Concentrated Electrolyte Solutions Research Articles

Development of a consistent geochemical model of the Mg(OH)2–MgCl2–H2O system from 25°C to 120°C

The formation of magnesium chloride-hydroxide salts (magnesium hydroxychlorides) has implications for many geochemical processes and technical applications. For this reason, a thermodynamic database for evaluating the Mg(OH)2–MgCl2–H2O ternary system from 0 °C–120 °C has been developed based on extensive experimental solubility data. Internally consistent sets of standard thermodynamic parameters (ΔGf°, ΔHf°, S°, and CP) were derived for several solid phases: 3 Mg(OH)2:MgCl2:8H2O, 9 Mg(OH)2:MgCl2:4H2O, 2 Mg(OH)2:MgCl2:4H2O, 2 Mg(OH)2:MgCl2: 2H2O(s), brucite (Mg(OH)2), bischofite (MgCl2:6H2O), and MgCl2:4H2O. First, estimated values for the thermodynamic parameters were derived using a component addition method. These parameters were combined with standard thermodynamic data for Mg2+(aq) consistent with CODATA (Cox et al., 1989) to generate temperature-dependent Gibbs energies for the dissolution reactions of the solid phases. These data, in combination with values for MgOH+(aq) updated to be consistent with Mg2+-CODATA, were used to compute equilibrium constants and incorporated into a Pitzer thermodynamic database for concentrated electrolyte solutions. Phase solubility diagrams were constructed as a function of temperature and magnesium chloride concentration for comparisons with available experimental data. To improve the fits to the experimental data, reaction equilibrium constants for the Mg-bearing mineral phases, the binary Pitzer parameters for the MgOH+ — Cl− interaction, and the temperature-dependent coefficients for those Pitzer parameters were constrained by experimental phase boundaries and to match phase solubilities. These parameter adjustments resulted in an updated set of standard thermodynamic data and associated temperature-dependent functions. The resulting database has direct applications to investigations of magnesia cement formation and leaching, chemical barrier interactions related to disposition of heat-generating nuclear waste, and evaluation of magnesium-rich salt and brine stabilities at elevated temperatures.

Unlocking Electrode Performance of Disordered Rocksalt Oxides Through Structural Defect Engineering and Surface Stabilization with Concentrated Electrolyte

Abstract Li‐excess cation‐disordered rocksalt oxides can boost the energy density of rechargeable batteries by using anionic redox, but the inferior reversibility of anionic redox hinders its use for practical applications. Herein, a binary system of Li3NbO4–LiMnO2 is targeted and the systematic study on factors affecting electrode reversibility, i.e., percolation probability, electronic conductivity, defect concentrations, and electrolyte solutions, is conducted. A Mn‐rich sample, Li1.1Nb0.1Mn0.8O2, delivers a smaller reversible capacity compared with a Li‐rich sample, Li1.3Nb0.3Mn0.4O2, because of the limitation of ionic migration associated with insufficient percolation probability for disordered oxides. Nevertheless, a larger reversible capacity of Li1.3Nb0.3Mn0.4O2 originates from excessive activation of anionic redox, leading to the degradation of electrode reversibility. The superior performance of Li1.1Nb0.1Mn0.8O2, including Li ion migration kinetics and electronic transport properties, is unlocked by the enrichment of structural defects for nanosized oxides. Moreover, electrode reversibility is further improved by using a highly concentrated electrolyte solution with LiN(SO2F)2 through the surface stabilization on high‐voltage exposure. Superior capacity retention, >100 cycles, is achieved for nanosized Li1.1Nb0.1Mn0.8O2. The electrolyte decomposition and surface stabilization mechanisms are also carefully examined, and it is revealed that the use of highly concentrated electrolyte solution can effectively prevent lattice oxygen being further oxidized and transition metal ion dissolution.

Giant Thermoelectric Response of Confined Electrolytes with Thermally Activated Charge Carrier Generation.

