Morphologies and structures of carbon coated on Li4Ti5O12 and their effects on lithium storage performance

• Morphologies and structures of coated carbon on Li4Ti5O12 are investigated.
• Porous carbon coated Li4Ti5O12 exhibits excellent lithium storage performance.
• The porous carbon layer can be easily prepared via a pre-coating route.

Three Li4Ti5O12/C composites (LTO/C) with diverse carbon morphologies and structures were synthesized via a simple solid-state method, along with carbon coating performed at different periods. The morphologies and structures of the coated carbon were characterized by means of electron microscopy and Raman spectroscopy. Effects of varied coated carbon on lithium storage performance, especially high rate capability of LTO/C composites were investigated. The results revealed that the porous and homogeneous carbon layer was more facile to achieve the balance between the good electron conduction and Li ion diffusion than the island-like carbon layer and the compact one, and thus the corresponding LTO/C composite exhibited more excellent electrochemical performance. At low current rate of 0.2 C, its reversible capacity was as high as 171 mAh g−1. At 5 C, the high capacity of 150 mAh g−1 had no loss after 300 cycles. Especially at the high charge/discharge rate of 30 C, the reversible capacity still kept a high level of 82 mAh g−1.