Hollow triple-shelled SiO2/TiO2/polypyrrole nanospheres for enhanced lithium storage capability

We demonstrate the hollow triple-shelled SiO 2 /TiO 2 /polypyrrole (Ppy) nanospheres (NSs), which are readily synthesized through the hard templating method and sequential vapor deposition polymerization (VDP), for application in lithium ion battery (LIB) anodes. The resultant NSs with a hetero-composition show a uniform hollow spherical nanomorphology consisting of SiO 2 , TiO 2 , and Ppy layers, as verified by the Si, Ti, C, and O signals of the STEM images. The hollow SiO 2 /TiO 2 /Ppy NSs have about a threefold higher capacity of 433 mA h/g compared to 147 mA h/g of TiO 2 at a specific current of 44 mA/g, which is close to the theoretical value of TiO 2 . In particular, the hollow triple-shelled NSs exhibit good rate (76% capacitance retention in the range of 44−440 mA/g) and cyclic (98% in the fifty cycles) performances due to the reversible redox reaction occurring on the Ppy outer shell. The enhanced performance of the SiO 2 /TiO 2 /Ppy NSs is attributed to the synergistic effect of the 0D nanostructure and hetero-composition.