The electrophoretic effect for the case of electrolyte mixtures

The ionic electrophoretic effect for solutions of mixed electrolytes of any type is calculated. The calculation is based on the well-known treatment due to Chen with the same distance of closest approach for all the ions in solution. The improved iterative method used for the relaxation-field treatment is applied. For the latter the electrophoretic velocity results are derived to the second iteration in the perturbation method.     

Apparent molar heat capacities and volumes of aqueous electrolytes at 25°C: Cd(ClO4)2, Ca(ClO4)2, Co(ClO4)2, Mn(ClO4)2, Ni(ClO4)2, and Zn(ClO4)2

We have used a flow calorimeter and a flow densimeter for measurements leading to apparent molar heat capacities and apparent molar volumes of aqueous solutions of Cd(ClO₄)₂, Ca(ClO₄)₂, Co(ClO₄)₂, Mn(ClO₄)₂, Ni(ClO₄)₂, and Zn(ClO₄)₂. The resulting apparent molar quantities have been extrapolated to infinite dilution to obtain the corresponding standardstate apparent and partial molar heat capacities and volumes. These latter values have been used for calculation of conventional ionic heat capacities and volumes.     

Ionic interactions in solutions. IV. Conductance theory of binary electrolytes for hamiltonian models

From the basic equations for the pair distribution function in nonequilibrium, solution methods are elaborated. It is verified that the distribution functions depend on conductance coefficients, which lead to feedback loop or echo effects. For explicit calculation the strong-coupling approximation for distances smaller than the Bjerrum distance proves to be practical and efficient. It can be applied to any Hamiltonian models for the system without complicated mathematics. A method of deriving information concerning the Gurney cosphere overlap effects is presented.     

Comparative studies of calculation methods for activity coefficients of unsymmetrical mixed electrolytes

Several methods for the calculation of activity coefficients for binary mixed electrolytes are compared. Their accuracies are analysed and the reasons for the different degrees of accuracies are given.     

Electrolytes for Rechargeable Lithium–Air Batteries

Lithium–air batteries are promising devices for electrochemical energy storage because of their ultrahigh energy density. However, it is still challenging to achieve practical Li–air batteries because of their severe capacity fading and poor rate capability. Electrolytes are the prime suspects for cell failure. In this Review, we focus on the opportunities and challenges of electrolytes for rechargeable Li–air batteries. A detailed summary of the reaction mechanisms, internal compositions, instability factors, selection criteria, and design ideas of the considered electrolytes is provided to obtain appropriate strategies to meet the battery requirements. In particular, ionic liquid (IL) electrolytes and solid‐state electrolytes show exciting opportunities to control both the high energy density and safety.     

Conductance theory of concentrated electrolytes in an MSA-type approximation

A closed system of equations for the nonequilibrium pair-distribution function is given which corresponds to the mean spherical approximation (MSA) in equilibrium. The electrophoretic contribution to the conductance is calculated exactly in the framework of the MSA. For the calculation of the remaining contributions the equilibrium distribution function due to Henderson and Smith was used. The final expressions for the conductance are given in analytic terms using the restricted primitive model. The calculated curves are in good agreement with experimental data for 1-1 electrolytes up to about 1 M and qualitatively show the right behaviour up to rather high concentrations.     

Effect of ion solvation on the diffuse layer structure in mixed electrolytes

A “solvionic” model of a multicomponent electrochemical system (mixed electrolyte) is considered. An ion in the solution is considered as a point charge rigidly fixed inside its solvation shell. The corresponding equations for the diffuse layer on an ideally polarizable electrode are derived, and an effective method of their numerical solution is formulated. The calculations are performed in order to follow the changes in the diffuse layer structure with variations in the electrode charge and electrolyte composition. Far from the zerocharge potential of solution, the dependences of distributions of solution components over the diffuse layer on the electrode charge radically differ from those within the classic Gouy-Chapman theory. Analytical equations (asymptotics at large electrode charges) for concentrations of solvated ions in the plane of their maximum approach and for their “surface excesses” (diffuse adsorption) are determined. Results of numerical calculations for a 0.2 M LiCl + 0.05 M BaCl₂ solution are plotted.     

