Development of Operando X-Ray Diffraction-Raman Dual System for a Solid Battery

Li-ion batteries (LIBs), becoming one of the daily necessities in human lives, have been widely used primarily for the achievement of carbon neutrality, toward which the replacement of fossil-fuel-based vehicles with eco-friendly electric vehicles are progressing rapidly. In addition, if the urban air mobility market opens within the next 10 years, the environmental safety and stability of these batteries will become key issues. Currently, there is significant enthusiasm for research on solid batteries using solid electrolytes owing to the safety issues of batteries using liquid electrolytes. Thus, the research and development of advanced batteries utilizing the chemical and electrical stability of solid batteries, high-voltage anode materials, and lithium anode materials have been an extensive. For the measurement technology, challenges arise on spatial tracking of non-uniform electrochemical and interfacial chemical reactions in a cell, and understanding the cause of such reactions for the pursuance of safe battery design. The non-uniform lithiation/delithiation upon battery material location also requires the development of advanced measurement systems that incorporate two or more specialized techniques.<br/>In situ/operando Raman spectroscopy is a technique that characterizes dynamic battery materials. Moreover, X-ray diffraction (XRD) is an essential technique for conducting secondary battery research to understand a crystal structure and perform multiphase quantitative analysis. Both techniques are a part of the state-of-the-art technologies that aim for a highly realistic environmental system with the most confidential measurements toward the characterization and development of next-generation materials. We have developed the XRD-Raman dual system, which is advantageous in assessing the non-uniform electrochemical reaction of the active material. Home-made fiber-type Raman system was unified with the conventional XRD system. The excitation laser can be irradiated to the sample in variable angles. The Raman signal, scattered from that, was collected into an off-axis parabolic mirror, which directs it to the spectrometer and detector. In addition, we developed a special coin cell to observe the dynamic behavior of the battery material in the assembled device. First, we chose transparent materials and attached them to the holed coin cell lid, so that the X-ray and visible light source can simultaneously transmit and reflect. Second, we fabricated the coin cell with a gap between the chosen transparent film and cathode materials to reduce the unwanted background. This coin cell enabled for XRD-Raman measurements to be performed during the battery operation under the same environmental conditions. The XRD-Raman dual operando measurement technology for material diagnosis in real systems will be of great help in improving the performance of secondary batteries.