2D titanoniobate-titaniumcarbide nanohybrid anodes for ultrafast lithium-ion batteries

Abstract Mixed titanium-niobium oxides are considered to be promising anode candidates due to the high theoretical capacity based on the presence of multiple redox couples (Nb5+/Nb4+, Nb4+/Nb3+ and Ti4+/Ti3+). Among them, layered titanoniobates with a two-dimensional (2D) nanosheet structure are expected to expose most surface and near-surface active sites and a minimal Li+ diffusion pathway, and thus could exhibit ultrafast pseudocapacitive dominated lithium storage performance. This work presents the synthesis of 2D HTiNbO5/H-Ti3C2Tx nanohybrid anodes via a combined exfoliation and co-flocculation strategy taking advantage of the ultrathin 2D structure of HTiNbO5 nanosheets and the high electronic conductivity of H-Ti3C2Tx nanosheets. This leads to the random restacking of these two nanosheets and the formation of plane-to-plane contact, insuring excellent transfer kinetics of electrons as well as Li+ ions. Benefitting from such unique 2D lamellar structure, the HTiNbO5/H-Ti3C2Tx nanohybrid anode with an optimized (3:1) mass ratio is able to exhibit fast lithium storage process by delivering a high capacity of 111.5 mAh•g−1 at a current density of 5 A g−1 (∼20.6C). Our results demonstrate the feasibility of such co-flocculation strategy for designing new high-rate anode material, which outperforms the original bulk HTiNbO5 compound, making it a promising candidate for application in ultrafast lithium-ion batteries.