The thermoelectric response of thermally activated electrolytes (TAEs) in a slit channel is studied theoretically and by numerical simulations. The term TAE refers to electrolytes whose charge carrier concentration is a function of temperature, as recently suggested for ionic liquids and highly concentrated aqueous electrolyte solutions. Two competing mechanisms driving charge transport by temperature gradients are identified. For suitable values of the activation energy that governs the generation of charge carriers, a giant thermoelectric response is found, which could help explain recent experimental results for nanoporous media infiltrated with TAEs.

Unified understanding and mitigation of detrimental phase transition in cobalt-free LiNiO2

Ni-enriched layered materials are used as electrode materials of Li-ion batteries for electric vehicle applications. Stoichiometric LiNiO2 with cationic Ni3+/Ni4+ redox is the ideal electrode material, but the gradual loss of capacity at the high voltage region, associated with Ni ion migration, hinders its use for practical applications. Therefore, to improve electrode reversibility of LiNiO2, less abundant Co ions and/or other electrochemically inactive ions, e.g., Al3+ ions, are in part substituted for Ni ions. Nevertheless, a unified understanding of improvement by metal substitution is as yet not established. In this study, the origin causing detrimental phase transition in LiNiO2 is discussed through the detailed analysis on LiNiO2 integrated with nanosized Li3PO4 derived from a metastable and rocksalt LiNiO2–Li3PO4 solid solution sample. LiNiO2 derived from the metastable rocksalt oxide has approximately 6 % anti-site defects, and the particle size growth is suppressed by uniformly dispersed nanosized Li3PO4. In low crystallinity LiNiO2 with partial structural disordering, the Ni ion migration to tetrahedral sites is effectively suppressed because of repulsive electrostatic interaction from Ni ions in Li layers. Moreover, from these findings, non-stoichiometric Li0.975Ni1.025O2 with smaller particle size has been directly synthesized without high-energy milling and Li3PO4 integration, and significant improvement of electrode reversibility is achieved. Electrode reversibility of non-stoichiometric Li0.975Ni1.025O2 is further improved through surface stabilization in a highly concentrated electrolyte solution. The unified understanding of deterioration mechanisms for LiNiO2 offers a new criterion to design Co-free LiNiO2 without metal substitution, leading to full utilization of a reversible capacity for layered materials.

Transformations in crystals of DNA-functionalized nanoparticles by electrolytes.

Colloidal crystals have applications in water treatments, including water purification and desalination technologies. It is, therefore, important to understand the interactions between colloids as a function of electrolyte concentration. We study the assembly of DNA-grafted gold nanoparticles immersed in concentrated electrolyte solutions. Increasing the concentration of divalent Ca2+ ions leads to the condensation of nanoparticles into face-centered-cubic (FCC) crystals at low electrolyte concentrations. As the electrolyte concentration increases, the system undergoes a phase change to body-centered-cubic (BCC) crystals. This phase change occurs as the interparticle distance decreases. Molecular dynamics analysis suggests that the interparticle interactions change from strongly repulsive to short-range attractive as the divalent-electrolyte concentration increases. A thermodynamic analysis suggests that increasing the salt concentration leads to significant dehydration of the nanoparticle environment. We conjecture that the intercolloid attractive interactions and dehydrated states favour the BCC structure. Our results gain insight into salting out of colloids such as proteins as the concentration of salt increases in the solution.

Electrical conductivity of heterogeneous ion exchange membranes in solutions of mono-, di- and tricarboxylic acids and its effect on the process of electrodialysis of solutions containing organic acids

