Why Is Tetrahydrofuran a Good Solvent for Calcium Batteries? Insights From Ab Initio Molecular Dynamics Simulations

Calcium batteries are rapidly emerging as a potential, future energy storage technology; however, their advancement relies heavily on understanding of the liquid electrolyte component in terms of stability and interactions with a calcium metal anode. Tetrahydrofuran, a cyclic ether, is an experimentally common and promising solvent for the preparation of stable and efficient calcium electrolytes. However, insights into the reasons why are lacking, which could unveil key principles to electrolyte design. In this report, we provide a theoretical study employing ab initio molecular dynamics (AIMD) simulations of the interactions of Ca metal with the cyclic ether tetrahydrofuran (THF). The results show that the electrochemical breakdown and decomposition of THF at the Ca surface is highly orientation- and surface-site dependent, thereby significantly reducing the likelihood of its instability in a randomly organized bulk solvent. Likewise, in bulk electrolytes, its likelihood for breakdown is further diminished, in preference for coordination Ca2+ to form solvated structure. Hence, the finding that molecules require such strict conditions for their decomposition is an important selection and design principle for any solvent to prepare suitable calcium electrolytes. These findings are critical to the advancement of the calcium batteries.

Why Is Tetrahydrofuran a Good Solvent for Calcium Batteries? Insights From Ab Initio Molecular Dynamics Simulations

Calcium batteries are rapidly emerging as a potential, future energy storage technology; however, their advancement relies heavily on understanding of the liquid electrolyte component in terms of stability and interactions with a calcium metal anode. Tetrahydrofuran, a cyclic ether, is an experimentally common and promising solvent for the preparation of stable and efficient calcium electrolytes. However, insights into the reasons why are lacking, which could unveil key principles to electrolyte design. In this report, we provide a theoretical study employing ab initio molecular dynamics (AIMD) simulations of the interactions of Ca metal with the cyclic ether tetrahydrofuran (THF). The results show that the electrochemical breakdown and decomposition of THF at the Ca surface is highly orientation- and surface-site dependent, thereby significantly reducing the likelihood of its instability in a randomly organized bulk solvent. Likewise, in bulk electrolytes, its likelihood for breakdown is further diminished, in preference for coordination Ca2+ to form solvated structure. Hence, the finding that molecules require such strict conditions for their decomposition is an important selection and design principle for any solvent to prepare suitable calcium electrolytes. These findings are critical to the advancement of the calcium batteries.

Modifications of Liquid Electrolyte for Monolithic Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSC) has been well known as a highly competitive photovoltaic technology owing to its interesting characteristics, such as, low-cost, simple, and convenient to modify both chemically and physically. One way to reduce the production cost of DSSCs is to conduct a structural modification in the form of a monolithic structure by using a single conductive substrate to accommodate both photoelectrode and counter electrode. However, the photovoltaic performance of monolithic DSSCs is typically still lacking compared to its conventional DSSCs counterparts that uses sandwich structure. One of the crucial factors that determine the photovoltaic performance of a monolithic DSSC is its electrolyte. In this work, the performance of monolithic DSSCs were studied through modifications of the electrolyte component. Two types of commercial liquid electrolytes that have different chemical properties were used and combined into various compositions, and the resulting DSSCs performances were compared. The stability of the monolithic cells was also monitored by measuring the cells repeatedly under the same condition. The result showed that during the first measurement the highest performance with a power conversion efficiency of 1.69% was achieved by the cell with a higher viscosity electrolyte. Meanwhile, the most stable performance is shown by the cell containing lower viscosity electrolyte, which achieved an efficiency of 0.66% that measured on day 35.

INFLUENCE OF PLASMA-ELECTROLYTIC OXIDATION PROCESS TECHNOLOGICAL PARAMETERS OF ALUMINUM ON COATING GROWTH RATE

There has been carried out an analysis of methods of oxide covering formation productivity increasing during plasma electrolytic oxidation of aluminum in electrolyte. There has been developed a technology of blank manufacturing and part strengthening by plasma electrolytic oxidation in the electrolyte, as well as the workbench has been modernized. There has been studied the process of oxidoceramic coating synthesis for the D16T aluminum deformed alloy of during plasma electrolytic oxidation in the electrolyte for different process parameters. It is established that the growth rate of oxidoceramic coating can be significantly increased by electrolyte component concentration involved in aluminum oxidation and rational choice of process electrical parameters. Hydrogen peroxide addition leads to obtained oxoceramic coating thickness increasing due to O, O2, OH, OH– concentration increasing in the electrolyte. It is established that the optimal concentration of H2O2 ranges from 5 g/l to 7 g/l. A further increase of peroxide concentration leads to a decrease in peroxide effect on oxoceramic coating growth rate on the D16T aluminum deformed alloy due to pH changes of the electrolyte and the deterioration of the oxide coating.

Investigation of Electrical Properties, Structure and Morphological Characterization of Mg+2 Ions Conducting Solid Polymer Electrolyte Based on Poly(vinyl alcohol)

In the present work, solid polymer electrolyte using poly(vinyl alcohol) (PVA) and magnesium perchlorate (Mg(ClO4)2) in different compositions has been prepared by the solution-casting technique method. Surface feature of films was characterized by scanning electron microscopy (SEM) measurement. X-ray diffraction (XRD) was used to determine the complexation of the polymer with the salt. The electrophysical characteristics were measured and analyzed as dependent on the concentration, nature of the solid polymer electrolyte component and ambient temperature. A maximum ionic conductivity value of ∼10–4 S/cm at 303 K is obtained for PVA0.6/(Mg(ClO4)2)0.4 composite. The ionic transference number of Mg+2 mobile ions has been estimated by a dc polarization method. The result reveals that the conducting species are predominantly ions.