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Stoichiometric two-dimensional non-van der Waals AgCrS2 with superionic behaviour at room temperature

Abstract

Layered materials have attracted tremendous interest for accessing two-dimensional structures. Materials such as graphite or transition metal dichalcogenides, in which the layers are held together by van der Waals interactions, can be exfoliated through a variety of processes in a manner that retains the structure and composition of the monolayers, but this has proven difficult for solids with stronger interlayer interactions. Here, we demonstrate the exfoliation of AgCrS2, a member of the AMX2 family (where A is a monovalent metal, M is a trivalent metal and X is a chalcogen), through intercalation with tetraalkylammonium cations, chosen for their suitable redox potential. The as-exfoliated nanosheets consist of Ag layers sandwiched between two CrS2 layers, similar to their structure in the bulk. They show superionic behaviour at room temperature, with an ionic conductivity of 33.2 mS cm−1 at 298 K that originates from Ag+ ions rapidly hopping between neighbouring tetrahedral interstices; in the bulk, this behaviour is only observed above 673 K.

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Fig. 1: Stoichiometric AMX2 nanosheets.
Fig. 2: The composition and structure of AgCrS2 nanosheets.
Fig. 3: Silver ion distribution in AgCrS2 nanosheets.
Fig. 4: Ionic transport in AgCrS2 nanosheets.

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Data availability

The experimental procedures and characterization of all AMX2 compounds and corresponding 2D structures are provided in the Supplementary Information. Source data are provided with this paper. All other data supporting the findings of this study are available within this article and its Supplementary Information.

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Acknowledgements

C.W. acknowledges support from the National Key R&D Program on Nano Science & Technology of the MOST (2017YFA0207301), the National Natural Science Foundation of China (21925110, 21890751 and 91745113), the National Program for Support of Top-notch Young Professionals, the Fundamental Research Funds for the Central Universities (WK2060190084), the Major Program of Development Foundation of Hefei Center for Physical Science and Technology (2016FXZY001) and the Users with Excellence Project of Hefei Science Center CAS (2021HSC-UF004). Y.X. acknowledges support from the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB36000000). X.W. acknowledges support from the National Key R&D Program on Nano Science & Technology of the MOST (2016YFA0200602, 2018YFA0208603) and the National Natural Science Foundation of China (22073087). J.P. acknowledges support from the National Natural Science Foundation of China (22005284) and the National Postdoctoral Program for Innovative Talents (BX20190308). Y.G. acknowledges support from the National Natural Science Foundation of China (U2032161) and the Youth Innovation Promotion Association CAS (2018500). All calculations were supported by the Super Computer Center of USTCSCC and SCCAS.

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Contributions

C.Z.W. conceived the idea and experimentally realized the study, co-wrote the paper and supervised the entire project and is responsible for the infrastructure and project direction. J.P., Y.H.L. and H.F.L. contributed equally to this work; they experimentally realized the study, analysed the data and co-wrote the paper. This work was assisted by Y.Q.S., J.J.W., H.F.L. and Y.Q.G. HAADF-STEM data were collected by Y.L. Theoretical calculations were carried out by H.F.L., Y.X.L., Z.W.Z. and X.J.W. Y.X. supervised the whole experimental procedure and co-wrote the paper. All authors discussed the results and commented on and revised the manuscript.

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Correspondence to Changzheng Wu.

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Peer review information Nature Chemistry thanks Kian Ping Loh and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–25, Tables 1 and 2, Discussion and refs. 1–19.

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Statistical source data.

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Peng, J., Liu, Y., Lv, H. et al. Stoichiometric two-dimensional non-van der Waals AgCrS2 with superionic behaviour at room temperature. Nat. Chem. 13, 1235–1240 (2021). https://doi.org/10.1038/s41557-021-00800-4

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