In this study, the electrical conductivity of cation-exchange and anion-exchange membranes was studied in solutions containing both strong (sodium chloride and acetate) and weak (acetic, succinic and citric acids) electrolytes. The results obtained indicate that the concentration dependence of the electrical conductivity of membranes in weak electrolytes differs significantly from that observed for solutions of strong electrolytes. In the case of an acetic acid solution, the electrical conductivity of the membranes is higher than that of the equilibrium solution over the entire range of concentrations that were studied. It has been shown that existing models of the transport and structural organization of membranes allows describing the structural parameters of ion-exchange membranes in contact with strong electrolytes. In sodium chloride and sodium acetate solutions, the obtained dependences were processed within the framework of microheterogeneous and three-wire models to establish the influence of the nature of the electrolyte on the transport and structural characteristics of the membranes. The dependence of electrical conductivity on the concentration of a weak electrolyte solution does not allow the use of either microheterogeneous or extended three-wire models for the description of the structure-property relationship of ion-exchange materials. It has been shown that in acetic acid and partially succinic acid solutions, the solution provides the main contribution to the resistance of the electromembrane system. Based on the results obtained from measuring electrical conductivity, changes in the design of a laboratory electrodialyzer were proposed and experiments were carried out on desalting a solution of acetic acid. It has been shown that the use of thinner intermembrane separators in the desalting chamber leads to an increase in the integral current efficiency (from 0.32 to 0.44 at 0.6 A/dm2 and the same degree of desalination) and a reduction in specific energy consumption (from 3.0 to 1.9 kWh/mol at 0.6 A/dm2) during desalination of acetic acid. The results obtained can be further used to improve the parameters of the process of obtaining weak acids by bipolar electrodialysis.

Development of Durable Large-Sized CO2 Electrolysis Cells for Industrial Applications

Utilization of carbon dioxide (CO2) as a feedstock of valuable chemicals is necessary to achieve carbon neutrality. Toshiba is developing the low-temperature zero-gap type CO2 electrolysis cells to produce carbon monoxide (CO) [1,2]. CO can further be converted into various chemicals and fuels by catalytic reactions with hydrogen. To make the CO2 electrolysis technology industrially feasible, it is necessary to establish high-throughput system by expanding the electrode area and stacking the cells. Large-sized cells and stacks often suffer from low Faradaic efficiency for the CO production, which is related to insufficient and nonuniform supply of reactant CO2 gas to the cathode reaction sites. This time we focused on the development of large-sized single cells and fabricated an electrolysis cell with 400 cm2 electrodes. With properly designed gas flow plates and gaskets, the cell voltage and the CO Faradaic efficiency of the fabricated cell at a current density of 400 mA cm-2 were comparable to those of the previously developed smaller cells with 4 cm2 electrodes. The CO concentration in the cathode outlet gas reached ca. 80% by controlling the inlet CO2 flow rate. Stability is another essential property of CO2 electrolysis cells required for the industrial application. Cathode flooding and salt precipitation are major stability issues characteristic of relatively short-term operations, whose detailed mechanism is still in debate [3]. To mitigate those stability issues, we focused on the cathode inlet humidity and the pressure difference between the cathode and the anode. The former is related to the salt concentration in electrolyte solution around the cathode reaction sites, and the latter is related to the convection of electrolyte from the anode side to the cathode side. By controlling those parameters, stable performance over 100 h was achieved.Part of this work was commissioned by Ministry of the Environment, Government of Japan.[1] Y. Kofuji, A. Ono, Y. Sugano, A. Motoshige, Y. Kudo, M. Yamagiwa, J. Tamura, S. Mikoshiba, and R. Kitagawa, Chem. Lett., 50, 482-484 (2021).[2] Y. Kiyota, Y. Kofuji, A. Ono, S. Mikoshiba, and R. Kitagawa, 242nd ECS Meeting, I05-1942 (2022).[3] M. Sassenburg, M. Kelly, S. Subramanian, W. A. Smith, and T. Burdyny, ACS Energy Lett., 8, 321-331 (2023).

