Interfacial reaction between electrode and electrolyte for a ramsdellite type Li2+xTi3O7 anode material during lithium insertion

The material stability of ramsdellite type Li2+xTi3O7 has been investigated from the view of the correlation between structural and electrochemical behaviors during Li insertion and extraction. The interfacial reaction of Li2+xTi3O7 is identified by using AC-impedance spectroscopy and various electrochemical measurements are carefully conducted to interpret each elemental reaction of the complicated interfacial reaction. The impedance spectra indicate three semi-circles in the frequency range from 1 MHz to 5 mHz which fit expectations well. Li+ insertion at the interface is explained by applying the adatom model that includes desolvation and absorption of lithium ions through electron transfer and lattice incorporation.

► The interfacial reaction of ramsdellite type Li2+xTi3O7 is identified by using AC-impedance spectroscopy.
► The structural variation and electrochemical properties of Li2+xTi3O7 were investigated to confirm the material stability.
► Li+ insertion process of Li2+xTi3O7 is a topo-chemical reaction without side reactions.
► Interfacial reaction of Li2+xTi3O7 is explained by the adatom model.
► Material stability would be important to understand complicated reactions of interfacial reactions.