Anion‐Driven Solvent Degradation Networks in High‐Concentration Battery Electrolytes

ABSTRACT High‐concentration electrolytes (HCEs) are investigated for their ability to form robust, inorganic‐rich solid electrolyte interphases (SEI). While the SEI composition in HCEs differs from that in dilute electrolytes, the specific anion‐mediated reaction network driving this transformation remain poorly understood. The network complexity and transient nature of the radical intermediates involved have precluded the development of a comprehensive mechanistic map of initial SEI formation. Here, the reaction networks governing anion‐mediated electrolyte degradation are established using automated reaction discovery and microkinetic modeling (MKM). The study encompasses the decomposition pathways of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and acetonitrile (AN) in the presence of reduced anion species derived from LiFSI and LiTFSI. The results reveal a kinetically accessible landscape for solvent decomposition driven by fluoride () and fragments, identifying specific pathways that favor the formation of inorganic LiF and open‐ring organic carbonates. Microkinetic modeling further indicates that acts as a rapidly consumed driver, shifting the product distribution toward thermodynamically stable fluoro‐organic species. These results provide a molecular‐level rationalization for the unique SEI chemistries observed in HCEs and suggest that tuning the anion‐solvent interaction is a viable pathway for controlling interphase growth.