Spectroscopic and Computational Evaluation of Electrochemical Stability of Electrolyte Solutions; Solvents, Electrolytes and Their Concentration Dependence

Since the introduction of Lithium-ion batteries (LIBs) into commercial use, great improvements have been achieved in their performance such as energy density, durability, and safety. However, there still remain many technical issues to meet the increasing demands for a longer driving range of electric vehicles, a larger storage for renewable energy. Research and development of electrode active materials are extensively progressing to respond those market needs, and R&D for electrolyte solutions are also active in order to utilize the fullest extent of the newly developed electrode materials.Various kinds of characteristics are required for electrolyte solutions in LIBs. Ideally, the electrochemical stability in a wide potential range is needed, but almost all the electrolyte solutions reductively decompose on negative electrodes, and the decomposition products precipitate on the electrode to form a protective surface film, which is referred to as SEI (solid electrolyte interphase). Because the nature of SEI is influenced by chemical structures of electrolyte solutions, the solvents and lithium salts need to be combined properly to realize LIBs with better performance. Although the conventional electrolyte solutions show satisfactory performance to some extent, there still remain some disadvantages; instability against moisture and temperature, and volatility and flammability of carbonate ester solvents. Great efforts have been made to overcome those disadvantages in the conventional electrolyte solutions, for example, utilization of ionic liquid, polymer electrolytes and inorganic solid state electrolytes, and recently, highly concentrated electrolyte solution gathers a lot of attention.Based on these background, solid electrolyte interphase (SEI) formed on graphite in conventional and highly concentrated electrolyte solutions was thoroughly characterized by a combined experimental and computational study. The comprehensive understanding revealed that a chemical composition of SEI, as well as the solvation structures unstable to reductive potential, can be predicted by a profound understanding of density functional theory (DFT) calculation results of the solvates containing a counter anion. The solvation structures were determined by Raman spectroscopy to evaluate electron affinity (EA) and LUMO of the solvates containing an anion by DFT calculation. The chemical composition of SEI was quantitatively analyzed by X-ray photoelectron spectroscopy (XPS), and the results were compared with a prediction based on the calculation. The formation mechanism of SEI during charge and discharge process can be partly estimated by the combination of experiment and theoretical calculation. These results indicate that electrolyte solutions can be efficiently designed by predicting the physicochemical properties of SEI through the more effective utilization of DFT calculation. Thus, a combination of DFT prediction and experimental analysis is proved to be an effective approach to reveal SEI formation mechanisms, and can be utilized as a versatile approach to develop new solvents, electrolyte salts, and additives, and to design electrolyte solutions with appropriate concentration.It is expected that the oxidative stability and reaction mechanism of electrolyte solutions at the positive electrode can be estimated using similar approaches. Here, it is necessary to predict oxidative stability using ionization potentials (IP), rather than EA. In the same way, other solvents than carbonate, such as ethers and sulfones, which have been difficult to put into practical use in conventional electrolytes, can also be the target to be studied. By analyzing the solvation structure and estimating its chemical stability, we believe it will be possible to get many insights on the reactions that proceed at the interface between the electrode and the electrolyte. Figure 1

Simulation Study of Li-Ion Batteries Considering the Porosity and Tortuosity of Separator

