LiClO4 Solutions Research Articles

Elektrohemijsko ponašanje resintetisanog katodnog materijala iz potrošenih litijum jonskih baterija u organskom elektrolitu

The excessive use of Li-ion batteries has resulted in the growing necessity of developing a recycling procedure for them, particularly stemming from their negative impact on the environment as well as the fact that the natural-ore metals contained in them can be replaced. This work presents a re-synthesis of cathode material obtained from spent Li-ion batteries using the co-precipitation method in order to recycle it. The structure of the re-synthesized metal was characterized by XRD and the morphology by SEM. The chemical content of the spent cathode material was determined by FAAS. In order to prove functionality, the electrochemical behaviour was examined in a 1M solution of LiClO4 in propylene carbonate by galvanostatic charging and discharging. Since the initial capacity of the re-synthesized material was 70.6 mAh g-1 when the current of charging/discharging was 100 mA g-1, the fade of capacity was 13% after the initial five cycles. The electrochemical properties of the re-synthesized material were then finally compared to the material re-synthesized by the citrate gel combustion method.

Relationship between Ionic Interaction and NMR Relaxation Behavior in LiClO4-PC Solution Coexisting with Fumed Metal Oxide

Dynamic properties related to 1H NMR relaxation in SiO2 fine powder/non-aqueous LiClO4 solution was measured for using propylene carbonate (PC) and PC-1,2-dimethoxyethane (DME). The influence of solid phase and variation of effect of DME on ionic mobility is also discussed. For 1H NMR spectra of PC-DME binary solution, adding of SiO2 powder caused the broadening of NMR signal of 1H in PC and DME molecules. In pure PC-DME system, since DME is preferentially affected by solids rather than PC, as the ratio of DME increased, values of solvent molecules detected by NMR decreased. In 1 mol/L LiClO4/PC-DME system, as the ratio of DME in solution was higher, The interaction between the PC and the Li+ ion is weakened by the decrease of the dissociation degree, and the mobility of the PC was restored.

Ionic Conduction of Non-Aqueous Lithium Electrolyte Solution through Surface Modified Anodized Alumina Membrane Prepared By LPD Process Using Aqueous-Organic Mixed Solvent

The reduction of the internal resistance by the accelerations of Li+ transport and electron transfer promotes the high-speed charge/discharge of lithium ion batteries (LIBs). Recently, the improving charge/discharge has been attempted by exploiting model porous electrodes which have mesoporous structures such as anodic aluminum oxide (AAO) [1]. AAO is a suitable template for the preparation of the multi layered structures using its regular nanopore array. TiO2 thin films have potential application in the negative electrodes of LIBs, so we prepared the SiO2 or TiO2/AAO nanocomposite by the liquid phase deposition (LPD) procedure in this work. The LPD method involves a metal oxide and hydroxide thin films synthetic procedure using the hydrolysis equilibria reactions of metal-fluoro complexes as follows; (Hydrolysis reaction) MF x (x-2n)- + H2O → MO n + xF- + 2nH+ (F- scavenging reaction) Al3+ + 6HF → H3AlF6 + 3/2H2 Previously, TiO2 was deposited on the surface of AAO mesopores by the LPD within 250 nm, and in this study, the TiO2 thin film onto AAO mesopore wall which has the extreme small diameter, i.e., ca. 20-40 nm, was prepared by the LPD. In this research, the achievement of the LPD reaction at 0 °C or less by the use of the H2O/EtOH mixed solvent and the deposition of oxide thin film to mesopore inner wall owing to the decrease of the LPD reaction activity under low temperature were executed. Furthermore, the specific ion conductivity of the electrolyte solution in the mesopore channels in the prepared TiO2/AAO nanocomposites was evaluated. AAO membranes were prepared by two-step anodization as previous report [1,2]. AAO template whose thichness is ca. 500 m (i.e. the aspect ratio of a AAO membrane thichness to a mesopore diameter is ca. 5000) was dipped in (NH4)2SiF6 or (NH4)2TiF6 solution of various concentration for 0-60 h at -20-40 °C. Prepared SiO2 or TiO2/AAO nanocomposite was used as a separator of a four-electrode cell and an impedance measurement was carried out. LiClO4/EC:DEC = 1:1 (v/v) of 0.5 to 2.5 mol L-1was used as an electrolyte solution. The results of LPD reaction using (NH4)2TiF6 solution of 10 mol L-1 in 1 : 1 (v/v) H2O/EtOH at -20-5 °C (The LPD reaction solution was still liquid-state at -20 °C) for 10 h were shown in Fig. 1. The TiO2 thin film deposition within the deep mesopores without collapse of the mesopore structure was achieved at -13.5 °C. The AAO mesopore structure collapsed because the LPD reaction reactivity was too high at 5 °C, and the TiO2 thin film was not generated because the reactivity was too low at -20 °C. It is suggested that the moderate decrease in the LPD reaction activity by using an aqueous/organic solvent mixture was necessary to achieve oxide thin films deposition on the AAO mesopore wall, while retaining the AAO mesoporous structure. The Nyquist plots for four-electrode cells using SiO2 or TiO2/AAO nanocomposites show two semicircles for each nanocomposite. The lower frequency region of the semi-circle was assigned as ion transport resistance in the SiO2 and TiO2 modified mesopore walls, and the fitting of the semicircle in the low frequency region, the specific conductivity in the pore was calculated. For a LiClO4 solution of 0.5-2.5 mol L-1, the specific Li+ ion conductivities after SiO2 or TiO2 thin film coating by LPD in the mesopore of the AAO nanocomposites was compared with those without thin film coating (i.e. as-prepared AAO). The conductivity for the TiO2/AAO nanocomposite is 3 times that for as-prepared AAO, whereas that the conductivity for the SiO2/AAO nanocomposite is similar for as-prepared AAO. Even if the concentration was changed, the ratios of the specific Li+ ion conductivity in the SiO2 or TiO2 modified mesopore to the electrolyte solution and as-prepared AAO were almost constant. These activation energies of Li+ ion conduction in mesopores for each sample are 14.6 (as-prepared AAO), 13.8 (SiO2/AAO), 13.2 kJ mol-1 (TiO2/AAO), respectively. It is suggested that the ionic conduction are influenced by surface electric potential of oxides. This work was supported by CREST, JST. [1] T. Fukutsuka, et al., Electrochim. Acta., 199, 380 (2016) [2] H. Masuda et al., Science, 268, 1466 (1995) Figure 1

