硅材料表面人工固态电解质界面层的构筑与作用机理研究

Silicon has been recognized as the most promising material for replacing the commercial graphite anodes because of its extremely high capacity of storing lithium ions. However, its large volume change during lithium-ion insertion/extraction causes pulverization and uncontrolled growth of solid electrolyte interphase (SEI), seriously shortening the cycle-life of silicon-based batteries. Here, we are planning to address this critical issue using an “interface chemistry” strategy. Specifically, fluorinated silane molecules are utilized to chemically tailor the surface of silicon materials. The characteristic of electrochemical reactions of those fluorinated silane molecules enable themselves self-assemble into an elastic and structurally stable monolayer on the silicon surface, that is, the in-situ formation of an artificial SEI. The interaction of different fluorinated silane molecules with the growth mechanisms, chemical compositions and electrochemical properties of the artificial SEI will be investigated and summarized. This project could provide new insights into the controllable growth of SEI on the silicon surface and developments of silicon-based lithium-ion batteries.

硅材料因其储锂比容量高被认为是有望取代锂离子电池石墨负极的最佳选择。然而，硅在嵌脱锂过程中的巨大体积变化导致其表面固体电解质界面层的破裂和持续生长，严重缩短了电池循环寿命。针对此关键科学问题，本项目拟采用界面化学策略进行试验探索。通过含氟硅烷分子修饰硅材料表面，利用其电化学反应特性在硅表面原位构筑可伸缩性高且结构稳定的 “人工” 固体电解质界面层。探索不同结构的含氟硅烷分子对 “人工” 固体电解质界面层的形成机理、化学组分以及电化学性能的作用规律，为克服硅表面固体电解质界面层的持续生长和硅基锂离子电池的研发提供新思路。

硅具有比容量高、储量丰富、环境友好等诸多优点，有望成为下一代锂离子电池负极材料，但硅在脱嵌锂的电化学过程中存在的体积变化导致其表面固体电解质界面层的破裂和持续生长，严重制约其循环寿命。本项目采用界面调控策略，将含氟硅烷分子修饰到硅材料表面，论证了原位构筑可伸缩性高、稳定性好的人工固体电解质界面层的合理性。本项目进一步优化了硅结构的选择，通过纳米结构的调控构筑稳定的固体电解质界面层。提出了一种成本低、操作简单、可放大的硅碳纳米负极材料的制备方法；对硅碳材料孔隙结构进行了调控，阐明了硅纳米结构对缓冲硅体积膨胀的作用规律及其与电化学性能之间的构效关系，并进一步筛选得到了具有优异循环稳定性的硅碳复合材料。最后，将结构优化的硅负极与商业化正极磷酸铁锂匹配组装成全电池，论证了硅基负极的潜在应用前景。本项目为克服硅表面固体电解质界面层持续生长问题提供了新的研究思路，对实现硅基负极的大规模应用具有重要意义。