Lithium-ion batteries (Li-ion batteries) offer high energy and power densities, making them the most widely used battery technology for energy storage in various applications such as grid-scale, automotive, and electronic devices. One of the critical components of a Li-ion battery is the porous separator which can impair performance at high charge/discharge rates. Separator has a considerable influence on the transport of lithium ions. The structural properties of the separator, such as porosity and tortuosity can have a significant impact on heat generation and polarization of lithium concentration as well as the current density distribution inside the separator. The porosity of a porous separator is a well-defined feature that may be easily determined. In contrast, the tortuosity of separators, is more difficult to assess.To model and calculate the separator properties, in this study, the simulated structural separator was constructed by numerical analysis1 based on actual separator structure from Cryo-FIB-SEM. The numerical simulation of the ion-transport model for concentrated electrolyte solutions using the model developed by Newman et al2. Different structures of separators provided different behaviors at different charge/discharge rates. To evaluate overall battery performance, using the previously reported structural information3,4, lithium nickel manganese cobalt oxides (NCM), 1.0 M LiPF6 solution in EC-DEC solvent, and graphite were used for the cathode, electrolyte, and anode, respectively.This work simulated and compared three different separator structures: foam, non-woven fabric, and stretched structure with three different constant charging rate (C-rate) conditions (1 C, 5 C and 8 C). The calculation of porosity and tortuosity has been done for through-plane model. The higher C-rate will increase the heat generation significantly and affect the battery`s thermal behavior. The tortuosity and porosity have correlation on the effective ionic conductivity σeff = (ε/τ)*σ and effective diffusion coefficient Deff = (ε/τ)*D. Higher separator porosity can effectively increase the effective diffusion coefficient, hence improving mass transfer and reducing resistance. The separator with uniform porosity and smaller tortuosity showed smaller diffusion polarization because Li+ can be transported easily and uniformly in it, leading to lower heat generation even in high C-rate condition. The model developed in this study is intended to be valuable in understanding behavior of porous separators and optimizing the battery design.Acknowledgement: This research was carried out under the project (Grant Number JPMJMI21G4) supported by the JST-Mirai Program, Japan.

The Effect of electrolyte concentration and temperature at electroplating with copper on the plate thickness and corrosion rate of plated gray cast iron

This study aims to determine the effect of variations in electrolyte solution concentration and copper electroplating temperature on gray cast iron to achieve the desired copper layer thickness and reduce the corrosion rate of gray cast iron impeller pumps. A total of 30 test specimens made from gray cast iron were used, with dimensions conforming to the ASTM G31-72 standard for corrosion rate testing. The specimens were coated with copper electroplating using three different solutions: solution 1 (195 g/L copper sulfate, 45 g/L sulfuric acid), solution 2 (205 g/L copper sulfate, 50 g/L sulfuric acid), and solution 3 (215 g/L copper sulfate, 55 g/L sulfuric acid). Each solution was used with dipping temperatures of 30 – 34 °C, 40 – 44 °C, and 50 – 54 °C. After being coated with copper, the layer thickness was measured using a digital coating thickness gauge (F&NF type). The corrosion rate was then tested using the weight loss method, following the ASTM G31-72 standard, by immersing the specimens in seawater for 240 hours. The test results showed that the highest average thickness was achieved with solution 3 and a plating temperature of 50 – 54 °C, measuring 27.46 μm. The lowest average thickness was with solution 1 and a plating temperature of 30 – 34 °C, measuring 26.23 μm. The lowest corrosion rate was observed with solution 3 and a plating temperature of 50 – 54 °C, at 0.0041 mmpy, whereas the highest corrosion rate was found with solution 1 and a plating temperature of 30 – 34 °C, at 0.0079 mmpy. For comparison, the average corrosion rate of uncoated specimens was 2.2947 mmpy.

Modification of e-CPA for estimating phase equilibria and development of predictive models for electrical conductivity in aqueous electrolyte solutions

We modify the electrolyte cubic plus association equation of state (e-CPA EoS) and inetgrate it with two electrical conductivity models to estimate the electrical conductivity of 11 monovalent electrolytes solutions in water. The e-CPA EoS is modified by including the ion-ion and ion-solvent association interactions and tuned using experimental data of mean ionic activity coefficient and density of the electrolyte solutions. The modified e-CPA model shows a better performance in estimating the bubble pressure data. The hybridization of two electrical conductivity models with e-CPA results in two predictive models for estimating the electrical conduction of dilute and concentrated electrolyte solutions. Finally, we generalize these predictive models by correlating their model fitting parameters to the electrolyte physical parameters such as mean hard-sphere diameter or to association volume. The two predictive electrical conductivity models estimate electrical conductivity with AARD of 11.15 % and 13.87 % over wide ranges of temperature and electrolyte concentration.

