Work

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

Year: 2019

Type: article

Abstract: The first-cycle behavior of layered Li-rich oxides, including Li 2 MnO 3 activation and cathode electrolyte interphase (CEI) formation, significantly influences their electrochemical performance. However, the Li 2 MnO 3 activation pathway and the CEI formation process are still controversial. Here, the first-cycle properties of x Li 2 MnO 3 ·(1– x ) LiNi 0.3 Co 0.3 Mn 0.4 O 2 ( 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 2 MnO 3 and LiNi 0.3 Co 0.3 Mn 0.4 O 2 structures can significantly affect the activation pathway of Li 1.2 Ni 0.12 Co 0.12 Mn 0.56 O 2, leading to an extra-high capacity. It is demonstrated that Li 2 MnO 3 activation in Li-rich materials is dominated by electrochemical decomposition (oxygen redox), which is different from the activation process of pure Li 2 MnO 3 governed by chemical decomposition (Li 2 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.

Source: ACS Applied Materials & Interfaces

DOI: 10.1021/acsami.9b02236