Relationship between Ionic Interation and NMR Relaxation Behavior in LiClO4-PC Solution Coexisting with Fumed Metal Oxide

Lithium ion battery (LIBs) is indispensable to various electrochemical devices in practical use such as a cell phone, electric vehicle due to its high energy density, high voltage. Although the extended use of LIBs technology, batteries which have higher capacity and can stand up to high speed charge/discharge than those of LIBs are demanded. Various studies have reported that the liquid phase occurring adjacent to solid particles has an anomalous behavior when compared to bulk solution[1]. Solid-liquid interface is performed as a base in charge-discharge of LIBs, so an elucidation of liquid phase properties of solid-liquid interface in the non-aqueous electrolyte solution system is important for improving the performance of energy storage devices such as LIBs. In addition, properties of the highly-concentrated electrolytes for performance improvement of LIBs are attracted. In this study, NMR spectroscopic behavior of non-aqueous LiClO4 solution mixed with fumed oxide nanoparticles as model system of gel electrolyte for LIBs, and their dynamic properties and influences to solvent molecules from solid phase or Li+ ion by measurement of the spin-spin (T 2) relaxation time and electrochemical measurement. Samples were prepared in Ar glovebox by mixing propylene carbonate(PC) or LiClO4/PC of predetermined concentration (1-3 mol L-1) and fumed silica(FS) (200 ± 20 m2 g-1), amorphous silica nanoparticles with self-cohesive properties, fumed alumina(FA) (130 ± 20 m2 g-1) and fumed titania(FT) (90 ± 20 m2 g-1) in NMR tube. A content of liquid phase were ranged from 90-100 vol% by gravimetry. We measured 1H and 7Li NMR spectroscopy (Varian INOVA 400; 9.39 T) and 1H spin–spin relaxation time; T 2measurements (XiGo Nanotools Acorn area ; 0.3 T). In 1H NMR spectra, a broad signal was confirmed under the existence solid-phase. It was shown that the dynamic property of PC molecules largely decreased in comparison with the case only for liquid phases. In PC/FS and PC/FA system, 1H NMR spectra shifted to higher magnetic field with the decrease of liquid content. For the shielding effect to the 1H nucleus of the PC molecules by the surface charge of fumed silica, a signal continues to shift to highly-magnetic field as a content of solid-phase increases. This result suggested that the apparent charge densities around the proton of PC molecules increased by fumed silica because fumed silica has a negative charge. In alumina dispersion, NMR signal shifted to higher magnetic field than that of fumed silica. From this result, alumina gives more influence on dynamics properties of liquid phase. A similar result was observed in 1-3 mol L-1 LiClO4/PC and solid coexisting system. From the liquid content dependences of the 1H NMR detection ratios of propylene carbonate, almost same amount of PC molecules were detected in PC/FS coexisting system. This result indicated that fumed silica formed network structure but H of PC molecules remained its dynamics. On the other hand, in fumed alumina or fumed titania dispersion, values of PC molecules detected by NMR decreased compared to the theoretical value of detected amount of PC by 1H NMR. It suggests that the mobility of PC molecules in fumed alumina and titania system were restricted than that in silica system. T2 in solid-liquid coexisting system is also shown in Fig. 1. From Fig.1, in all systems, the T2 value decreases because the dynamics of water molecules of the liquid phase decrease. The T2 value decreased in order of PC/FA, PC/FT, PC/FS system. The influence of the solid surface to solvent mobility in fumed alumina dispersion is the least of the three. This result supports a signal of the NMR and the result of 1H qNMR measurement. We will also discuss the NMR relaxation behavior for LiClO4-PC solution coexisting with te same fumed metal oxides. This study was supported by the JST Core Research for Evolutional Science and Technology (CREST). 【Reference】 [1] M. Mizuhata et al., J. Mol. Liq., 83, 179, (1999). Figure 1

