRMO) are regarded as promising cathode materials for powering electric applications due to their high capacity (250 mAh g–1) and energy density (∼900 Wh kg–1). However, poor cycle stability and capacity fading have impeded the commercialization of this family of materials as battery components. Surface modification based on coating has proven successful in mitigating some of these problems, but a microscopic understanding of how such improvements are attained is still lacking, thus impeding systematic and rational design of LRMO-based cathodes. In this work, first-principles density functional theory (DFT) calculations are carried out to fill out such a knowledge gap and to propose a promising LRMO-coating material. It is found that SrTiO3 (STO), an archetypal and highly stable oxide perovskite, represents an excellent coating material for Li1.2Ni0.2Mn0.6O2 (LNMO), a prototypical member of the LRMO family. An accomplished atomistic model is constructed to theoretically estimate the structural, electronic, oxygen vacancy formation energy, and lithium-transport properties of the LNMO/STO interface system, thus providing insightful comparisons with the two integrating bulk materials. It is found that (i) electronic transport in the LNMO cathode is enhanced due to partial closure of the LNMO band gap (∼0.4 eV) and (ii) the lithium ions can easily diffuse near the LNMO/STO interface and within STO due to the small size of the involved ion-hopping energy barriers. Furthermore, the formation energy of oxygen vacancies notably increases close to the LNMO/STO interface, thus indicating a reduction in oxygen loss at the cathode surface and a potential inhibition of undesirable structural phase transitions. This theoretical work therefore opens up new routes for the practical improvement of cost-affordable lithium-rich cathode materials based on highly stable oxide perovskite coatings.