高电压电解液添加剂在钴酸锂/石墨软包电池中的作用机理

The Working Mechanism of Additive in High Voltage Electrolyte for Lithium Cobaltate/Graphite Pouch Cell

1,2,3-三(2-氰氧基)丙烷(1,2,3-Tris(2-cyanoethoxy)propane,TPPN)作为一种新的电解液添加剂,可应用于4.55 V高电压钴酸锂(LiCoO_(2))/石墨软包电池。通过对比不含和含有TPPN添加剂的锂电池的循环性能,发现加入质量分数为2%的TPPN能大幅提高电池性能。3.00~4.55 V下以1C/1C倍率充放电,含有2%TPPN的电池在25℃下循环900周容量保持率为86.4%,而未添加TPPN的样品仅为8.7%。从理论计算和线性扫描数据可知,TPPN较电解液溶剂优先分解。从LiCoO_(2)表面上X射线光电子能谱的N 1s谱可知,TPPN在钴酸锂表面形成界面膜。从阻抗数据可知,该界面膜具有低阻抗和高稳定性质。从理论计算、LiCoO_(2)表面上扫描、透射电镜、X射线衍射谱和石墨表面上X射线光电子能谱的Co 2p谱可知,该界面膜能有效抑制电解液分解和钴离子的溶出,确认了界面膜的高稳定性质。

1,2,3-Tris(2-cyanoethoxy)propane(TPPN)as a new electrolyte additive has been investigated in 4.55 V high voltage lithium cobaltate(LiCoO_(2))/graphite pouch cells.By comparing the cycle performance of cells without and with TPPN,it is found that the addition of TPPN can improve the performance,and the optimal weight proportion is 2%.At 3.00-4.55 V and 1C/1C,the cells with 2%TPPN has a capacity retention rate of 86.4%at 25℃for 900 cycles compared with the capacity retention rate of 8.7%that without 2%TPPN.According to the theoretical calculation and linear sweep voltammetry,the decomposition of TPPN is preferred to that of the electrolyte solvent.It can be seen from N 1s spectra from X-ray photoelectron spectroscopy on LiCoO_(2) surface that TPPN forms an interfacial film on the LiCoO_(2) surface.It can be seen from the impedance data that the interface film formed by TPPN has low impedance and high stability.From theoretical calculation,scanning,transmission electron microscopy,X-ray diffraction on LiCoO_(2) surface and Co 2p spectra from X-ray photoelectron spectroscopy on graphite surface,it is revealed that the interface film formed by TPPN can effectively suppress the decomposition of electrolyte and the dissolution of cobalt ions,confirming the high stability of the interface film formed by TPPN.