功能添加剂对锂离子电池的防过充电化学行为研究

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

研究了功能添加剂3-氯苯甲醚(3CA)和联苯(BP)联合使用在锂离子电池电解液中的防过充行为.通过采用微电极循环伏安法、动电位扫描分析、扫描电镜法和充放电法等手段研究表明:联苯和3-氯苯甲醚混合添加剂的聚合电位随3-氯苯甲醚含量的增加由4.7V前移至4.6V(vs.Li/Li+);电池在正常工作电压(2.75～4.2V)下,添加剂不参与电池反应过程;当电压高于4.2V电池发生过充时,3-氯苯甲醚在电极表面首先发生氧化还原飞梭分流限压对电池进行过充保护;电压继续升高时,联苯在电极表面发生电聚合反应,生成的聚合膜表面光滑致密是电子的良导体能有效地阻止Li+的嵌入与脱出,并通过自放电使电池处于安全状态,防止电池过充发生爆炸.两种防过充机制共同作用,对电池实施多重护防,提高了电池的安全性能.

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 polymeri zation 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.