Hierarchical Graphene Trees As Anode Materials for Lithium Ion Batteries with High Rate Capability

Abstract

We introduce monolithically structured reduced graphene oxide (rGO), prepared from a highly concentrated and conductive rGO paste, as an anode material for lithium ion batteries (LIBs) with high rate capacities. The rGO structure is mechanically robust, flexible, and easy to handle. This is achieved by a mixture of rGO paste and the water-soluble polymer with freeze drying. Unlike previous three-dimensional (3D) graphene porous structures, the monolithic graphene resembles “densely branched pine trees” and have high mechanical stability with strong adhesion to the metal electrodes. They contain numerous large surface area open pores that facilitate lithium ion diffusion, while the strong hydrogen bonding between the graphene layers and SCMC provides high conductivity and reduces the volume changes that occur during cycling. Ultrafast charge/discharge rates were obtained with outstanding cycling stability and the capacities are higher than those reported for other anode materials. The fabrication process is simple and straightforward to adjust and is therefore suitable for mass production of anode electrodes. This approach is also possible for the application of graphene-based anodes for next generation flexible batteries.