Operando Imaging of Battery Interfaces through Combined Analysis of Broadband Optical Backgrounds and Raman Features

Abstract Solid-state batteries promise improved safety and energy density, but their performance is governed by buried interfaces where ion transport, chemical reactions, and stress evolution are strongly coupled. Resolving these processes during operation remains challenging. Here, we present an operando spectroscopic strategy that jointly analyzes broadband optical backgrounds and characteristic electrolyte Raman features within a single measurement. Asymmetric least-squares baseline (ALS) estimation extracts broadband optical contrast associated with lithium distribution, while Raman band intensities and peak positions provide complementary information on interfacial chemistry and local stress estimates. This capability provides a unified optical framework for visualizing structural, chemical, and mechanical evolution at battery interfaces and offers a broadly applicable route to interrogate buried interphases in diverse electrochemical systems. More generally, by enabling real-time, multimodal insight into interfacial dynamics, this method advances efforts toward safer, longer-lasting, and more predictable energy-storage technologies.