The transformation of anatase TiO2 to TiSe2 to form TiO2–TiSe2 composites for Li+/Na+ storage with improved capacities

Abstract

Titanium diselenide (TiSe₂) is a very attractive two-dimensional (2D) semiconductor material which is significantly different from titanium dioxide (TiO₂). In this regard, various strategies have been developed to synthesize TiSe₂ to improve the electrochemical properties of TiO₂ based composites towards Na⁺/Li⁺ storage. In this paper, we fabricated TiO₂–TiSe₂-carbon nanofibers (denoted as TiO₂–TiSe₂-CNFs) by simple electrospinning, carbonization and selenylation procedures. It was found that anatase (TiO₂-A) can be converted to TiSe₂ under certain conditions while rutile cannot. As anodes for sodium ion batteries (SIBs), TiO₂–TiSe₂-CNFs showed a specific capacity of 230 mA h g⁻¹ over 600 cycles at a current density of 0.1 A g⁻¹. As anodes for lithium ion batteries (LIBs), their initial discharge capacity was 749 mA h g⁻¹ at 0.1 A g⁻¹. Moreover, the reversible capacity can retain 470 mA h g⁻¹ after 200 cycles, showing high capacity and good stability. The discovery of the transformation of anatase to TiSe₂ may provide a new insight into the synthesis and application of TiSe₂ and TiO₂.