Impedance spectroscopy of lithium and nickel electrodes in propylene carbonate solutions of different lithium salts A comparative study

This paper reports on the studies of both Li and Ni electrodes in propylene carbonate (PC) solutions containing various Li salts. Impedance spectroscopy and, to a limited extent, surface sensitive Fourier-transform infrared spectroscopy were used. The impedance spectra were modelled by equivalent analogs of resistance-capacitance (RC) circuits in series which is in line with the expected multilayer structure of the Li-solution interphase formed in PC solutions. The calculated C and R values of the various time constants separated by the modelling and related simulation enable the thickness and resistivity of the various films formed to be estimated and their changes upon storage, salt concentration and contamination level to be followed. It was found that the Li salt used has a remarkable impact on the interfacial properties of Li electrodes in these solutions. The comparative study of the surface films formed on Ni electrodes at low potentials in these solutions enabled a better understanding of the ageing process of the surface films formed on Li.