Beyond Electrochemical Analysis: 2D, 3D, and 4D Microscopy of LIBs

摘要

Li-ion batteries (LIBs) represent an important pathway for the development of many modern devices, ranging from portable electronics to hybrid- and fully-electric vehicles. In these consumer applications, it is important to understand how the batteries perform over time, how they respond to stressful conditions (such as elevated temperatures or impact conditions), and what happens when the batteries fail. The motivations for these studies range from increasing electrochemical efficiencies and extending the range of electric vehicle batteries, to ensuring safe, reliable operation of the battery products. In spite of these desires, there remains a relatively poor understanding of what dictates battery performance and how the batteries ultimately fail. To begin answering the key questions governing battery operation and evolution, a growing number of researchers are turning toward microscopy to complement their existing electrochemical analysis routines. Recent research has demonstrated the power of imaging for characterizing the tiny features of a porous separator, the cracks that form and/or close within cathode layers of a commercial 18650, and have even permitted reverse-engineering of cell designs and chemistries. From characterizations of 2D and 3D structures to 4D studies of microstructure evolution, microscopy is providing unique insight into today's battery research challenges. Here, we present the development of a multi-scale suite of microscopy instrumentation, incorporating both structural and chemical analysis routines (as shown in Figure 1). We will demonstrate how each imaging modality provides a unique view into the processes governing battery operation, evolution, and failure, spanning electrode layers, polymeric and multi-phase separators, and fully packaged, sealed products. Combining the high-resolution capabilities of scanning electron microscopy (SEM) with the non-destructive 3D volumetric imaging provided by X-ray microscopy (XRM), we will show how researchers may survey a packaged battery, locate areas of defects or contamination, and enlarge them using FIB-SEM. We will show how these techniques may be further coupled with high-resolution light microscopy and spectroscopic chemical analysis techniques, creating an integrated, multi-scale investigation platform capable of satisfying the demanding needs of battery research and characterization engineers.