Hideto Momose

X-ray photoelectron spectroscopy analyses of lithium intercalation and alloying reactions on graphite electrodes

Abstract Electrochemical lithium intercalation reactions occurring in silver-supported graphite anodes were investigated by X-ray photoelectron spectroscopy (XPS). The binding energy of Li(1s) of intercalating lithium was higher than that of lithium metal, which suggests that lithium exists in the form of a positive ion in the graphite layers. The core level of the C(1s) signal of lithium intercalated graphite was higher than that of graphite, which implies that the carbon in lithium-intercalated graphite has a negative charge. This finding agrees with previous XPS studies indicating that carbon has a negative charge in a graphite-intercalation compound produced by a molten lithium intercalation reaction to graphite. Lithium carbonate, lithium fluoride and organic compounds were produced on the graphite surfaces in charge/discharge reactions in 1 M LiPF 6 /EC—DMC electrolytic solution. It was also confirmed that the initial charge current supplied to the graphite electrode with a potential between 2.8 and 0.6 V did not cause a lithium-intercalation reaction. It caused, however, other reactions such as decomposition of the electrolytic solution and production of passivating films.

Polarization-Modulation Emission FT-IR Measurement of Thin Organic Films on Metal Surfaces

A polarization-modulation technique has been combined with Fourier transform infrared (FT-IR) spectrometry to eliminate the large background radiation which interferes with the infrared emission from thin organic films on metal surfaces. A step scan and a continuous scan interferometer which were combined with a photoelastic modulator were also studied, and the step scan system was found to be stabler and have a better S/N. The spectrum of a 12-nm perfluoropolyether film was obtained at 120°C by this system.