原位透射解析增强界面实现“厚密”硅负极

A thick yet dense silicon anode with enhanced interface stability in lithium storage evidenced by in situ TEM observations

为提高锂离子电池的体积能量密度,电极的密度和厚度需要尽可能提高,以降低非活性组分在整个电池中的体积占比.但是,电极密度与厚度的增加,对电极,特别是对高容量硅负极循环过程中的力学稳定性提出了巨大的挑战.本工作针对硅碳复合电极材料,通过碳/硅界面的强化设计,实现"厚密"硅负极构建.利用可流动的硫模板法实现碳网络可控收缩,为硅纳米颗粒的定制限域碳笼,并辅以聚多巴胺界面修饰,以提高硅碳界面结合作用,最终获得增强界面的碳笼缓冲结构.进一步地,基于原位透射电子显微镜技术的平面压缩、垂直剪切等力学测试,以及力学-电化学耦合表征等解析硅碳增强界面对嵌锂膨胀硅纳米颗粒所发挥的力学缓冲作用.最终,基于此硅碳复合材料,获得具有高体积比容量和高面容量、稳定循环的"厚密"硅负极.

Increasing the density and thickness of electrodes is required to maximize the volumetric energy density of lithium-ion batteries for practical applications.However,dense and thick electrodes,especially highmass-content(>50 wt%) silicon anodes,have poor mechanical stability due to the presence of a large number of unstable interfaces between the silicon and conducting components during cycling.Here we report a network of mechanically robust carbon cages produced by the capillary shrinkage of graphene hydrogels that can contain the silicon nanoparticles in the cages and stabilize the silicon/carbon interfaces.In situ transmission electron microscope characterizations including compression and tearing of the structure and lithiation-induced silicon expansion experiments,have provided insight into the excellent confinement and buffering ability of this interface-strengthened graphene-caged silicon nanoparticle anode material.Consequently,a dense and thick silicon anode with reduced thickness fluctuations has been shown to deliver both high volumetric(>1000 mAh cm^-3) and areal(>6 mAh cm^-2)capacities together with excellent cycling capability.