Ion Migration Rate Research Articles

Tuning the crystal structure and oxygen defect by doping lithium vanadate

For its high specific discharge capacity and low working voltage, lithium vanadate is considered a promising anode material. However, inherent low conductivity and unsatisfactory cycle performance limit its further application. In this work, doping at the V site does not destroy the crystal structure of lithium vanadate but also increases the lattice volume. Moreover, the increased content of oxygen defect in the presence of redox reaction effectively improves the electrochemical properties of lithium vanadate. At the same time, the enhancement of hydrophilicity effectively improves the migration rate of ions. Among all LiLa x V 3-x O 8 samples, LiLa 0.01 V 2.99 O 8 (LVO-La-10) demonstrates better rate and cycle performance. LVO-La-10 delivers specific discharge capacities of 93.5 mAh g 1 at 0.5 C, and 42.8 mAh g −1 at 7 C, which is 17.4 and 16.7 mAh g −1 larger than that of lithium vanadate, respectively. Moreover, the capacity retention rate of LVO-La-10 (87.8%) is still higher than that of lithium vanadate (75.8%) at the rate of 0.2 C after 100 cycles. This work exhibits that increasing the lattice volume and oxygen defect of lithium vanadate effectively improves its electrochemical performance.

Relationships of pulsed frequency and anammox bacteria growth rate, at low temperatures

ABSTRACT This study explored pulsed frequency that could enhance the anammox bacteria growth rate and TN removal rate at low temperatures (16 ± 1°C). The results showed that the growth rate of anammox bacteria in R1 (1000 Hz) was significantly higher than in R2 (30 Hz) and R3 (106Hz). The relative abundance values of anammox bacteria R1 were higher by 52.21% and 172.41% than R2 and R3, while that of MLSS were as high as 241.07% and 471.36% than R2 and R3, with the nitrogen loading rate was 6.84 kg-N/m³/d. Besides, the dynamics also showed that the specific anammox activity (SAA) and the cellular yield of R1 were higher than R2 and R3. The intermediate frequency could enhance the cell division by stimulating the anammoxosome and reduce the ionic hydration layer to accelerate the ion migration rate, further improving the number of anammox bacteria even at low temperatures. The pulsed frequency could enhance the anammox growth rate and the doubling time is just 5 d.

Interlayer-expanded MoS2@C hollow nanorods for enhanced sodium storage

Molybdenum disulfide (MoS2) can as a aussichtsreich electrode for sodium-ion batteries (SIBs) considering multi-electron redox processes, which can meet the requirements of high discharge capacity and superb rate performance. However, Molybdenum disulfide tends to agglomerate during the preparation process, resulting in low mass energy density. In this paper, hollow rod shape MoS2@C composite is prepared by using hydrothermal method. The remarkable structure increases specific surface area and facilitates ion migration rate. The alternating superposition of MoS2 and carbon layer expand the material layer spacing, and maintain the structure stability sue to the van der Waal’s force interaction in multilayer film. As expected, the MoS2@C shows significant electrochemical performance the first lap specific capacity can reach 1003.5 mAh/g, and Coulomb efficiency (CE) reaches 66.2%. The specific capacity is 401.2 mAh/g at 100th cycle, and the CE achieves 100%. This work demonstrates the feasibility of this synthesis strategy in preventing structural degradation of template materials.

Experimental study of mechanical properties and durability of green concrete containing slag, waste rubber powder and recycled aggregate with artificial neural network

In this experimental study, the impact of using waste materials such as ground granulated blast furnace slag (GGBFS), waste rubber powder (WRP), and recycled concrete aggregate (RCA) were evaluated on the compressive, tensile and, flexural strengths and durability test of rapid chloride migration test (RCMT) of concrete. It was observed that the mechanical properties of concrete decreased by raising the proportions of recycled materials in all replacement ratios. Because of the adverse effects of the WRP and RCA on the cement matrix and the interfacial transition zone, the reduction of the mechanical properties is higher for the concrete specimens with both recycled materials. In the case of durability, the migration rate of chloride ions in concrete is reduced by increasing the WRP rates due to the blockage of micro-pores connections. However, adding the RCA has a negative effect on the durability performance of concrete. Regarding the simultaneous effect of slag, rubber powder, and recycled aggregate on the migration of chloride ions, it can be derived that durability of samples containing 20% slag, 2.5% rubber powder, and 25% recycled aggregate at the age of 7 days on average is 14.8% higher compared to the reference sample. As the age of the samples increases to 28 days, the migration of chloride ions in the samples reduced 9.5% compared to 7 days.

