1,3-二氧戊环对锂的表面改性机理

Surface modification mechanism of lithium electrode with 1,3-Dioxolane

摘要:

为研究预处理液对二次金属锂电极的表面改性机理,采用1,3-二氧戊环作为预处理液,对锂电极进行浸泡处理,然后与LiCoO2组装成扣式电池.测试电池的循环性能和放电性能,并对循环到第10次和第70次的电池在不同放电电压下进行电化学阻抗谱(EIS)研究,提出一种合理的等效电路模型分析锂电极各部分阻抗的变化.结果表明,用13,-二氧戊环处理可使锂电极性能得到较大提高.EIS分析表明,处理后生成的SEI膜结构更稳定,而且与锂基体的界面相容性更好,使电子转移更容易进行.锂负极在循环过程中性能下降的主要原因是其表面膜电阻和电荷传递电阻越来越大,导致锂离子在SEI膜中的迁移阻力增大,电子转移阻力也增大.

Abstract:

Lithium metal electrode was pre-treated with 1,3-dioxolane in order to study the surface modification mechanism on it,then coin cells were assembled with LiCoO2 cathode and the cycle and discharge performance were tested.The electrochemical impedance spectroscopy(EIS) were employed on the cells in the 10th and 70th cycle at different discharge voltage,and a reasonable equivalent circuit was proposed to analyze the changement of impedance values correspondingly.It is found that the electrode properties are improved greatly.The EIS analysis shows that 1,3-dioxolane can form a stable SEI layer on the surface of Li electrode.This layer is able to enhance the interfacial compatibility without depressing Li ions kinetic behavior.The reason for the performance of lithium electrode getting worse in cycleability is the increment of surface membrane resistance and charge transfer resistance,which leads to the higher lithium ions migration resistance and electron transfer resistance.