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

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-Ti₃C₂T_x 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-Ti₃C₂T_x 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-Ti₃C₂T_x 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.