Spectroelectrochemistry by Confocal Raman Microspectrometry

Confocal Raman Microspectrometry is shown to be a powerful technique to study electrochemical devices under working conditions with a spatial resolution of about l μm3. This is first illustrated on a Li/P(EO)20, LiTFSI/Li symmetrical cell where salt concentration gradients in the polymer electrolyte are measured as a function of current density and time. These data give access to transport properties of the polymer electrolyte, namely transport numbers and diffusion coefficients. A second example is provided by electrostatic supercapacitors using activated carbon fabrics of high specific surface area and proton conducting liquid electrolytes. A mapping of a carbon fiber and of the surrounding electrolyte is recorded for ± IV polarizations. The relative intensity and the frequencies of the D and G Raman lines of carbon are found to be very sensitive to the carbon charge.