Graphene/Molybdenum Disulfide/Tin Disulfide Composite As Anode Materials For Batteries

Graphene（GNS） and molybdenum disulfide（MoS₂） have many superior physical and chemical characteristics due to their unique molecular structure. Owing to their matching crystal structure and micro-morphology as well as their complementary electrical properties, the duo constitutes excellent hybrid materials thanks to the synergistic effects between layered MoS₂ and graphene. We report a facile liquid-phase exfoliation method for layered MoS₂ and graphene in l-methyl-2-pyrrolidinone（NMP）. GNS and layered MoS₂ ultrasonic mixed at the rate of 1:3,1:6,1:10 in mass and named them as GNS@MoS₂-1/3, GNS@MoS₂-1/6 and GNS@MoS₂-1/10.The samples were systematically investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and transmission electron microscopy（TEM）. The electrochemical properties of the samples as active anode materials for lithium-sodium ion batteries were examined by constant current charge –discharge cycling. It is demonstrated that the obtained GNS@MoS₂ composites show more excellent structure characteristic and electrochemical performances as electrode materials. The composite with weight radio between GNS and MoS₂ of 1:6 had the highest specific capability among all the samples and its reversible capacity of lithium ion batteries after 100 cycles was 582.5mAh/g at a current of 80 mA/g. And its reversible capacity of sodium ion batteries after 100 cycles was 100mAh/g. It also exhibited excellent cycling stability and high-rate capability. The superior electrochemical performance of GNS@MoS₂ composites as battery anodes are attributed to their robust composite structure and the synergistic effects between layered MoS₂ and GNS.Tin disulfide（SnS₂） has been considered to be ideal anodic candidates for batteries with high energy-density and power density. However, even though Sn S₂ exhibits high initial discharge capacity,the large volume changes and loss of electrical contact during intercalation and deintercalation result in capacity fading of the compound.With graphene and MoS₂ as conductive matrix,homogeneous distribution of SnS₂ nanoparticles can be ensured and volume changes of the nanoparticles. In this way,it can not only improve the conductivity of electrons and ions but also optimize the electrochemical performance. GNS@MoS₂@SnS₂ composites were prepared via a hydrothermal method with three different loding of SnS₂. The structure and morphology of the prue SnS₂ and the composites were characterized by XRD,SEM,TEM. Electrochemical performances were evaluated in two-electrode cellsversus metallic lithium and sodium. The result revealed that hexagonal SnS₂ was obtained and the SnS₂ particles distributed homogeneously on GNS and MoS₂ sheets. The composite with weight ratio among GNS, MoS₂ and SnS₂ of 1:6:7 had the highest rate capability among all the samples and at a current of 80 mA/g its reversible capacity of lithium ion battery after 100 cycles was 743.8 mAh/g, and the sodium ion battery after 100 cycles was 173.2 m Ah/g. It also exhibited excellent cycling stability and high-rate capability which was much higher than that of the prue SnS₂ and GNS@MoS₂-1/6 materials. GNS and MoS₂ not only improve the electrical conductivity of the electrode materials but also effectively accommodate volume changes during the charge and discharge processes,which results in good electrochemical performance of the composites.