Electrodeposition of Molybdenum in LiTFSI-CsTFSI Melt at 150ºC

Electrodepostion of molybdenum was studied in the eutectic LiTFSI-CsTFSI (0.07: 0.93 in mole fraction, m.p., 112ºC) melt at 150ºC. MoCl5 was selected as molybdenum ion sources. Metallic molybdenum was electrodeposited on nickel substrate. Quality of the deposits was improved by using galvanostatic electrolysis and pulsed current electrolysis

Novel composite electrolyte membranes consisting of fluorohydrogenate ionic liquid and polymers for the unhumidified intermediate temperature fuel cell

Novel composite electrolyte membranes consisting of [EMIm](FH)ₙF (EMIm = 1-ethyl-3-methylimidazolium, n = 1.3 and 2.3) ionic liquids and fluorinated polymers were synthesized and their physical and electrochemical properties were measured under unhumidified conditions for their application to the intermediate temperature fuel cells. The ionic conductivities of composite membrane, P(VdF-co-HFP)/s-DFBP-HFDP/[EMIm](FH)₂.₃F (1/0.3/1.75 in weight ratio), were 11.3 and 34.7 mS cm⁻¹ at 25 and 130 °C, respectively. The open circuit voltage (OCV) observed for the single cell using [EMIm](FH)₂.₃F composite electrolyte was ∼1.0 V at 130 °C for over 5 h. The maximum power density of 20.2 mW cm⁻² was observed under the current of 60.1 mA cm⁻² at 120 °C. From the high thermal stability and high ionic conductivity, the fluorohydrogenate ionic liquid composite membranes are regarded as promising candidates for the electrolytes of the unhumidified intermediate temperature fuel cells

Charge-discharge Performance of an Ionic Liquid-based Sodium Secondary Battery in a Wide Temperature Range

A sodium secondary battery has been constructed by using a nonvolatile and nonflammable Na[FSA]-[C(3)C(1)pyrr][FSA] (FSA = bis(fluorosulfonyl)amide, C(3)C(1)pyrr = N-methyl-N-propylpyrrolidinium) ionic liquid, a NaCrO(2) positive electrode and a Na metal negative electrode. The charge-discharge performance is evaluated over a wide temperature range of −20–90℃. It has been demonstrated that the sodium secondary battery has long cycle lives both at a high temperature of 90℃ and at a low temperature of 0℃. Thus, the ionic liquid-based sodium secondary battery is expected to be a viable alternative to lithium ion battery for many applications

Formation of Si Nanowires by Direct Electrolytic Reduction of Porous SiO₂ Pellets in Molten CaCl₂

The effects of starting material and catalyst on the morphology of produced Si have been investigated for the direct electrolytic reduction of porous SiO₂ pellets in molten CaCl₂ at 1123 K. The Si nanowires (SiNWs) were produced using amorphous SiO₂ pellets with a tetrapod-like microstructure as the starting material, whereas plate-like Si was obtained from pellets made of spherical fumed SiO₂. The SiNWs showed irregular branching and a wide distribution of diameters as the electrolysis proceeded. On the other hand, elongated SiNWs were formed during the electrolysis of pellets comprised of Au nanoparticles (AuNPs) and tetrapod-like microstructured SiO₂ powder. This suggests that AuNPs work as catalysts for longitudinal nanowire growth in the present electrolytic process

Simple Fabrication of Silicon Nanowires by Zinc-Thermal Reduction of Silicon Tetrachloride at 773 K

This paper reports a simple Si nanowire (SiNW) production process based on zinc-thermal reduction of SiCl₄ in a sealed Pyrex® tube at 773 K. SiNWs with a diameter of about 300 nm were produced without any catalysts. The SiNWs consisted mainly of an amorphous phase, but also including a minor microcrystalline component. The introduction of Au nanoparticles to the reaction tube wall facilitated crystallization and resulted in the growth of thinner SiNWs. The typical diameter of these SiNWs was 10–20 nm. The simple apparatus and low operating temperature of this new process are advantageous in producing SiNWs on both industrial and laboratory scales

Charge–Discharge Performance of Copper Metal Positive Electrodes in Fluorohydrogenate Ionic Liquids for Fluoride-Shuttle Batteries

In search of room-temperature electrolytes for fluoride-shuttle batteries, fluorohydrogenate ionic liquids (FHILs) have emerged, showing high ionic conductivities and better operational practicality. To enhance the performance of these electrolytes, the charge–discharge behavior of copper metal as positive electrodes in FHILs was investigated in this study. In the [C₂C₁im][(FH)₂.₃F] (C₂C₁im = 1-ethyl-3-methylimidazolium) FHIL electrolyte, although the 1st discharge capacity of 599 mAh (g-Cu)⁻¹ included the reductive reaction of surface oxide films, the 2nd discharge capacity of 444 mAh (g-Cu)⁻¹ that corresponds to 53% of the theoretical capacity was achieved. However, the capacity declines to 167 mAh (g-Cu)⁻¹ at the 20th cycle, indicating low capacity retention. In contrast, the adoption of [C₂C₁pyrr][(FH)₂.₃F] (C₂C₁pyrr = N-ethyl-N-methylpyrrolidinium) electrolyte confers improved cycleability across the cycles with a higher discharge capacity of 210 mAh (g-Cu)⁻¹ at the 20th cycle. Scanning electron microscopy and energy-dispersive X-ray spectroscopy performed on the electrode surfaces confirm reduced electrode degradation characterized by suppressed aggregation of copper particles in [C₂C₁pyrr][(FH)₂.₃F] due to its low CuF₂ solubility compared with [C₂C₁im][(FH)₂.₃F]. Herein, we demonstrate the use of FHILs with low CuF₂ solubilities as a strategy for improving the charge–discharge performance of copper metal positive electrodes in fluoride-shuttle batteries

Novel inorganic ionic liquids possessing low melting temperatures and wide electrochemical windows: Binary mixtures of alkali bis(fluorosulfonyl)amides

Thermal properties of alkali bis(fluorosulfonyl)amides, MFSI (M = Li, Na, K, Rb, Cs), have been investigated. Binary phase diagrams of LiFSI–KFSI and NaFSI–KFSI systems have been constructed. Eutectic point for LiFSI–KFSI is 338 K at (xLi, xK) = (0.45, 0.55) and, that for NaFSI–KFSI is 330 K at (xNa, xK) = (0.45, 0.55). The electrochemical window of the eutectic LiFSI–KFSI is as wide as 6.0 V at 348 K with the cathode limit being lithium metal deposition. The electrochemical window of the eutectic NaFSI–KFSI is 5.0 V at 340 K with sodium metal deposition at the cathode limit. These new inorganic ionic liquids are highly promising for various electrochemical applications

Thermal Properties of Mixed Alkali Bis(trifluoromethylsulfonyl)amides

Phase diagrams of binary mixtures of alkali bis(trifluoromethylsulfonyl)amides have been constructed, and their eutectic compositions and temperatures have been determined. It has been revealed that the molten salt electrolytes having the melting points in the intermediate temperature range (373 to 473) K are easily formed by simple mixing of two kinds of single alkali bis(trifluoromethylsulfonyl)amide salts. The 1:1 or 3:1 double salt is occasionally formed for some binary systems