在透射电子显微镜中直接观察材料锂化动力学行为

Directly observe the kinetic behavior of lithium inside a transmission electron microscope

锂离子电池的电极材料是决定其性能的关键因素之一,电极材料的储锂与失效机制是开发高性能锂离子电池的重要基础科学问题。本文在透射电子显微镜内以目标材料为工作电极搭建锂离子半电池,利用透射电子显微镜的原子结构表征技术对电极材料在锂化动态反应过程中的形貌、成分、结构等进行原位表征,开展锂离子动力学过程和电化学储能机制研究。结果表明,硅负极纳米线的锂化以及能源利用率存在明显的尺寸效应,在二维材料MoS2中首次观察到了锂离子嵌入导致的2H-1T的相转变过程。本研究对理解锂离子电池工作的原子机制和开发新型锂离子电池材料具有重要意义。

This work mainly focuses on realizing lithium battery inside the transmission electron microscope(TEM) to measure and understand electrochemical lithiation mechanisms in electrode nanomaterials. Based on the use of a nanomanipulator to assemble an electrochemical cell inside a TEM thatconsists of battery materials,e. g.,Si nanowires and MoS2 nanosheets,a Li-containing counter electrode,and an ionic liquid electrolyte or a solid-state electrolyte(Li2 O). To directly capture the dynamic structural changes of electrode materials during lithiation process,the lithium cells were characterized via realtime in-situ high resolution transmission electron microscopy(HRTEM) imaging,electron diffraction(ED) and electron energy-loss spectroscopy(EELS). Based on the in-situ TEM method,we accomplished several implements related to understanding Li-ion battery electrochemical mechanism at the atomic to nano-scale and we identified the remarkable electrochemical mechanisms associated with anode lithiation and delithiation.