Lithium Storage Properties Of Graphene-Based Two-Dimensional Nanocomposites

This paper reports new graphene-based two-dimensional nanocomposites as the anode of lithium-ion battery to improve the lithium storage performances, including enhancing lithium storage capacities and cyclabilities. Here, graphene based nanocomposites are synthesized by hydrothermal methods and wet chemical methods, and their enhanced lithium storage properties as lithium-ion battery anodes are obtained because of the structure properties of graphene and the electrochemical properties of metal oxide. This paper is focused on three nanomaterials to illustrate the structure and lithium storage properties of graphene and graphene based nanocomposites.The first one is graphene nanosheet. The pure graphene nanosheets are synthesized by hydrothermal method. The lithium storage properties of graphene are better than that of graphite due to its good structure and electrochemical properties. More importantly, graphene can also be used in composites with metal oxide nanomaterials because graphene layers have large surface-to-volume ratio and broad electrochemical activity.The second one is the composite of SnO2and nanocarbon families. The SnO2/nanocarbon families are synthesized by wet chemical methods. The nanocarbon families in the nanocomposites are graphene nanosheets (GNSs), multi-wall carbon nanotubes (MWCNTs), single-wall carbon nanotubes (SWCNTs) and carbon nanospheres (CNSs). The aggregation of SnO2is not observed and SnO2nanoparticles are uniformly distributed on the surface of nanocarbon families. To compare lithium storage properties of the nanocarbon families, graphene based nanocomposites have relatively high lithium storage capacities and cyclabilities. Such behaviors can be attributed to large surface area, good mechanical flexibility and high electron conductivity of graphene and high lithium storage capacities of metal oxide nanomaterials. These results further illustrate that graphene nanosheets have better structure and electrochemical properties than other nanocarbon families. The third one is a-Fe2O3/graphene nanocomposit. The a-Fe2O3nanostructures in nanocomposites appear as nanoparticles with some appearing as nanorods and are uniformly located on graphene nanosheets. The X-ray diffraction peaks are in good agreement with that of a-Fe2O3crystal given by the standard files and a-Fe2O3nanocrystals have relatively high crystal purities. a-Fe2O3/graphene nanocomposites have higher lithium storage performance than pure a-Fe2O3nanostructures. In this work, four mechanisms have been mentioned to explain high lithium performance of a-Fe2O3/graphene nanocomposites which further prove that high performance lithium-ion battery can be realized by a-Fe2O3/graphene nanocomposites.Nanocomposites have important applications not only in high performance lithium batteries, but also in high performance gas sensors. At the end of this paper, we introduce other types of metal oxide nanocomposites in the field of applications of gas sensorsPd-ZnO nanocomposites and In2O3/a-Fe2O3nanocomposites which have uniform morphologies are synthesized by simple hydrothermal methods. High sensing performances are obtained from both of them. Such behaviors can be attributed to Schottky contact at Pd-ZnO interface and catalytic activity of Pd nanoparticles. And the heterostructure of In2O3/a-Fe2O3nanocomposites will be changed in special environments, which have great influence on the conductance of materials. Such a new gas sensing mechanism greatly improves the gas sensing performance of In2O3/a-Fe2O3nanocomposites. These works greatly improve the gas sensing performance and we further confirm that nanocomposite materials have more advantages than single nanomaterials in physical and chemical properties. Therefore, other forms of nanocomposite materials also have high scientific research value and can facilitate the practical applications of the technologies.