Spatio-Compositional Characterization of the Solid Electrolyte Interphase in Solid-State Batteries via Nanobeam Electron Diffraction Microscopy

Abstract Solid state batteries (SSBs), utilizing a solid electrolyte (SE) and Li metal anode, promise long-range electric vehicles due to improvements in energy density and safety compared to current Li-ion technologies. Crucial to the practicality and optimization of SSBs is an understanding of the solid electrolyte interphase (SEI), a nanoscale and heterogeneous layer that forms between the Li anode and SE, governing ionic transport and degradation processes. However, in-depth characterisation of the SEI is challenging due to its thin, buried, and reactive nature. Here, we introduce a sample preparation method to isolate the Li-SEI-SE interface and use nanobeam electron diffraction microscopy to map the spatio-compositional structure of the interphase at room temperature. We showcase the capabilities of this approach by characterizing the SEI formed between two chemically and microstructurally distinct sulphide-based SEs and a Li metal anode.