Unravelling the Chemistry and Microstructure Evolution of a Cathodic Interface in Sulfide-Based All-Solid-State Li-Ion Batteries

All-solid-state lithium-ion batteries (SSLIBs) are promising candidates to meet the requirement of electric vehicles due to the intrinsic safety characteristics and high theoretical energy density. A stable cathodic interface is critical for maximizing the performance of SSLIBs. In this study, operando X-ray absorption near-edge spectroscopy (XANES) combined with transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) is employed to investigate the interfacial behavior between the Ni-rich layered cathodes and sulfide solid-state electrolyte. The study demonstrates a metastable intermediate state of sulfide electrolyte at high voltage and parasitic reactions with cathodes during the charge/discharge process, which leads to the surface structural reconstruction of Ni-rich cathodes. Constructing a uniform interlayer by atomic layer deposition (ALD) is also employed in this study to further investigate the cathodic interface stability. These results provide new insight into the cathodic interface reaction mechanism and highlight the importance of advanced operando characterizations for SSLIBs.