NSRRC Activity Report 2023

Energy Science 057 diffraction to analyze the structure, stress, and defects of microcrystalline samples. It also employs energy-dispersive nanodiffraction (ED-XND) to study crystal orientation distributions and variations in thin films, flakes, and microstructures. 1 For spectroscopy, the endstation can conduct nanoscale X-ray fluorescence (n-XRF) analysis to understand the distribution of different elements in the sample. Additionally, it can perform the measurements of nanoscale X-ray absorption spectroscopy (n-XAS) for different regions. For semiconductor samples, it can collect nanoscale X-ray excited optical luminescence spectroscopic (n-XEOL) signals. Moreover, this beamline includes a dedicated in situ cell that is compatible with a standard-type CR2032 coin battery. This cell facilitates in situ charge– discharge experiments and allows for the adjustment of sample temperatures between 140 and 800 K. With all these advanced features, the TPS 21A is a powerful beamline for researchers conducting cutting-edge materials science studies. As the world moves towards electric vehicles, Tesla, the global leader in electric vehicles, relies on high-nickel lithium-ion batteries to power its products. However, the limitations of such batteries, which rely on liquid electrolytes and polymer separators, pose a significant challenge to wider adoption. All-solid-state batteries (ASSB), which use solid electrolytes instead of liquid ones, eliminate risks associated with leakage, contamination, and separator damage that may lead to short circuits and explosions. ASSBs have demonstrated superior safety, Fig. 2 : Valence mapping including different elements and conditions: (a) LFP@OCV + C, (b) LFP@100% SOC + C, (c) LFP@OCV + LPSC, and (d) LFP@100% SOC + LPSC. [Reproduced from Ref. 9] higher energy density, and a broader operating temperature range, positioning them as a promising technology for the future. 2−4 Specifically, sulfide-based solid electrolytes, such as lithium argyrodite sulfide electrolytes (Li 6 PS 5 Cl; LPSC), have displayed impressive ionic conductivity. 5 However, sulfide-based ASSBs face challenges, such as a limited electrochemical window and significant interface reactions between electrodes and solid electrolytes, which can result in poor interfacial properties and performance degradation. 6−8 Recent studies have shown that transition metals in the cathode can catalyze the decomposition of sulfide-based electrolytes through chemical or electrochemical reactions. Addressing these issues regarding interface reactions is critical to overcome the developmental bottlenecks associated with sulfide-based ASSBs. Bing Joe Hwang (National Taiwan University of Science and Technology), Ching-Yu Chiang (NSRRC), and their teams collaborated to investigate the interactions at the interface between the cathode material and the sulfide-based solid electrolyte. The researchers used n-XRF and n-XAS mapping techniques to visualize nanoscale interfacial reactions and the valence state distribution of the LiFePO 4 (LFP) and LPSC interface during different charging conditions, as shown in Fig. 1 . The pre-edge in the Fe K-edge X-ray absorption near edge structure results was utilized to monitor valence state changes in a single LFP grain. Figures 1(a) and 1(b) illustrate the Fe K-edge spectra from the boundary to the center of the LFP grain in the open-circuit voltage