Ethylene ethyl phosphate as a multifunctional electrolyte additive for lithium-ion batteries

The effects of ethylene ethyl phosphate (EEP) as a multifunctional electrolyte additive on safety characteristics and electrochemical performance of lithium-ion batteries are investigated. Based on the flammability test, the self-extinguishing time of the electrolyte with 10% EEP is only less than half of the baseline electrolyte, which indicates that EEP is a highly efficient flame retardant for the electrolyte. During overcharging the LiNi_1/3Co_1/3Mn_1/3O₂/Li cells, incorporation of EEP into the electrolyte can postpone the sharp voltage rise. Therefore, EEP is an improver of safety characteristics of lithium-ion batteries, both in terms of flame resistance and overcharge protection. Furthermore, the EEP-containing electrolyte in the half-cells and full-cells both exhibit higher initial coulombic efficiency and cycling stability than the baseline electrolyte. It is concluded that EEP is a good film-formation additive not only for the graphite anode, but also for the LiNi_1/3Co_1/3Mn_1/3O₂ cathode. Therefore, EEP is proposed as a promising multifunctional electrolyte additive for lithium-ion batteries.