Electrochemical Behavior of Function Additive for Overcharge Protection of Li-ion Batteries

The overcharge protection and electrochemical property of lithium ion batteries were studied by microelectrode voltammetry, potentiodynamic polarization experiments, charge-discharge measurements and SEM characterization of cell components, when functional additives such as biphenyl (BP) and 3-chloroanisole (3CA) were co-used in the electrolyte. The experimental results reveal that the polymerization potential of electrolyte with mixed additives was moved forward from 4.7 to 4.6 V, as the content of 3-chloroanisole increased. When overcharged, 3-chloroanisole molecules were oxidized in the form of redox shuttle reaction at the positive electrode, but biphenyl molecules were polymerized forming a compact film on the surface of electrode. This film formed can effectively prevent the insertion and extraction of Li+. In this way, the safety performance of lithium ion batteries can be improved by the co-use of the two additives with different overcharge protection mechanisms.