A novel organic ionic plastic crystal, N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)amide ([C2mpyr][FSA]), was synthesized, and its thermal properties and conductivity were investigated. [C2mpyr][FSA] showed a high melting point at 205 °C and exhibited plastic crystalline behavior over a wide temperature range from −22 °C to melting, which was also in a desirable temperature range for electrochemical devices. The ionic conductivity of [C2mpyr][FSA] was 1.23 × 10−6 S cm−1 at 25 °C.

No abstract

In this study, we investigated the physicochemical and electrochemical properties of LiFSI solution comparing with those of LiPF6 in EC/DEC (3/7, v/v), and discuss the difference in ionic conductivity between these electrolyte solutions based on self-diffusion coefficients measured by PFG-NMR. Self-diffusion coefficients of solvent molecules and ions in 1M LiFSI solution are about 1.5 times larger than those of 1M LiPF6 solution. On the other hand, the degree of dissociation of LiFSI estimated by the Nernst-Einstein Equation from measured ionic conductivity and self-diffusion coefficients of Li+ and FSI- is lower than that of LiPF6. Therefore it is strongly suggested that almost the same ionic conductivity of 1M LiFSI solution as that of 1M LiPF6 in EC/DEC (3/7, v/v) is the result of cancelation of these two factors in the opposite direction.

No abstract

No abstract

Abstract:Copolymer-pendant Ru(bpy)32: grafted onto silk fibroin was prepared by at first grafting c o p o l y ( 4 -m e t h y l -4 ' -v i n y l -2 , 2 ' -b i p y r i d i n e -methylmethacrylate) onto non-woven silk fabric, and then by reacting the grafted sample with cis-R~( b p y )~C l . Photoluminescence of this silk-poly Ru complex an$ its quenching by oxygen were studied in g a s , methanol and water phases.The relative emission intensity and the emission lifetime of the silk-poly Ru showed that there are two kinds of sites for the Ru complex.The major, longer lifetime component ( 1 0 7 0 ns, 77.1 % , under Ar gas) i s considered to be surrounded by polymer matrices, and the minor, shorter one (288 ns, 22.9 % ) seems to be exposed and is subjected to concentration quenching. The shorter lifetime species are quenched by oxygen more effectively than the longer ones.The mechanism of the quenching by oxygen and its application to oxygen sensor were discussed.

Novel boric ester-type molten salt was prepared using 1-(2-hydroxyethyl)-3-methylimidazolium chloride as a key starting material. After an ion exchange reaction of 1-(2-hydroxyethyl)-3-methylimidazolium chloride with lithium (bis-(trifluoromethanesulfonyl) imide) (LiNTf2), the resulting 1-(2-hydroxyethyl)-3-methylimidazolium NTf2 was reacted with 9-borabicyclo[3.3.1]nonane (9-BBN) to give the desired boric ester-type molten salt in a moderate yield. The structure of the boric ester-type molten salt was supported by 1H-, 13C-, 11B- and 19F-NMR spectra. In the presence of two different kinds of lithium salts, the matrices showed an ionic conductivity in the range of 1.1 × 10−4–1.6 × 10−5 S cm−1 at 51 °C. This was higher than other organoboron molten salts ever reported.

Aprotic ionic liquids have been investigated as the alternative electrolytes for rechargeable lithium batteries because of less inflammability, which is expected to improve safety of the batteries in case of accident. However, the battery performance using ionic liquid electrolytes has been reported to be inferior to that using conventional organic electrolytes since the viscosity of ionic liquids is generally higher than that of the organic electrolytes. The viscosity of electrolytes is considered to affect not only the mobility of lithium ion but also charge transfer at both anode and cathode reaction. Quantitative evaluation of the charge transfer rates of the active materials is often difficult in composite electrodes involving binders and conductive additives. In the present study, the charge transfer resistance of lithium cobalt oxide (LiCoO2) thin film was evaluated by electrochemical impedance measurements in different ionic liquids. LiCoO2 thin film was prepared by RF magnetron sputtering of LiCoO2 target with Ar on a gold substrate and then annealed in the air at 700°C. MPPTFSA, BMPTFSA, MOMMPTFSA, MPPFSA and MOMMPFSA (MPP+ = 1-methyl-1-propylpyrrolidinium, BMP+ = 1-butyl-1-methylpyrrolidinium, MOMMP+ = 1-methoxymethy-1-methylpyrrolidinium, TFSA– = bis(trifluoromethysulfonyl)amide and FSA–= bis(fluorosulfonyl)amide) containing 1 M LiTFSA or LiFSA were used as the electrolytes. 1 M LiTFSA / EC + DEC (1 : 1 vol%, EC = ethylene carbonate, DEC = diethyl carbonate) was also used as the electrolyte as a control. Lithium metal was used as a reference and counter electrode. An air-tight three electrode cell was assembled in a glovebox of dry Ar atmosphere. Electrochemical impedance measurements were conducted using PARTSTAT 2263 or 2273 with the ac amplitude of 5 mV-rms, and the frequency range from 2 Hz to 5 kHz at a constant potential of 4 V. Charge and discharge of the LiCoO2 thin film electrode was confirmed to be possible in the ionic liquid electrolytes by galvanostatic charge-discharge test at ±20 μA cm–2. A slightly distorted semi-circle was observed in the Nyquist plots for the ac impedance measurement of the LiCoO2 thin film electrode in each electrolyte. The charge transfer resistance was calculated by assuming a Randles-type equivalent circuit with an electrolyte resistance, constant phase element and charge transfer resistance. The charge transfer resistance decreased with an decrease in the viscosity of the electrolytes, suggesting the charge transfer process is affected by the dynamics of the electrolytes, as reported for Li+/Li reaction in an organic electrolyte[1]. The activation energy of the charge transfer resistance was larger than that of the viscosity of the electrolytes, implying the charge transfer process is related to not only the dynamics of the electrolytes but also the activation processes at the interface between the active material and the electrolytes. Reference [1] Y. Kato, T. Ishihara, Y. Uchimoto, and M. Wakihara, J. Phys. Chem. B, 108, 4794 (2004).