Ni-based multi-interface engineering on MXene (Ti3C2Tx) modified electrode for all-pH-value hydrogen evolution

The research of electrocatalysts with high efficiency and stability towards hydrogen evolution reaction (HER) in all-pH-value plays a vital role in advancing clean energy development, while it is still a huge challenge. In this article, Ni3S2 was effectively attached to the surface of MXene-modified nickel foam (NF) (Ni3S2@ MXene/NF) using an electrodeposition method, resulting in loose flower-like structures with a larger surface area. Furthermore, the concentration of electrolyte solution affects the catalytic performances. Impressively, the optimized Ni3S2@MXene/NF shows remarkable HER performances in 0.5 M H2SO4, 1 M KOH, and 1 M PBS (pH = 7), demanding overpotentials of 239, 172, and 94 mV to attain 30 mA cm−2 with excellent stability, respectively. The results from in-situ X-ray diffraction (XRD) revealed that stability is determined by the crystal planes of (020), (120), and (221) in a neutral solution. Furthermore, density functional theory (DFT) showed that the multi-interface engineering is constituted by the combination of MXene and Ni3S2, which can maximum optimize the free energy of the catalyst surface adsorption of H2O and H* within a wide pH range. This research presents a pioneering approach to catalyst modification for enhancing hydrogen production efficiency in all-pH-value electrolyte.

Development of a photoelectrocatalytic method to improve the efficiency of E. coli removal

The photoelectrocatalytic technology has attracted significant attention for effectively eliminating organic matter and microbiological pollutants in the environment, owing to its remarkable efficiency and low power consumption. The major goal of this research is to develop and determine the optimal conditions that will facilitate the photoelectrocatalytic technique's enhancement of E. coli eradication. The WO3/BiVO4 photoanode was fabricated on a conductive glass substrate using the automatic dip coating process, employing a layer-by-layer deposition method. Subsequently, the WO3/BiVO4 photoanode was calcinated at 550 °C for 60 minutes. The produced WO3/BiVO4 electrodes were employed as working electrodes to investigate and determine the optimal parameters for enhancing the eradication of E. coli process. The primary factors investigated in this study were the concentration of KCl electrolyte solution and the applied potential. These parameters were examined to identify the best circumstances that would result in the highest efficiency for the degradation of E. coli in a photoelectrochemical system. The study also aimed to comprehend the catalytic mechanism implicated in eliminating E. coli by implementing three different processes: photocatalysis, electrocatalysis, and photoelectrocatalysis. We discovered that the key factors directly influencing E. coli eradication effectiveness under the photoelectrocatalytic process were applied potential and electrolyte solution concentration. The optimum conditions eliminated 99.99% of E. coli in 150 minutes with an initial concentration of 106 CFU/ml, an electrolyte concentration of 0.01 M KCl, and an applied potential of 2.0 V. The study confirmed photoelectrocatalytic cells' efficacy in removing microorganisms and recommended their application in a wider range of wastewater treatment systems.

Modified electrode decorated with silver as a novel non-enzymatic sensor for the determination of ammonium in water

Ammonium is an essential component of the nitrogen cycle, which is essential for nitrogen cycling in ecosystems. On the other hand, ammonium pollution in water poses a great threat to the ecosystem and human health. Accurate and timely determination of ammonium content is of great importance for environmental management and ensuring the safety of water supply. Here we report a highly sensitive electrochemical sensor for ammonium in water samples. The modified electrode is based on the incorporation of silver nitrate (AgNO3) into a carbon paste embedded with 1-aminoanthraquinone and supported by multi-walled carbon nanotubes, which are commercially available. A potential of 0.75 V is applied to the modified electrode, followed by activation in hydrochloric acid. The modified electrode was used for square wave voltammetry of ammonium in water in the potential range of − 0.4–0.2 V. The performance of ammonium analysis was determined in terms of square wave frequency, square wave amplitude and concentration of electrolyte solution (sodium sulphate). The calculation of the surface area according to the Randles–Sevcik equation resulted in the largest surface area for the Ag/pAAQ/MWCNTs/CPE. The modified electrode exhibited a linear range of 5–100 µM NH4+ in 0.1 M Na2SO4 with a detection limit of 0.03 µM NH4+ (3σ). In addition, the modified electrode showed high precision with an RSD value of 9.93% for 10 repeated measurements. No interfering effect was observed at twofold and tenfold additive concentrations of foreign ions. Good recoveries were obtained in the analysis of tap and mineral water after spiking with a concentration of ammonium ions.

