Shen B H, Wang S, Tenhaeff W E
Department of Chemical Engineering, University of Rochester, Rochester, NY 14627, USA.
Sci Adv. 2019 Jul 19;5(7):eaaw4856. doi: 10.1126/sciadv.aaw4856. eCollection 2019 Jul.
Electrochemical reduction of lithium ion battery electrolyte on Si anodes was mitigated by synthesizing nanoscale, conformal polymer films as artificial solid electrolyte interface (SEI) layers. Initiated chemical vapor deposition (iCVD) was used to deposit poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane) (pV4D4) onto silicon thin film electrodes. pV4D4 films (25 nm) on Si electrodes improved initial coulombic efficiency by 12.9% and capacity retention over 100 cycles by 64.9% relative to untreated electrodes. pV4D4 coatings improved rate capabilities, enabling higher lithiation capacity at all current densities. Impedance spectroscopy showed that SEI resistance grew from 50 to 191 ohms in untreated Si and only 34 to 90 ohms in pV4D4-coated Si over 30 cycles. Post-cycling Fourier transform infrared and x-ray photoelectron spectroscopy showed that pV4D4 moderated electrolyte reduction and altered SEI composition, with LiF formation being favored. This work will guide further development of polymeric artificial SEIs to mitigate electrolyte reduction and enhance capacity retention in Si electrodes.
通过合成纳米级的保形聚合物薄膜作为人工固体电解质界面（SEI）层，减轻了锂离子电池电解质在硅阳极上的电化学还原。采用引发化学气相沉积（iCVD）将聚（1,3,5,7 - 四乙烯基 - 1,3,5,7 - 四甲基环四硅氧烷）（pV4D4）沉积到硅薄膜电极上。相对于未处理的电极，硅电极上的pV4D4薄膜（25纳米）使初始库仑效率提高了12.9%，在100次循环后的容量保持率提高了64.9%。pV4D4涂层改善了倍率性能，在所有电流密度下都能实现更高的锂化容量。阻抗谱表明，在30次循环过程中，未处理的硅中SEI电阻从50欧姆增加到191欧姆，而在pV4D4涂层的硅中仅从34欧姆增加到90欧姆。循环后的傅里叶变换红外光谱和X射线光电子能谱表明，pV4D4减缓了电解质还原并改变了SEI组成，有利于LiF的形成。这项工作将指导聚合物人工SEIs的进一步发展，以减轻电解质还原并提高硅电极中的容量保持率。