Observation and Simulation of Transient Anion Oligomers (LiClO4)n– (n = 1–4) in Diethyl Carbonate LiClO4 Solutions

NMR measurements show that diethyl carbonate (DEC, a solvent with a low dielectric constant) solutions of LiClO4 contain (LiClO4)n oligomers. The reduction of these species by solvated and presolvated electrons is followed by picosecond pulse radiolysis measurements. The data analysis shows that several anions absorbing in the near-infrared (NIR) and visible range are formed after the 7 ps electron pulse. In contrast with tetrahydrofuran (THF) solutions of LiClO4, the anionic monomer (LiClO4)- is not observed in DEC solutions. This is due to the fact that DEC is a nonpolar solvent favoring the clustering of monomers in the nonirradiated solution, as shown by NMR results, and also due to the instability of the anionic monomer. The absorption spectra of the anionic dimer (LiClO4)2-, trimer (LiClO4)3-, and tetramer (LiClO4)4- are clearly observed in NIR and visible ranges. Compared to the results obtained for the same system in THF and in agreement with simulated absorption spectra, the experimental results show that the absorption bands are shifted to the blue end of the spectrum when n increases. The kinetics recorded for the molar LiClO4 solution indicates that the solute is only in the form of oligomers (LiClO4)n with a large n value and that the reduced species absorb weakly in the visible region. Lastly, and contrary to what is known for well-separated ions in polar solvents, it is shown that the (LiClO4)n- anions are not stable with respect to self-reduction, leading to the decomposition of perchlorate anions. In this reaction, the perchlorate anion ClO4- is reduced by the Li atom into a chlorate anion ClO3-. This is proved by the presence of ClO3- and chlorinated species detected by mass spectrometry measurements in irradiated DEC solutions containing LiClO4.

Electrochemical analysis of 25H-NBOMe by Square Wave Voltammetry

The emergence of new illicit drugs, like N-benzyl-substituted phenethylamines (NBOMes), for recreational purposes has prompted researchers to develop fast and sensitive methods for their detection in seized samples, especially in blotters. Conducting the chemical characterization of new substances entering the drug abuse market is also essential, and obtaining their electrochemical profile is desirable. Here, we have analyzed 25H-NBOMe by Square Wave Voltammetry to verify whether this technique is feasible for detection of NBOMes in blotter samples. We used a methanolic solution of LiClO4 to detect the oxidative peak in a system that employed glassy carbon as the working electrode. This enabled us to analyze the target compound at 1.28·10−6molL−1 with an accuracy of 96.44%. We also tested this technique to analyze 25H-NBOMe extracted from a simulated blotter. This is one of the first validated voltammetric methodologies for analysis of 25H-NBOMe in forensic laboratories.

Analysis of Prepeak Structure of Concentrated Organic Lithium Electrolyte by Means of Neutron Diffraction with Isotopic Substitution and Molecular Dynamics Simulation.

The prepeak structure of a 3 mol/kg solution of LiClO4 in propylene carbonate (PC) was studied by both neutron diffraction with isotopic substitution (NDIS) and molecular dynamics (MD) simulation. The NDIS data showed that the intensity of the prepeak decreases experimentally with an increase in the scattering length of the lithium atom from 7Li to 6Li in PC-d6. On the other hand, although the prepeak was observed in solutions of both PC-d6 and PC-h6, it disappears when the 1:1 mixture of PC-d6 and PC-h6 was used as the solvent. The prepeak structure and its variation with the isotope substitution were reproduced well by MD simulation, and they were explained in terms of the contrast of the scattering length densities of the ionic and nonpolar domains.

