Significant Enhancement of Lithium Intercalation Into Mesoporous Titania with Trace TiO2-B On Surface

TiO₂ is expected to play an important role in addressing the problems of clean energy supply and global warming on account of its promising applications in photovoltaics, photocatalytic oxidation and splitting of water. It is well recognized that in order to implement these applications, TiO₂ should own a large surface area, a high crystallinity and high thermal stability simultaneously. Our group has developed a template-free method to fabricate mesoporous Titania (m-TiO₂) nanofibers with all these properties. Trace TiO₂-B was proved by high resolution transmission electron microscopy and Raman spectra. However, its contribution in terms of performance was not perfectly specified.

 

In this work, we report on lithium-ion intercalation/deintercalation reaction in two differrent m-TiO₂ with or without trace TiO₂-B and find significant intercalation increasement of m-TiO₂ with trace TiO₂-B on surface. TiO₂-B is a metastable monoclinic polymorph of TiO₂ different from anatase. Its open structure, characterized as large and continuous channels, makes it well suited as a host for Li⁺ ion intercalation. It can be seen that the cyclic voltammetry of m-TiO₂ exhibits a pair of cathodic/anodic peaks at 1.70 and 2.05V, which are attributed to lithium-ion intercalation/deintercalation reaction in anatase phase. In addition to that, the voltammogram of m-TiO₂ with trace TiO₂-B shows another two pairs of peaks with formal potentials in the range of 1.5-1.6 V vs. Li⁺/Li, respectively. This notation can be assigned to the reaction of lithium-ion intercalation/ deintercalation reaction in TiO₂-B phase lattice. The first discharge capacity of m-TiO₂ with trace TiO₂-B can reach up to 247 mA·h·g^-1 at the current rate of 130 mA·g^-1 which is about 50 mA·h·g^-1 higher than that of m-TiO₂ without TiO₂-B. Stable cycling discharge capacity attains 170 mA·h·g^-1 at the discharge rate of 155 mA·g^-1 and 110 mA·h·g^-1 even up to 4000 mA·g^-1. These findings indicate that m-TiO₂ with trace TiO₂-B on surface represents a promising material in lithium ion delivery and storage.