Evidence of two-phase formation upon lithium insertion into the Li1.33Ti1.67O4 spinel

Li(1.33)Ti(1.6)7O(4) synthesized from Li2CO3 and TiO2 was electrochemically inserted with lithium at room temperature. The defect spinel Li1.33Ti1.67O4 and the fully lithiated Li2.33Ti1.67O4 with ordered rock-salt-type structure show nearly identical X-ray diffractions. Due to similar lattice constants of both phases and the low scattering factor of the lithium ions, the identification of the insertion mechanism using X-ray powder diffraction is possible only by using high angle X-ray scans of several samples inserted with different amounts of Lithium. Precise analysis of the obtained data supplies the evidence for the presence of two distinct phases which are mutually interconvertible upon lithium exchange. This result is in good agreement with electrochemical data postulating a two-phase mechanism from the constant electrical potential found during cycling. (C) 1999 The Electrochemical Society. S0013-4651(98)06-031-1. All rights reserved.