摘要
将传统锂盐六氟磷酸锂(LiPF_6)与新型锂盐双氟代磺酰亚胺锂(LiFSI)混合作为高功率锂离子电池电解液的导电锂盐,可充分发挥LiFSI离子导电性好、不易水解的优势,相比传统的LiPF_6电解液,混合锂盐电解液应具有更好的功率特性和化学稳定性。利用恒电位极化法、循环伏安法及交流阻抗谱等电化学测试手段,详细研究了(LiPF_6/LiFSI)/(EC+DMC+EMC)(质量比1∶1∶1)电解液在以LiFePO_4为正极的锂离子电池中的电化学性能。结果表明,适量LiFSI的加入能明显提高电解液的电导率和Li+迁移数,改善LiFePO_4电极Li+嵌入/脱出反应的可逆性并降低电极界面阻抗。18650型全电池的倍率放电结果表明,在大倍率放电情况下,混合盐电解液表现出明显优于纯LiPF_6电解液的性能。
LiPF_6 and lithium bis(fluorosulfonyl)imide(LiFSI) were blended as lithium salt used in electrolyte of high-power lithium-ion batteries. Compared with LiPF_6, LiFSI has higher ion conductivity and hydrolytic stability which may improve the power property and chemical stability of the electrolyte. The electrochemical behaviors of the blend salts in ethylene carbonate + dimethyl carbonate + ethylmethyl carbonate [(EC+DMC+EMC),ω(EC) ∶ω(DMC) ∶ω(EMC)=1∶1∶1], were investigated by potentiostatic polarization method, CV test and EIS test. The results show that the appropriate amount of LiFSI can increase the Li+ transference number and ion conductivity of electrolyte; the rever phase sibility of the two-charge/discharge reaction with LiFSI contained electrolyte systems is much better than pure LiPF_6 electrolyte systems. Meanwhile, the results of impedance spectroscopy suggest that the addition of LiFSI has good influence on the LiFePO_4 electrode surface. The result of discharge test at 1 C to 20 C shows that the rate performance of 18650 LiFePO_4/AG battery is remarkably improved by blending LiFSI and LiPF_6 salts compared to those of pure LiPF_6-based electrolyte system, especially at 20 C.
出处
《电源技术》
CAS
CSCD
北大核心
2018年第1期12-15,共4页
Chinese Journal of Power Sources
