Two-dimensional graphene-based Li4Ti5O12 with hierarchical pore structure and large pseudocapacitive effect as high-rate and long-cycle anode material for lithium-ion batteries

Abstract

Spinel lithium titanate (Li4Ti5O12) is deemed as a promising anode material for high-rate and long-cycle lithium-ion batteries, but its practical application is hindered by its poor electrical conductivity and relatively low capacity. In this work, large-scale two-dimensional (2D) graphene-based Li4Ti5O12 with hierarchical pore structure is fabricated by controllable synthesis of amorphous TiO2 nanofilms on graphene and subsequent conversion to nanoparticle-assembled Li4Ti5O12 nanosheet by reaction with LiOH at high temperature. The small nanoparticle composition (6∼10 nm) and designed micro-mesopores (1.3∼1.6 and 2.7∼3.4 nm) of Li4Ti5O12 nanosheets not only facilitate the Li+ diffusion, but also offer a large interface for Li+ adsorption and provide considerable pseudocapacitive Li storage for Li4Ti5O12. Meanwhile, the graphene substrate serves as conductive support and preserves this 2D shape structure during cycling. Therefore, this hierarchically structured Li4Ti5O12 composite exhibits superior reversible capacity and cycling stability at high rates (e.g., 168 mA h g-1 at 10 C after 1000 cycles). This newly developed method can be employed in the design of high-performance 2D structural materials for energy storage and conversion devices.