Electrochemical and electron paramagnetic resonance study of the mechanism of oxidation of 2,3,5,6-tetra-Me-pyrazine-di-N-oxide as a mediator of electrocatalytic oxidation of isopropyl alcohol at glassy carbon and single-walled carbon nanotube electrodes

The mechanism of oxidation of 2,3,5,6-tetra-Me-pyrazine-di-N-oxide (Pyr2) as a mediator of electrooxidation of isopropyl alcohol was studied by cyclic voltammetry at glassy carbon (GC) and single-walled carbon nanotubes (SWCNT) electrodes in 0.1M LiClO4 solutions in acetonitrile. The adsorption of Pyr2 at SWCNT electrode in 0.1M LiClO4 solution in acetonitrile was investigated by measurement of the dependence of the differential double layer capacitance of the electrode C on potential E. The effect of isopropyl alcohol on the shape of cyclic voltammograms (CVs) of Pyr2 and the intensity of EPR signal of its radical cation was investigated. The catalytic currents were recorded at the oxidation of Pyr2 at SWCNT and GC electrodes in the presence of isopropyl alcohol. The effect of acid and water (as a base) on the catalytic process was studied. The results were explained in terms of the E1C1E2C2 mechanism of two-stage electrode process characterized by catalytic current recorded at the second electrode stage. The overall two-electron catalytic oxidation of isopropyl alcohol in complex with the Pyr2 radical cation was assumed to occur. It was found that the use of SWCNT electrode instead of GC one increases the catalytic efficiency of i-PrOH oxidation by 17 times.

Graphene oxide nanoplatforms to enhance catalytic performance of iron phthalocyanine for oxygen reduction reaction in bioelectrochemical systems

Abstract We report the development of electrocatalysts based on iron phthalocyanine (FePc) supported on graphene oxide (GO), obtained by electrochemical oxidation of graphite in aqueous solution of LiCl, LiClO4, and NaClO4. Structure, surface chemistry, morphology, and thermal stability of the prepared materials were investigated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic force microscopy (AFM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The catalytic activity toward oxygen reduction reaction (ORR) at neutral pH was evaluated by cyclic voltammetry. The experimental results demonstrate that the oxidation degree of GO supports affects the overall catalytic activity of FePc/GO, due to a modulation effect of the interaction between FePc and the basal plane of GO. On the basis of electrochemical, spectroscopic, and morphological investigations, FePc/GO_LiCl was selected to be assembled at the cathode side of a microbial fuel cell prototype, demonstrating a good electrochemical performance in terms of voltage and power generation.

Interpenetrated triple polymeric layer as electrochemomechanical actuator: Solvent influence and diffusion coefficient of counterions

Full polymeric trilayers formed by two lateral polypyrrole-dodecylbenzoesulfate (PPyDBS) films interpenetrating a polyvinylidene fluoride (PVdF) central membrane were electrochemically characterized. Square wave voltammetric and square wave amperometric responses in 0.5M LiClO4 solutions using different solvents was undertaken with parallel video-recording of the reversible angular displacements. According to the bending movements in aqueous and ethylene glycol (EG) solutions the PPyDBS films shrunk upon oxidation and swelled during reduction: the electrochemical reactions drive the exchange of cations in both solvents. In propylene carbonate (PC) and acetonitrile (AN) solutions the PPyDBS films swelled and shrunk by oxidation and reduction, respectively, driven by the exchange of anions. Propylene carbonate and acetonitrile hinder the dissociation of the LiDBS ionic couples inside the PPyDBS film forcing the exchange of anions to compensate polarons on polypyrrole. The diffusion coefficient of the exchanged ions and the angular rates follow the sequence: aqueous>PC>AN>EG solutions. Whatever the solvent, actuators are Faradaic devices: the described angle is a linear function of the consumed charge.

Monitoring of lithium plating by neutron reflectometry

The development of high-capacity rechargeable and safe metallic lithium negative electrodes for next-generation batteries requires an in-depth understanding of reasons for nonuniform lithium plating during lithium-metal battery charge. It drives the interest for the tools enabling efficient monitoring of electrochemical interfaces where lithium electrodeposition occurs. We report on a three-electrode electrochemical cell designed to track lithium electrodeposition from aprotic electrolytes by neutron reflectometry (NR) in the specular reflectivity mode. We performed a case study of Li plating from LiClO4 solution in propylene carbonate. The sensitivity was optimized by tuning the neutron scattering contrast for a given electrode material (Cu film) and the electrolyte, which was done employing a deuterated solvent. The analysis of the scattering length density (SLD) profiles derived from the modeling of the reflectivity data clearly demonstrated that the deposition of nm-thin Li layers above initially formed solid-electrolyte interphase (SEI) layer can be detected and their roughness, which is a characterizing parameter of electrodeposition nonuniformity, can be estimated. It makes NR a proper tool for further studies of “dendritic” lithium growth.

