Synthesis And Electrochemical Properties Of Nanostructure SnS₂ By Hydrothermal Method As Negative Electrode Material For Lithium Ion Batteries

In recent years, large energy density of non-carbon negative electrode materials is research mainstream direction of lithium ion battery cathode materials. Tin base materials has high theoretical specific capacity when conduct for lithium ion battery cathode material, it cause the extensive concern of researchers and become promising anode materials for replacing carbon materials.In this material, tin disulfide（SnS₂） has excellent performance for lithium ion storage, but in the process of charging and discharging, electrode volume change is bigger, lead to the electrode pulverization, making the specific capacity greatly attenuation. Studies have shown that the lithium storage properties of tin disulfide largely depend on purity, morphology and particle size.At present, improving the cycle performance of tin disulfide mainly through nanocrystallization, multipolarity and composition. In this paper, we prepared tin disulfide that the morphology are 3D-flowerlike multilevel nanostructures and two-dimensional hexagonal nanolakes by a simple solvent method. Inored to enhance cycle performance of SnS₂, we improve the performance and optimize the structure. Summarizing the work, it has the following content of several aspects:We synthesis 3D-flowerlike multilevel nanostructures of SnS₂, stannous chloride（SnCl₂ï¹'2H₂O）, thioacetamide（TAA） and anhydrous ethanol as raw material. XRD spectrum showed that SnS₂ sample has flowerlike multilevel nanostructures with single phase of hexagonal crystal system. SEM and TEM images displayed that SnS₂ pattern is nano-petal self-assembed, its thickness is about 20-30 nm and diameter is about 8μm. HRTEM images and the corresponding SAED spectrum showed that the interplanar spacing is 0.31 nm of {100} crystal planes. In this experiment, we collect product of different holding time and study formation process of SnS₂ nanostructure by testing component and observing morphology for proposing the growth mechanism. We use the sample that holding time is 12 h to prepare electrode, assemble Lithium ion battery and test their electrochemical properties. The results show that the initial discharge specific capacity is 1270.4 m Ah g-1, the first time the reversible specific capacity of 616.2 m Ah g-1, after 20 cycles, specific capacity is 558.6 m Ah g-1, the reversible capacity remain at a rate of 90.6%.Flowerlike nanostructure SnS₂ was synthesized by Triton X-100 assisted hydrothermal method, the effect of different amounts of surfactant on the sample’s ingredient, morphology and electrochemical properties were studied.X-ray diffraction（XRD） and Energy dispersive spectroscopy（EDS） test present the material was single-phase SnS₂ and the crystal structure was hexagonal Cd I2. Scanning electron microscopy（SEM） indicates that Triton X-100 plays a dominative role in controlling the microscopy of SnS₂. Moreover, When the dosage of 0.5 ml Triton X-100, the sample have the highest crystallinity, pattern structure and microscopy are perfect. Electrochemical testing shows that as anode materials of rechargeable Li-ion batteries, the as-prepared flowerlike SnS₂ nanostructure revealed a higher initial discharge specific capacity and reversible capacity are 1598 m Ah g-1 and 656 m Ah g-1 in 0.01-1.2V voltage and 0.15 C rate, respectively. After 50 cycles, at 0.15 C, the specific capacities retain 572 m Ah g-1 and capacity retention rate can reach 87.2%. Comparing with not added Triton X-100 sample, the cycle stability, discharge capacity and retention ratio are improved.Hexagonal SnS₂ nanosheets were synthesized by using one-pot hydrothermal method with SnCl₂ï¹'2H₂O, TAA and deionized water as staring materials. At 180℃ heat holding 10 h, the as-prepared SnS₂ nanosheets’ lateral diameter is 100-200 nm and thickness is about 50 nm. XRD spectrum showed that SnS₂ sample is hexagonal crystal system. In addition, we proposed the formation mechanism of hexagonal SnS₂ nanosheets by studying the substrate composition and morphology, We believe that the nano crystals in the process of growth, forming a layer of substrate at the bottom of the autoclave, nano crystals attached to the substrate surface. Gradually, it has a ‘ball’ effect, the different degree ‘spherical particles’ appear on the different locations of substrate. Surface tension as growth driving force promote the whole process, with the spherical particles grew older, the energy of the system increasing. In the synergy of surface tension and reduce the system energy, in order to overcome the potential barrier the larger size spherical particles cracked, forming a single nano-meter chips.