title: Atomic-Scale Probing of the Dynamics of Sodium Transport and Intercalation-Induced Phase Transformations in MoS₂.
abstract: For alkali-metal-ion batteries, probing the dynamic processes of ion transport in electrodes is critical to gain insights into understanding how the electrode functions and thus how we can improve it. Here, by using in situ high-resolution transmission electron microscopy, we probe the dynamics of Na transport in MoS2 nanostructures in real-time and compare the intercalation kinetics with previous lithium insertion. We find that Na intercalation follows the two-phase reaction mechanism, that is, trigonal prismatic 2H-MoS2 → octahedral 1T-NaMoS2, and the phase boundary is ∼2 nm thick. The velocity of the phase boundary at <10 nm/s is 1 order smaller than that of lithium diffusion, suggesting sluggish kinetics for sodium intercalation. The newly formed 1T-NaMoS2 contains a high density of defects and series superstructure domains with typical sizes of ∼3-5 nm. Our results provide valuable insights into finding suitable Na electrode materials and understanding the properties of transition metal dichalcogenide MoS2.
authors.affiliation: School of Physics, Center for Nanochemistry, and Collaborative Innovation Center of Quantum Matter, Peking University , Beijing 100871, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China , Chengdu 610054, China.
authors.forename: Liping
authors.initials: L
authors.lastname: Wang
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Yuyang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Huang
authors.affiliation: School of Physics, Center for Nanochemistry, and Collaborative Innovation Center of Quantum Matter, Peking University , Beijing 100871, China.
authors.forename: Kaihui
authors.initials: K
authors.lastname: Liu
keywords: in situ TEM; molybdenum disulfide; phase transition; sodium-ion battery; transition metal dichalcogenide