Revealing of the Activation Pathway and Cathode Electrolyte Interphase Evolution of Li-Rich 0.5Li2MnO3·0.5LiNi0.3Co0.3Mn0.4O2 Cathode by in Situ Electrochemical Quartz Crystal Microbalance

Zu-Wei Yin; Xin-Xing Peng; Jun-Tao Li; Chong-Heng Shen; Ya-Ping Deng; Zhen-Guo Wu; Tao Zhang; Qiu-Bo Zhang; Yu-Xue Mo; Kai Wang; Ling Huang; Haimei Zheng; Shi-Gang Sun

doi:10.1021/acsami.9b02236

Revealing of the Activation Pathway and Cathode Electrolyte Interphase Evolution of Li-Rich 0.5Li₂MnO₃·0.5LiNi_0.3Co_0.3Mn_0.4O₂ Cathode by in Situ Electrochemical Quartz Crystal Microbalance

ACS Appl Mater Interfaces. 2019 May 1;11(17):16214-16222. doi: 10.1021/acsami.9b02236. Epub 2019 Apr 19.

Authors

Zu-Wei Yin¹, Xin-Xing Peng¹, Jun-Tao Li, Chong-Heng Shen, Ya-Ping Deng, Zhen-Guo Wu², Tao Zhang, Qiu-Bo Zhang^{1

3}, Yu-Xue Mo, Kai Wang², Ling Huang, Haimei Zheng^{1

4}, Shi-Gang Sun

Affiliations

¹ Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
² School of Chemical Engineering , Sichuan University , Chengdu 610065 , China.
³ SEU-FEI Nano-Pico Center, Key Laboratory of MEMS of Ministry of Education, School of Electronic Science and Engineering , Southeast University , Nanjing 210018 , China.
⁴ Department of Materials Science and Engineering , University of California , Berkeley , California 94720 , United States.

PMID: 30951277
DOI: 10.1021/acsami.9b02236

Abstract

The first-cycle behavior of layered Li-rich oxides, including Li₂MnO₃ activation and cathode electrolyte interphase (CEI) formation, significantly influences their electrochemical performance. However, the Li₂MnO₃ activation pathway and the CEI formation process are still controversial. Here, the first-cycle properties of xLi₂MnO₃·(1- x) LiNi_0.3Co_0.3Mn_0.4O₂ ( 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 Li₂MnO₃ and LiNi_0.3Co_0.3Mn_0.4O₂ structures can significantly affect the activation pathway of Li_1.2Ni_0.12Co_0.12Mn_0.56O₂, leading to an extra-high capacity. It is demonstrated that Li₂MnO₃ activation in Li-rich materials is dominated by electrochemical decomposition (oxygen redox), which is different from the activation process of pure Li₂MnO₃ governed by chemical decomposition (Li₂O 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.

Keywords: CEI evolution; Li-rich materials; Li2MnO3 activation; in situ EQCM; oxygen redox.