硅负极表面构建人造SEI膜及软包电池应用研究

Construction of Artificial SEI Film on Silicon Anode Surface and Application of Soft-pack Battery

硅基材料在脱嵌锂过程产生较大的体积变化,造成SEI膜的破损和不断重构,限制了其大规模应用。本文将聚丙烯酸和聚环氧乙烷通过层层组装技术,包覆在硅负极表面,形成人造SEI膜,通过红外、SEM等分析了构建人造SEI膜后硅负极材料结构及表面变化情况。并将该硅负极材料组装成软包全电池,评估了25℃和45℃循环测试、EIS等性能。结果表明通过构建人造SEI膜可以明显提升硅负极电池循环容量保持率和减低电芯厚度,25℃循环600T,容量保持率由87.9%提高到92.6%,电芯的膨胀率为10.7%下降到9.4%。45℃循环500T,容量保持率由83.5%提高到85.9%,电芯的膨胀率为12.6%下降到10.9%。循环后通过截面SEM表征显示,构建PAA/PEO人造SEI膜后的硅颗粒循环后总SEI膜厚度由0.35μm降低到0.2μm,具有很好的应用前景。

The large volume change of silicon-based materials during the lithium-deintercalation process results in the damage and continuous reconstruction of the SEI film, which limits its large-scale application. In this paper, polyacrylic acid and polyethylene oxide are used to construct artificial SEI films on the surface of silicon anode by layer-by-layer assembly technology. The silicon anode material was assembled into a soft-pack full battery, and the performances such as cycle test at 25 and 45 ℃ and EIS were evaluated. The results show that by constructing an artificial SEI film, the cycle capacity retention rate of silicon anode battery can be significantly improved and the thickness of the cell can be reduced. After 600 T cycle at 25 ℃, the capacity retention rate increased from 87.9 % to 92.6 %, and the cell expansion rate decreased from 10.7 % to 9.4 %. After 500 T cycle at 45 ℃, the capacity retention rate increased from 83.5 % to 85.9 %, and the expansion rate of the cell decreased from 12.6 % to 10.9 %. The cross-sectional SEM characterization after cycling shows that the total SEI film thickness of the silicon particles after the construction of the PAA/PEO artificial SEI film is reduced from 0.35 to 0.2 μm after cycling, which has a good application prospect.