Direct Fabrication of Densely Packed Idiomorphic Li4Ti5O12 Crystal Layers on Substrates by Using a LiCI-NaCI Mixed Flux and Their Additive-Free Electrode Characteristics

Thin layers of densely packed idiomorphic Li4Ti5O12 crystals were prepared directly on a Pt substrate by using a LiClNaCl mixed flux. The thin film of colloidal anatase nanoparticles with an similar to 30 nm diameter was fully converted into Li4Ti5O12 crystals with a diameter of 100-200 nm having polyhedral shapes with well-defined {111} faces during the evaporation-driven flux growth. Cross-sectional structure analysis revealed that the interface between the crystals and the substrate seemed to be atomically bonded. Galvanometric charge and discharge properties strongly supported our consideration of interface formation. The Li4Ti5O12 crystal layer exhibited a large capacity close to its theoretical value under 0.1C rate with no assistance from additional electroconductive materials and binders, meaning that the interfaces provide seamless charge transportation pathways. We also addressed the formation mechanism of the Li4Ti5O12 crystal layer accompanied by the experimental results of in situ X-ray diffraction, thermogravimetric and differential thermal analysis, and scanning electron microscopy observation.