Multiple reinforcement effect induced by gradient carbon coating to comprehensively promote lithium storage performance of Ti2Nb10O29

Abstract

The synchronous improvement of ionic diffusivity and electronic conductivity of Ti2Nb10O29 (TNO) is of enormous significance for boosting its high electrochemical performance. In our work, a novel gradient carbon coating strategy was first proposed to synthesize the pomegranate-type N-doped carbon coated TNO microspheres (TNO@NPC), in which not only TNO microspheres but also TNO secondary nanoparticles surfaces are uniformly coated with an ultrathin carbon film. The study results demonstrate that such ingenious configuration can combine conductive coatings, nanocrystallization technology, and defect engineering together to greatly improve the ionic diffusivity and electronic conductivity. Moreover, the carbon coatings as the armor can effectively inhibit the volume change of TNO, and thus enhance its cycling durability. Density functional theory (DFT) calculations were also employed to illustrate the nature influence on lithium-ion diffusion coefficient and electronic conductivity. Attributing to the synergistic effect, the TNO@NPC exhibit superior rate capability (328 mA h g−1 at 0.1 C and 258 mA h g−1 at 10 C) and remarkable cyclability (210 mA h g−1 at 10 C after 1000 cycles) in half-cells. The full-cell of LiFePO||TNO@NPC also show notable rate capability (271 mA h g−1 at 0.2 C and 211 mA h g−1 at 10 C) and remarkable cyclability (178 mA h g−1 at 10 C after 1000 cycles). This ingenious structural design may provide a new direction for the construction of other high-quality electrodes in lithium-ion batteries (LIBs).