Synthesis And Electrochemical Performance Of Sn-containing Composites For Anode Materials Of Lithium-ion Batteries

As one of environmental and efficient chemical power sources, lithium-ion batteries ?LIBs? have been widely used in the application of portable devices and electric vehicals ?EVs?. It also has great prospect in the large energy storage system. However the widely used anode material of graphite delivers a theoretical capacity of only 372 mAh g-1, which could not meet the need of high-performance LIBs with long life and high-power densities. Compared with the traditional anode materials of graphite, the tin oxide has higher mass specific capacity and volume specific capacity. This would have great potential in future application. However the the huge volume expansion of tin oxides during lithiation/delithiation will cause the pulverization and reunion of electrode material, thus the lifetime and capacity of LIBs will decay rapidly. Combining with other materials will play a role in the mutual segregation of heterogeneous oxides during the delithiation and lithiation. This can make full use of the high specific capacity of tin dioxide.The main contents of this paper are as follows:?1? Ti-Sn-O composite oxides with various Ti/Sn molar ratios were prepared by a simple precipitation method followed by coating carbon using pyridine, pyrrole and glucose. When used as anode materials in LIBs, the pyridine carbon coated composite oxides exhibit better cycling performance than that of the single oxides. And when the molar ratio of Ti/Sn is 1.7/0.3 the composite oxides exhibit the best electrochemical performance. The enhanced performance could be ascribed to the stable structure of TiO2 and the smaller particle size of Ti-Sn-O than the individual and the effects of the mutual segregation of heterogeneous oxides during lithiation and delithiation.?2? The composite of Fe3O₄, FeSn, Fe3C and carbon nanotubes ?Sn-Fe-O-C? was prepared by one step reaction between tin oxalate and ferrocene with different ratios. Used as anode materials in LIBs, when the ratio of tin oxalate/ferrocene is 1/9 obtained the better electrochemical performance. The enhanced performance could be ascribed to the synergistic effect of various components. In the composite, the carbon nanotubes could improve the electrical conductivity and suppress the volume expression and aggression of the material. The Fe element in the Fe-Sn alloy also could relieve the volume expression in the access of forming the Li-Sn alloy and improve the electrical conductivity. And the Fe3C around Fe3O₄ could not only improve the electronic conductivity but also alleviate the volume change of Fe3O₄.