Hybrid nanotubes constructed by confining Ti0.95Nb0.95O4 quantum dots in porous bamboo-like CNTs: superior anode materials for boosting lithium storage

Abstract

Current commercial lithium ion battery (LIB) anodes comprising graphite and Li₄Ti₅O₁₂ inevitably suffer from safety risk and low energy density. Hence, a novel anode material of Ti_0.95Nb_0.95O₄/C hybrid nanotubes was developed via a modified sol–gel method combined with subsequent calcination. The hybrids consist of Ti_0.95Nb_0.95O₄ quantum dots that are homogeneously embedded in the walls of porous bamboo-like CNTs. The high capacity feature of multiple redox couples of Ti–Nb–O based anodes is demonstrated by ex situ XPS in the hybrids. With the advantages of stimulative lithium storage, increased conductivity and robust mechanical properties due to the unique hybrid structure, the hybrids exhibit a high capacity (516.8 mA h g⁻¹ at 0.2 A g⁻¹), superior long-term cycling stability (142.7 mA h g⁻¹ at 5 A g⁻¹ after 3000 cycles) and an ultra-high rate capability (234.6 mA h g⁻¹ at 1 A g⁻¹ and 125 mA h g⁻¹ at 8 A g⁻¹). Meanwhile, the hybrids showed superior electrochemical performance compared with the reported Li₄Ti₅O₁₂ and Ti–Nb–O based anodes. Furthermore, the GITT measurements revealed the fast Li⁺ transport for the charge–discharge processes of the hybrids. Such prominent merits of the Ti_0.95Nb_0.95O₄/C hybrid nanotubes make them more likely candidates that can replace graphite and Li₄Ti₅O₁₂ anodes in LIBs.