Surface-enhanced Raman scattering study on passivating films of Ag electrodes in lithium batteries

Li/Ag and Li/Al electrochemical cells composed of smooth Ag or Al electrode sheets, respectively, and matched with nonaqueous electrolytes were assembled and discharged. Discharged Ag electrodes were investigated using micro-Raman spectromety. Raman bands attributed to the components of the passivating film on the surface of the discharged Ag electrode, such as Li2CO3 and other species, were observed. No characteristic bands from discharged Al electrodes were present in the Raman spectra. This indicates that the Raman signals for the passivating layer are surface-enhanced by discharged Ag electrodes. The formation of a nanometer-scale rough surface caused by a Li-Ag alloy reaction during the discharging process is an important factor in the enhancement. It was also shown that the passivating films formed in various electrolytes could be distinguished by SERS.