First‐Principles Design of Na‐ion Superionic Conductors: Interstitial‐Based Na Diffusion in NaCuZrS3

• Published in: Chemistry : a European journal Vol. 28; no. 32; pp. e202200234 - n/a
• Main Authors: Wang, Yuandong, Lin, Aming, Chai, Jun, Ming, Chen, Sun, Yi‐Yang
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 07.06.2022
• Subjects: Batteries; Chemistry; Computation; Conductors; Diffusion; Electrolytes; first-principles calculations; Free energy; Frenkel defects; Heat of formation; Interstitials; Ion currents; Ion transport; layered compounds; Lithium; Lithium-ion batteries; Molecular dynamics; Molten salt electrolytes; Na-ion batteries; Perovskites; Principles; Sodium; Sodium-ion batteries; Solid electrolytes; solid-state electrolytes; sulfides
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202200234

In recent years all‐solid‐state sodium‐ion batteries (SS‐SIBs) have drawn significant attention due to their potential to be safer and lower cost than lithium‐ion batteries. However, the lack of sodium solid‐state electrolytes with high ionic conductivity has become one of the major challenges. Here, with first‐principles computation we took NaCuZrS3, consisting of earth‐abundant and environmentally benign elements only, as an example to study Na‐ion transport in the post‐perovskite‐like structure and used computation‐guided design to improve its potential as a solid‐state electrolyte. With ab initio molecular dynamics simulation and nudged elastic band calculation, we studied possible diffusion mechanisms in this material and found that Na ion interstitials have a favorable migration barrier of 0.22 eV, which is among the smallest in the literature reported values. Considering the large formation energy of Frenkel defects, we proposed doping strategy to introduce extra Na interstitials in the material. Our study suggests that the post‐perovskite‐like sulfides are worth of exploration for applications in SS‐SIBs. Solid‐state electrolytes are usually based on vacancies of diffusing ions to enhance diffusivity. NaCuZrS3 with a post‐perovskite‐like structure exhibits an interstitial‐based Na ion diffusion mechanism. The low diffusion barriers of the order of 0.22 eV in the two ‐ dimensional interlayer channels suggest a new class of Na‐ion superionic conductors for further exploration. Doping by trivalent ions (such as La) on Zr sites could help introduce Na interstitials.