Study of the insertion mechanism of lithium into anatase by operando X-ray diffraction and absorption spectroscopy

• Analysis of Li + insertion mechanism of anatase via operando XRD and XAS
• Three domains of lithium insertion into anatase were identified by XRD.
• Electronic and local structure changes were monitored by XANES.
• EXAFS reveals modification of local structure during biphasic transformation domain.
• No tetragonal LiTiO2 is formed although > 0.7 Li + was inserted.

Operando X-ray diffraction (XRD) and X-ray absorption (XAS) were used to study Li+ insertion into TiO2 anatase during electrochemical cycling in a Li cell. The evolution of long range order and local structure with the amount of lithium reacted were analyzed to identify and characterize the individual insertion domains. These results agree with a three-step insertion process, firstly solid solution, followed by characteristic biphasic plateau corresponding to the transformation from tetragonal to orthorhombic phase which is succeeded by a monophasic insertion.