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
Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
School of Chemical Engineering , Sichuan University , Chengdu 610065 , China.
ACS Appl Mater Interfaces. 2019 May 1;11(17):16214-16222. doi: 10.1021/acsami.9b02236. Epub 2019 Apr 19.
The first-cycle behavior of layered Li-rich oxides, including LiMnO activation and cathode electrolyte interphase (CEI) formation, significantly influences their electrochemical performance. However, the LiMnO activation pathway and the CEI formation process are still controversial. Here, the first-cycle properties of xLiMnO·(1- x) LiNiCoMnO ( 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 LiMnO and LiNiCoMnO structures can significantly affect the activation pathway of LiNiCoMnO, leading to an extra-high capacity. It is demonstrated that LiMnO activation in Li-rich materials is dominated by electrochemical decomposition (oxygen redox), which is different from the activation process of pure LiMnO governed by chemical decomposition (LiO 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.
富锂层状氧化物的首次循环行为，包括LiMnO活化和阴极电解质界面（CEI）形成，对其电化学性能有显著影响。然而，LiMnO活化途径和CEI形成过程仍存在争议。在此，采用原位电化学石英晶体微天平（EQCM）研究了xLiMnO·(1 - x)LiNiCoMnO（x = 0, 0.5, 1）阴极材料的首次循环性能。结果表明，层状LiMnO和LiNiCoMnO结构之间的协同效应可显著影响LiNiCoMnO的活化途径，从而导致超高容量。结果表明，富锂材料中的LiMnO活化主要由电化学分解（氧还原）主导，这与纯LiMnO由化学分解（LiO析出）控制的活化过程不同。CEI演变与锂的脱嵌密切相关。富锂材料中金属离子（Ni、Co、Mn）的价态变化可促进CEI形成。该研究对于理解和设计基于富锂阴极的电池具有重要意义。
