Physicochemical Properties Of Electrolytes Research Articles

The mechanism of in-homogeneous mass transfer process of separators in lithium-ion batteries.

The liquid-phase mass transport is the key factor affecting battery stability. The influencing mechanism of liquid-phase mass transport in the separators is still not clear, the internal environment being a complex multi-field during the service life of lithium-ion batteries. The liquid-phase mass transport in the separators is related to the microstructure of the separator and the physicochemical properties of electrolytes. Here, in-situ local electrochemical impedance spectra were developed to investigate local inhomogeneities in the mass transfer process of lithium-ion batteries. The geometric microstructure of the separator affects the mass transfer process, with a reduction in porosity leading to increased overpotentials. There is a competitive relationship among porosity, tortuosity, and membrane thickness in the geometric parameters of the separator, resulting in a peak of polarization. The resistance of the liquid-phase mass transfer process is positively correlated with the viscosity of the electrolyte, making ion migration difficult due to high viscosity. Polarization is closely related to the electrochemical performance, so a phase diagram of battery performance and inhomogeneous mass transfer was developed to guide the design of the battery. This study provides a guiding basis for the development of high stability lithium-ion batteries.

Atomic Insights into Advances and Issues in Low‐Temperature Electrolytes

AbstractThe design of low‐temperature electrolytes is a key technology to improve the low‐temperature performance of electrochemical energy storage devices and expand their application fields. However, the current design strategies for low‐temperature electrolytes remain in the optimization of formula, without systematic and in‐depth consideration of the internal relationship between the fundamental interactions and performances of electrolytes at low temperature. Here, starting from the four fundamental interactions among cations, anions, and solvents in the electrolyte, this review for the first time analyzes the temperature‐dependent mechanisms of their interactions and corresponding physicochemical properties of electrolytes from atomic insights. Then, the research progress in low‐temperature electrolytes is summarized according to the relationships of these interactions. The possible new development directions in the future are also pointed out. This review provides a theoretical reference for the design of low‐temperature electrolytes.

Discussion on Operational Voltage and Efficiencies of Ionic-Liquid-Based Electrochemical Capacitors

In this article, we explore electrical double-layer capacitors (EDLCs) based on ionic liquids (IL), focusing on their stability and efficiencies (Coulombic and energetic). We analyze the conventional voltammetric methods to determine the electrochemical stability window, pointing out that a simple analysis of Coulombic efficiency, under different current and voltage conditions in galvanostatic experiments, has the advantage of being more representative for real cells, especially when studied together with energy efficiency. In addition, we study how IL-based EDLCs differ from aqueous and organic ones in terms of energy efficiency correlating with the physicochemical properties of electrolytes. Finally, we discuss the high resistance of this type of EDLC that has a detrimental effect on energy efficiency and cycling performance, even when the Coulombic efficiency is close to 100%.

Physicochemical Properties of Industrial Aluminum Electrolytes Enriching Li and K: The Liquidus Temperature

The alumina contains plenty of Li2O and K2O as a result of using low-grade bauxite in China. Thus, LiF and KF will be enriched in the electrolytes with the operation of the cell, so that the composition and physicochemical properties of electrolytes have been changed. The effects of LiF, KF, and CR on the liquidus temperature of electrolytes based on the xNaF·AlF3-5 wt pct CaF2-2.5 wt pct Al2O3-0.5 wt pct MgF2 system have been investigated in this study. The results show that the liquidus temperature decreases by 5.13 K to 10.74 K (5.13 °C to 10.74 °C) per 1 wt pct addition of LiF and that the liquidus temperature decreases by 1.63 K to 3.8 K (1.63 °C to 3.8 °C) with per 1 wt pct addition of KF. When adding LiF and KF together, it has the interplay between LiF and KF. Under different electrolyte systems, the interplay between LiF and KF is complex. The effect of CR on liquidus temperature has been related to the concentration of LiF and KF.

Epoxy-silica hybrid organic–inorganic electrolytes with a high Li-ion conductivity

Organic–inorganic hybrid electrolytes were prepared by co-hydrolysis and co-condensation of 3-glycidoxipropyltrimethoxysilane (GPTMS) and tetraethyl orthosilicate (TEOS) doped with lithium acetate as self-supported materials and thin-films. The effects of the relative molar content of LiAc on the physicochemical properties of electrolytes, such as morphology, thermal, chemical and electrochemical properties were investigated. Two and four probes test cells were designed for comparative studies of ionic conductivity of hybrid electrolytes using electrochemical impedance spectroscopy (EIS). Similar ionic conductivities were obtained using both measurement methods, reaching a maximum ionic conductivity value of around 10−6S/cm at 25°C. The conductivity mechanism presents Arrehenius behavior with the increase of the temperature from 25°C to 120°C. The electrochemical stability window is found to be in the range of 0–5V, which ensures that hybrid organic–inorganic materials are potential electrolytes for solid-state rechargeable lithium ion batteries.

Electrochemical Production of Ultrathin Silicon Dioxide Films

Low-temperature synthesis of ultrathin (≤20 nm) SiO2 films, by anodizing semiconductor single-crystal silicon wafers, is studied. Effects of physicochemical properties of electrolyte and single-crystal silicon on the films' dielectric characteristics are considered.

Relationship between the Physicochemical Properties of Electrolytes and the Electronic Structure of Solvated Alkali Metal Cations

Group theoretical analysis and linear combinations of molecular orbitals of the cation and solvent are used to establish the nature and stability of bonds and hence the electric mobility of the cation and the viscosity of the electrolyte depending on the type of cation (Li+, Na+, K+, Rb+, Cs+) and molecules (H2O, NH3, H2CO, (CH3)2CO, CH3CN). Solvation effects on the UV photoelectron and intramolecular vibrational IR and NMR spectra are revealed.

Cleaning low mineral water by electrodialysis

One way to intensify mass transfer when cleaning low-mineral water is to use ion-exchange filler in electrodialyzer cells. A model is proposed of an electrodialysis process which takes into account the effect of process parameters, geometrical dimensions of cells, and the physicochemical properties of electrolytes on the efficiency of demineralization. On the basis of our investigations and tests in working conditions, a design for an electrodialyzer with fibrous ion-exchange filler is recommended and a flow sheet is presented which combines the demineralization of low-mineral water with the simultaneous removal of potentially hazardous impurities from it.