Decoupling Electrolyte Degradation Pathways With Diverse Li Plating Processes on Graphite Electrodes

ABSTRACT Lithium plating on graphite anodes is a critical degradation pathway in lithium‐ion batteries (LIBs), yet quantitative decoupling of its contribution from normal anode aging remains challenging. Here, we designed controlled Li plating tests using negative‐to‐positive ( N/P ) ratio < 1 LiFePO ₄ /graphite cells and then compared them with practical fast‐charging cells ( N/P > 1), quantifying the decomposition of each electrolyte component (solvent, salt, additives) using nuclear magnetic resonance (NMR), mass spectrometry titration (MST), and gas chromatography‐mass spectrometry (GC‐MS). Controlled Li plating occurs after full graphite lithiation, and it leads to rapid vinylene carbonate (VC) depletion, time‐dependent non‐Faradaic consumption of hexafluorophosphate (PF ₆ ⁻ )/ethyl methyl carbonate (EMC)/ethylene carbonate (EC), and more organic solid‐electrolyte interphase (SEI) formation at higher rates. In routine fast‐charging aging, Li plating occurs before graphite saturation, and we find pronounced EMC consumption under high‐rate conditions compared with low ‐ rate. Our comparative analysis indicates that VC consumption during fast charging originates not only from plating but also significantly from baseline graphite aging. Li plating likely induces SEI rupture, leading to direct contact with electrolyte, thus more organic SEI formation. This quantitative study enables decoupling of Li plating‐induced side reactions from general aging without plating, informing battery design and predictive aging models.