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Analysis of the Stable Interphase Responsible for the Excellent Electrochemical Performance of Graphite Electrodes in Sodium‐Ion Batteries
Author(s) -
Wang Zhaohua,
Yang Haoyi,
Liu Yiran,
Bai Ying,
Chen Guanghai,
Li Ying,
Wang Xinran,
Xu Huajie,
Wu Chuan,
Lu Jun
Publication year - 2020
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.202003268
Subject(s) - graphite , electrolyte , materials science , anode , chemical engineering , electrochemistry , fourier transform infrared spectroscopy , electrode , x ray photoelectron spectroscopy , chemistry , composite material , engineering
Considerable efforts have been exerted to understand the formation and properties of the solid electrolyte interphase (SEI) in sodium ion batteries. However, the puzzling existence and role of SEI behind the huge volume changes of the graphite electrodes need to be answered. Herein, the reason of how ether‐derived SEI maintains excellent reversibility despite the huge volume changes during cycling is unraveled. Theoretical simulations and Fourier‐transform infrared spectroscopy demonstrate the formation mechanism of an SEI between the graphite anode and electrolyte. Furthermore, the high mechanical tolerance of the ether‐derived SEI is confirmed in atomic force microscopy. A depth profile of X‐ray photoelectron spectroscopy points to a multilayer structure of the ether‐derived SEI. The outer layer comprises organics (sodium alkoxide), while the inorganics (Na 2 CO 3 , NaF) in interior region are mixed with some organics. Notably, the presence of organics ensures the adaptability of the SEI to the volume expansion of graphite during cycling, and the concentrated distribution of inorganics improves the Young's modulus (resistance to deformation). Therefore, the graphite anode exhibits high cycle stability (96.6% capacity retention ratio at 1 A g –1 over 860 cycles) and efficiency (≈99.5%).