Synthesis And Lithium Storage Properties Of（Sn S₂, MoS₂, CaGeO₃）/Graphene Nanocomposites

In this paper, we synthesized a series of graphene nanocomposites using simple liquid phase method and expect these new composite materials hold the high capacity and good safety performance.(1) The Sn S2/graphene(Sn S2/RGO) composites were prepared by one pot solvothermal method using the anhydrous Sn Cl4 and thiourea as the reagents, the ethylene glycol as solvent. The TEM results revealed the Sn S2 quantum dots(3-5 nm) distributed uniformly on the surface of graphene. When tested as the anode material, the initial charge-discharge capacities of Sn S2/RGO were 782.8 and 1830.3 m Ahg-1. After 200 cycles the reversible capacity maintained 520 m Ahg-1 at 100 m Ag-1 and the capacity retention was about 66.45%. However, the reversible capacity of pure Sn S2 was only 66.7 m Ahg-1, the capacity retention was 10%.(2) The sodium molybdat dihydrat was choosed as the molybdenum source and the mercaptoacetic acid was the sulfur source. With the adding of the graphene oxide, We synthesized the Mo S2/graphene(Mo S2/RGO) composites with porous structure by in situ hydrothermal method. The first charge-discharge capacities of Mo S2/RGO composites were 652.2 and 1039.5 m Ahg-1. The composites exhibited a large reversible capacity, up to 660.5 m Ahg-1 even after 200 cycles at 100 m Ag-1, with the capacity retention about 101.3%. The capacity of the pure Mo S2 dropped to 107.5 m Ahg-1 and the capacity retention was only 24.22%.((3) Choosing the sodium molybdat dihydrat and thiourea as the reactors and adding the graphene oxide, one-step hydrothermal method process was using to synthesize the Mo S2/graphene(Mo S2/RGO) composites. The characterization showed the hierarchical Mo S2 nanoflowers cladded with the ultrathin graphene. The electrochemical performances of Mo S2/RGO composites were tested. The first charge-discharge capacities were 1212.0 and 2145.5 m Ahg-1. After 300 cycles, the reversible capacity still remained 861.9 m Ahg-1 and the capacity retention up to 71.11%. But the reversible capacities of Mo S2/graphene paper and pure Mo S2 were only 372.8 m Ahg-1and 70.6 m Ahg-1. The capacity retention of them were 75.21% and 9.51%, respectively.(4) The Ca Ge O3 microrods(r Ca Ge O3) and Ca Ge O3 nanowires(w Ca Ge O3) were prepared through a facile hydrothermal method. When the graphene oxide added, we got the Ca Ge O3/RGO composites(r Ca Ge O3/RGO and w Ca Ge O3/RGO). The results showed the diameter of the one-dimensional(1D) Ca Ge O3 microrods was 400 nm and the lengh was 7 μm. The diameter of the Ca Ge O3 nanowires was 60 nm. When used as the anode material, the initial charge-discharge capacities of Ca Ge O3 microrods were 148.5 and 790.1 m Ahg-1. The capacity attenuated tremendously and was only 94.6 m Ahg-1 after 100 cycles at 100 m Ag-1 current density, with the capacity retention 63.70%. Because the adding of the grephene, the electrochemical performances of r Ca Ge O3/RGO composites were greatly enhanced. The initial charge-discharge capacities were 537.1 and 2416.9 m Ahg-1. The reversible capacity was 592.3 m Ahg-1 after 100 cycles and the capacity retention was as high as 110.3%, showing good electrochemical performances and the potential of as the lithium ion batterisa anode materials.The reversible capacities and cyclic performances of the composites have been significantly improved. The graphene nanocomposites are competent as next generation anode materials for high-performance lithium-ion batteries.