关键词: 锂离子电池, 纳米硅负极, 高浓度电解液, 添加剂

Abstract:

In this paper, the effects of additives on the cycling performance of silicon nanoparticles in LiFSI-(PC)₃ based concentrated electrolytes were systematically studied. The structures of silicon nanoparticle electrodes and the evolution of solid-electrolyte-interphase were characterized by scanning electron microscopy (SEM）, attenuated total reflection Flourier transformed infrared spectroscopy (ATR-FTIR） and X-ray photoelectron spectroscopy (XPS). The results indicated that the additives can efficiently improve the cycling performance of silicon nanoparticle electrodes. In LiFSI-(PC)₃ concentrated electrolyte, the capacity became 574.8 mAh·g^-1 after 300 cycles with the initial capacity of 3296.1 mAh·g^-1. In contrast, the 3% LiDFOB, 3% FEC and 3% TMSB-containing systems reached 1142.9, 1863.6 and 1852.2 mAh·g^-1 after 300 cycles, respectively. The comprehensive analysis indicates that the reduction of LiFSI takes priority over PC on the surface of silicon nanoparticles in LiFSI-(PC)₃ concentrated electrolyte, and the SEI film is composed of an inner layer dominated by inorganic products and an outer layer dominated by organic products. While in the concentrated electrolyte containing additives, the additives and LiFSI participate in the formation of SEI inner layer synergistically, and the SEI inner layer can suppress the reduction of PC which contribute to the formation of SEI outer layer. The SEI film formed on this mechanism could suppress the excessive growth of the SEI film, mitigate the pulverization of silicon nanoparticles, and enhance the structure stability of the silicon nanoparticle electrode, thus, the silicon nanoparticle electrodes exhibited better cycling performance.

Key words: lithium-ion batteries, silicon nanoparticle electrode, concentrated electrolyte, additive