Probing Blended-Additive-Regulated Interface Chemistry Based on a Dynamic Competition Mechanism in Lithium Metal Batteries

Engineering a durable electrode-electrolyte interphase is critical for high-voltage lithium metal batteries. A fundamental obstacle to this goal is the unresolved complexity of interface chemistry, especially involving blended electrolyte additives. Here, by revealing the decomposition pathway of lithium difluorophosphate (LiDFP) under the dynamic competition mechanism (DCM), we unravel the interface chemistry in blended-additive formulations combining LiDFP with other mainstream additives. When co-used, the LiNO₃ priority decomposition and LiDFP protonation alter interfacial evolution and trigger harmful H₃PO₄ and HF accumulation. Notably, fluoroethylene carbonate (FEC) remains undecomposed alongside LiDFP, defying its typical sacrificial role. The stable-existence FEC modulates the local chemical environment by directing targeted competitive H⁺ adsorption, which in turn drives more complete LiDFP decomposition to construct an inorganic-enriched interphase dominated by Li₃PO₄ and LiF. Building upon these insights, we propose a universal DCM framework that optimizes a multi-additive electrolyte system by tailoring additive synergies. This work shifts focus from empirical additive screening to a mechanism-driven design paradigm, offering an instructive blueprint for navigating complex interface chemistry.