Hierarchical assembly of Ti(iv)/Sn(ii) co-doped SnO2 nanosheets along sacrificial titanate nanowires : Synthesis, characterization and electrochemical properties

Hierarchical assembly of Ti(iv)/Sn(ii)-doped SnO₂ nanosheets along titanate nanowires serving as both sacrificial templates and a Ti(iv) source is demonstrated, using SnCl₂ as a tin precursor and Sn(ii) dopants and NaF as the morphology controlling agent. Excess fluoride inhibits the hydrolysis of SnCl₂, promoting heterogeneous nucleation of Sn(ii)-doped SnO₂ on the titanate nanowires due to the insufficient oxidization of Sn(ii) to Sn(iv). Simultaneously, titanate nanowires are dissolved forming Ti⁴⁺ species under the etching effect of in situ generated HF resulting in spontaneous Ti⁴⁺ ion doping of SnO ₂ nanosheets formed under hydrothermal conditions. Compositional analysis indicates that Ti⁴⁺ ions are incorporated by substitution of Sn sites at a high level (16-18 at.%), with uniform distribution and no phase separation. Mössbauer spectroscopy quantified the relative content of Sn(ii) and Sn(iv) in both Sn(ii)-doped and Ti(iv)/Sn(ii) co-doped SnO ₂ samples. Electrochemical properties were investigated as an anode material in lithium ion batteries, demonstrating that Ti-doped SnO₂ nanosheets show improved cycle performance, which is attributed to the alleviation of inherent volume expansion of the SnO₂-based anode materials by substituting part of Sn sites with Ti dopants. © The Royal Society of Chemistry 2013.