Dynamic Properties on NMR Spectroscopy of Non-Aqueous Electrolyte Solution Coexisting with Fumed Silica Dispersion

In this study, the non-aqueous LiClO4 solution mixed with fumed silica as model system of LIBs was applied, and the dynamic properties and influences which solvent molecules received from solid phase or Li+ ion in using the NMR spectroscopy and the relaxation time(T1, T2 ) measurements were evaluated. The NMR signal of 1H in PC molecules is influenced by coexisting solid phase in LiClO4-PC solution /oxide powder. The dynamic property of the PC molecules drastically decreased in comparison with the system of the liquid only system. In IR spectra of PC/Alumina systems, the vibration in higher wavenumber range are predominantly observed due to indirect electron-donation from solid surface. The signal intensity depends on influenced liquid content from solid phase. Especially, the LiClO4-PC solution /alumina systems, the intensity is abruptly decreased due to widely spread influences of solid phases. Moreover, the influence from the solid phase to the PC molecules is much smaller than the water molecules from the 1H spin-spin relaxation time (T 2). As for the electrolyte concentration dependence, PC system was more remarkable than the water solution system, namely the network structure of the whole PC solvent is greatly affected by the addition of the Li+ ion, and it is thought that relaxation time largely decreased.

Dynamic Properties on NMR Spectroscopy of Non-Aqueous Electrolyte Solution Coexisting with Fumed Silica Dispersion

For various electrochemical devices in practical use, porous solid materials are widely fabricated for holding electrolyte solutions. It is reported that electrolyte solutions related to ion-solvent interaction indicate different properties by coexistence of solid phase[1], and an elucidation of liquid phase properties of solid-liquid interface in the non-aqueous electrolyte solution system is important for improving the performance of energy storage devices such as lithium ion batteries(LIBs). In addition, in late years the study of new electrolyte materials used highly-concentrated electrolytes attracts attention. Dahn et al.[2], report that highly-concentrated aqueous electrolyte solutions improve charge rate and wider overvoltage. It is also very important to investigate properties of the highly-concentrated electrolytes in aiming at the performance enhancement of LIBs. In this study, NMR spectroscopic behavior of non-aqueous LiClO4 solution mixed with fumed silica as model system of gel electrolyte for LIBs, and their dynamic properties and influences to solvent molecules from solid phase or Li+ ion by measurement of the spin-lattice(T 1) and spin-spin (T 2) relaxation phenomena. Samples were prepared in Ar glovebox by mixing propylene carbonate(PC) or LiClO4/PC of predetermined concentration (1-3 M) and fumed silica(FS) (200 ± 50 m2 g-1), amorphous silica nanoparticles with self-cohesive properties in NMR tube. A content of liquid phase were ranged from 90-100 vol% by gravimetry. We measured 1H and 7Li NMR spectroscopy (Varian INOVA 400; 9.39T) , spin–lattice relaxation time; T 1 measurements, and spin–spin relaxation time ;T 2 measurements (XiGo Nanotools Acorn area ; 0.3T). In 1H NMR spectra, little amount of solid phase (fumed silica) at around 1% affected to NMR signal which was deformed to the broadened band. It was shown that the dynamic properties of the PC molecules drastically decreased in comparison with the system of the liquid system only. Owing to the shielding effect to the 1H nucleus of the PC molecules by the surface charge of fumed silica, a signal continues to shift to higher magnetic field with the increasing of the solid-phase content without the depending on the LiClO4 concentration. This phenomenon also observed in the water solution system equally. From the calculation of the integrated intensity of the 1H NMR signals, that is the 1H qNMR analysis, in 90-100 vol%, the relatively slight influence in comparison with the aqueous-solid system which the hydrogen nucleus of propylene carbonate affected by fumed silica was observed. It is suggested that the influence from the solid phase to the PC molecules is much smaller than the water molecules from the 1H spin-spin relaxation time (T 2) as shown in Fig. 1. Dependences of T 1 and T 2 relaxation time on liquid content indicated that the interaction between the fumed silica surface and the PC molecules is much smaller than the case of the water molecules. On the other hand, as for the electrolyte concentration dependence, more remarkable variation was observed in the system containing PC rather than that of the aqueous system. Because the molar ratio of water molecules to Li+ ions is ca. 53 in 1 mol L-1 LiClO4 aqueous solution, the water molecule participating in the hydration to Li+ ion is a small portion, and most water molecules form a hydrogen bonding network. Whereas most PC molecules solvate with Li+ ion because the molar ratio of water molecules to Li+ ions is ca. 11 in 1 mol L-1 PC LiClO4 solution. Therefore the network structure of the whole solvent is greatly affected by the addition of the Li+ ion, and it is thought that relaxation time largely decreased. This result is supported from the increase of viscosity with the increase of the electrolyte concentration of the LiClO4/PC solution. Furthermore, from result of a measurements of the 7Li NMR and the Li+ ion conductance, it was shown that the interaction between the fumed silica surface and the Li+ ion in the PC solvent was smaller than in the water solvent. The details of the liquid phase properties in other solvents and the comparison with the PC system will be also reported in this research. This study was supported by the JST Core Research for Evolutional Science and Technology (CREST). 【Reference】 [1] M. Mizuhata et al., J. Mol. Liq., 83, 179, (1999). [2] Wu Li, J. R. Dahn, D. S. Wainwright, Science, 264, 1115, (1994). Figure 1

