锂离子电池电解液过充添加剂的行为

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

制备了 3种 1mol/LLiPF6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 3C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 .72V(vsLi/Li+ ) ,联苯的为 4 .5 4V(vsLi/Li+ ) ;以 1mA电流循环 2 0次后 ,联苯的铂电极锂循环效率为 15 .7% ,环己基苯的为 5 9.3% ;锂离子电池以 1C循环 15 0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 。

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.