Trigonal Na₄Ti₅O₁₂Phase as an Intercalation Host for Rechargeable Batteries

Abstract

Trigonal Na4Ti5O12 with a tunnel-structured three-dimensional framework was first examined as an anode material for Li ion batteries. The nanosized Na4Ti5O12 was synthesized at 600 degrees C using the solid state method with carbon-coated nanosized TiO2 anatase. Carbon layers on TiO2 play an important role of inhibiting the growth of Na4Ti5O12 particles. Li ions are reversibly de/intercalated in the Na4Ti5O12 structure, and this shows the reversible capacity of ca. 100 mA h g(-1) with no capacity fading over 100 cycles. During the repeated charge and discharge, the ion exchange between Na ion and Li ion happens to form LixNa4-xTi5O12, and this causes an increase of the relative tunnel size due to smaller Li ion, resulting in decreasing polarization of voltage profiles. Also, trigonal Na4Ti5O12 was additionally examined as an anode for Na ion batteries.