TEMPO-Mediated Electro-Oxidation of 1,2-Diol on Boron-Doped Diamond Electrode

Electroorganic synthesis is an attractive method, in which only electrons serve as reagent and therefore complies with a “green chemistry” condition. In addition, reactions of electroorganic synthesis can be regarded as a special heterogeneous catalytic one. Furthermore, products can be obtained with high selectivity and efficiency by optimizing a reaction condition, such as electrode materials, potential, and others. Recently, a boron-doped diamond (BDD) electrode attracts much attention in the field of electroorganic chemistry. This is particularly because the BDD electrode enables to generate active species such as a hydroxyl radical with high efficiency under an appropriate electrolysis condition. Here, we report on the electroorganic synthesis using BDD electrode, especially TEMPO-mediated oxidation of the 1,2-diol derivative. TEMPO (2,2,6,6,-tetramethylpyperidine-1-oxyl) has been widely used as a catalyst in organic synthesis, for converting primary alcohol to an aldehyde selectively even in the presence of a secondary alcohol. However, the conventional TEMPO oxidation reaction requires a co-oxidant such as sodium hypochlorite and a hypervalent iodine compound. First, we prepared an electrolyte solution of TEMPO (0.1 mmol) and LiClO4 (0.1 M in CH3CN) or n-Bu4N•PF6 (0.1 M in CH2Cl2). Cyclic voltammetry (CV) was performed to examine an electrochemical behavior of TEMPO. For CV measurementsusinan undivided cell, BDD, Pt wire, and Ag/AgCl electrodes were used as the working, counter, and reference electrode, respectively. Next, for an electrolysis experiment, a diol substrate, 3-phenyl-1,2-propanediol, was synthesized according to the previous report. The diol substrate (10 mmol) was added to the electrolyte solution (10 mL), and a constant current electrolysis (1 F/mol for the diol substrate) was conducted at room temperature. After electrolysis, a resulting compound containing in solution was evaluated by 1H NMR. For acetylation of a hydroxyl group in oxidized products, pyridine (20 mmol) and acetic anhydride (20 mmol) was added and stirred at room temperature for 6 h. The resulting acetylated products were analyzed by a thin layer chromatography (TLC). In the cyclic voltammogram of TEMPO solution, oxidation and reduction peaks of TEMPO were clearly observed at 0.8 V and 0.6 V (vs. Ag/AgCl), respectively. On the other hand, the reduction peak of TEMPO almost disappeared in the presence of 3-phenyl-1,2-propanediol. Based on the reaction mechanism of TEMPO oxidation, such a CV behavior would ascribed to oxidation of 3-phenyl-1,2-propanediol substrate by TEMPO catalyst. Next, we examined the solvent dependence of TEMPO-mediated electro-oxidation. When using CH3CN electrolyte solution, surface of the Pt cathode was covered with a black film and the current dropped immediately. On the other hand, in case of CH2Cl2 electrolyte solution, a couple of oxidized products were detected by a TLC analysis. Furthermore, in the 1H NMR spectrum, a signal at 10 ppm derived from an aldehyde group was detected. We investigated TEMPO-mediated selective electro-oxidation using a BDD electrode. First, we confirmed both oxidation and reduction of TEMPO on a BDD electrode. Next, TEMPO-mediated electro-oxidation of 3-phenyl-1,2-propanediol gave a couple of products containing an aldehyde group.

Heat Capacities of Aqueous Solutions of Lithium Sulfate, Lithium Perchlorate, and Lithium Trifluoromethanesulfonate at 298.15 K

Isobaric heat capacities of aqueous solutions of Li2SO4, LiClO4, and LiCF3SO3 have been measured at 298.15 K and 0.1 MPa up to high concentrations using a Picker flow calorimeter. Apparent molar isobaric heat capacities, Cp,ϕ, derived from these data were fitted within the limits of experimental precision with an extended Redlich–Rosenfeld–Meyer type of equation, which was also used to estimate the standard state (infinite dilution) quantities, Cp,ϕo, for each salt. The latter values were combined with appropriate literature data to produce a robust estimate of Cp,ϕo (Li+(aq)) = −3 ± 2 J·K–1·mol–1. Where comparison was possible, Cp,ϕ(LinX) values were closely parallel to those of the corresponding acids over the whole concentration range, even when the shapes of the curves were highly unusual. In contrast, Cp,ϕ(NanX) values always exhibited a crossover with the lithium salt data at a concentration of about 1 mol·kg–1, which appears to reflect differences in the hydration of the two cations.

