Investigation of electronic and ionic transport properties in α-MoO3 cathode material by electrochemical impedance spectroscopy

Electrochemical impedance spectra (EIS) for lithium ion insertion and extraction in α-MoO₃ cathode material were obtained at different potentials during initial discharge–charge cycle. A significant “three semicircles” were obtained at 0.5 V in the Nyquist diagram, and were assigned to lithium ion migration through solid electrolyte interphase (SEI) film, the electronic properties of the material as well as charge transfer step, respectively. An equivalent circuit that includes elements related to the electronic and ionic transport, in addition to the charge transfer process, is proposed to simulate the experimental EIS data. The variations of the resistance of SEI film, the electronic conductivity of the material and the resistance of charge transfer along with the increase and decrease of electrode polarization potential were quantitatively analyzed, and the reasonable explanation is given. Furthermore, the chemical diffusion coefficients of lithium ion in α-MoO₃ cathode material were calculated.