4-Bromoanisole (4BA) as Additive for Overcharge Protection of Lithium-Ion Batteries

4-Bromoanisole (4BA) is recommended for LiNi0.6Co0.2Mn0.2O2 (NCM 622) cathode materials as a safety electrolyte additive. The effect of anti-overcharge on NCM 622 cathodes are analyzed by cyclic voltammetry, constant current charge and discharge, AC impedance and scanning electron microscopy (SEM) measurement. The overcharge test results show that 4BA can be effectively electropolymerized at 4.45 V (vs. Li/Li + ), which can consume the overcharge current and protect the working electrode from voltage runaway. The time for the voltage rising to the overcharge state is availably delayed from about 16 hours to about 37 hours. The strategy can block off further oxidation of the active material and electrolyte, and finally promote the overcharge tolerance of the Li-ion batteries. Moreover, it is also found that the use of 4BA as a safety electrolyte additive does not obviously effect the electrochemical performance of NCM 622 and can effectively improve its cycle stability at high cut-off voltage (4.7 V).