吡咯类离子液体电解质性质对锂空气电池放电性能的影响

Pyrrolidinium-based Ionic Liquids as Electrolytes and Discharge Performance for Lithium Air Cell

利用循环伏安法、电池充放电装置等电化学手段,测试了所选离子液体N-甲基-N-丙基吡咯双三氟甲基磺酸基酰亚胺(PYR13TFSI)、N-甲基-N-丁基吡咯双三氟甲基磺酸基酰亚胺(PYR14TFSI)和N-甲基-N-甲氧乙基吡咯双三氟甲基磺酸基酰亚胺(PYR1(201)TFSI)的饱和氧溶解度、溶液电导率及氧电化学行为随锂盐浓度的变化。结果显示:室温离子液体的溶液电导率和氧扩散系数与锂盐质量摩尔浓度呈负相关,氧气溶解度随着锂盐质量摩尔浓度的增加呈现先降后升的"火山形"趋势;在0.6mol/kg LiTFSI条件下,PYR1(201)TFSI离子液体的氧电还原反应活性较高,而PYR14TFSI离子液体的相对较低;PYR14TFSI,PYR1(201)TFSI和PYR13TFSI离子液体组成的锂空气电池的放电电容分别是1 068,1 084,1 249mAh/g,PYR13TFSI离子液体的放电电压最高,明显高于有机电解液(EC、DMC、EMC体积比为1∶1∶1)锂空气电池的放电电容及电压。

The ionic liquids were characterized by cyclic voltammetry and cell discharge/charge test and other measurements in order to study the saturated oxygen solubility, electrolyte conductivity and oxygen electro chemical properties with varying Li-salt concentration for N-butyl-N- methyl pyrrolidinium bis （trifluoromethanesulfonyl） imide （PYR14 TFSI）, N-methoxyethyl-N- methyl pyrrolidinium bis （trifluoromethanesulfonyl） imide （PYR1（201） TFSI） and N-propyl-N- methyl pyrrolidinium bis （trifluoromethanesulfonyl） imide （PYR13TFSI）. The results show that the electrolyte conductivity and oxygen diffusion coefficient in RTILs electrolytes were inversely proportional to Li-salt concentration. The saturated oxygen solubility dectreased and then increased with the increase of Li-salt concentration in RTILs. The activity of oxygen reduction was best in PYR1（201） TFSI and worst in PYR14TFSI in the presence of 0.6 mol/kg LiTFSI. The discharge capacity for lithium air cell with PYR14 TFSI, PYR1（201） TFSI and PYR13 TFSI in the presence of 0.6 mol/kg LiTFSI was 1 068, 1 084,1 249 mAh/g, respectively. Lithium air cell with 0.6 mol/kg LiTFSI-PYR13TFSI had the highest discharge plateau and obviously higher than the lithium air cell with organic electrolyte （VEC： VDMC ： VEMC=1： 1 ： 1）.