Effect of Titanium Content in MWCNT@Sn_1-xTi_xO₂ Composites on the Lithium Ion Storage Process

We report the synthesis of multiwall carbon nanotubes@metal oxide composites (MWCNT@Sn_1-xTi_xO₂) and explore the lithium storage capacity and mechanisms in a broad range of compositions. The composite structures were synthesized by hydrothermal method using SnCl₄ and TiCl₄ as Sn and Ti sources, respectively. Oxide adherence on the carbon surface, as well as an optimum ratio between surface area and porosity, seem to be promoted by Sn content, with MWCNT@Sn_0.75Ti_0.25O₂ showing the best performance in terms of Li capacity and structure stability. Cycled in a potential range of 3 to 1 V vs Li/Li⁺, the composite shows an insertion mechanism reported for solid solutions with low Sn content, whereas at cut off potential of 0 V vs Li/Li⁺ the alloying mechanism expected for SnO₂ is dominant. Nevertheless, the presence of Ti during the transformation of the solid solution impacts positivily the performance of these electrodes.