title: In Situ Study of Lithiation and Delithiation of MoS2 Nanosheets Using Electrochemical Liquid Cell Transmission Electron Microscopy.
abstract: We report the observation of lithiation/delithiation of MoS2 nanosheets in a LiPF6/EC/DEC commercial electrolyte for the application of lithium-ion batteries using electrochemical liquid cell transmission electron microscopy (TEM). Upon discharge in a voltage range of 1.8-1.2 V, MoS2 on the Ti electrode underwent irreversible decomposition resulting in fragmentation of the MoS2 nanosheets into 5-10 nm MoS2 nanoparticles. Repeated experiments also show that some MoS2 nanosheets do not decompose upon lithiation. Instead, lithiation induced structural expansion and deformation has been observed. A solid-electrolyte interface (SEI) was formed on the anode side of the Ti electrode in contact with Li metal. The SEI layer is composed of LiF nanocrystals distributed within the entire layer with the constituent elements C, O, and F. However, no passivation film was observed on the cathode side of the Ti electrode with MoS2 nanosheets on it. Such an in situ electrochemical liquid cell TEM study sheds light on battery degradation mechanisms.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Zeng
authors.affiliation: §National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Zhang
authors.forename: Karen
authors.initials: K
authors.lastname: Bustillo
authors.affiliation: ⊥Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States.
authors.forename: Kaiyang
authors.initials: K
authors.lastname: Niu
authors.affiliation: ⊥Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States.
authors.forename: Christoph
authors.initials: C
authors.lastname: Gammer
authors.affiliation: §National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Xu
authors.affiliation: ⊥Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States.
authors.forename: Haimei
authors.initials: H
authors.lastname: Zheng
keywords: Liquid cell TEM; MoS2; electrochemical liquid cell; lithium-ion batteries; solid electrolyte interface