Fabrication of Li 4 Ti 5 O 12 -TiO 2 Nanosheets with Structural Defects as High-Rate and Long-Life Anodes for Lithium-Ion Batteries.

Development of high-power lithium-ion batteries with high safety and durability has become a key challenge for practical applications of large-scale energy storage devices. Accordingly, we report here on a promising strategy to synthesize a high-rate and long-life Li4 Ti5 O12 -TiO2 anode material. The novel material exhibits remarkable rate capability and long-term cycle stability. The specific capacities at 20 and 30 C (1 C = 175 mA g-1 ) reach 170.3 and 168.2 mA h g-1 , respectively. Moreover, a capacity of up to 161.3 mA h g-1 is retained after 1000 cycles at 20 C, and the capacity retention ratio reaches up to 94.2%. The extraordinary rate performance of the Li4 Ti5 O12 -TiO2 composite is attributed to the existence of oxygen vacancies and grain boundaries, significantly enhancing electrical conductivity and lithium insertion/extraction kinetics. Meanwhile, the pseudocapacitive effect is induced owing to the presence of abundant interfaces in the composite, which is beneficial to enhancing specific capacity and rate capability. Additionally, the ultrahigh capacity at low rates, greater than the theoretical value of spinel Li4 Ti5 O12 , may be correlated to the lithium vacancies in 8a sites, increasing the extra docking sites of lithium ions.