(201x) 3D Graphene-Carbon Nanotube-Fe3O4 anode for High-Performance Li-Ion Batteries

With the increase in global demand for renewable energy, interest in lithium-ion batteries (LIBs) has increased because of their low self-discharge rate and high energy density. Current LIBs utilize graphite-based anodes that are plagued with relatively low theoretical specific capacity (372 mAh g^-1) and capacity fading during cycling. Using a composite of metal oxide nanoparticles and nanocarbon-based materials, an improved capacity and durability can be observed. Here, we have used iron oxide (Fe₃O₄) nanoparticles because they have a high theoretical capacity, low toxicity, and are relatively inexpensive. However, a drawback of using Fe₃O₄ nanoparticles is that pulverization of the cell components occurs due to the volume expansion that arises during cycling. If not paired with another material which can accommodate the volume expansion of the Fe₃O₄ nanoparticles, the capacity of the cell decreases significantly with each cycle the cell. Graphene and carbon nanotubes (CNTs) were both utilized to fabricate a hybrid current collector due to their high electrical conductivity and ability of resulting structure to support high rate capability. The combination of graphene and CNTs act as a framework to accommodate the volume expansion of the Fe₃O₄ nanoparticles. In our work, porous and wrinkled Fe₃O₄/graphene/CNT anode material was prepared via a wet-chemical reaction and novel magnet-induced method. The highly porous/wrinkled structure of the anode exhibits enhanced reversible capacity accompanied by stable cyclability due to the increased surface area and high theoretical capacity of Fe₃O₄ (920 mAh g^-1), as well as a buffer region offered by the graphene/CNT network that accommodates the volume expansion.