七氟丁酸酐电解液添加剂提升锂金属负极性能

Heptafluorobutyric anhydride as an electrolyte additive to improve the performance of lithium metal anode

锂金属负极由于其较高的理论比容量和较低的电极电势被认为是负极材料中的“圣杯”,但锂枝晶的生长严重阻碍了锂金属负极的实际应用.本文研究了七氟丁酸酐(HFAA)作为电解液添加剂对锂金属负极电化学性能的影响,通过理论计算、循环伏安测试、扫描电镜和X射线光电子能谱等分析手段,研究了HFAA添加剂在锂金属负极中的作用机制.结果表明,HFAA添加剂可以优先在锂金属负极表面发生还原反应,生成更多含LiF和—CO_(2)Li组分的有机/无机复合固态电解质界面膜,能有效地抑制锂枝晶的生长.在基础电解液中加入3%(质量分数)HFAA添加剂后,Li/Li对称电池在0.5 mA/cm^(2)的电流密度下能稳定循环480 h,Li/LiFePO^(4)电池在5 C倍率下循环300圈后的容量保持率为83%.

Lithium metal anode is considered to be the"holy grail"of anode materials because of its high theoretical specific capacity and low electrode potential.However,the growth of lithium dendrites seriously hinders the practical application of lithium metal anode.In this paper,the influence of heptafluorobutyric anhydrid(HFAA)as an electrolyte additive on the electrochemical performance of lithium metal anode was investigated.The action mechanism of HFAA additive in lithium metal anode was explored by means of theoretical calculation,cyclic voltammetry,scanning electron microscope and X-ray photoelectron spectroscopy.The results showed that HFAA additive could preferably result in a reduction reaction on the surface of lithium metal anode to form an organic/inorganic composite solid electrolyte interface film containing more LiF and—CO_(2)Li.Thus,it effectively inhibited the growth of lithium dendrites.By adding 3%(mass fraction)HFAA additive into the base electrolyte,the Li/Li symmetrical cell stably cycled for 480 h at a current density of 0.5 mA/cm 2,and the capacity retention rate of the Li/LiFePO_(4)cell was 83%after 300 cycles at a rate of 5 C.