Fluorinated Electrolyte Additive for Lithium Battery Swelling Control

The patent introduces a fluorinated cyclic carbonate additive as an intermediary substance that mediates between the electrolyte and the positive electrode. This additive forms a stable passivation film (interphase layer) on the electrode surface, which acts as a protective barrier. The passivation film prevents direct contact and harmful reactions between the electrolyte and electrode, thereby suppressing swelling and improving cycle-life while maintaining high voltage operation capability.

The patent modifies the chemical composition parameters of the electrolyte by incorporating fluorinated cyclic carbonate compounds with specific molecular structures (containing F, C=O, and cyclic carbonate groups). This parameter change in the electrolyte composition leads to the formation of a more stable solid electrolyte interface (SEI) layer and passivation film, which enhances battery reliability and reduces swelling at high temperature and voltage conditions.

The patent optimizes the concentration parameter of the fluorinated cyclic carbonate additive within a specific range (0.01-5 wt%, preferably 0.1-3 wt%). This parameter optimization ensures sufficient passivation film formation to reduce swelling while maintaining adequate charge/discharge efficiency. The precise control of additive concentration balances the competing requirements of swelling reduction and productivity.

The patent applies partial action by using a small but sufficient amount of the fluorinated cyclic carbonate additive (0.01-5 wt%) to achieve the desired passivation film formation. This partial action is sufficient to create an effective protective layer without excessive additive concentration that would overly impede ion transport and reduce charge/discharge efficiency.