Study of Capacitive Behavior and its Inter-Relationship with Electrolyte Solution Concentration in Hybrid Ionogels

Ionogels are synthesized by confining ionic liquids within a solid/polymer matrix. Ionogels received wide attention owing to their high ionic conductivity and mechanical properties. Recent research has revolved around augmenting the ionic conductivity and mechanical stability of ionogel. Nevertheless, a detailed understanding of the inherent capacitive behavior is indispensable to ensure the application of ionogels in rechargeable lithium-ion batteries, sensors, and supercapacitors. Even though studies on the cyclic voltammetry of ionogels have been previously established, there are limited studies on evaluating the specific capacitance of ionogel, with respect to the amount of electrolyte solution present in the ionogel system. In this study, the ionogel is fabricated through sol-gel route, and the charge storage capacity of ionogel is investigated with varying concentrations of electrolyte solution. Electrochemical Methods such as Linear Sweep Voltammetry (LSV) and cyclic voltammetry (CV) are used to characterize the electrochemical performance of ionogel. The most effective concentration of electrolyte solution is determined to be 30 vol% in this study and has attained high electrochemical stability, up to 3.2 V. The ionogel has excellent charge-discharge characteristics, with a specific capacitance of ∼18.90 F g−1. Meanwhile, the ionogel also exhibits good thermal stability, 358 °C. The combination of promising electrochemical properties and thermal sability allows the practical application of ionogel.

Improvement of tear ferning patterns of artificial tears using dilute electrolyte solutions

The purpose of the research was to examine how the addition of dilute solutions of sodium chloride (NaCl), potassium chloride (KCl), or a combination of the two would impact the tear ferning (TF) patterns in artificial tears. Artificial tears (1 μL) were mixed with solutions (1–7 μL) of NaCl, KCl, or both (10–30 mg), prepared in double-distilled water (100 mL), to produce homogenous mixtures. A sample (1 μL) of each mixture was dried on a microscopic glass slide at 20 °C and with less than 20% humidity. The TF patterns were inspected using a light microscope, graded, and compared with the corresponding TF grades of pure artificial tears. Significant improvements (Wilcoxon test, P = 0.001) in the TF grades of the artificial tears were observed after the addition of solutions of NaCl and KCl or a mixture of both. The TF grades of the artificial tears decreased after adding different volumes and concentrations of electrolyte solutions. Generally, NaCl was more efficient than KCl in improving such grades. The TF grades of Blink Contact Soothing Eye Drops and Refresh Plus Tears were noticeably improved compared to the other grades. For example, Blink Contact Soothing Eye Drops' TF grade improved from 1.7 to 0.6 when 6 μL of NaCl solution (30 mg/100 mL water) was added to 1 μL of the eye drops. When a mixture of NaCl and KCl (1:2; 5–7 μL; 30 mg each in 100 mL water) was added, the TF grade improved to 0.5. In conclusion, the TF test evaluated the effect of adding dilute electrolyte solutions to artificial tears in vitro. Adding dilute solutions of NaCl and KCl, or a mixture of both, significantly improved the TF grades of artificial tears.

