锂离子电池电解液过充添加剂的行为

制备了3种1 mol/L LiPF6电解液,溶剂组成分别为:1)碳酸乙烯酯,碳酸二甲酯和碳酸甲乙酯;2)碳酸乙烯酯,碳酸二甲酯,碳酸甲乙酯和4%联苯;3)碳酸乙烯酯,碳酸二甲酯,碳酸甲乙酯和4%环己基苯.采用线性电压扫描法、锂循环效率法、锂离子电池的循环性能法和3 C倍率过充的方法测试了联苯与环己基苯电解液过充添加剂的行为.结果表明:环己基苯是一种较实用的锂离子电池电解液过充添加剂,环己基苯的电化学稳定性比联苯的高,环已基苯的氧化电势为4.72 V(vs Li/Li ),联苯的为4.54 V(vs Li/Li );以1 mA电流循环20次后,联苯的铂电极锂循环效率为15.7%,环己基苯的为59.3%;锂离子电池以1 C循环150次后,环己基苯的容量保持率为88%,联苯的为76.3%.环己基苯与联苯添加剂都改善了锂离子电池的耐过充性能,且两者的效果十分接近.

Behavior of overcharging additives for electrolyte used in Li-ion batteries

Three kinds of 1 mol/L LiPF_6 electrolytes were prepared in various mixed solvents. The components of the electrolytes were as follows: 1) ethylene carbonate (EC), dimethylene carbonate (DMC), ethylmethyl carbonate (EMC); 2) EC, DMC, EMC 4% biphenyl (BP); 3) EC, DMC, EMC 4% cyclohexylbenzene (CB). The behaviors of electrolytes were analyzed by linear sweep voltage, lithium cycling efficiency, cycling performance and overcharging with 3C of lithium-ion batteries. The results show that CB is a kind of practical overcharging additive for electrolyte. The CB exhibits better electrochemical stability than BP due to the oxidation potential 4.72 V vs Li/Li~ for CB and 4.54 V vs Li/Li~ for BP. The lithium cycling efficiency of Pt electrode is 15.7% for BP electrolyte and 59.3% for CB electrolyte after 20 cycles with 1 mA. The capacity holding ratio of prismatic lithium-ion batteries is 88% for CB electrolyte and (76.3%)for BP electrolyte after 150 cycles at 1C. The overcharging tolerance of the lithium-ion batteries with CB and BP electrolyte are improved, and both of efficiencies are similar.