Crystalline Sb or Bi in amorphous Ti-based oxides as anode materials for sodium storage

A simple synthesis has been developed for watermelon-like nanocomposites with Ti-based oxides as the matrix. Using the case of Sb nanocrystals in amorphous TiPOx as an example, in-situ/ex-situ techniques, first-principle calculations and control experiments confirm that the formation of Ti-based oxides promotes the reduction of Sb3+ to Sb by NH3 at an elevated temperature. A similar synthesis process also succeeds for Sb nanocrystals in amorphous TiO2 and for Bi nanocrystals in amorphous TiPOx, confirming the promising potential of this synthesis. More importantly, the nanocomposite composed by crystalline Sb in an amorphous TiPOx matrix, as the anode material for sodium storage, concurrently exhibits a long cycle life (similar to 1000 cycles) and a high capacity retention (similar to 82%), suggesting the advantages of watermelon-like structures.