Intermediate phases in sodium intercalation into MoS₂ nanosheets and their implications for sodium-ion batteries

Journal Article · 03 June 2017 · Nano Energy

DOI: https://doi.org/10.1016/j.nanoen.2017.05.055 · OSTI ID:1478400

Li, Qianqian ^[1]; Yao, Zhenpeng ^[1]; Wu, Jinsong ^[1]; Mitra, Sagar ^[2]; Hao, Shiqiang ^[1]; Sahu, Tuhin Subhra ^[2]; Li, Yuan ^[1]; Wolverton, Chris ^[1]; Dravid, Vinayak P. ^[1]

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1. Northwestern Univ., Evanston, IL (United States)
2. Indian Institute of Technology (IIT), Mumbai (India)

Alkali metal ion intercalation into layered transition-metal dichalcogenide structures is a promising approach to make next generation rechargeable batteries for energy storage. It has been noted that the number of Na-ions which can be reversibly intercalated and extracted per MoS₂ is limited, and the chemical and electrochemical processes/mechanisms remain largely unknown, especially for nano-sized materials. Here, in this study, sodiation of MoS₂ nanosheets are studied by in-situ electron diffraction and the phase transformations in sodiation are identified with the aid of DFT calculations to reveal the reaction mechanism. Several thermodynamically stable/metastable structures are identified in the sodiation pathway of MoS₂ nanosheets, previously unnoticed in bulk MoS₂. The gradual reduction of Mo⁴⁺ upon Na-ion intercalation leads to a transition of the Mo-S polyhedron from a trigonal prism to an octahedron around 0.375 Na per MoS₂ inserted (i.e. Na_0.375MoS₂). When the intercalated Na-content is larger than 1.75 per MoS₂ structural unit (i.e. Na_1.75MoS₂), the MoS₂ layered structure collapses and the intercalation reaction is replaced by an irreversible conversion reaction with the formation of Na₂S and metal Mo nanoparticles. The calculated sodiation pathways reproduce the experimental sodiation voltages. The current observations provide useful insights in developing sodium-ion batteries with high cycling stability.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Energy Frontier Research Centers (EFRC) (United States). Center for Electrical Energy Storage (CEES)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); National Science Foundation (NSF); USDOE
• Grant/Contract Number: AC02-06CH11357; FG02-07ER46433; AC02-05CH11231; NNCI-1542205; DMR-1121262
• OSTI ID: 1478400
• Alternate ID(s): OSTI ID: 1550154
• Journal Information: Nano Energy, Vol. 38, Issue C; ISSN 2211-2855
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English