Preparation of a spinel Li4Ti5O12 (1 1 1) surface from a rutile TiO2 single crystal

Spinel Li4Ti5O12 is a very promising material for electrodes in a wide range of Li-ion battery applications because of its unique Li-insertion/extraction properties. Although the bulk properties of Li4Ti5O12 have been studied intensively, there have been few reports about the structure and properties of Li4Ti5O12 surfaces in spite of the importance of solid/electrolyte interfaces. This is because of the difficulty in preparing Li4Ti5O12 samples with accessible flat surfaces suitable for scanning probe microscopy study. To address this, we have successfully prepared a flat Li4Ti5O12 crystal surface by solid state reaction from a rutile TiO2 (1 1 1) wafer with LiOH·H2O powder. Out-of-plane X-ray diffraction (XRD) and transmission electron microscopy revealed that a highly oriented and crystallized Li4Ti5O12 (1 1 1) film was formed on the TiO2 (1 1 1) wafer. Atomic force microscopy observations revealed that an atomically flat Li4Ti5O12 (1 1 1) surface was formed on the film with terraces of 200-300 nm width and steps of a {1 1 1}interplanar height. The formed thin films were also investigated by cyclic voltammetry and galvanostatic experiments, revealing that the films have electrochemical activity as battery electrodes.