Insights into the Li+ storage mechanism of TiC@C-TiO2 core-shell nanostructures as high performance anodes

Abstract

Titanium carbide @ carbon-doped titanium dioxide (TiC@C-TiO2) core-shell nanostructures are designed, prepared and demonstrated for the application in lithium ion battery anode. Synthesis of these specific core-shell nanostructures is achieved via a facile, novel, and one-pot approach using oxidative growth of C-TiO2 onto TiC nanoparticles, which has a higher electrochemical activity than those of pure P25 and TiC nanoparticles. The core-shell nanostructured anodes exhibit a high lithium storage capacity (352.8 mAh g−1 at 100 mA g−1), good rate capability (253.6 mAh g−1 at 1 A g−1, 158.1 mAh g−1 at 10 A g−1), and outstanding cycle stability in lithium ion batteries (LIBs) (~ 150 mAh g−1 at 10 A g−1 after 400 cycles), which is about 48 times and 7 times higher than that of TiO2 electrode (~ 3.3 mAh g−1 at 10 A g−1) and TiC (~ 25 mAh g−1 at 10 A g−1). According to the first-principle calculation, the ultrahigh capacity and cycle stability of the as-prepared anode is ascribed to the enhancement of Li+ absorption and diffusion ability through formation of C-TiO2 porous layer onto the conductive TiC particles. Moreover, the increase of electron density around the Fermi level is found to be mainly caused by the core-shell nanostructures. The results demonstrate that the presence of TiC plays an important role in providing high conductivity and the novel core-shell nanostructure can buffer the huge volume expansion and contraction during prolonged cycling, resulting in great potential applications in LIBs.