Preparation And Electrochemical Performance Of Sn-SnO_x/C Composite Electrode For Lithium-ion Battery

Advanced lithium-ion secondary batteries are attractive for use in consumer electronic and electric vehicle application due to a favorable combination of energy density, voltage, cycling performance, self-discharge and environmental protection. Recently, lithium-ion batteries have been widely used in camcorders, cellular phones and notebook computers. Meanwhile, they have great potential for using in electric vehicles. However, at present high rate ability and high reversible capacity of lithium ion batteries are urgently needed to improve because they are the large obstacles for application of lithium ion batteries in electric vehicles.Effect of properties of anode material on characteristics of lithium ion batteries is one of the most important factors. The anode material plays an important role on the performance of lithium ion battery. Currently graphite anode is in use. However, its capacity is not enough to satisfy the market new demand. As one of the researching hotspots of next generation Lithium ion batteries, Tin and its oxide possess high mass specific area and volume specific area. However, there are also some disadvantages. During the intercalated process of Li, bulk expansion may lead to the pulverization and peeling of the active material, which reduces the cycling performance.With the goal of solving this problem, carbon/tin composites were prepared by carbothermal method in consideration of utilizing the advantages of high capacity of tin materials and cycling stability of carbon materials. SEM/EDS, XRD, BET and electrochemical tests (such as cyclic voltammetry, AC impedance, reversible capacity and coulomb efficiency) were used to investigate the composites' surface topography structure and electrochemical performances as anode material of lithium ion battery. The characterization results showed that Sn-SnOx nano-particles were obtained within the carbon matirx.Nano-particles of Sn-SnOx with crystalline state and carbon with amorphous state were well combined. Sn-SnOx particles embedded inside or were bonded on the surface of skeleton carbon. That means Sn-SnOx/C (active/inactive) composites were prepared. The electrochemical tests showed that the initial reversible capacity as high as 600mAh/g was obtained at a charge-discharge current density of 100mA/g. Moreover, good cycle performance of the electrode was achieved that high capacity of ca.376mAh/g was kept even after 50 cycles of charge-discharge. Carbon could buffer the change of the volume, which effectively prevented the pulverization of the electrode, therefore the cycling performance of the electrode was greatly improved.The results also showed that the temperature of carbonization had a significant effect on the surface topography of the prepared electrode materials, which influenced the electrochemical charge/discharge performances of the materials. The higher carbonization temperature, the more serious conglobation of Tin, the lower reversible capacity of the electrode material. The addition of K2CO3 during the preparation process could increase the porosity of the materials, so the specific area was increased, the polarization was decreased and then electrochemical performance was enhanced. Meanwhile the influence of different binders on the electrochemical performance of electrode materials was studied. The electrode with the use of water-soluble binder PAA exhibited better cycling perfomiance than that with the use of PVdF.