INFRARED PHOTOTHERMAL DEFLECTION SPECTROSCOPY - A NEW PROBE FOR THE INVESTIGATION OF ELECTROCHEMICAL INTERFACES

An infrared photothermal deflection spectroscopy system has been devel oped using infrared tunable diode lasers in the wavelength region from 8 to 16 mu m. This system allows the collection of in situ optical ab sorption spectra of species at electrode/electrolyte interfaces in an electrochemical cell. The infrared spectra of LiOH and Li2CO3 formed o n the surface of a lithium foil were recorded. The infrared phototherm al deflection spectroscopy technique has been used to monitor the lith ium electrode surface in an operating cell, Li/P(EO)(2)LiN(CF3O2)(2)/N i. The in situ spectra (in the 800-1000 cm(-1) region) show that the f ilm formation at Li/polymer electrolyte interfaces is dominated by LiO H, although there also appears to be organic species in the surface fi lm.