Symmetric Electrolyte Research Articles

Three-Dimensionally Printed Ionogel-Coated Ceramic Electrolytes for Solid-State Lithium Batteries.

Stereolithography three-dimensional (3D) printing technology enables the customization of ceramic-based solid electrolyte structures with desired electrochemical properties; however, formulating slurries that both are highly ceramic-loaded and have low viscosity for printing poses a challenge. Here, we propose an ionogel-coated ceramic approach to prepare a shear-thinning fast-ion conductor ceramic (Li6.5La3Zr1.5Ta0.5O12) slurry, which possesses both a high ceramic content of 50 wt % and a low viscosity of 1.53 Pa·s. Utilizing this slurry, 3D symmetric honeycomb briquette-like electrolyte films are printed, and solid-state lithium batteries are easily fabricated by filling the cathode and anode slurries into the respective symmetric honeycombs. The atomic-level interaction between ceramic/ionogel interfaces and the integrated electrode/electrolyte interface facilitates rapid Li+ transport across multiscale interphases in batteries. Additionally, the interactions of ceramic nanoparticles and ionic liquids with Li salt substantially increase the concentration of free Li+, both of which enhance the ionic conductivity and ensure stable Li+ transport efficiency. Solid-state lithium batteries can cycle stably 500 times without obvious degradation at 0.5 C and 50 °C. The strategy offers a feasible solution for printing customized solid-state ceramic-based electrolytes.

Development on the electrochemical stability and performance of symmetric supercapacitor-based proton-conducting alginate biopolymer electrolytes

Development on the electrochemical stability and performance of symmetric supercapacitor-based proton-conducting alginate biopolymer electrolytes

Analysis on the Propagation and Assembly of Metallic Nanoparticles through Subwavelength Apertures with Overlapping Electrical Double Layers.

Hybrid nanoplasmonic structures composed of subwavelength apertures in metallic films and nanoparticles have recently been demonstrated as ultrasensitive plasmonic sensors. This work investigates the electrokinetically driven propagation of the assembly mechanism of the metallic nanoparticles through nanoapertures. The Debye-Hückel approximation for a symmetric electrolyte solution with overlapping electrical double layers (EDLs) is used to obtain an analytical solution to the problem. The long-term silver nanoparticle concentration response is derived using the homogenization method and a multiscale analysis. The results indicate that uncharged nanoparticles will flow through the nanohole array if the nanochannel height is larger than the Debye length (h 0 > λD), while a trapping mechanism occurs, due to the overlapping of the EDL, when h 0 ∼ 3.8λD. For charged nanoparticles, the response to the electric field occurs locally with the walls of the nanochannel, regardless of its height. For a critical value of the nanochannel length, the leading order of the concentration field becomes purely diffusive.

Electrostatic Interaction of Dielectric Particles in an Electrolytic Solution

On the basis of the Poisson-Boltzmann equation the electrostatic interaction between two charged dielectric spherical particles in a symmetric electrolyte solution is considered. The interaction forces between particles of the same radius under the condition of uniform charge distribution on their surfaces in the absence of an external field have been calculated by the finite element method. The dependence of the electrostatic repulsion forces between the particles on the magnitude of the particle charges and the dielectric permittivities of the particle materials and the surrounding medium has been analyzed.

Comparison of liquid–liquid phase equilibrium behavior of acetonitrile–water system using choline chloride salt and water-based deep eutectic solvent

