硅藻土作锂离子电池硅基复合负极材料的制备及电化学性能研究

Preparation and electrochemical properties of lithium ion battery using diatomite as silicon-based composite anode

硅藻土作为一种自然材料,拥有很多优异的理化特性。介绍了如何从硅藻土中提取出高纯度SiO_2,并用金属热还原法制备出多孔硅,将其与商业硅进行对比研究。同时采用溶剂热法制备了SiO_2/TiO_2复合材料和球磨法制备SiO/TiO_2复合材料,分别对这三种材料进行粉末衍射、扫描电镜等表征。然后将这三类材料作为锂离子电池的负极材料,以锂片作为正极制作锂离子半电池,并对锂离子半电池的循环稳定性,恒流充放电等电化学性能进行表征。结果表明,制备的单质硅具有孔道结构,电池的循环性能比商业硅好。将本实验所用的三类负极材料进行比较可以发现:在首次充放电容量方面,硅和SiO/TiO_2/Mg复合材料明显高于SiO_2/TiO_2复合材料;在循环稳定性方面,复合材料的循环性能明显高于多孔硅,SiO_2/TiO_2复合材料处于绝对领先地位。

Diatomite is a kind of natural material, and has excellent physical and chemical properties. The high purity SiO2 was extracted from the diatomite, and then the porous silicon was prepared by using the metallothermics. The performances of the prepared porous silicon and the commercial products were compared. In addition, the SiO2/TiO2 composite was prepared by the solvent-thermal method and the SiO/TiO2 was prepared by ball milling process. Three materials were investigated by XRD and SEM. The lithium ion half-cell was fabricated by using the three materials as the anode materials and using the lithium plates as cathode materials. The electrochemical properties of cycle stability, constant-current charge-discharge were characterized. The results demonstrate that the prepared Si has regular pore structure, and its circulation property is obviously enhanced compared with the commercial silicon. By comparing these three anode materials, it is find that the first charge and discharge capacity of Si and SiO/TiO2/Mg are both significantly higher than that of SiO2/TiO2, and the composites show significantly excellent cycle stability, especially for SiO2/TiO2 composite.