Construction of Localized High-Concentration PF₆ ^- Region for Suppressing NCM622 Cathode Failure at High Voltage

High-voltage Li||LiNi_0.6 Co_0.6 Mn_0.2 O₂ (NCM622) batteries have obtained great interest owing to their high energy density. However, some obstacles hinder their practical applications, e.g., the structural failure of NCM622 and corrosion of the Al current collector, which lead to limited cycling life. Herein, an electrolyte additive strategy is proposed for constructing localized high-concentration PF₆ ^- zone near the cathode to form an efficient cathode electrolyte interphase (CEI) for protecting NCM622 and preventing Al current collector from the corrosion. Potassium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide is used as the additive to regulate the sheath structure of Li⁺ solvation to force PF₆ ^- anions away from the solvated Li⁺ . During the charge process, the nonsolvated PF₆ ^- anions gather on NCM622 surface to form a localized high-concentration PF₆ ^- zone to facilitate the formation of F-rich CEI on NCM622 for protecting its structural stability and Al current collector.