【摘要】 Si负极材料理论容量高,但其电子电导率低和脱嵌锂过程体积变化大易粉化,使其循环稳定性和倍率性能差以及高性能硅基锂离子电池负极材料成本高,这均妨碍了其大规模产业化应用。本研究提出以太阳能电池硅片切割废料Si粉和TiN粉为原材料,采用低成本的活性气体机械球磨法制备了一种高性能的Si/TiN/TiSi₂多相复合负极储锂材料。研究发现,Si在H₂气氛球磨过程中与部分TiN发生反应,原位生成了纳米尺度的TiSi₂,TiN和新形成的TiSi₂弥散于亚微米尺度的Si基体中。Si/TiN/TiSi₂复合材料的电化学性能与TiN的添加量紧密相关。其中,物质的量比Si/0.2TiN的体系具有最佳的电化学性能,在300 mA·g^-1电流密度下,其首次可逆容量为2394 mA·h·g^-1,首次库伦效率达75.8%,经过200次循环后,容量仍保持1295 mA·h·g^-1,保持率高达54%。在2.0 A·g^-1电流密度下的可逆容量达到609 mA·h·g^-1。机理分析表明:高导电的惰性相TiSi₂和TiN弥散在Si基体中不仅有利于电极材料在充放电循环过程中的电子传输,且有效缓冲了Si在嵌脱锂过程的巨大体积变化。这是TiN添加改善硅基复合负极材料电化学性能的主要原因。更多还原

【Abstract】 Si anode material offers high theoretical capacity, however, it suffers from low electronic conductivity and large volume change during lithiation and delithiation, which result in its poor cyclic stability and low rate capability. In addition, high-performance silicon-based anode materials are high-cost. All of these impede the large-scale commercial applications. In this work, a high-performance Si/TiN/TiSi₂ composite is prepared by low-cost mechanical ball milling in active gas, in which the industrial waste of Si powder and TiN powder are used as raw materials. Si is found to react with some TiN to in situ form nano-sized TiSi₂ in the milling process. TiN and newly formed TiSi₂ are dispersed in submicron Si matrix. The electrochemical performance of Si/TiN/TiSi₂ composites is closely associated with the amount of TiN. Among them, Si/TiN/TiSi₂ composite prepared by milling Si/0.2 TiN mixture shows the best electrochemical performance. At the current density of 300 mA·g^-1, it delivers the first-cycle reversible capacity of 2394 mA·h·g^-1 with the initial coulombic efficiency of 75.8%. After 200 cycles, the reversible capacity is still as high as 1295 mA·h·g^-1, corresponding to the retention rate of 54%. The reversible capacity reaches 609 mA·h·g^-1 at 2.0 A·g^-1. The mechanism analysis reveals that the dispersion of the inert phase TiSi₂ and TiN in the Si matrix is not only beneficial to the electronic conduction of the electrode material in the charge/discharge cycle, but also effectively buffers the huge volume changes of Si in the process of lithium removal. This is the main reason for TiN addition to improve the electrochemical performance of silicon-based composites.更多还原