微米尺寸Si/TiO2-x多级结构的构筑及储锂机制研究

Among the various anode materials for lithium-ion batterys, silicon has been considered as the most promising candidate owing to the merits of incomparable theoretical capacity, abundant raw materials and appropriate charge-discharge potentials. However, the practical application of silicon has been hampered by poor conductivity and unfavorable volume change during the charge and discharge processes. For the case of oxides, the volume expansion of robust titania is negligible which can enhance the structural integrity of Si anodes. The conductivity of titania can be greatly improved with the introduction of Ti3+. Herein, we are aimed at integrating multilayer TiO2-x and nanosized silicon through facile experiment conditions under 250 ℃. The prepared Si/TiO2-x anode will be beneficial to the high volumetric capacity, area capacity and tap density owing to the unique micrometre-size microstructures with rational nanopores and void spaces. Moreover, the Si/TiO2-x microstructures composed of nanoscale subunits can alleviate the problem of poor electrical transfer between adjacent nanoparticles. It is anticipated to establish the correlations between components ratios, heterogeneous distribution, porous structure and experimental conditions. Another project is to disclose the internal affiliations between the structure and electrochemical properties. Our research has significance in improving the performance of silicon anode and offering the proposal for practical application.

硅负极具有储锂比容量高、原料来源丰富、充放电平台合适等优点，应用价值极大。然而，硅在储锂过程中存在导电性差和体积变化大等问题。TiO2在脱嵌锂过程中结构稳定性好，通过引入Ti3+（TiO2-x）能提高其导电性。本项目拟以TiO2-x壳和纳米硅构建微米尺寸多级结构（Si/TiO2-x），合理调控空穴和纳米孔分布，提升硅导电性的同时，为硅的体积变化提供缓冲空间。相对于单一纳米材料，项目中由次级纳米单元构筑的微米尺寸多级结构在提高硅振实密度，单位面积比容量和体积比容量等电池性能的同时，缓解了纳米粒子之间较差的电传导问题，以较全面地改善硅负极的电池性能。项目旨在探究以简单易行的实验条件（小于250℃）制备Si/TiO2-x复合材料，实现材料中不同组分的分布，含量及结合方式和孔结构的有效控制，通过实验论证和理论计算理清复合材料结构和性能之间的构效关系，为硅负极的应用提供技术参考和理论指导。

作为锂离子电池负极材料，硅具有较高的理论比容量等优点，但也存在导电性差、充放电过程中体积变化大，纳米硅振实密度有待提高等问题。本项目针对这些问题，成功制备出硅纳米颗粒和氮掺杂碳组装的微米尺寸复合结构，系统地研究了实验条件和材料结构之间的关系。该材料中氮掺杂碳有效地缓解了硅导电性差和体积变化大问题；纳米单元组装的微米结构，能有效提高复合材料的振实密度。采用类似的方法，将纳米二氧化硅复合材料和氮掺杂碳组装成微米结构，经熔盐法还原处理过程，将材料中的二氧化硅还原成硅，制备了不同构造纳米硅和氮掺杂碳复合的微米材料，丰富了该类材料的制备手段。然后，经过电化学性能测试和结构表征数据分析，探究了材料结构和储锂性能之间的关系。此外，结合溶剂热法和煅烧过程，制备了纳米硅、二氧化锡和碳的复合材料，材料中二氧化锡和碳结构共同用来改善硅负极复合材料的电化学性能。以上研究内容从改善硅负极的不足之处开展工作，所取得的实验结果可以为硅复合材料结构的合理设计和储锂性能的提升提供理论指导和实验参考。