含硫添加剂对石墨负极低温性能的研究

Effects of Sulfur-Containing Additive on Low Temperature Performance of Graphite Anode

锂离子电池的低温性能主要取决于石墨负极,通过添加剂来改善负极的低温性能是研究的焦点之一.本文比较了3种具有不同含硫官能团的添加剂DTD(ethylene sulfate)、1,3-PS(1,3-propane sultone)和ES(ethylene sulfite)对传统商业化材料人造石墨负极低温性能的影响. DFT(密度泛函理论)计算、扫描伏安法(CV)、扫描电子显微镜(SEM)和电化学测试结果表明,3种含硫添加剂均可在人造石墨负极表面参与成膜,并对其低温性能产生比较大的影响.其中,DTD对石墨负极低温性能改善最为明显,1,3-PS对石墨负极的低温性能造成不利影响,而ES则没有明显作用.电化学交流阻抗(EIS)和X射线光电子能谱(XPS)表明,这3种添加剂的不同作用主要在于其所形成的电极界面膜在电化学阻抗方面存在着明显的差异.

The low temperature performance of lithium ion battery mainly depends on the graphite anode, and one of the research focuses is to improve the low temperature performance of the anode by additives. In this paper, the effects of different sulfur-containing functional groups such as DTD(ethylene sulfate), 1,3-PS(1,3-propane sultone) and ES(ethylene sulfite) on low temperature performances of artificial graphite materials were systematically studied. The results in density functional theory(DFT) calculations, cyclic voltammetry(CV), scanning electron microscopy(SEM) and charge-discharge measurement clearly demonstrated that all three sulfur-containing additives could participate in formation of films on the surface of electrode, which had a greater impact on the low temperature properties. The apparent enhancement was achieved with DTD because of the film formed with a smaller resistance. In contrast, the reduced performance was observed with 1,3-PS due to its non-conductive film formed at low temperatures, while no obvious effect with ES. The data in electrochemical impedance spectroscopy(EIS) and X-ray photoelectron spectroscopy(XPS) indicated that these three kinds of additives influenced differently the low temperature performances of lithium ion battery due mainly to their significantly different impedances resulted from the films formed at the interfaces of electrodes.