Effects of Graphene Quality on Lithium Storage Performances of Fe3O4/Thermally Reduced Graphene Oxide Hybrid Anodes

Till now, there are no systematic reports on the effect of the quality of thermally reduced graphene oxide (TRG) on lithium storage properties, as the reported methods to fabricate graphene-based electrodes are usually not effective enough to reduce graphene oxides to graphene. Herein, graphite oxide is thermally exfoliated and annealed with a high-temperature graphitization oven at different temperatures (800-2000 degrees C). A series of Fe3O4/TRG hybrids are synthesized as anode materials for lithium-ion batteries with TRGs acting as substrates of in-situ formed Fe3O4 nanoparticles. Both, the electroconductivity of the TRGs and their interfacial interaction with Fe3O4 influence the lithium storage performances of the hybrids. However, the electroconductivity of the TRGs and the formation of interfacial bonds are conflicting. Because the oxygen-containing groups and defects of TRG are greatly removed leading to enhanced electrical conductivity with the increase of thermal annealing temperature. Hence, the resulting Fe3O4/TRG hybrids show first decreased then increased electrochemical performances with increasing annealed temperatures. In a word, the effect of interfacial interaction is dominant at a relatively low annealing temperature, while the effect of conductivity is dominant at a relatively high annealing temperature. The optimized hybrids exhibit excellent cycling and rate performances. This work should provide useful information for the rational design and construction of high-performance electrodes for energy storage applications.