Si@TiO_(2)复合材料的制备与性能研究

Study of preparation and properties of Si@TiO_(2) composite materials

结合并改进典型的Stöber法,利用聚合物蚀刻硅氧化合物材料的内部并加入钛源制备前驱体,采用低温熔盐法还原得到球形Si@TiO_(2)复合材料,借用X射线光电子能谱分析(XPS)、X射线衍射分析(XRD)和扫描电子显微镜分析(SEM)等手段对材料的组成、结构、形貌进行表征。结果表明,TiO_(2)可以均匀分布在硅颗粒的外表面,与硅颗粒形成核壳结构。TiO_(2)在外层起到了保护及缓冲层的作用,能有效的隔绝电解液与硅材料的直接接触,降低电池内部热量的产生,显著改善硅材料的热稳定性,同时,TiO_(2)与硅材料的结合有助于提高复合材料的电导率,这二者的协同效应可提升电池循环稳定性。在0.1 A/g电流密度下,Si@TiO_(2)复合材料的首次放电比容量为2910.8 mAh/g。在0.5 A/g电流条件下循环300次,其放电比容量为1058.4 mAh/g;且在3 A/g大电流条件下循环500次,仍具有894.6 mAh/g的可逆比容量。这表明TiO_(2)的包覆对提高硅负极的电化学性能的作用是非常明显的。

Combined with the typical Stöber method,the silicon oxide material was etched by polymer and the precursor was prepared by adding titanium source,and the spherical Si@TiO_(2) composite was obtained by low temperature molten salt reduction.X-ray photoelectron spectroscopy(XPS),X-ray diffraction analysis(XRD)and scanning electron microscope analysis(SEM)were used to characterize the structure of the materials.The results show that TiO_(2) can be evenly distributed on the outer surface of silicon particles,forming a core-shell structure with silicon particles.TiO_(2) plays a role of protection and buffer layer in the outer layer,which can effectively isolate the direct contact between electrolyte and silicon materials,reduce the generation of heat inside the cell,and significantly improve the thermal stability of silicon materials.At same time,the combination of TiO_(2) and silicon material helps to improve the conductivity of the composite material,and the synergistic effect of the two can improve the cycle stability of the battery.The initial discharge specific capacity of Si@TiO_(2) composite is 2910.8 mAh·g-1 at the current density of 0.1 A·g-1.The discharge capacity is 1058.4 mAh·g-1 after 300 cycles at the current density of 0.5 A·g-1.The reversible specific capacity of 894.6 mAh·g-1 is still obtained after 500 cycles under 3 A·g-1 high current.This indicate that the coating of TiO_(2) has a very obvious effect on improving the silicon anode to show a good electrochemical performance.