Fast Ion Transport Mechanism and Electrochemical Stability of Trivalent Metal Iodide-based Na Superionic Conductors Na3XI6 (X = Sc, Y, La, and In)

He Huang; Cheng Chi; Jingyan Zhang; Xinqi Zheng; Yanfei Wu; Jianxin Shen; Xiao Wang; Shouguo Wang

doi:10.1021/acsami.2c09814

Fast Ion Transport Mechanism and Electrochemical Stability of Trivalent Metal Iodide-based Na Superionic Conductors Na₃XI₆ (X = Sc, Y, La, and In)

ACS Appl Mater Interfaces. 2022 Aug 17;14(32):36864-36874. doi: 10.1021/acsami.2c09814. Epub 2022 Aug 8.

Authors

He Huang¹, Cheng Chi², Jingyan Zhang¹, Xinqi Zheng¹, Yanfei Wu¹, Jianxin Shen¹, Xiao Wang¹, Shouguo Wang¹

Affiliations

¹ Beijing Advanced Innovation Center for Materials Genome Engineering, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China.
² Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.

PMID: 35938862
DOI: 10.1021/acsami.2c09814

Abstract

The exploration of solid-state sodium superionic conductors with high sodium-ion conductivity, structural and electrochemical stability, and grand interface compatibility has become the key to the next-generation energy storage applications with high energy density and long cycling life. Among them, halide-based compounds exhibit great potential with the higher electronegativity of halogens than that of the sulfur element. In this work, combined with first-principles calculation and ab initio molecular dynamic simulation, the investigation of trivalent metal iodide-based Na superionic conductors C2/m-Na₃XI₆ (X = Sc, Y, La, and In) was conducted, including the fast ion transport mechanism, structural stability, and interface electrochemical compatibility with electrode materials. Along with the tetrahedral-center saddle site-predominant three-dimensional octahedral-tetrahedral-octahedral diffusion network, C2/m-Na₃XI₆ possesses the merits of high Na ionic conductivities of 0.36, 0.35, and 0.20 mS cm^-1 for Na₃ScI₆, Na₃YI₆, and Na₃LaI₆, respectively. Benefiting from its structural stabilities, C2/m-Na₃XI₆ exhibits lower interface reaction energy and better electrochemical compatibility in contact with both Na metal and high-voltage poly-anion (fluoro)phosphate cathode materials than those of sulfide-based ones. Our theoretical work provides rational design principles for screening and guiding iodide-based C2/m-Na₃XI₆ (X = Sc, Y, La, and In) as promising Na superionic conductor candidates used in all-solid-state energy storage applications.

Keywords: Na-ion transport; ab-initio molecular dynamic simulation; electrochemical stability; first-principles calculation; iodide-based solid electrolyte.