Percolating networks of TiO2 nanorods and carbon for high power lithium insertion electrodes

Anatase TiO2 nanorods (NRs), with an average diameter of 3–4 nm and an average length of 25–30 nm were investigated as Li-insertion material. The NRs, capped with oleic acid, were synthesized by a low temperature colloidal route based on thermal decomposition of the precursors in presence of coordinating agents. A highly porous and connective network of NRs and carbon was prepared by taking advantage of this organic capping to inhibit the nanoparticle agglomeration and to act as a precursor for the formation of a carbonaceous percolating network. Composite electrodes, made of such material, were able to deliver reversible capacities of about 250 mAh g−1 (corresponding to 0.75 equiv. of Li per TiO2 unit). Reversible capacities of 210 mAh g−1 (0.63 Li per TiO2), 194 mAh g−1 (0.58 Li per TiO2), 165 mAh g−1 (0.49 Li per TiO2), and 130 mAh g−1 (0.39 Li per TiO2) were observed during cycle tests at 1C, 2C, 5C, and 10C, respectively, confirming the excellent high rate performance of the well-dispersed NRs. Finally, the electrodes showed excellent cycle life performance.

► Congruent TiO2 nanorods are made using an organic capping agent. ► Carbonization of the capping agent leads to the formation of electronically conductive carbon percolating network embedding TiO2 nanorods. ► Electrodes composed of such material show an exceptional combination of high capacity, rate capability and cycle lifetime.