Three-Dimensional Network Microstructure Design of the Li4Ti5O12/rGO Nanocomposite as an Anode Material for High-Performance Lithium-Ion Batteries

Abstract

At present, the wide commercial application of Li4Ti5O12 (LTO) is limited as an anode for lithium-ion batteries because of its poor conductivity and lower rate performance. In this paper, LTO nanoparticles were embedded in a reduced graphene oxide (rGO) conductive network by an in situ electrostatic self-assembly effect using a simple hydrothermal reduction method. The microstructure and electrochemical performance of the LTO/rGO composite were investigated. The highlighted results showed that LTO nanoparticles were combined with rGO nanosheets by a Ti–O–C covalent bond, which was more stable than other bonding methods. At the same time, the addition of rGO not only enriches the structure and increases the specific surface area but also effectively prevents the agglomeration of LTO. The higher conductivity of LTO nanoparticles was bestowed by the rGO three-dimensional (3D) network, causing structural stability and high electrochemical performance. The LTO/rGO composite has high first discharge capacity (643.9 mAh/g at 0.5C), remarkable rate performance (290 mAh/g at 10C), and excellent cycle stability (271.7 mAh/g after the 1000th cycle at 10C) when tested in a half battery. Furthermore, it has higher discharge capacity (181.8 mAh/g at 1C, the first Coulombic efficiency was 90.1%) and excellent cycle stability (142.8 mAh/g after 500 cycles at 20C) when assembled into a full battery as the anode with commercial LiFePO4 (LFP) as the cathode. The lithium storage mechanism of the LTO/graphene composite was further discussed by first-principles calculations. With the addition of graphene to LTO, the electron transport ability was improved and the diffusion energy barrier was reduced. This made the composite expected to become a promising anode material for lithium-ion batteries.