Graduate University of Chinese Academy of Sciences , Beijing 100039, P.R. China.
Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences , Chengdu, Sichuan 610041, P.R. China.
ACS Appl Mater Interfaces. 2016 Jul 20;8(28):18439-49. doi: 10.1021/acsami.6b04644. Epub 2016 Jul 11.
Dealing with the water molecule on the surface of LiNi0.6Co0.2Mn0.2O2 (NCM) cathode and hydrogen fluoride in the electrolyte is one of the most difficult challenges in Li-ion battery research. In this paper, the surface polymerization of tetraethyl orthosilicate (TEOS) on NCM to generate ethoxy-functional polysiloxane (EPS) wrapped NCM (E-NCM) cathode under mild conditions and without any additions is utilized to solve this intractable problem. The differential scanning calorimetry, transmission electron microscopy, and X-ray photoelectron spectroscopy results show that the formed amorphous coating can provide a protective shell to improve the NCM thermal stability, suppress the thickening of the solid electrolyte interphase (SEI) layer, and scavenge HF in the electrolyte. The E-NCM composite with 2 mol % EPS delivers a high discharge capacity retention of 84.9% after 100 cycles at a 1 C discharge rate in the 2.8-4.3 V potential range at 55 °C. Moreover, electrochemical impedance spectroscopy measurements reveal that the EPS coating could alleviate the impedance rise during cycling especially at an elevated temperature. Therefore, the fabricated E-NCM cathode with long-term cycling and thermal stability is a promising candidate for use in a high-energy Li-ion battery.
处理锂离子电池研究中最困难的挑战之一是在 LiNi0.6Co0.2Mn0.2O2（NCM）阴极表面的水分子和电解质中的氢氟酸。在本文中，利用正硅酸乙酯（TEOS）在温和条件下和不添加任何物质的情况下在 NCM 表面聚合，生成包裹 NCM 的乙氧基功能化聚硅氧烷（EPS）（E-NCM）阴极，以解决这个棘手的问题。差示扫描量热法、透射电子显微镜和 X 射线光电子能谱结果表明，形成的无定形涂层可以提供保护层，提高 NCM 的热稳定性，抑制固体电解质界面（SEI）层的增厚，并清除电解质中的 HF。在 55°C 下，在 2.8-4.3 V 电位范围内以 1 C 的放电速率进行 100 次循环后，具有 2 mol%EPS 的 E-NCM 复合材料的放电容量保持率高达 84.9%。此外，电化学阻抗谱测量表明，EPS 涂层可以减轻循环过程中的阻抗上升，特别是在高温下。因此，制备的具有长期循环和热稳定性的 E-NCM 阴极是用于高能锂离子电池的有前途的候选材料。