The liquid–liquid equilibrium (LLE) data for the ternary systems of (acetonitrile (ACN) + water (W) + choline chloride (ChCl)) and (ACN + W + water-based deep eutectic solvent (WDES) consisting of ChCl:W (1:3)) were measured at 298 K. The consistency of tie-lines was verified by the Bachman and Othmer–Tobias correlations. ChCl as an organic salt and its WDES (within the water content range of less than 50 w%) as green extractants represent feasible performances in terms of selectivity and distribution coefficients for separation of water from acetonitrile-water system in comparison to other inorganic salts and hydrophobic DESs. ChCl in the (ACN + W + ChCl) system can separate water from the solution in the form of hydrate ions while WDES in the (ACN + W + WDES) system tends to absorb water by intermolecular forces. The experimental data of the (ACN + W + ChCl) system was correlated using the symmetric electrolyte non-random two liquid (e-NRTL) model while the equilibrium data of the (ACN + W + WDES) system was correlated using NRTL and universal quasi-chemical activity coefficient (UNIQUAC) models. ChCl in the form of salt represents a better separation performance than WDES for water removal from the acetonitrile mixture. Meanwhile, WDES might be considered to be superior compared to ChCl in terms of regeneration energy consumption and operating considerations.

Electrical conductance study of Schiff base in different solvents and temperatures: DFT calculation

The electrical conductivities of the N-(2-chlorobenzylidene)benzylamine (NCB) as Schiff bases (SB) compound in water and methanol were studied in different temperatures, the mixtures of methanol and water studied in various percentages of methanol at 298 K. Initially, the relationship between equivalent conductivity and the square root of molar concentration was plotted to find electrolyte types using Kohlrausch equations. The plot indicates that NCB was weakly associated with water, methanol, and mixtures. Lee-Wheaton equation treated the experimental results of symmetrical electrolytes (1:1) to calculate the conductivity confines: equivalent conductance at infinite dilution Λₒ, association constant KA, and the main distance between ions in solution (R) at best-fit values of (ϬΛ). Thermodynamic quantities for the ion association reaction (∆Go, ∆Ho and ∆So) have been measured. Also, the theoretical calculation was used to optimize the energy of the molecule in the gas phase then measured many descriptors by using (AM1, PM3) then DFT. In addition, recalculated the optimization energy in water, and methanol. After theoretical calculation and analysis, it was found that the Λₒ value is related to the molecular volume of the system (molecules assembled in the solvent). As the molecular volume increases, the Λₒ value decreases due to association. KEY WORDS: Schiff bases, Electrical conductivities, Lee-Wheaton equation, Thermodynamic parameter, DFT Bull. Chem. Soc. Ethiop. 2025, 39(1), 177-187. DOI: https://dx.doi.org/10.4314/bcse.v39i1.15

Image charge effects under metal and dielectric boundary conditions.

Theimage charge(IC)effect is a fundamental problem in electrostatics. However, proper treatment at the continuum level for many-ion systems, such as electrolyte solutions or ionic liquids, remains an open theoretical question. Here, we demonstrate and systematically compare the IC effects under metal and dielectric boundary conditions (BCs), based on a renormalized Gaussian-fluctuation theory. Our calculations for a simple 1:1 symmetric electrolyte in the point-charge approximation show that the double-layer structure, capacitance, and interaction forces between like-charged plates depend strongly on the types of boundaries, even in the weak-coupling regime. Like-charge attraction is predicted for both metal and dielectric BCs. Finally, we comment on the effects of a dielectricallysaturated solvent layer on the metal surface. We provide these results to serve as a baseline for comparison with more realistic molecular dynamics simulations and experiments.

Analysis of electroviscous effects in electrolyte liquid flow through a heterogeneously charged uniform microfluidic device

