Research Of New Anode Material For Lithium-ion Batteries

Tin-based and silicon-based cathode material has obtained the massive research for their high gravitational and volumetric capacity. The main disadvantage of these two materials is the large volume expansion-contraction that takes place during lithium allying-dealloyingprocess, which caused exfoliation and poor cycleability. Up to now, the main methods to resolve this problem concentrates in: 1) nano- material; 2) alloying with other materials; 3) adding someone inactive or active material as the structure support. In this paper, we tried two methods to improve the cycling performance. Firstly, producting nano-patices; Secondly, introduction carbon material carries.The SnO₂/graphite compound materials obtained through sol-gel, XRD and SEM research indicated that two materials maintained own characteristic. The electrochemical test demonstration graphite material may enhance the first coulombic efficiency and improve the cycle performance of SnO₂. The first reversible capacity of the compound material (carbon 70%) is 409.4mAh/g, the first efficiency is 77%, and the capacity maintains 68% after 30 cycles.The modified Sn/graphite/amorphouse carbon compound materials is obtained though hydrothermal process. Analysied result through SEM, XRD, CV and electrochemical test indicate: the Sn/graphite/amorphous carbon sample has a kind of nuclear shell structure in which Sn is the center, amorphous carbon surrounding and the graphite filling. Compound materials performed good cycle life, after 50 cycles the capacity still maintains 81.1%.Furfuryl alcohol is taken as the raw material to modify Si-based material through polymerization and carbonization. Analysied result of the obtained compound materials with XRD, SEM, TEM and EDXA indicate that the compound materials have the nuclear shell structure of Si-SiO₂, the particle size about 50nm, in which silicon nucleus was 20nm, and the carbon material dispersion in pellet surround the particle. The first reversible capacity reached to 762.8mAh/g, the first efficiency is 75%.There is only one discharge platform voltage about 0.1V-0.3V. The material cycle performance has been improved, and the capacity maintains 80.1% after 50 cylces.TiO₂ and LiOH ? H2O are taken as raw materials to synthesis lithium titanat samples through high temperature solid system. SEM and XRD analysis showed that the samples are micron and submicron size, the material is pure phase and well crystalline spinel Li₄Ti₅O₁₂. High rate charge and discharge test show that the material has excellent fast charge and discharge performance, 10C charge rate: 92.5%, 10C discharge rate: 94.8C%, voltage platforms drops 0.1V or so.Contrast microwave and high temperature solid system, SEM and XRD results show that: microwave can synthesize well crystallized Li₄Ti₅O₁₂ in a short time. But the microwave is easy to make lithium evaporation than solid state, resulting in products of titanium dioxide excessive.