关键词: 锂离子电池, 电聚合, 过充保护, 联苯

Abstract: The electropolymerization of biphenyl at overcharged positive electrode was investigated for overcharge protection of Li_ion batteries. Biphenyl in electrolyte as an additive can electrochemically polymerize at 4.5～4.75 V(vs. Li/Li+) to form a layer of conductive film on cathode surface. The surface film increases the internal resistance and the gases released during the electropolymerization also increases the internal pressure of the batteries, which therefore enhance the sensitivities of the electrical disconnecting devices. During prolonged overcharge, the growth of the conductive polymer film can create short circuit between the positive and negative electrodes and cause self_discharge of the batteries to a safer state. Furthermore, no severe detrimental effects were observed on the battery performances in normal state of charge_discharge.