Revealing of the Activation Pathway and Cathode Electrolyte Interphase Evolution of Li-Rich 0.5Li 2 MnO 3 ·0.5LiNi 0.3 Co 0.3 Mn 0.4 O 2 Cathode by in Situ Electrochemical Quartz Crystal Microbalance

• Published in: ACS applied materials & interfaces Vol. 11; no. 17; pp. 16214 - 16222
• Main Authors: Yin, Zu-Wei, Peng, Xin-Xing, Li, Jun-Tao, Shen, Chong-Heng, Deng, Ya-Ping, Wu, Zhen-Guo, Zhang, Tao, Zhang, Qiu-Bo, Mo, Yu-Xue, Wang, Kai, Huang, Ling, Zheng, Haimei, Sun, Shi-Gang
• Format: Journal Article
• Language: English
• Published: United States 01.05.2019
• Subjects: CEI evolution; Li-rich materials; in situ EQCM; Li2MnO3 activation; oxygen redox
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.9b02236

The first-cycle behavior of layered Li-rich oxides, including Li MnO activation and cathode electrolyte interphase (CEI) formation, significantly influences their electrochemical performance. However, the Li MnO activation pathway and the CEI formation process are still controversial. Here, the first-cycle properties of xLi MnO ·(1- x) LiNi Co Mn O ( x = 0, 0.5, 1) cathode materials were studied with an in situ electrochemical quartz crystal microbalance (EQCM). The results demonstrate that a synergistic effect between the layered Li MnO and LiNi Co Mn O structures can significantly affect the activation pathway of Li Ni Co Mn O , leading to an extra-high capacity. It is demonstrated that Li MnO activation in Li-rich materials is dominated by electrochemical decomposition (oxygen redox), which is different from the activation process of pure Li MnO governed by chemical decomposition (Li O evolution). CEI evolution is closely related to Li extraction/insertion. The valence state variation of the metal ions (Ni, Co, Mn) in Li-rich materials can promote CEI formation. This study is of significance for understanding and designing Li-rich cathode-based batteries.