Cu纳米颗粒诱导生长多孔Si基负极材料的储锂特性

The application of Si anode material, which shows much higher theoretical specific capacity and better safety in comparison with traditional graphite electrodes, has been greatly restricted due to its low initial Coulombic efficiency, poor cycling and rate performances that are caused by the huge volume changes of active materials during cycling, slow electrochemical reaction kinetics and instability of solid electrolyte interphase (SEI) film on electrode surface. Therefore, the design concept of this project is directed against the aforementioned main problems of Si electrode to synthesize microscale porous Si-based (Si-Cu) thin film anodes with the pre-deposited Cu nanoparticles as the growth direction template through a plasma-gas-aggregation-type cluster beam deposition technique. The effect of porous construction of active materials and the incorporation of three dimensional Cu conductive network on the structural integrity of electrode and the electrochemical reaction kinetics will be discussed, respectively. The reasons for the enhanced stability of SEI film related to the in situ construction of interface modification layer on the surface of Si electrode will be discussed. The compensation mechanism of the initial Coulombic efficiency for Si-based anodes by prelithiation treatment of active materials will be proposed. After that, the application of the obtained Si-based thin film anodes with high initial Coulombic efficiency, large specific capacity, outstanding cycling and rate performances, in lithium ion full batteries will be investigated, which will provide the experimental and theoretical foundations for the Si-based electrodes from the experimental study to the practical application.

Si作为锂离子电池负极材料具有比传统的石墨类负极更高的理论比容量和更好的安全性，然而充放电过程中电极材料剧烈的体积变化、缓慢的嵌脱锂动力学性能以及电极表面SEI膜不稳定导致的首次库伦效率低、循环及倍率性能不理想的问题严重制约其应用。本项目针对上述Si负极存在的问题进行设计，拟采用实验室自行研制的纳米粒子束流复合沉积设备，实现Cu纳米颗粒诱导微米级厚度的多孔Si基(Si-Cu)薄膜负极的原位可控制备。系统研究活性材料多孔结构设计与三维Cu导电网络复合对电极结构的稳定作用及嵌脱锂动力学性能的增强机制；深入研究Si电极表面修饰层原位构筑对界面SEI膜稳定性的改善作用及其影响规律；查清电极预锂化对其首次库伦效率的补偿机制，获得具有高首效、高比容、高循环及倍率性能的Si基薄膜负极。在此基础上考察该Si基薄膜负极在锂离子全电池中的应用研究，为Si基负极从实验探究向实际应用的迈进提供实验依据和理论基础。

针对Si负极材料充放电过程中循环与倍率性能差、库伦效率低的问题，本项目设计制备了厚度可控的多孔Si基薄膜负极，系统研究了电极材料微观结构设计与成分调控对电极结构及界面的稳定作用和嵌脱锂动力学性能的增强机制，有效提升了Si基薄膜负极的储锂性能。通过项目的实施，主要取得了以下研究成果：（1）采用纳米粒子束流复合沉积技术，以预沉积的多孔Cu纳米颗粒膜为生长导向模板溅射Si活性层，并通过逐层原位溅射的方式制备出层数可控的多层多孔Cu/Si复合薄膜。研究发现，单层多孔Cu/Si薄膜负极在1 A g-1下能够稳定循环1000次，容量保持率为95%。当层数由2层增加到4层时，多层薄膜负极的比容量变化不大，表明通过多层构筑确实能在维持比容量的基础上有效增加Si的负载量。4层Cu/Si薄膜负极在1 A g-1下循环250次后的可逆容量为1825 mA h g-1。ZnO和Al2O3界面修饰能够降低电极界面副反应，提升SEI层稳定性和库伦效率。（2）以多孔Zn纳米颗粒膜为生长模板制备出层数可控的多层多孔Zn/Si/ZnO复合薄膜。利用ZnO与Li+逆转化反应可逆性差的特点构筑了LiZn-Li2O复合人工SEI层，提高了该Si基薄膜负极的循环稳定性和库伦效率。随着层数增加，该Si基薄膜负极的比容量出现先增加（1-4层）后减少（4-6层）的现象，4层复合薄膜电极具有最优的储锂性能，这与其适中的Si含量和Li+扩散距离以及多层和多孔结构有利于缓解活性物质体积变化有关。（3）采用磁控溅射法，通过逐层溅射制备出图案化的Si/ZnO/C薄膜负极。巧妙构筑的具有电子和离子双传导的Li2O-Zn/C复合界面修饰层有效提升了Si/ZnO/C薄膜负极的循环稳定性和库伦效率。在10.0 A g-1下循环6000次后该Si基负极表现出高的可逆容量（1400 mAh g-1）和库仑效率（>99.0%）。项目的研究结果为Si基负极从实验探究向实际应用的迈进提供了理论和实验依据。