Structural evolution of ramsdellite-type Li xTi 2O 4 upon electrochemical lithium insertion–deinsertion (0 ≤ x ≤ 2)

Abstract

Structural evolution during topotactical electrochemical lithium insertion and deinsertion reactions in ramsdellite-like Li x Ti 2O 4 has been followed by means of in situ X-ray diffraction techniques. The starting Li x Ti 2O 4 ( x = 1) exists as a single phase with variable composition which extends in the range 0.50 ≤ x ≤ 1.33. However, beyond the lower and upper compositional limits, two other single phases, with ramsdellite-like structure, are detected. The composition of these single phases are: TiO 2 upon lithium deinsertion and Li 2Ti 2O 4 upon lithium insertion. Both TiO 2 and Li 2Ti 2O 4 are characterized by narrow compositional ranges. The close structural relationship between pristine LiTi 2O 4 and the inserted and deinserted compounds together with the relative small volume change over the whole insertion–deinsertion range (not more than 1.1% upon reduction) is a guaranty for the high capacity retention after long cycling in lithium batteries. The small changes in cell parameters well reflect the remarkable flexibility of the ramsdellite framework against lithiation and delithiation reactions.