The effect of adding polyethylene glycol to electrolyte solution on micro-arc oxidation coating on pure aluminum

Micro-arc oxidation (MAO) is a surface treatment technology that enhances the performance of metal surfaces by growing ceramic layers on the valve metal surface to meet the demand of the application. This paper aims to improve the performance of ceramic coatings on pure aluminum surfaces by varying the concentration of polyethylene glycol (PEG) in electrolytes. As an active agent, the PEG extends the ionic activity, and the increasing rate of ion migration in electrolytes improves the reaction rate. And the PEG long chain is also beneficial to electron conduction, which will promote the discharge effect in the MAO process. The MAO coating was characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), the wear resistance of MAO coating was evaluated by tribological experiments, and the corrosion resistance of MAO coating was evaluated by the Neutral salt spray test (NSST). The experimental results showed that the MAO coating had the best wear resistance when the concentration of PEG was 2 g/L. The coatings prepared by adding PEG to the electrolyte have good wear and corrosion resistance, which enhance the service life and application range of the metal and are expected to promote the development of valve metal in application fields.

Dual metal ions and water molecular pre-intercalated δ-MnO2 spherical microflowers for aqueous zinc ion batteries

Layered δ-MnO2 is a promising cathode material for aqueous zinc ion batteries (AZIBs) due to its high theoretical capacity, high operating voltage and low cost. However, the dissolution of MnO2 and the disproportionation of Mn3+ will lead to irreversible reaction and serious structural degradation of the material during cycling process. In this work, the Al3+ pre-intercalated K0.27MnO2·0.54H2O was prepared by a one-step hydrothermal method with citric acid as the complexing agent and weak reducing agent. Based on the pillars of bimetallic ions K+, Al3+ and water, the framework and interlayer of δ-MnO2 is stabilized. Besides, a certain amount of Al3+ facilitates the increase of crystal water compared with the pure K0.27MnO2·0.54H2O, which is not only conducive to promote the construction of porous and loose 3D morphology, but also beneficial to improve the stability of layered structure and accelerate the migration rate of zinc ions. Contributed to the dissolution/deposition reaction mechanism combined with H+/Zn2+ co-insertion/co-extraction mechanism, it has achieved the high capacity with the maximum reversible specific capacity of 269.5 mAh g−1 at 0.5 A g−1 and excellent stability with 205.8 mAh g−1 even after 300 cycles in Zn//Al-KMO battery.

Ta2O5-Rgo Nanocomposite As Emerging Anode Material for Sodium Ion Storage Via Extrinsic Pseudo-Capacitive Red-Ox Process

Ta2O5 nanoparticles (NPs) are an emerging conversion type anode material which store sodium ion via extrinsic pseudo-capacitance behaviour. Ionic liquid supported hydrothermal synthesis method was adopted to synthesise pure Ta2O5 NPs followed by hydrothermal route to prepare Ta2O5–reduced graphene oxide (Ta2O5-rGO) nanocomposite. Ta2O5–rGO composite possesses specific discharge capacity of 19 mAhg-1 after 500 cycles at a current rate of 0.1 C compared to bare Ta2O5 NPs where it shows 18 mAhg-1 @ 150 cycles. The stable electro-chemical performance of Ta2O5–rGO composite could be accessible by 2-D net work structure of graphene with excellent surface area and very low electrical resistivity enhances the electron and ion migration rate. Finally, the present study urges electrochemist to design and fabricate advance Ta2O5-rGO composites for sodium- ion battery applications.

Effects of Fe doping on the electrochemical performance of LiV1−xFexPO4F/C (x = 0, 0.01, 0.02, 0.04) cathode materials for lithium‐ion batteries

AbstractThe Fe‐doped LiVPO4F/C cathode material was synthesized by a one‐step solid‐state reaction method. The effects of Fe doping content on the structure and electrochemical performance of LiVPO4F/C were investigated. X‐ray diffraction (XRD) analyses demonstrated that the appropriate addition of Fe3+ did not destroy the lattice structure of LiVPO4F/C. Scanning electron microscopy (SEM) showed that the surface of LiVPO4F/C is covered by a carbon film. The decreased grain size of the Fe‐doped LiVPO4F/C could shorten the ion transport path and thus improve the migration rate of lithium ions. X‐ray photoelectron spectroscopy (XPS) showed that the Fe ion exists in the Fe‐doped LiVPO4F/C as Fe3+ ion. At the discharge rate of 1 C, the initial discharge capacity and capacity retention rate of the LiV0.98Fe0.02PO4F/C after 500 cycles were 123.5 mAh/g and 88.6%, respectively.

