New insight into the atomic-scale bulk and surface structure evolution of Li4Ti5O12 anode.

Identifying the structure of electrodes at atomic-scale remains a key challenge but is a fertile realm for groundbreaking fundamental research in the advanced Li-ion battery material field. In this context, the subtle structure evolution taking place during lithiation/delithiation in the bulk/surface of Li(4)Ti(5)O(12) spinel (LTO) was probed using scanning transmission electron microscopy and found to undergo significant structure torque, namely Ti-O bond stretching/shrinking at different state-of-charge (SOC), which is not identified previously. This kind of nanostructure change plays an important role in facilitating the formation of capturing centers for the electron/hole pairs in a 3.80 eV insulating material as is LTO. Furthermore, with the aid of electron energy loss spectroscopy, the spontaneous charge transfer process, Ti(3+) ↔ e(-) + Ti(4+), was confirmed in the fully lithiated Li(7)Ti(5)O(12) surface as an essential step of the gas-releasing phenomenon. This new insight paves the way toward deeper comprehension and ultimately control of the electrochemical process for this and other important Li-ion battery materials.