用于锂离子电池负极材料的锡/碳复合材料研究

采用分散聚合的方法在氧化锡的表面包覆聚对位二乙烯基苯,再热解制备了锡基颗粒在碳基体中均匀分散的锡/碳复合材料.该复合材料具有良好的循环性能.在该复合材料中无定形碳起到了至关重要的作用,它一方面保证了复合材料的导电性能,另一方面有效地抑制了锡基颗粒的团聚与粉化.只有当小尺寸的锡基颗粒均匀地分散在碳基体中时,锡/碳复合材料才具有稳定的电化学性能.

Sn/C COMPOSITES AS ANODE MATERIAL FOR LITHIUM ION BATTERY

In order to improve the cycle stabilities of tin based anode materials and keep their high capacities,Sn/C composites with different carbon contents were prepared by disperse polymerization and pyrolysis of poly(para-divinyl benzene)-encapsulated tin dioxide nanoparticles.The morphologies of Sn/C composites were analyzed by means of transmission electron microscope(TEM) and powder X-ray diffraction(XRD).Tin-based particles(about 100 nm) can be uniformly distributed in carbon matrix when the carbon content in composite exceeded 50 wt%.With the decrease of carbon content,the aggregation of tin oxides became serious for no enough carbon as barrier,and the diameter of tin based particles increased.During the pyrolysis of poly(para-divinyl benzene),part of SnO_2 was reduced into metallic tin and SnO,and as the carbon content in composite increased,the degree of reduction increased.The electrochemical performances of Sn/C composites as electrodes were compared.Electrochemical performances of the Sn/C composite depended on morphologies of tin and carbon phases.The reversible capacities of Sn/C composites increased with the decrease of carbon content because the pyrolyzed carbon showed a low reversible capacity.On the other hand,the cycle ability of Sn/C composites increased as the carbon content increased because the carbon effectively suppressed the sintering agglomeration of tin based material and maintained the electrical conductivity of composites.Further,the morphologies of electrodes were analyzed by SEM and XRD.With the increase of carbon content,the electrochemical sinter of tin based material in electrode was inhibited.The different morphologies of various electrodes were consistent with their different cycle performances.According to the analysis results of morphologies and properties of Sn/C composites,stable electrochemical performances of the Sn/C composites can only be achieved by homogeneous dispersion of the tin-based particles in carbon matrix so as to avoid aggregation of tin and its pulverization and to keep conductivity of the Sn/C composites.