Microscopic Structure of Contact Ion Pairs in Concentrated LiCl- and LiClO4-Tetrahydrofuran Solutions Studied by Low-Frequency Isotropic Raman Scattering and Neutron Diffraction with (6)Li/(7)Li Isotopic Substitution Methods.

Low-frequency isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for (6)Li/(7)Li and H/D isotopically substituted *LiCl- and *LiClO4-tetrahydrofuran (*THF) solutions in order to obtain microscopic insight into solvated Li(+), Li(+)···Cl(-) and Li(+)···ClO4(-) contact ion pairs formed in concentrated THF solutions. Symmetrical stretching vibrational mode of solvated Li(+) in LiCl and LiClO4 solutions was observed at ν = 181-184 and 140 cm(-1), respectively. The stretching vibrational mode of Li(+)···Cl(-) and Li(+)···ClO4(-) solvated contact ion pairs formed in 4 mol % (6)LiCl-THF-h8 and (7)LiCl-THF-h8 solutions was found at ν = 469 and 435 cm(-1), respectively. Detailed structural properties of solvated Li(+) and the contact ion pairs were derived from the least-squares fitting analyses of the first-order difference function, ΔLi(Q), obtained from neutron diffraction measurements on (6)Li/(7)Li isotopically substituted THF-d8 solutions. It has been revealed that Li(+) takes 4-fold coordination in the average local structure of Li(+)X(-)(THF)3, X = Cl and ClO4. The nearest neighbor Li(+)···O(THF) distance was determined to be 2.21 ± 0.01 Å and 2.07 ± 0.01 Å for 4 mol % *LiCl- and 10 mol % *LiClO4-THF-d8 solutions, respectively. The Li(+)···anion distances for Li(+)···Cl(-) and Li(+)···O(ClO4(-)) contact ion pairs were determined to be 2.4 ± 0.1 Å and 2.19 ± 0.01 Å, respectively. The nearest neighbor Li(+)···THF interaction is significantly modified by the anion in the first solvation shell.

Large-scale synthesis and electrochemical properties of hydrated tungsten trioxide-based hierarchical microstructures

Hierarchically self-assembled micro-/nanostructures of o-WO3.1/3H2O were successfully synthesized by surfactant-assisted hydrothermal reaction at 180 °C for 76 h in acidic medium (pH = 1). The effect of the surfactant n-alkyl chain length CnH(2n+1)SO4Na (with n = 10, 12 and 14) on the morphology and the crystallite sizes were investigated. The as-synthesized samples were characterized by different techniques. When sodium decylsulfate is used, agglomerates of irregular particles of orthorhombic WO3.1/3H2O (o-WO3.1/3H2O) are obtained. The sample obtained by the use of sodium dodecylsulfate, consists of o-WO3.1/3H2O microdisk-like structure formed by self-assembled nanosheets (with an average thickness of about 20 nm), resembling chrysanthemum flower. O-WO3.1/3H2O microsheres-like 3D architectures constructed from 2D sheets intervened out-of-order, resembling sand roses, are obtained with sodium tetradecylsulfate as surfactant. The prepared o-WO3.1/3H2O hierarchical assemblies are used as electrode materials to study the electrochemical properties in propylene carbonate containing 1 M LiClO4 solution, by cyclic voltammerty. It was found that o-WO3.1/3H2O microdisks and microspheres exhibit reversible redox behavior accompanied by reversible intercalation/deintercalation of Li+ cations into crystal matrix. It has been revealed also that higher currents were measured for microdisk-like structure and higher diffusion coefficient of Li+ (2.93 × 10−10 cm2/s) compared to microsphere-like structure (2.02 × 10−10 cm2/s).

First-Principles Study of Li-Ion Diffusion Mechanism in Highly Concentrated Li-Salt Electrolye