Charge-heterogeneity (i.e., surface charge variation in the axial direction of the device) introduces non-uniformity in flow characteristics in the microfluidic device. Thus, it can be used for controlling practical microfluidic applications, such as mixing, mass, and heat transfer processes. This study has numerically investigated the charge-heterogeneity effects in the electroviscous (EV) flow of symmetric (1:1) electrolyte liquid through a uniform slit microfluidic device. The Poisson’s, Nernst-Planck (N-P), and Navier–Stokes (N-S) equations are numerically solved using the finite element method (FEM) to obtain the flow fields, such as total electrical potential (U), excess charge (n *), induced electric field strength (E x), and pressure (P) fields for following ranges of governing parameters: inverse Debye length (2 ≤ K ≤ 20), surface charge density (4 ≤ S 1 ≤ 16), and surface charge-heterogeneity ratio (0 ≤ S rh ≤ 2). Results have shown that the total potential (∣ΔU∣) and pressure (∣ΔP∣) drop maximally increase by 99.09% (from 0.1413 to 0.2812) (at K = 20, S 1 = 4) and 12.77% (from 5.4132 to 6.1045) (at K = 2, S 1 = 8), respectively with overall charge-heterogeneity (0 ≤ S rh ≤ 2). Electroviscous correction factor (Y, i.e., ratio of effective to physical viscosity) maximally enhances by 12.77% (from 1.2040 to 1.3577) (at K = 2, S 1 = 8), 40.98% (from 1.0026 to 1.4135) (at S 1 = 16, S rh = 1.50), and 41.35% (from 1 to 1.4135) (at K = 2, S rh = 1.50), with the variation of S rh (from 0 to 2), K (from 20 to 2), and S 1 (from 0 to 16), respectively. Further, a simple pseudo-analytical model is developed to estimate the pressure drop in EV flow, accounting for the influence of charge-heterogeneity based on the Poiseuille flow in a uniform channel. This model predicts the pressure drop ± 2%–4% within the numerical results. The robustness and simplicity of this model enable the present numerical results for engineering and design aspects of microfluidic applications.

Microstructural Analysis of Lithium-Ion Battery Cathode Carbon-Binder Domain across Processing Conditions

Improvement of lithium-ion battery (LIB) energy density and rate capability is necessary to increase adoption of electric vehicles (EVs) and curb transportation emissions. The cathode structure must support facile ion and electron transport, enabling rapid charging while maintaining near-theoretical capacity. Much investigation focuses on active material design for fast-charging cathodes, [1] but less is understood about the effect of electrode processing on carbon-binder domain (CBD) structure and its impact on rate capability. As conductive carbon facilitates electron transfer, slow Li+ diffusion through cathode micropores is rate-limiting and prevents full active material utilization at high charge rates. [2,3] However, efforts to improve Li+ diffusion, such as increasing porosity, introduce charge-transfer limitations. [4] Thus, cathode processing conditions and resulting microstructure must be carefully designed to optimize for both electronic and ionic conductivity. For example, an increase in coating shear rate and decrease in slurry solid content improves long-range electronic pathways [5,6] and calendaring strengthens active material-carbon contacts to reduce charge-transfer resistance. [2] However, the impact of processing variations on ionic transport pathways, which can be described by CBD porosity and tortuosity, is not well understood. Further, because the CBD is traditionally characterized as a single phase, the distinct influences of insulating binder and conductive carbon distributions on structure and performance are poorly defined.In this talk, I will discuss how electrode coating conditions impact pathways available to Li+ and electrons within the CBD with the goal of identifying optimal microstructures for efficient transport. We fabricate cathodes with varying solid content, coating shear rate, and degree of calendaring to explore disparate CBD microstructures. We use electrochemical impedance spectroscopy (EIS) with a symmetric cell & blocking electrolyte to determine cathode resistivity and tortuosity and plasma focused ion beam scanning electron microscopy (PFIB-SEM) to examine CBD morphology over a representative cathode volume (~80 x 80 x 50 µm3). We then use small-angle neutron scattering (SANS) with solvent contrast variation to distinguish between binder and carbon distributions and determine the surface area of each component within the CBD. Relationships between processing conditions, structural variations, and rate capability will be discussed, informing the design of the CBD for facile transport and improved fast charging performance. Further, reducing ionic transport limitations through intentional design of LIB cathodes will enable thicker electrodes to increase cell energy density.

