A robust strategy for crafting monodisperse Li4Ti5O12 nanospheres as superior rate anode for lithium ion batteries

The ability to synthesizing monodisperse Li4Ti5O12 (LTO) nanospheres is the key to reducing the irreversible capacity of LTO materials, and thus improving their power performance. However, it remains a grand challenge to achieve uniform precursors of LTO nanospheres and maintain their spherical structures after annealing. Herein, we develop a robust strategy for the synthesis of monodisperse LTO nanospheres with an average diameter of 120nm via the use of titanium nitride (TiN) as a titanium source for lithium ion batteries (LIBs). The precursors composed of uniform TiO2/Li+ nanospheres were formed in a stable alkaline environment during the course of heating of the solution of peroxo-titanium complex as a result of the dissolution of TiN, while TiO2/Li+ microspheres were easily yielded with the decrease in pH value of the precursor solution. The OH− anion was found to effectively retard the hydrolysis of peroxo-titanium complex as well as the aggregation of TiO2/Li+ nanoparticles. Intriguingly, a uniform polyvinyl pyrrolidone (PVP) layer formed in-situ on the surface of TiO2/Li+ nanospheres rendered LTO to retain the monodisperse spherical morphology after annealing. Notably, the as-prepared monodisperse LTO nanospheres comprised of the interconnected LTO nanograins with an average size of ~15nm uniformly coated by a carbon layer derived from the carbonization of PVP exhibited a high tap density (1.1gcm−3) and an outstanding rate-cycling capability. The charge specific capacities at 1, 10, 50 and 80C were 159.5, 151.1, 128.8 and 108.9mAh g−1, respectively. More importantly, the capacity retention after 500 cycles at 10C was as high as 92.6%. This work opens up an avenue to craft the uniform precursors of LTO and thus monodisperse LTO nanospheres that possess superior rate performance with high volumetric energy densities and long-term cyclic stability.