Zhang Xiaozhen, Liu Gaopan, Zhou Ke, Cheng Yong, Jiao Tianpeng, Huang Lin, Zou Yue, Wang Ming-Sheng, Yang Yong, Zheng Jianming
State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China; State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Materials, Xiamen University, Xiamen 361005, China.
J Colloid Interface Sci. 2022 Jul 15;618:431-441. doi: 10.1016/j.jcis.2022.03.089. Epub 2022 Mar 24.
Nickel-rich (Ni-rich) cathode materials, LiNiCoMnO (NCM, x ≥ 0.9, x + y + z = 1) hold great promise for developing high energy density lithium ion batteries especially for vehicle electrification. However, the practical application of Ni-rich cathode materials is still suffered from fast structural and interfacial degradation, and the resulted capacity decay. In this study, a diazacyclo type electrolyte additive, 2-fluoropyrazine (2-FP), was explored for the first time to boost the interfacial stabilization of single crystal LiNiCoMnO (NCM90) cathode. The capacity retention of the NCM90 is evidently promoted from 72.3% to 82.1% after 200 cycles at 1C (180 mA g) when adding 0.2% 2-FP into the electrolyte. The improvement of the electrochemical performance is ascribed to the generation of a compact and homogeneous cathode electrolyte interphase (CEI) film through ring-opening electrochemical polymerization of 2-FP upon the NCM90 electrode particles. This enhanced CEI layer benefits the suppression of the decomposition of LiPF electrolyte and the dissolution of the transition metals (Co and Mn), thus preventing the detrimental side reactions between the NCM90 electrode and the electrolyte.
富镍（Ni-rich）正极材料LiNiCoMnO（NCM，x≥0.9，x + y + z = 1）在开发高能量密度锂离子电池，特别是用于车辆电气化方面具有巨大潜力。然而，富镍正极材料的实际应用仍然受到快速的结构和界面降解以及由此导致的容量衰减的困扰。在本研究中，首次探索了一种二氮杂环型电解质添加剂2-氟吡嗪（2-FP），以增强单晶LiNiCoMnO（NCM90）正极的界面稳定性。当向电解质中添加0.2%的2-FP时，NCM90在1C（180 mA g）下循环200次后的容量保持率从72.3%显著提高到82.1%。电化学性能的改善归因于2-FP在NCM90电极颗粒上通过开环电化学聚合生成致密且均匀的正极电解质界面（CEI）膜。这种增强的CEI层有利于抑制LiPF电解质的分解和过渡金属（Co和Mn）的溶解，从而防止NCM90电极与电解质之间的有害副反应。
