Atomic structure and migration dynamics of MoS2/LixMoS2 interface. (June 2018)

• Record Type: Journal Article
• Authors: Chen, Shulin; Wang, Liping; Shao, Ruiwen; Zou, Jian; Cai, Ran; Lin, Jinhuang; Zhu, Chongyang; Zhang, Jingmin; Xu, Feng; Cao, Jian; Feng, Jicai; Qi, Junlei; Gao, Peng
• Is Part Of: Nano energy. Volume 48(2018)
• Page Start: 560
• Page End: 568
• Publication Date: 2018-06
• Subjects: in situ TEM -- 2D materials -- Lithium ion diffusivity -- Phase transition -- Phase interface -- Aberration corrected STEM; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2018.03.076
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: The performance of alkali-metal-ion batteries largely depends on the migration behavior of alkali metal ions in the electrodes. Probing the atomic structure of the reaction interface and the dynamic process during ion transport in the electrodes will help better understand the underlying electrochemical mechanisms and inspire rational electrode designs. In this study, by combining in situ transmission electron microscopy (TEM) and aberration-corrected scanning TEM (STEM), we track the reversible lithium ion transport in MoS2 nanostructures to reveal the atomic structure and dynamic behaviors of the reaction interface. We find that lithium ions insertion triggers complex phase transformations. Three different phases co-exist at the interface: a pristine 2H phase, a 1T phase with a shrank lattice constant of − 3.3% ( ± 2.3%), and a distorted 1T phase (called 1Tˊ phase) with an expanded lattice constant of 5.5% ( ± 2.5%). The atomically resolved Z-contrast image shows that the expanded 1Tˊ phase has distorted Mo arrangements. Furthermore, the lithium ions migration causes defects at the reaction front, and the diffusion on the surface is faster than that inside, forming a core-shell structure at the reaction interface. The diffusivity of lithium ions is directly measured to be ~1000–30, 000 nm 2 /s, which is significantly higher than that of sodium insertion (~10–20 nm 2 /s). The atomic-scale observations of lithium-ion-migration-induced complex structural evolutions would help understand the properties of MoS2 nanostructures and shed light on the design of alkali-metal-ion batteries with general transition-metal dichalcogenide electrodes. Graphical abstract: A combination of in situ transmission electron microscopy, aberration-corrected scanning transmission electron microscopy and electrochemical measurements are employed to probe the dynamics and atomic structure of reaction interface during reversible lithium ion migration in MoS2 nanostructures. fx1 Highlights: Diffusion dynamics of alkali metal ions in MoS2 nanostructures is revealed. Reversible lithium ion transport in MoS2 nanostructures is observed. Co-existence of 2H, shrank 1T, and expanded 1T′ phases is observed at the interface. Diffusivity of Li + is compared with Na + from in situ TEM and electrochemical tests. Atomic structure of the expanded 1T′ phase shows the distorted Mo clusters.