Expeditious and effectual capacitive deionization performance by chitosan-based carbon with hierarchical porosity

Capacitive deionization (CDI) technology is a high-efficiency, energy-saving, green and environmentally friendly new water treatment technology, which will have potential in the field of low-salinity seawater desalination. Current carbon-based electrode materials have limited desalination capacity and rate due to insufficient ion-accessible specific surface area and slow ion transmission rate. Here, we demonstrate layered porous carbon (CHPC) derived from Chitosan, colloidal SiO2 and polytetrafluoroethylene (PTFE) mixed carbonization for efficient CDI desalination. CHPC has abundant macropores that are connected with mesopores. This layered porous structure enables CHPC to have a faster ion migration rate. The salt removal capacity of CHPC reaches 26.5 ± 1.5 mg/g, and the average adsorption rate is 8.8 ± 0.5 mg/g/min, which are about 1.6 and 10 times than that of commercial activated carbon, respectively. In addition, CHPC has extremely strong anti-interference performance against organic macromolecules, which could maintain more than 95% adsorption capacity after 30 cycles. Our work helps to promote the practical application of hierarchical porous structures based on typical biomass in large-capacity and fast-rate CDI desalination technology.

Multiple Emission of Phosphonium Fluorophores Harnessed by the Pathways of Photoinduced Counterion Migration

AbstractIn the emerging field of intramolecular charge transfer induced counterion migration, we report the new insights into photophysical features of luminescent donor–acceptor phosphonium dyes (D−π−)nA+[X−] (π=−(C6H4)x−). The unique connectivity of the phosphorus atom affords multipolar molecules with a variable number of arms and the electronic properties of the acceptor group. In the ion‐paired form, the transition from dipolar to quadrupolar configuration enhances the low energy migration‐induced band by providing the additional pathways for anion motion. The multipolar architecture, adjustable lengths of the π‐spacers and the nature of counterions allow for efficient tuning of the emission and achieving nearly pure white light with quantum yields around 30 %. The methyl substituent at the phosphorus atom reduces the rate of ion migration and suppresses the red shifted bands, simultaneously improving total emission intensity. The results unveil the harnessing of the multiple emission of phosphonium fluorophores by anion migration via structure and branching of donor–acceptor arms.

Influence of applied bias for A-site and X-site ion exchange reaction dynamics in perovskite quantum dots

Due to the excellent photophysical properties of perovskite quantum dots, their introduction into solar driven chemistry and optoelectronic devices has been taken up as an attractive alternative. Despite the outstanding photophysical properties and successful application to photovoltaic devices, applied electrical field induced phenomena could induce various component change and time dependent variations in the perovskite quantum dots. In this study, we investigated the behavior of X-site halide and A-site cation exchange processes in between the perovskite quantum dots. Through in-situ photoluminescence spectroscopy under the applied bias, we figured out the role of applied bias and current to the exchange process to the exchange process. Through these studies, we were able to track the enhanced migration rate of ions in the batch solution could facilitate the ion interdot exchange reaction dynamics in between the perovskite quantum dots. This study can be used to develop the practical strategy to apply the perovskite quantum dots to the solar driven chemistry and the optoelectronic devices.

The positive role of the single crystal morphology in improving the electrochemical performance of Li-rich cathode materials

Submicron-sized single crystal Li1.2Mn0.54Ni0.13Co0.13O2 was prepared to enhance the structural stability and lithium ion migration rate of Li-rich cathode materials. The preparation process of single crystal particles was beneficial for materials with good layered structures and low cation mixing degrees. Due to the single crystal morphology of the materials, the particles remained intact without cracks after cycling, which reduced side reactions between the cathode material and electrolyte, thus preventing the structural phase transformation. The preparation of submicron-sized single crystal particles provides a new strategy to improve the electrochemical properties of Li-rich cathode materials.

Prediction of mechanical and durability characteristics of concrete including slag and recycled aggregate concrete with artificial neural networks (ANNs)

This research aims to create an artificial neural networks (ANN) model to forecast mechanical and durability properties (compressive strengths and the durability test of rapid chloride migration test (RCMT)) of waste-included concrete according to the features of the reference samples. Moreover, this experimental study evaluated the mechanical characteristics and long-term durability of concrete when using a synergic of ground granulated blast furnace slag (GGBFS) and recycled concrete aggregate. This experimental study evaluated concrete's mechanical characteristics and long-term durability when using a synergic of ground granulated blast furnace slag (GGBFS) and recycled concrete aggregate. Concrete samples were made with different binder content and water to binder ratios, including the RCA at substitution levels of 25 percent and 50 percent as well as slag at substitution levels of 20 percent and 40 percent by weight of Portland cement in order to evaluate the influence of waste materials on concrete mixtures. The mechanical characteristics of concrete deteriorated when the quantities of recycled aggregate increased in all replacement ratios. However, the findings of the mechanical characteristics suggest that slag can reduce the detrimental effects of substituting coarse aggregate with RCA in the early ages of the samples. In the case of durability, applying RCA increases the chloride ion migration rate in concrete. Slag mitigates the detrimental impacts of recycled aggregate by enhancing hydration products, except for early stages.

