Atomistic phase transition mechanism of zero-strain electrode material: Transmission electron microscopy investigation of Li₄Ti₅O₁₂ spinel lattice upon lithiation.

This article focuses on the atomistic phase transition mechanism of spinel Li₄Ti₅O₁₂ (LTO), a zero-strain electrode material used in Li-ion batteries, investigated via high-resolution transmission electron microscopy (TEM). The study reveals that during lithiation, lithium atoms shift asymmetrically from tetrahedral (8a) to octahedral (16c) sites within the spinel lattice, causing anisotropic changes in the {022} lattice fringes, indicative of spontaneous symmetry breaking in the phase transition. The authors prepared single-crystalline LTO (100) specimens and induced lithiation in situ through electron-beam-assisted methods, enabling direct observation of the phase transition from spinel to rock-salt structures. The findings suggest that anisotropic lithium ordering during lithiation is a fundamental characteristic of LTO's zero-strain behavior, providing insights into its stable charge–discharge performance in battery applications.