CNT branching of three-dimensional steam-activated graphene hybrid frameworks for excellent rate and cyclic capabilities to store lithium ions

The hierarchically architectured graphene-based materials are considered as a promising active or supporting material for the lithium ion batteries (LIBs). However, it faces critical challenges of the limited stored capacity, the mechanical brittleness, and the contact resistance. Herein, we demonstrate the unique hierarchical structures, where carbon nanotubes (CNTs) are branched onto the modified surfaces of three-dimensional (3D), steam-activated reduced graphene oxide (sRG-O) frameworks, prepared by self-assembly, steam activation, and microwave methods. The surface sites of 3D sRG-O are critical for controlling crystalline structure and deposition density of Fe3O4 nanoparticles through a microwave induced synthesis, as well as for providing a large surface area and conducting pathway. Simultaneously, the bamboo-like CNT branches are grown on the Fe3O4 nanoparticles acting as catalysts to stabilize and conductively connect 3D sRG-O/Fe interparticles for the enhanced rate and cyclic performances of LIB. Such a unique structure consisting of 1D nanostructure branched on the activated surface of 3D macroporous structure with decoration of OD nanoparticles provides high specific capacity of 1757 mAh g(-1) at 50 mA g(-1), good rate capability of 73.31% at 1000 mA g(-1), and gradual increase from 1490 to 2890 mAh g(-1) after 100 cycles. (C) 2017 Elsevier Ltd. All rights reserved.