Transient Plasmonic Imaging of Ion Migration on Single Nanoparticles and Insight for Double Layer Dynamics

AbstractSingle‐nanoparticle electrochemistry offers electrochemical behaviors of individual entities beyond the ensemble system. An electric double layer (EDL) exists on any charged particle–liquid interface because of counter‐ion accumulation, while direct measuring of the interfacial ion migration remains a challenge. Herein, a plasmonic‐based transient microscopic method, with a temporal resolution of 1–2 μs, was demonstrated to directly track the ion migration dynamics on single charged nanoparticles. We found that the dynamics of EDL formation might deviate significantly from the prediction made by using the classical resistance–capacitance (RC) model under nanoscale and transient conditions. Under ultrafast charging, due to the limit migration rate of ions in the solution, the actual time scale of the EDL formation could be up to 5 times slower than the predicted value from the RC model. We then proposed a new theoretical model to describe the transient dynamics of EDL formation. These results may expand our current knowledge about nano‐electrochemistry and transient electrochemistry.

MnCo2O4/g-C3N4 composite material preparation and its capacitance performance

MnCo2O4/g-C3N4 composite material was synthesized by the hydrothermal method, compared with MnCo2O4 without g-C3N4, it has excellent electrochemical performance. The composite material can reach a specific capacitance of 350 Fg[Formula: see text] at 1 Ag[Formula: see text]. The capacity retention rate is 96% after 1000 cycles at the rate of 2 Ag[Formula: see text]. Experiments show that g-C3N4 can effectively disperse and improve the conductivity of urchin-like MnCo2O4, and the composite of sufficient g-C3N4 can give full play to the performance of urchin-like MnCo2O4, provide faster electronic transport channels, effectively improve the ion migration rate, and make urchin-like MnCo2O4 increase the rate performance under high charge and discharge rates.

Unraveling the microstructural properties of cement-slag composite pastes incorporated with smart polymer-based corrosion inhibitors: From experiment to molecular dynamics

Incorporation of corrosion inhibitor into the cement-slag composite pastes can effectively improve the resistance to seawater erosion. However, corrosion inhibitor inevitably affects the microstructures and transport properties of cement-slag composite pastes, which poses a great challenge for the engineering application prospects of the composite pastes modified by corrosion inhibitor. In this paper, a smart organic polymer with hydrophilic and hydrophobic components is designed as corrosion inhibitors, and a combination of experiments and molecular dynamics (MD) simulations is employed to investigate the effect of this smart polymer-based corrosion inhibitor on cement-slag composite pastes under seawater erosion. Experiments show that this smart polymer-based corrosion inhibitor has profound effect on the hydration properties, pore structures and ions resistance of cement-slag composite pastes, with an optimum content of approximately 6%. MD simulations reveal the nano-mechanism by which this smart polymer-based corrosion inhibitor hinders water and ion transport in the calcium aluminate-silicate hydrate (CASH) nanopores. Analysis suggests that strong electrostatic interactions, originating from the CaCASH-Oinhibitor pairs and the H-bond networks, are the primary sources of the corrosion inhibitor-CASH bonding mechanism. Besides, the migration rates of water and ions are reduced as the large cluster structures formed among the corrosion inhibitor molecules, water molecules and erosive ions.

Proteomic Analysis: Explosive Salt Accumulation in Leaves of Morus alba L. under Salt Stress

The salt tolerance of glycophytes is thought to be related to their ability to restrict sodium access to their aboveground parts. A previous study on the mulberry (Morus alba L.) revealed a phenomenon of explosive salt accumulation in the leaves after exceeding a certain treatment concentration. Here, we aim to observe the internal state of mulberry seedlings under salt stress by the proteomic method and to identify the possible inducements associated with salt bursts. In this study, the target treatments for TMT-label free quantitative analyses were determined by measuring the sodium content in the roots and leaves. The results showed that the expressions of proteins classified as “plant hormones”, “ion channels”, “REDOX homeostasis”, “cytoskeleton” and “cell wall” changed significantly after salt bursts. This phenotype is associated with the destruction of the apoplast, in which the assembly of the Casparian strip may be affected by the inhibition of some key proteins, indirectly increasing the rate of ion migration through the endodermis into the shoots.

