A Deep Insight into the Microscopic Dynamics of the Electrode–Electrolyte Interface under Extreme Operating Conditions

Understanding the interfacial dynamics during operation is critical for electrochemistry to make great advancements. However, breakthroughs on this topic under extreme conditions are very scarce. Here, as an example, we employ operando Raman spectroscopy to decode the interfacial dynamics of titanium electrolysis using a tailored instrument. Direct spectral evidence not only confirms the two-step reduction pathway and the key intermediate (TiF 5 2– ) in molten fluorides with high-temperature and strong-corrosion conditions but also unravels the origins of the undesirable shuttling effect of TiF 5 2–, which are the sluggish reduction kinetics and outward diffusion behavior of TiF 5 2– . Moreover, an insightful atomic scenario of the electric double layer (EDL) under varied potentials has been established. These quantitative understandings guide us to design economical-feasible regulation protocols─the rational combination of a high-concentration, low-valence Ti-ion electrolyte with appropriate applied potential. Impressively, the current efficiency is greatly promoted from 27.7 to 81.8% using our proposed protocols. Finally, this work also demonstrates a bottom-up technological research paradigm for extreme electrochemistry based on mechanism insights rather than phenomenological findings, which will accelerate the advancement of extreme electrochemistry.