Electrochemical Characteristics of Elastic, Non-Polar Polyurethane-Based Polymer Gel Electrolyte for Separator-Less Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have undergone countless enhancements in the past decade, mainly improvements in the basic components: electrodes, electrolyte, and separator. The separator, which acts as a physical barrier between the two electrodes, does not directly participate in the charge and energy storage.However, it is involved in the safety, form factor, and packaging density of the LIBs. While it occupies relatively less internal space than other components, the separator can be replaced with active materials such as gel polymer electrolytes (GPEs) which can serve as both the electrolyte and physical barrier between the electrodes. GPEs can potentially minimize the risks of liquid electrolytes, including flammability, electrolyte leakage, and explosion. Here we report the characteristics of polyurethane (PU)-based gel swollen in concentrated electrolyte solutions in separator-less cells. The poreless PU-based gel electrolyte conducts lithium ions, while preventing internal short-circuits. This is attributed to the presence of soft segments, which allow ion transport, and hard segments, which ensure mechanical integrity. Electrochemical measurements carried out in LFP half cells and symmetric Li cells revealed that the separator-less cells were operable between 0.2 C to 1 C rates, and that during long term cycling, the cells achieved stable Li electroplating overpotential, as the number of cycles increased.

Molecular dynamics study of ion clustering in concentrated electrolyte solutions for the estimation of salt solubilities

Molecular dynamics study of ion clustering in concentrated electrolyte solutions for the estimation of salt solubilities

Theory of electrolyte solutions in a slit charged pore: Effects of structural interactions and specific adsorption of ions.

In this paper, we present a continuation of our research on modeling electrolyte solutions within charged pores. We make use of the model developed by Blossey et al. [Phys. Rev. E 95, 060602 (2017)], which takes into account the structural interactions between ions through a bilinear form over the gradients of local ionic concentrations in the grand thermodynamic potential, as well as their steric interactions through the lattice gas model. The structural interactions may describe the effects of the molecular structure of ions at a phenomenological level. For example, these effects include steric effects due to non-spherical shapes of ions, their conformational lability, and solvent effects. In addition, we explore their specific interactions with the pore walls by incorporating external attractive potentials. Our primary focus is on observing the behavior of ionic concentration profiles and the disjoining pressure as the pore width changes. By starting with the local mechanical equilibrium condition, we derive a general expression for the disjoining pressure. Our findings indicate that considering the structural interactions of ions leads to a pronounced minimum on the disjoining pressure profiles at small pore widths. We attribute this minimum to the formation of electric double layers on the electrified surfaces of the pore. In addition, our results demonstrate that the inclusion of the attractive interactions of ions with the pore walls enhances this minimum and shifts it to smaller pore thicknesses. Our theoretical discoveries may be useful for those involved in supercapacitor electrochemical engineering, particularly when working with porous electrodes that have been infused with concentrated electrolyte solutions.

Investigating the Correlation between Electrolyte Concentration and Electrochemical Properties of Ionogels

Ionogels are hybrid materials comprising an ionic liquid confined within a polymer matrix. They have garnered significant interest due to their unique properties, such as high ionic conductivity, mechanical stability, and wide electrochemical stability. These properties make ionogels suitable for various applications, including energy storage devices, sensors, and solar cells. However, optimizing the electrochemical performance of ionogels remains a challenge, as the relationship between specific capacitance, ionic conductivity, and electrolyte solution concentration is yet to be fully understood. In this study, we investigate the impact of electrolyte solution concentration on the electrochemical properties of ionogels to identify the correlation for enhanced performance. Our findings demonstrate a clear relationship between the specific capacitance and ionic conductivity of ionogels, which depends on the availability of mobile ions. The reduced number of ions at low electrolyte solution concentrations leads to decreased ionic conductivity and specific capacitance due to the scarcity of a double layer, constraining charge storage capacity. However, at a 31 vol% electrolyte solution concentration, an ample quantity of ions becomes accessible, resulting in increased ionic conductivity and specific capacitance, reaching maximum values of 58 ± 1.48 μS/cm and 45.74 F/g, respectively. Furthermore, the synthesized ionogel demonstrates a wide electrochemical stability of 3.5 V, enabling diverse practical applications. This study provides valuable insights into determining the optimal electrolyte solution concentration for enhancing ionogel electrochemical performance for energy applications. It highlights the impact of ion pairs and aggregates on ion mobility within ionogels, subsequently affecting their resultant electrochemical properties.