Frequency Response of the Diffuse-Charge Dynamics in Electrochemical Systems with a Graphene Electrode

We investigate the frequency response of diffuse-charge dynamics related to a 1:1 symmetric electrolyte containing a graphene electrode by solving the governing Poisson-Nernst-Planck equations subjected to appropriate boundary conditions in the asymptotic limit ε = λ D /H → 0, where λ D is the Debye screening length and H is the half-thickness of the electrolyte. Using the method of matched asymptotic expansion, we first solve the leading order non-linear problem for equilibrium state at a nonzero applied DC voltage in the presence of Stern layer(s). Then, we extend the leading order asymptotic analysis to derive an analytic expression for the impedance of the graphene-based electrochemical cell when a small AC voltage perturbation is added to the applied DC voltage. Finally, we use a suitable scaling of the impedance parameters to expose the impacts of the ion concentration and the DC bias voltage on the frequency response for possible applications involving the graphene-electrolyte interface.

Sedimentation of a Charged Soft Sphere within a Charged Spherical Cavity.

The sedimentation of a soft particle composed of an uncharged hard sphere core and a charged porous surface layer inside a concentric charged spherical cavity full of a symmetric electrolyte solution is analyzed in a quasi-steady state. By using a regular perturbation method with small fixed charge densities of the soft sphere and cavity wall, a set of linearized electrokinetic equations relevant to the fluid velocity field, electrical potential profile, and ionic electrochemical potential energy distributions are solved. A closed-form formula for the sedimentation velocity of the soft sphere is obtained as a function of the ratios of core-to-particle radii, particle-to-cavity radii, particle radius-to-Debye screening length, and particle radius-to-porous layer permeation length. The existence of the surface charge on the cavity wall increases the settling velocity of the charged soft sphere, principally because of the electroosmotic enhancement of fluid recirculation within the cavity induced by the sedimentation potential gradient. When the porous layer space charge and cavity wall surface charge have the same sign, the particle velocity is generally enhanced by the presence of the cavity. When these fixed charges have opposite signs, the particle velocity will be enhanced/reduced by the presence of the cavity if the wall surface charge density is sufficiently large/small relative to the porous layer space charge density in magnitude. The effect of the wall surface charge on the sedimentation of the soft sphere increases with decreases in the ratios of core-to-particle radii, particle-to-cavity radii, and particle radius-to-porous layer permeation length but is not a monotonic function of the ratio of particle radius-to-Debye length.

Asymmetric Rectified Electric Fields for Symmetric Electrolytes.

In this paper, building upon the numerical discovery of asymmetric rectified electric fields (AREFs), we explore the generation of AREF by applying a sawtooth-like voltage to 1:1 electrolytes with equal diffusion coefficients confined between two planar blocking electrodes. This differs from an earlier approach based on a sinusoidal AC voltage applied to 1:1 electrolytes with unequal diffusion coefficients. By numerically solving the full Poisson-Nernst-Planck equations, we demonstrate that AREF can be generated by a slow rise and a fast drop of the potential (or vice versa), even for electrolytes with equal diffusion coefficients of the cations and anions. We employ an analytically constructed equivalent electric circuit to explain the underlying physical mechanism. Importantly, we find that the strength of AREF can be effectively tuned from zero to its maximal value by only manipulating the time dependence of the driving voltage, eliminating the necessity to modify the electrolyte composition between experiments. This provides valuable insights to control the manipulation of AREF, which facilitates enhanced applications in diverse electrochemical systems.

Effect of cation species on pressure-driven electrokinetic energy conversion in charged conical nanochannels

Electrokinetic energy conversion (EEC) offers a promising avenue for transforming elusive natural energy into electric power, showing a wide application spectrum. Unlike prevalent studies that chiefly utilize symmetrical electrolyte solution (e.g., KCl) and uniformly structured negatively charged nanochannels for EEC, this paper delves into a thorough examination of EEC characteristics—streaming current, streaming potential, and output power—in both positively and negatively charged conical nanochannels with symmetrical and asymmetric (CaCl2 and LaCl3) electrolytes solutions. Operating under the assumption that the electrolyte solutions (KCl, CaCl2, and LaCl3) possess equivalent ionic strength and, thereby, a common Debye length, our findings reveal a significant dependency of EEC characteristics and their regulation parameters on the electrolyte type, nanochannel charge polarity, and ionic strength. As the ionic strength increases, both the streaming current and output power initially rise to a peak before subsequently declining, with the ionic strength at the peak being influenced by the cation valence: lower valence leads to lower ionic strength. In asymmetric electrolyte scenarios, optimal EEC characteristic is observed in positively charged conical nanochannels under a reverse pressure difference, attributed to the ion-selective and ionic concentration distribution in the charged conical nanochannels. Moreover, the complex behaviors of the regulation parameters of EEC characteristics are unveiled. Notably, a tri-valent electrolyte's regulation parameters exceed those of a bi-valent electrolyte, indicating that ionic valence asymmetry enhances the regulation effects on EEC in conical nanochannels.