Three-Dimensional Fast Na-Ion Transport in Sodium Titanate Nanoarchitectures via Engineering of Oxygen Vacancies and Bismuth Substitution.

Layered sodium titanates (NTO), one of the most promising anode materials for advanced sodium-ion batteries (SIBs), feature high theoretical capacity and no serious safety concerns. The pristine NTO electrode, however, has unfavorable Na+ transport kinetics, due to the dominant two-dimensional (2D) Na-ion transport channels within the crystal along the low energy barrier octahedron layers, which impedes the practical application of this class of potential materials. Herein, an interesting concept of opening three-dimensional (3D) fast ion transport channels within the intrinsic NTO frameworks is proposed to enhance the electrochemical performance through a combination of oxygen vacancy generation and cation substitution strategies, by which the interlayer spacing of the NTO frameworks is expanded for fast 3D Na-ion transport. It is evidenced that the oxygen-deficient and bismuth-substituted HBNTO (BixNa2-xTi3Oy, 0 < x < 2, 0 < y < 7, HBNTO) exhibits obvious enhancements on the reversible capacity (∼145% enhancement at 20 mAh g-1 compared with NTO), the rate capability (∼200% enhancement at 500 mAh g-1 compared with NTO), and the cycling stability (∼210% enhancement of retention capacity after 150 cycles at 20 mAh g-1 compared with NTO). The molecular dynamic simulations and theoretical calculations demonstrate that the enhanced performance of HBNTO is contributed by the multiplied sodium diffusion pathways and the increased ion migration rates with the successful opening of 3D internal ion transport channels. This work demonstrates the effectiveness of the strategies in opening the 3D intercrystal ion transport channels for boosting the electrochemical performance of SIBs.

Evaluating the synergic effect of waste rubber powder and recycled concrete aggregate on mechanical properties and durability of concrete

The use of waste materials in the concrete mixture can help human beings to preserve the environment and achieve environmentally-friendly concrete. In this study, the influences of simultaneous replacements of cement by waste rubber powder (WRP) and coarse aggregate by recycled concrete aggregate (RCA) on the mechanical properties and durability of concrete were investigated experimentally. To do so, concrete specimens containing the WRP with the replacement ratios of 0 %, 2.5 %, and 5 % by weight of cement, and the RCA with the replacement levels of 0 %, 25 %, and 50 % of coarse aggregate were prepared. Moreover, different water to binder ratios and binder content were used. Mechanical properties of the concrete specimens consisting of compressive, flexural, and tensile strengths and the durability test of rapid chloride migration test (RCMT) were carried out at different ages. It was observed that the mechanical properties of concrete decrease by raising the proportions of recycled materials in all replacement ratios. Because of the negative effects of the WRP and RCA on, respectively, the cement matrix and the interfacial transition zone, the reduction of the mechanical properties are higher for the concrete specimens with both recycled materials. In the case of durability, the migration rate of chloride ions in concrete reduces by increasing the WRP rates due to the blockage of micro-pores connections. However, adding the RCA has a negative effect on the durability performance of concrete. Finally, four equations were proposed and evaluated for the compressive, tensile, flexural strength reduction and durability factors of concrete containing the WRP and RCA using the genetic programming.

Dispersed nickel-cobalt double metal hydroxide self-assembled with polystyrene sulfonic acid polyelectrolyte for the preparation of carbon solid solid supercapacitors with wide temperature range and long cycle stability

Although polyelectrolytes with good electrochemical compatibility have been widely used in all solid-state supercapacitors, the random dispersion of polymer chains results in a narrow operating temperature range, which limits its further application. Herein, through the electrostatic attraction assembly strategy, the negatively charged polystyrene sulfonic acid (PSS) and the positively charged layered nickel-cobalt double hydroxide (NiCo-LDH) nanosheets are synthesized into PSS/NiCo-LDH composite electrolyte. Meanwhile, the polyelectrolyte shows a wide temperature application range (20–80 °C) and excellent electrochemical cycle stability in solid supercapacitor (capacitance retention rate reaches 96.2% after 5000 cycles) based on activated-carbon electrodes. The remarkable thermal stability and electrochemical performance are mainly attributed to the addition of NiCo-LDH, which is not only limit the thermal decomposition of PSS molecular chains, but also accelerate the migration rate of electrolyte ions. This work opens a way for the preparation of polyelectrolyte with wide temperature range and long cycle stability for application in solid-state supercapacitors.