Flower-like Li4Ti5O12 hollow microspheres consisting of nanosheets are prepared via a hydrothermal process, and subsequently wrapped by graphene through electrostatic interactions. In comparison with pristine Li4Ti5O12, Li4Ti5O12@graphene exhibited higher capacities and improved rate capability in the 0.01-3.0 V or 1.0-3.0 V potential range. Li4Ti5O12@graphene composite shows specific capacity of 272.7 mAh g(-1) at 750 mAg(-1) after 200 cycles in the potential range from 0.01 to 3.0 V, while the pristine Li4Ti5O12 only delivered a discharge capacity of 235.6 mAh g(-1). The improved electrochemical performances of Li4Ti5O12@graphene should be attributed to lower charge-transfer resistances, larger lithium-ion diffusion coefficient and lower activation energy. The electrons transfer at Li4Ti5O12/graphene heterojunction interface, originating from difference in the work function of two composites, reduces the localized work function of the composites, decreases energy required for electrons to escape and consequently results in the improved electrochemical performances.

lithium-ion batteries; lithium titanium oxide; graphene; diffusion coefficient; Work function

Fujian Normal University