Boosting Supercapacitor Efficiency with Amorphous Biomass-Derived C@TiO2 Composites.

Carbon materials are readily available and are essential in energy storage. One of the routes used to enhance their surface area and activity is the decoration of carbons with semiconductors, such as amorphous TiO2, for application in energy storage devices.

Diffusiophoresis of a Charged Soft Sphere in a Charged Spherical Cavity

The quasi-steady diffusiophoresis of a soft particle composed of an uncharged hard sphere core and a uniformly charged porous surface layer in a concentric charged spherical cavity full of a symmetric electrolyte solution with a concentration gradient is analyzed. By using a regular perturbation method with small fixed charge densities of the soft particle and cavity wall, the linearized electrokinetic equations relevant to the fluid velocity field, electric potential profile, and ionic concentration distributions are solved. A closed-form formula for the diffusiophoretic (electrophoretic and chemiphoretic) velocity of the soft particle is obtained as a function of the ratios of the core-to-particle radii, particle-to-cavity radii, particle radius to the Debye screening length, and particle radius to the permeation length in the porous layer. In typical cases, the confining charged cavity wall significantly influences the diffusiophoresis of the soft particle. The fluid flow caused by the diffusioosmosis (electroosmosis and chemiosmosis) along the cavity wall can considerably change the diffusiophoretic velocity of the particle and even reverse its direction. In general, the diffusiophoretic velocity decreases with increasing core-to-particle radius ratios, particle-to-cavity radius ratios, and the ratio of the particle radius to the permeation length in the porous layer, but increases with increasing ratios of the particle radius to the Debye length.

Colloidal phase behavior of high aspect ratio clay nanotubes in symmetric and asymmetric electrolytes

HypothesisImogolite nanotubes (INTs) are unique anisometric particles with monodisperse nanometric diameters. Aluminogermanate double-walled INTs (Ge-DWINTs) are obtained with variable aspect ratios by controlling the synthesis conditions. It thus appears as an interesting model system to investigate how aspect ratio and ionic valence influence the colloidal behavior of highly anisometric rods. ExperimentsThe nanotubes were synthesized by hydrothermal treatment for 5 or 20 days to modify the aspect ratio while the electrostatic interactions were investigated by comparing the colloidal stability in symmetric and asymmetric electrolytes. The phase behavior and their related microstructure were determined by optical observations and small-angle X-ray scattering measurements, coupled with interparticle distance modelling. FindingsWe revealed that colloidal suspensions of Ge-DWINTs prepared in NaCl are guided by repulsive double layer forces, undergoing different liquid crystal phase transitions before stiffen into a glass-like state. We found that the microstructure can be rationalized by taking into account the anisometric nature of the particles. By contrast, dispersions prepared with asymmetric electrolytes are governed by strong attractive forces and thus form space-filling gels containing large nanotubes aggregates.