Eigenmobilities in background electrolytes for capillary zone electrophoresis. I. System eigenpeaks and resonance in systems with strong electrolytes

A background electrolyte system for capillary zone electrophoresis which is composed of three strong univalent ionic constituents is investigated. The ion 1 is considered as a counter-ion and two ions, 2 and 3, are considered as co-ions in relation to the analyte ion 4. We investigate the linearized model of electromigration in such a system and calculate the eigenvalues of a corresponding matrix. The model is formulated in such a way that the eigenvalues of the system are certain mobilities, which we call eigenmobilites, which characterize specific features of the electrophoretic migration. One of the eigenmobilities is the system eigenmobility u_S causing the rise of the system peak, called here the system eigenpeak. A situation when the analyte has the same mobility as the system eigenmobility, u₄=u_S, is analyzed in detail. We show that it leads to the resonance—the mutual jump in the concentration profile of both co-ions, 2 and 3, has a shape of the spatial derivation of the originally sampled analyte profile and, moreover, it grows linearly with time. After a sufficiently long time it can be “amplified” to any value. The resonance has then a great impact on signals of indirect detection methods, like indirect UV detection or conductivity detection. In the framework of the linearized model the relative velocity slope S_X, a measure of electromigration dispersion, is expressed as S_X=F(u₁+u₄)(u₂−u₄)(u₃−u₄)/[u₄(u_S−u₄)], where u_i is the mobility of the ith ion and F is the Faraday constant. As in practice the concentration of the analyte is not infinitely small and has a certain finite value, the analyte will be at the resonance severely dispersed to a much broader spatial interval. When a specific detector is used, the signal of such an analyte can apparently be missed without any notice.     

Solubility determinations by the isopiestic method and application to aqueous lanthanide nitrates at 25°C

The isopiestic method is one of the most accurate methods for solubility determinations; an additional advantage is that solvent activity can be simultaneously determined for the saturated solution. In spite of this the method is rarely used for that purpose, and then almost exclusively for aqueous solutions at 25°C. This method is described, and its advantages and disadvantages discussed. Examples are given of the application of this method to solubility determinations, and new data are presented for the aqueous solubilities of Pr(NO₃)₃, Ho(NO₃)₃, Er(NO₃)₃, and Y(NO₃)₃ at 25°C. These new data are designed to refine results recently reviewed in the IUPAC Solubility Data Series.Presentation to First International Symposium on Solubility Phenomena, University of Western Ontario, London, Ontario, August 21–23, 1984.Work performed under the auspices of the U.S.Department of Energy by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48.     

First-Principles Design of Na-ion Superionic Conductors: Interstitial-Based Na Diffusion in NaCuZrS3

In recent years all-solid-state sodium-ion batteries (SS-SIBs) have drawn significant attention due to their potential to be safer and lower cost than lithium-ion batteries. However, the lack of sodium solid-state electrolytes with high ionic conductivity has become one of the major challenges. Here, with first-principles computation we took NaCuZrS₃, consisting of earth-abundant and environmentally benign elements only, as an example to study Na-ion transport in the post-perovskite-like structure and used computation-guided design to improve its potential as a solid-state electrolyte. With ab initio molecular dynamics simulation and nudged elastic band calculation, we studied possible diffusion mechanisms in this material and found that Na ion interstitials have a favorable migration barrier of 0.22 eV, which is among the smallest in the literature reported values. Considering the large formation energy of Frenkel defects, we proposed doping strategy to introduce extra Na interstitials in the material. Our study suggests that the post-perovskite-like sulfides are worth of exploration for applications in SS-SIBs.     

Current Production Processes on Metallic Electrodes in Contact with Oxygen-Conducting Solid Electrolytes with Face-Centered Cubic Lattice of the Fluorite Type

The data concerning the processes of current production that occur in the electrode system O₂, Pt/O²⁻, which are available from relevant literature sources, are considered. Major progress in the understanding of the kinetics of an oxygen reaction has been attained with the application of model electrodes and cells, as well as at the expense of the application of such physical methods as a radiotracer method and atomic force microscopy. A discussion of model notions on the specific features of the occurrence of an oxygen reaction, which are formed on the basis of consideration of experimental results is the major subject matter of this communication. It is claimed that modernization of an existing model with allowance made for the fact of the existence, on the surface of an electrolyte with a face-centered cubic lattice, of a layer with another structure gives one a chance to also describe experimental results that cannot be described in the framework of an existing model.__________Translated from Elektrokhimiya, Vol. 41, No. 7, 2005, pp. 787–803.Original Russian Text Copyright © 2005 by Shkerin.     

A new method for calculating activity coefficients of mixed electrolytes

In present work, a new method is developed from which activity coefficients for both electrolytes in admixture can be obtained simultaneously from the fitting of experimental activity coefficients of one of the electrolyte. The calculated results for the system HCl+KCl at 25°C are reported and discussed.     

以水作相分离造孔剂制备P(VDF-HFP)/PMMA聚合物电解质膜

介绍了一种以水代替常用的有机物质作为相分离造孔剂制备混合型聚合物电解质的新方法.所研究的混合型聚合物为聚(偏二氟乙烯-六氟丙烯)和聚甲基丙烯酸甲酯的混合物.扫描电镜SEM图表明这种混合型聚合物膜具有蜂窝状结构,有利于膜电导率的增加.利用FTIR,XRD和DSC等方法研究了混合型聚合物电解质中两种聚合物间的相互作用.用电化学交流阻抗方法测得在30℃下P(VDF-HFP)/PMMA摩尔比为1:1的混合型聚合物电解质的离子电导率为0.804×10^-3S/cm.对照其它方法,本方法具有制备容易、成本较低和有利于环境保护等优点.     

