Hierarchical Li₄Ti₅O₁₂-TiO₂ composite microsphere consisting of nanocrystals for high power Li-ion batteries

Highly mesoporous lithium titanate hierarchical microspheres (LTO-HS) consisting of nanosized octahedron-like crystals were innovatively designed as high performance and safe anode materials for lithium ion battery applications. This unique structural control allows us to capitalize on the exemplary surface areas (electrolyte contact) and short Li-ion diffusion path lengths of nanosized particles, while overcoming the challenge of low power tapping density by integrating them into microsized spheres. A thin carbon coating was applied on the surface of LTO-HS (C-LTO-HS) in order to overcome the inherently limited electronic conductivity of these oxide materials. Moreover, this coating technique was found to induce the formation of some anatase TiO₂, resulting in uniquely structured anode materials with active multi-component duality. Notably, the C-LTO-HS composite electrode delivers a remarkable capacity of over 230 mA h g^-1 when discharged at 0.2 C, which is much higher than the theoretical capacity of pure Li₄Ti₅O ₁₂ (175mAhg^-1) and ascribed to the existence of anatase TiO₂ (330mAhg^-1) in the C-LTO-HS structure. Furthermore, this electrode yielded excellent cycling and rate capabilities of about 120 mA h g^-1 (compared to 90 mA h g^-1 for LTO-HS) at a current density of 10 C for up to 100 cycles. These unique mesoporous spheres with deliberately controlled nanostructure arrangements show significant promise as anode materials for lithium ion batteries, fabricated by a simplistic two step hydrothermal procedures, and capable of providing high volumetric energy density and long cycle life.