Monodisperse core-shell Li4Ti5O12@C submicron particles as high-rate anode materials for lithium-ion batteries

Abstract

Monodisperse spinel Li4Ti5O12 (LTO) particles coated with a carbon layer (LTO@C) are prepared by using a solid-phase sintering reaction between pre-synthesized carbon-coated TiO2 particles and lithium carbonate. The core-shell structured LTO@C particles have an average size of about 320 nm, and a carbon shell thickness of about 10 nm. While the TiO2 particles that are pre-coated with a carbon layer generate LTO@C particles with monodisperse un-aggregated morphology, the TiO2 particles without carbon coating eventually lead to aggregated LTO particles with an irregular morphology. Much better rate performances are observed for LTO@C particles than the un-coated LTO particles. The discharge specific capacity of the typical LTO@C sample is about 165.5 mAh g−1 at 0.1 C and 147.7 mAh g−1 at 20 C. The discharge specific capacity still keeps at 133.6 mAh g−1 after 200 cycles. The results demonstrate that the presence of carbon shell on the surface of TiO2 particles can prevent the particle agglomeration and limit the growth of lithium titanate grains within the space of carbon shell, and finally generate monodisperse un-aggregated morphology which can increase the contact area between the active material and the electrolyte. Furthermore, the uniform carbon shell can establish a conductive network to improve the overall electronic conductivity, which is beneficial to the improvement of the rate performances of LTO anodes for the applications of lithium-ion batteries.