Li-salt concentration has been recently proposed as an important control parameter of reduction stability of electrolytes and high ion conductivity in Lithium-ion batteries (LIBs)1. The mechanism of the reduction stability improvement of high concentration (HC) systems has been revealed by our first-principles calculations1,2, while the rather high Li-ion conductivity under such high-viscosity environment remains an open question. In general, higher viscosity in the HC electrolyte decreases the diffusion coefficient and thus Li-ion conductivity according to the Stokes-Einstein and Nernst-Einstein equations. However, this regime does not seem to hold here. To elucidate this problem, we carried out extensive DFT-MD sampling to examine the Li-ion diffusion mechanism in the HC electrolytes. The LIBs are often classified by the mechanism of Li-ion diffusion. In conventional LIBs with dilute liquid electrolytes, Li-ions are coordinated only by solvent molecules, and the ions move to an electrode accompanied by the coordinated solvent molecules. In polymer electrolyte LIBs, Li-ions diffuse by “hopping” between oxygen sites of the polymer electrolyte and that fluctuation of the polymer backbone plays a predominant role in ion conduction. In contrast, in all-solid-state LIBs with solid electrolytes, the geometry of the backbone structure is fixed, and Li-ions are conducted through specific pathways in the crystal. In this study, we investigated the Li-ion diffusion mechanism in acetonitrile (AN) solvent with LiN(SO2F)2 (Li-FSA) and LiN(SO2CF3)2 (Li-TFSA) salts systems at some Li-salt concentrations by using density functional theory based molecular dynamics (DFT-MD) calculations. The diffusion coefficients of single-ion in HC systems were also investigated by means of solvation structure analysis. We calculated the diffusion coefficients of the Li ions, FSA and TFSA anions, and AN solvent molecules in the low-concentration (LC) and HC electrolytes to elucidate how Li-ion diffusion was affected by concentration (Fig. 1). The calculated diffusion coefficients of Li ions were 0.80 × 10-6 (1.4 × 10-6) cm2 s-1 and 7.7 × 10-6 (6.9 × 10-6) cm2 s-1, respectively, for the HC and LC TFSA (FSA) electrolytes. The calculated values for the Li-FSA/AN electrolyte were on the same order of magnitude as the experimental values. The diffusion coefficients for the HC electrolytes were approximately one order magnitude lower than those for the LC electrolytes. The reported Li-ion diffusion coefficient in a 1 mol dm-3 solution of LiClO4 in propylene carbonate3, which is a popular salt-solvent combination for LIBs, is 2.6 × 10-6 cm2 s-1. In contrast, in 2.75 mol dm-3 [Li(G4)][TFSA], a HC solvate ionic liquid that can also be used for LIBs4, the Li-ion diffusion coefficient is 0.13 × 10-6 cm2 s-1. These values suggest that the diffusion coefficients of Li ions in the HC electrolytes are large enough for practical use of these electrolytes in LIBs. In the LC electrolytes, we confirmed that each Li-ion is coordinated only by solvent molecules, and the Li-ions diffuse in the company of the coordinated solvent molecules (vehicle-type diffusion). In the HC electrolytes, the vehicle-type diffusion is difficult because the Li-ions are coordinated both by solvent molecules and by anions arranged in a specific network structure2, which results in high viscosity. We analyzed the motions of individual Li ions in the HC electrolytes, and found Li-ion hopping between the oxygen atoms of the anions in both FSA and TFSA anion systems. Additional DFT-MD calculations with different solvents also suggest the Li-ion hopping diffusion mechanism. We concluded that change of the diffusion mechanism can be an origin of the high Li-ion conductivity in the HC electrolytes. [1] Y. Yamada, K. Furukawa, K. Sodeyama, M. Yaegashi, K. Kikuchi, Y. Tateyama, A. Yamada, J. Am. Chem. Soc. 136, 5039-5046 (2014). [2] K. Sodeyama, Y. Yamada, K. Aikawa, A. Yamada, Y. Tateyama, J. Phys. Chem. C 118, 14091-14097 (2014). [3] J. M. Sullivan, D. C. Hanson, R. Keller, J. Electrochem. Soc. 117, 779-780 (1970). [4] T. Tamura, K. Yoshida, T. Hachida, M. Tsuchiya, M. Nakamura, Y. Kazue, N. Tachikawa, K. Dokko, M. Watanabe, Chem. Lett. 39, 753-755 (2010). Figure 1

Pd(II) complexes of Schiff bases and their application as catalysts in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions

Schiff bases of 2‐(phenylthio)aniline, (C6H5)SC6H4NCR (R = (o‐CH3)(C6H5), (o‐OCH3)(C6H5) or (o‐CF3)(C6H5)), and their palladium complexes (PdLCl2) were synthesized. The compounds were characterized using 1H NMR and 13C NMR spectroscopy and micro analysis. Also, electrochemical properties of the ligands and Pd(II) complexes were investigated in dimethylformamide–LiClO4 solution with cyclic and square wave voltammetry techniques. The Pd(II) complexes showed both reversible and quasi‐reversible processes in the −1.5 to 0.3 V potential range. The synthesized Pd(II) complexes were evaluated as catalysts in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions. Copyright © 2015 John Wiley & Sons, Ltd.

Effect of the nature of a ligand on electrochemical characteristic of tin films in cycling in lithium-ion batteries

Potentiodynamic and galvanostatic cycling in 1 M ethylene carbonate-dimethyl carbonate solution of LiClO4 were used to study electrolytic tin films deposited from complex (tartrate, citrate, and citrate-trilonate) electrolytes. It was shown that the nature of a ligand strongly affects the electrochemical characteristics, specific capacity of tin films, and efficiency of their cycling in lithium power sources. The most stable charge-discharge characteristics are inherent in tin films deposited from the citrate electrolyte.