Zhao Hui, Wei Yang, Qiao Ruimin, Zhu Chenhui, Zheng Ziyan, Ling Min, Jia Zhe, Bai Ying, Fu Yanbao, Lei Jinglei, Song Xiangyun, Battaglia Vincent S, Yang Wanli, Messersmith Phillip B, Liu Gao
Departments of Bioengineering and Materials Science and Engineering, UC Berkeley , Berkeley, California 94720, United States.
Beijing Key Laboratory of Environmental Science and Engineering, School of Material Science and Engineering, Beijing Institute of Technology , Beijing 100081, China.
Nano Lett. 2015 Dec 9;15(12):7927-32. doi: 10.1021/acs.nanolett.5b03003. Epub 2015 Nov 30.
High-tap-density silicon nanomaterials are highly desirable as anodes for lithium ion batteries, due to their small surface area and minimum first-cycle loss. However, this material poses formidable challenges to polymeric binder design. Binders adhere on to the small surface area to sustain the drastic volume changes during cycling; also the low porosities and small pore size resulting from this material are detrimental to lithium ion transport. This study introduces a new binder, poly(1-pyrenemethyl methacrylate-co-methacrylic acid) (PPyMAA), for a high-tap-density nanosilicon electrode cycled in a stable manner with a first cycle efficiency of 82%-a value that is further improved to 87% when combined with graphite material. Incorporating the MAA acid functionalities does not change the lowest unoccupied molecular orbital (LUMO) features or lower the adhesion performance of the PPy homopolymer. Our single-molecule force microscopy measurement of PPyMAA reveals similar adhesion strength between polymer binder and anode surface when compared with conventional polymer such as homopolyacrylic acid (PAA), while being electronically conductive. The combined conductivity and adhesion afforded by the MAA and pyrene copolymer results in good cycling performance for the high-tap-density Si electrode.
高振实密度硅纳米材料因其小表面积和最小的首次循环损失，非常适合作为锂离子电池的负极材料。然而，这种材料对聚合物粘结剂的设计提出了巨大挑战。粘结剂附着在小表面积上，以承受循环过程中的剧烈体积变化；而且这种材料导致的低孔隙率和小孔径不利于锂离子传输。本研究引入了一种新型粘结剂聚（1-芘甲基丙烯酸甲酯-共-甲基丙烯酸）（PPyMAA），用于高振实密度纳米硅电极，该电极能稳定循环，首次循环效率为82%，与石墨材料结合时，该值进一步提高到87%。引入MAA酸官能团不会改变最低未占分子轨道（LUMO）特征，也不会降低PPy均聚物的粘附性能。我们对PPyMAA的单分子力显微镜测量表明，与传统聚合物如均聚丙烯酸（PAA）相比，聚合物粘结剂与负极表面之间的粘附强度相似，同时具有导电性。MAA和芘共聚物提供的导电性和粘附性相结合，使得高振实密度硅电极具有良好的循环性能。
