Transmission electron microscopy (TEM) analysis of two-phase reaction in electrochemical lithium insertion within α-MoO3
Abstract The mechanism of a phase transition in electrochemical lithium insertion into α-MoO 3 was investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). α-MoO 3 was deposited on a special Au micro grid for TEM observation by pulsed laser ablation. The phase transition ranged from x =0 to 0.25 in Li x MoO 3 upon electrochemical lithium insertion into α-MoO 3 . In this two-phase coexistence region, the XRD (020) line of the lithium inserted phase (Li 0.25 MoO 3 ) grew at the expense of the (020) line of the pristine α-MoO 3 as lithium ions were inserted. However, the intensity of the lithium-inserted phase was much weaker than expected in the initial stage of the phase transition. TEM observation revealed that lithium ions were inserted randomly into some preferred crystallites of α-MoO 3 to form a disordered phase in the initial stage, which explained the presence of the induction period upon the growth of the lithium inserted phase.