Lithium Battery Electrolyte Additives for High-Temperature SEI Stability

The patent introduces specific chemical compounds (cesium salt and phosphazene) as additives to the electrolyte composition, changing the chemical parameters of the system. These additives modify the electrolyte's interaction with electrode surfaces, forming stable interface films that prevent decomposition reactions at high temperatures, thereby improving reliability without compromising basic operation.

The electrolyte is formulated as a composite system combining conventional components (lithium salt, non-aqueous organic solvent) with specialized additives (cesium salt compound and phosphazene compound). This composite approach allows the electrolyte to maintain its fundamental ionic conductivity while gaining enhanced thermal stability and electrode protection capabilities through the synergistic effects of the additive components.

The cesium salt and phosphazene compounds act as preliminary protective agents that decompose first during initial charging cycles to form stable solid electrolyte interface (SEI) films on the electrode surfaces. These pre-formed films prevent subsequent electrolyte decomposition and electrode material degradation at high temperatures, while the controlled composition ensures these films remain ion-conductive, avoiding excessive resistance buildup.

The phosphazene compound serves as an intermediary substance between the electrolyte and electrode surfaces. It forms a protective interface layer that mediates the interaction between the electrolyte components and electrode materials, preventing direct harmful reactions that would cause electrode decomposition. This intermediary layer maintains ion transport pathways, ensuring that resistance does not increase excessively while providing robust electrode protection.