Spontaneous Li-Ion Transfer from Spinel Li₄Ti₅O₁₂Surfaces: Deterioration at Li₄Ti₅O₁₂/Electrolyte Interfaces Stored at Room Temperature

Spinel lithium titanium oxide (LTO; Li 4 Ti 5 O 12 ) is one of attractive negative electrode materials for high-performance lithium-ion batteries. We studied the changes of LTO-electrode surfaces in contact with liquid electrolytes without electrochemical operation, as the basic state of a stored cell. The electrochemical properties of the LTO-crystal electrode were greatly deteriorated after soaking in a liquid electrolyte (1 M LiPF 6 in PC) for 2 weeks at room temperature. Spinel LTO structure was changed into rock-salt like structure at the surface region. The chemical compositions of Li and O were decreased at the surface region, suggesting spontaneous Li + and O 2− transfer from the LTO surface. The present structural and chemical changes of the surface region was explained as disordered-spinel phase generation with less Li-ion conductivity.