Li-Ion Electrolyte Composition for Low Self-Discharge Storage

The patent applies preliminary action by pre-forming a stable solid electrolyte interphase (SEI) layer on the negative electrode before the battery is put into service. This is achieved through specific electrolyte composition (containing fluoroethylene carbonate and carboxylate) and initial charging cycles that create a protective film. This pre-formed SEI layer prevents subsequent self-discharge and over-discharge during long-term storage, thereby maintaining battery safety and reliability without requiring external monitoring or recharging interventions.

The patent applies parameter changes by precisely controlling the aluminum content parameter in the positive active material within a specific range (0.01-1.00 mass%). This optimized aluminum concentration, combined with specific electrolyte composition parameters (m/n ratio between 0.3-55), creates an optimal balance that reduces self-discharge rate while maintaining good cycle performance, high-temperature storage performance, and low-temperature discharge performance. The parameter optimization ensures no single performance metric is sacrificed for another.

The patent applies composite materials by creating a composite electrolyte system that combines fluoroethylene carbonate (FEC) and carboxylate in specific proportions (m/n ratio between 0.3-55). This composite electrolyte formulation leverages the complementary properties of both components: FEC provides robust SEI formation while carboxylate enhances stability. The synergistic interaction between these two electrolyte additives produces a stable solid electrolyte interphase that effectively prevents self-discharge, while the defined composition ratios keep the system manageable despite the increased complexity.