Issue 40, 2021

Materials design of sodium chloride solid electrolytes Na3MCl6 for all-solid-state sodium-ion batteries

Abstract

All-solid-state sodium-ion batteries have attracted increasing attention owing to the low cost of sodium and the enhanced safety compared to conventional Li-ion batteries. Recently, halides have been considered as promising solid electrolytes (SEs) due to their favorable combination of high ionic conductivity and chemical stability against high-voltage cathode materials. Although a wide variety of lithium chloride SEs, Li3MCl6, have been developed for high-voltage all-solid-state batteries, only a limited number of sodium chloride SEs have been reported. This study aims to offer a material design insight for the development of sodium chloride SEs through systematic assessment of the phase stability, electrochemical stability, and transport properties of novel Na3MCl6 SEs. Structural calculations indicate that Na3MCl6 exhibits trigonal P[3 with combining macron]1c, monoclinic P21/n, and trigonal R[3 with combining macron] phases, and the stable phase of Na3MCl6 is dependent on the type and ionic radius of M. Na3MCl6 typically exhibits a high oxidation potential, demonstrating good electrochemical stability against cathodes. The bond-valence site energy and ab initio molecular dynamics calculations revealed that Na3MCl6 with P21/n and R[3 with combining macron] phases showed low ionic conductivity, while the P[3 with combining macron]1c phase slightly improved the ionic conductivity of Na3MCl6. The formation of Na vacancies by aliovalent substitution considerably increased the ionic conductivity up to four orders of magnitude for pristine Na3MCl6, exhibiting ∼10−5 S cm−1 for trigonal P[3 with combining macron]1c and R[3 with combining macron] phases. The formation of defects could further enhance the ionic conductivity of Na3MCl6, and the optimization of defect type and ratio can be helpful in developing superionic Na chloride SEs. The material design of Na3MCl6 in this study will provide fundamental guidelines for the development of novel sodium halide SEs for all-solid-state sodium-ion batteries.

Graphical abstract: Materials design of sodium chloride solid electrolytes Na3MCl6 for all-solid-state sodium-ion batteries

Supplementary files

Article information

Article type
Paper
Submitted
18 Aug 2021
Accepted
16 Sep 2021
First published
16 Sep 2021

J. Mater. Chem. A, 2021,9, 23037-23045

Author version available

Materials design of sodium chloride solid electrolytes Na3MCl6 for all-solid-state sodium-ion batteries

D. Park, K. Kim, G. H. Chun, B. C. Wood, J. H. Shim and S. Yu, J. Mater. Chem. A, 2021, 9, 23037 DOI: 10.1039/D1TA07050A

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