SiO has been extensively studied as a high-capacity negative electrode material for lithium-ion batteries (LIBs). However, battery performance degradation caused by the large volume change during the lithiation/delithiation hinders the...

Si is a promising anode material for lithium-ion batteries owing to its high theoretical capacity; however, due to its large volume fluctuation during lithiation/delithiation, significant decay in capacity occurs during charge–discharge cycling. Therefore, the selection of appropriate lithiation/delithiation conditions is important to suppress capacity decay. In this study, the cycling performance of silicon-based composite electrodes prepared using a cross-linked polyacrylate binder was examined at different cutoff voltages, and the degradation of the electrolyte and electrodes was investigated through gas chromatography–mass spectrometry (GC-MS) and synchrotron radiation X-ray photoelectron spectroscopy. When silicon–graphite (Si–G) electrodes were examined in a Li cell (with Li metal counter electrode), a rapid decrease in discharge capacity and Coulombic efficiency was observed at delithiation cutoff voltages of >0.7 V, which was attributed to the complete consumption of the electrolyte additive, fluoroethylene carbonate (FEC). After the decrease in FEC content, the main solvents of the electrolyte, such as ethylene carbonate and dimethyl carbonate, underwent electrolyte decomposition reactions and formed co-oligomers. The GC-MS results revealed that the FEC consumption rate increased with increasing delithiation cutoff voltage. Furthermore, higher cutoff voltage leads to oxidative decomposition and elution of the surface passivation film formed at the electrode surface because of the exposure to high voltage. FEC consumption was insignificant in the Si–G//LiFePO4 Li-ion cell (without Li metal in the cell), indicating that Li metal plating/stripping also consumed the FEC additive. The findings of this study can be used to gain insights into the degradation mechanisms of Si-based electrodes and can therefore act as a basis for research and development of Si-based electrodes for lithium-ion batteries.

An analytical method for the total content of a fungicide, (E)-4-chloro-a,a,a-trifluoro-N-(1-imidazole-l-yl-2-propoxyethylidene)-o-toluidine (triflumizole), and its metabolites in crops is described. Triflumizole and its metabolites having the 4-chloro-a,a,a-trifluoro-o-toluidine moiety in crops are converted to a derivative, 4-chloro-a,a,a-trifluoro-otoluidine, by hydrolyses in an acetate buffer solution, and then a sodium hydroxide solution; the derivative is cleaned by distillation, column chromatography and then determined by either high performance liquid chromatography or gas chromatography.The limit of detection was set at 0.02 ppm. The recoveries ranged from 69 to 97%. Many kinds of crops sprayed with triflumizole were analyzed by both the individual analytical method for triflumizole and its main metabolite and the total analytical method; the amounts of residues were compared. When samples having a short preharvest interval were analyzed, the obtained residue values from both methods were almost the same. In order to establish the tolerances from the maximum residue value for each crop, analyses by the individual analytical method are considered to be sufficient.

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