In order to prevent the electrolyte decomposition of liquid state Al-plastic film lithium-ion batteries during overcharge, the redox reactions of 2-chloro-1,4-dimethoxybenzene and 4-fluoro-1,2-dimethoxy-benzene as possible electrolyte additives were characterized by using overcharge tests, galvanostatic charge-discharge techniques, linear sweep voltammetry tests, rate capability tests, and cycling tests. Results indicate that for both additives, the initial charge reaction occurred at 4.1 V and their redox products were shuttled between the cathode and anode. The shuttle reactions will consume excess current, thus resulting in an improvement on overcharge performance for the batteries. In addition, the additives had little negative effects on the electrochemical performance when the current was low.