Stepwise strategies for overcoming limitations of membraneless electrolysis for direct seawater electrolysis

Direct seawater electrolysis (DSWE) has been investigated as a candidate solution for hydrogen (H2) production using abundant seawater without the water purification requirements of conventional electrolyzers. Costly perfluorinated membranes employed in contemporary water electrolyzers (PEMWE) fail in the presence of trace contaminants due to cation exchange for H+ and scaling resulting from Mg2+/Ca2+ hydroxide precipitation caused by local pH increases. Herein, we disclose a membraneless electrolyzer and explore how symmetric and asymmetric electrolyte recirculation schemes impact pH gradients and performance of the system using in-house developed near-neutral pH electrocatalysts. Under the asymmetric recycle scheme, unbuffered seawater feed can be used whereby pH differentials caused by electrolysis are re-balanced by recirculating the liquid anode and cathode effluent streams to the cathode and anode inlet ports, respectively. Cell voltages of 2.61 and 3.50 V were required to attain 100 mA cm−2 of current density under buffered (0.5 M phosphate buffer; pH 6.71) and unbuffered synthetic seawater operation, respectively, and 50 h of chronoamperometric stability at the same current density was achieved for the former. A mere 0.18 % of H2 crossover from the catholyte to the anolyte at 250 mA cm−2 of current density was recorded at prolonged operation.

Diffusioosmotic flow reversals due to ion-ion electrostatic correlations.

Existing theories of diffusioosmosis have neglected ion-ion electrostatic correlations, which are important in concentrated electrolytes. Here, we develop a mathematical model to numerically compute the diffusioosmotic mobilities of binary symmetric electrolytes across low to high concentrations in a charged parallel-plate channel. We use the modified Poisson equation to model the ion-ion electrostatic correlations and the Bikerman model to account for the finite size of ions. We report two key findings. First, ion-ion electrostatic correlations can cause a unique reversal in the direction of diffusioosmosis. Such a reversal is not captured by existing theories, occurs at ≈ 0.4 M for a monovalent electrolyte, and at a much lower concentration of ≈ 0.003 M for a divalent electrolyte in a channel with the same surface charge. This highlights that diffusioosmosis of a concentrated electrolyte can be qualitatively different from that of a dilute electrolyte, not just in its magnitude but also its direction. Second, we predict a separate diffusioosmotic flow reversal, which is not due to electrostatic correlations but the competition between the underlying chemiosmosis and electroosmosis. This reversal can be achieved by varying the magnitude of the channel surface charge without changing its sign. However, electrostatic correlations can radically change how this flow reversal depends on the channel surface charge and ion diffusivity between a concentrated and a dilute electrolyte. The mathematical model developed here can be used to design diffusioosmosis of dilute and concentrated electrolytes, which is central to applications such as species mixing and separation, enhanced oil recovery, and reverse electrodialysis.

Ionic Distribution of an Unequal Electrolyte Near an Air/Water Surface

The distribution of electrolytes near the air/water surface plays an essential role in many processes. While the general distribution is governed by classic Poisson-Boltzmann statistics, the analytical solution is only available for symmetric electrolytes. From the recent studies in the literature, it is evident that surface adsorption is dependent on specific ions as well as the H-bond structure at the surface. Experimental data can capture the macro properties of the surface, such as surface tension and surface potential. Yet, the underpinning mechanisms behind this experimental macro-observation remain unclear. To address the challenge, we developed a framework combining experimental studies and numerical calculations. The model was developed for electrolytes with unequal cationic and anionic charges. The asymmetric model was successfully applied to describe the surface charge of MgCl 2 aqueous solution. The results can be explained by the role of cationic size and charge on the surface layer.

Solvent Effects on Structure and Screening in Confined Electrolytes.

Using classical density functional theory, we investigate the influence of solvent on the structure and ionic screening of electrolytes under slit confinement and in contact with a reservoir. We consider a symmetric electrolyte with implicit and explicit solvent models and find that spatially resolving solvent molecules is essential for the ion structure at confining walls, excess ion adsorption, and the pressure exerted on the walls. Despite this, we observe only moderate differences in the period of oscillations of the pressure with the slit width and virtually coinciding decay lengths as functions of the scaling variable σ_{ion}/λ_{D}, where σ_{ion} is the ion diameter and λ_{D} the Debye length. Moreover, in the electrostatic-dominated regime, this scaling behavior is practically independent of the relative permittivity and its dependence on the ion concentration. In contrast, the crossover to the hard-core-dominated regime depends sensitively on all three factors.