Methyl difluoroacetate (MFA) was used as an electrolyte solvent in Li/CuCl2 batteries, and the LiPF6/MFA electrolyte was effective for the suppression of the self-discharge of Li/CuCl2 batteries. The dependence of self-discharge behavior on LiPF6 concentration (1.0, 1.4, 1.8, 2.2, and 2.7 mol dm−3) in MFA-based electrolytes was investigated. The lowest self-discharge was observed for a 2.2 mol dm−3 LiPF6/MFA electrolyte under the described conditions, and an initial discharge capacity of 395 mAh g−1 was maintained after 678 h (4 weeks) of rest. The cycling performance of the LiPF6/MFA electrolytes was evaluated, and the discharge capacity for the 2.2 mol dm−3 LiPF6/MFA electrolyte was found to be maintained at 183 mAh g−1 (10th cycle). Therefore, 2.2 mol dm−3 LiPF6/MFA electrolyte is confirmed to be effective for the suppression of the self-discharge of Li/CuCl2 batteries.
The study demonstrates the applicability of laser ionization time-of-flight mass spectrometry for real-time measurement of polychlorinated biphenyls (PCBs). Picosecond 266-nm laser light ionization reduced fragmentation and provided very high PCB detection sensitivity. This high sensitivity has advantages in terms of real-time monitoring capability as compared to the conventional GC-ECD or GC-MS methods, which require at least several days for the analysis of PCBs. Detection sensitivity of under 0.01 mg/Nm3 was achieved with a 1-min measuring time; this sensitivity is superior to the exhaust gas control guideline of 0.15 mg/Nm3 by a factor of 10. A prototype PCB monitoring device has been developed and tested in a pilot PCB treatment plant. The 1-min detection time represents a substantial advance in the monitoring of exhaust gas and the workplace atmosphere in accordance with safety regulations.
Polychlorinated aromatic hydrocarbons include many hazardous compounds, 1-5 such as PCBs (polychlorinated biphenyls), PCDDs (polychlorinated dibenzodioxins), PCDFs (polychlorinated dibenzofurans), polyhexachlorobenzene and pentachlorophenol. For protection from such chemicals, it is necessary to rapidly monitor their concentrations. Especially in PCB disposal plants, pollution of the surrounding environment must be strictly prevented, giving a strong imperative for the development of real-time measurement technology for PCB concentration monitoring.The conventional methods, such as GC-ECD (gas chromatograph with an electron-captured detector) and GC-MS (gas chromatograph-mass spectrometry), require extensive analysis time (several days per sample) and are not suitable for the above requirements.Recently, the development of the pulsed-laser technique has enabled us to measure aromatic hydrocarbons quite rapidly. In particular, the LI-TOFMS technique is expected to be a powerful method for on-line, selective and sensitive measurements. In the work reported here, real-time (1 min) LI-TOFMS measurements were carried out on gaseous 2 -4 chlorinated PCBs. With respect to laser ionization (as the key technology underpinning this method), in particular, the efforts to determine the laser wavelength and the pulse duration for PCB ionization resulted in the establishment of a technique having sufficient sensitivity (< 0.01 mg/Nm 3 ) for real-time PCBs measurements. Principle 2·1 Laser ionizationThe laser ionization principle used in this study is known as resonance-enhanced two-photon ionization. 6-10 A three-level ionization model (energy diagram) 27,28 is presented in Fig. 1, illustrating the principle behind this method. Here, X indicates the ground state of a molecule, R the exited state, and C the ionization potential. Molecules are excited to induce the R⇔X transition and ionized by the C←R transition. The notation "a" is the rate constant for the R⇔X transition, and "b" is that for the R←C transition. These are related to the number of photons (F) in terms of a∝F and b∝F. Notation kr is the rate constant for spontaneous emission, while knr indicates that for the nonradiative decay processes in state R. In the present study, Real-Time Measurements of Polychlorinated Biphenyls Using Laser Ionization Time-of-Flight Mass SpectrometryShinsaku DOBASHI, † Yoshihiro DEGUCHI, Takahiro KUBOTA, and Katsuhiko SHINODA Nagasaki Research and Development Center, Mitsubishi Heavy Industries Ltd., Japan Polychlorinated biphenyls (PCBs) are hazardous compounds for which there are few methods involving real-time measurement. Recently, the development of the pulsed-laser technique has enabled us to measure aromatic hydrocarbons quite rapidly. In particular, the LI-TOFMS (laser ionization time of flight mass spectrometry) technique is expected to be a powerful method for on-line, selective and sensitive measurements. In the context of developing a highly selective and sensitive technique, the effective laser wavelength and pulse du...
As the cathode materials in conversion-type lithium ion batteries, transition-metal chlorides are well-known to easily dissolve in many organic solvents. However, the LiPF 6 /methyl difluoroacetate (MFA; CHF 2 COOCH 3 ) electrolyte is effective in suppressing the dissolution of the CuCl 2 electrode, as reported for a Li/CuCl 2 battery. This effect did not arise in the MFA solvent without LiPF 6 , but did on slightly dissolving LiPF 6 in the MFA solvent. This was because a very small amount of film was formed on the surface of the CuCl 2 electrode due to the addition of the small amount of LiPF 6 , and the film was composed of copper fluoride hydroxide, partial release of Cl from CuCl 2 , and CuCl.
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