Analysis of the Stable Interphase Responsible for the Excellent Electrochemical Performance of Graphite Electrodes in Sodium‐Ion Batteries. Issue 51 (27th November 2020)

• Record Type: Journal Article
• Authors: Wang, Zhaohua; Yang, Haoyi; Liu, Yiran; Bai, Ying; Chen, Guanghai; Li, Ying; Wang, Xinran; Xu, Huajie; Wu, Chuan; Lu, Jun
• Is Part Of: Small. Volume 16:Issue 51(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-27
• Subjects: ether‐based electrolyte -- graphite anode -- sodium‐ion batteries -- solid electrolyte interphase; Nanotechnology -- Periodicals; Nanoparticles -- Periodicals; Microtechnology -- Periodicals; 620.5
• DOI: 10.1002/smll.202003268
• Languages: English
• ISSNs: 1613-6810

Abstract

Abstract: 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 (Na2 CO3, 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%). Abstract : In this study, the ether‐derived SEI on the graphite surface shows fast kinetics and excellent mechanical properties. The special properties are attributed to the multilayer structure of the ether‐derived SEI that comprised a primary inorganics interior and an organics exterior. The multilayer structure not only guarantees the stability of the SEI but also enhances the adaptability to high volume changes.