Nitrogen-Containing Electrolyte Additive for Stable SEI Film Formation

The patent changes the chemical parameters of the electrolyte additive by introducing a specific molecular structure with a nitrogen-containing six-membered aromatic ring and fluorinated alkyl groups. This structural modification alters the electrochemical behavior, enabling the additive to form a uniform and stable SEI film at high temperatures and voltages, thereby improving battery lifetime characteristics while maintaining composition stability.

The electrolyte additive combines multiple functional groups within a single molecular structure: a nitrogen-containing aromatic ring for SEI formation, fluorinated alkyl groups for stability and low reactivity, and specific substituents for controlling film uniformity. This composite molecular design creates an additive that simultaneously achieves uniform SEI film formation and high stability under extreme conditions, resolving the contradiction between film uniformity and stability.

The patent converts the potential harmful reactivity of the electrolyte additive into a beneficial effect by designing a molecule where the nitrogen-containing aromatic ring selectively reacts with lithium ions to form a protective SEI film, while the fluorinated alkyl groups prevent unwanted side reactions. The additive's reactivity is directed toward forming a beneficial coating rather than causing degradation, effectively converting potential harm into benefit.

The additive exhibits local quality differentiation through its molecular structure: the nitrogen-containing aromatic ring portion is reactive and localized at the electrode surface to form the SEI film, while the fluorinated alkyl groups remain relatively inert and provide stability throughout the electrolyte bulk. This spatial and functional differentiation allows the additive to achieve good coverage without causing widespread degradation or oxidation reactions.