FTIR study of ion solvation and ion-pair formation in alkaline and alkaline earth metal salt solutions in acetonitrile

The IR spectra of alkaline and alkaline earth metal perchlorate and of lithium bromide solutions in acetonitrile, obtained with the help of FTIR measurements in the region of the C-N stretching mode of the solvent, reveal bands produced by acetonitrile molecules in the solvation shells and bands of ClO ₄ ^– ions in contact and solvent separated ion pairs. The shift and the attenuation of the C-N stretching band of acetonitrile at 2254 cm^–1 is used for the calculation of cation solvation numbers for Li⁺(4), Na⁺(4), Mg²⁺(6), Ca²⁺(6), and Ba²⁺(6). No solvation is assumed for the contact ion pairs of LiClO₄, LiBr, NaClO₄, Mg(ClO₄)₂, Ca(ClO₄)₂, and Ba(ClO₄)₂. The association constants of the symmetrical electrolytes are compared to those obtained from other methods.     

Influence of Electrolytes on Foaming of Sodium Lauryl Sulfate

The influence of various electrolytes on the foamability of an anionic surfactant, sodium lauryl sulfate was studied. Foamability was measured by using a recently designed method for foam testing of surfactant solutions. The results are discussed in terms of foaming efficiency and foaming effectiveness. The addition of NaCl increases foaming efficiency whereas foaming effectiveness increased only marginally. The effect of cations on foaming efficiency and foaming effectiveness increased in the order, Li⁺< Na⁺<Cs⁺. This observation is explained in terms of the hydrated size of cations which decreases as Li⁺> Na⁺> Cs⁺.     

An algorithm for the calculation of the electrostatic repulsion between surface coated with a charge membrane

We propose a numerical procedure for the calculation of the electrostatic repulsion force between two identical, parallel surfaces immersed in anab electrolyte solution. These surfaces are coated with an ion-penetrable membrane carrying fixed charges. The amount of fixed charges is governed by the dissociation of the functional groups in the membrane phase. The effect of pH on the degree of dissociation of these functional groups is taken into account. The difficulty of extensive use of Jacobi elliptic function in the numerical treatment of Poisson-Boltzmann equation can be circumvented by resorting to the present algorithm.     

Estimation of activity coefficients at different temperatures by using the mean spherical approximation

A method of estimating activity coefficients for a variety of electrolytes at different temperatures is presented. The MSA approximation is used to calculate the activity coefficients from experimental data available in the literature. This strategy provides suitable results within a wide range of temperatures, electrolyte stoichiometries and concentrations of investigated solutions.     

Osmotic and activity coefficients of aqueous lithium sulfate solutions at 40°C

The osmotic coefficients for aqueous lithium sulfate solutions were experimentally determined at 40°C. Sodium chloride served as the isopiestic standard for the calculation of osmotic coefficients. The molality ranges covered in this study correspond to about 0.1–2.5 mol-kg^–1. The system of equations developed by Hamer-Wu and Pitzer were used to fit each set of osmotic coefficients. The parameters obtained from the fit were used to calculate the activity coefficients.     

Liquid-Free All-Solid-State Zinc Batteries and Encapsulation-Free Flexible Batteries Enabled by In Situ Constructed Polymer Electrolyte

Zn batteries are usually considered as safe aqueous systems that are promising for flexible batteries. On the other hand, any liquids, including water, being encapsulated in a deformable battery may result in problems. Developing completely liquid-free all-solid-state Zn batteries needs high-quality solid-state electrolytes (SSEs). Herein, we demonstrate in situ polymerized amorphous solid poly(1,3-dioxolane) electrolytes, which show high Zn ion conductivity of 19.6 mS cm⁻¹ at room temperature, low interfacial impedance, highly reversible Zn plating/stripping over 1800 h cycles, uniform and dendrite-free Zn deposition, and non-dry properties. The in-plane interdigital-structure device with the electrolyte completely exposed to the open atmosphere can be operated stably for over 30 days almost without weight loss or electrochemical performance decay. Furthermore, the sandwich-structure device can normally operate over 40 min under exposure to fire. Meanwhile, the interfacial impedance and the capacity using in situ-formed solid polymer electrolytes (SPEs) remain almost unchanged after various bending tests, a key criterion for flexible/wearable devices. Our study demonstrates an approach for SSEs that fulfill the requirement of no liquid and mechanical robustness for practical solid-state Zn batteries.