A hierarchical approach to designing a Na-rich phosphide solid-state electrolyte for Na-ion batteries

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 12; no. 18; pp. 1897 - 194
• Main Authors: Lin, Aming, Shi, Jing, Wei, Su-Huai, Sun, Yi-Yang
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 08.05.2024
• Subjects: Batteries; Crystal defects; Crystal structure; Diffusion; Electrolytes; Halides; Kinetics; Molten salt electrolytes; Phosphides; Rechargeable batteries; Sodium diffusion; Sodium-ion batteries; Solid electrolytes; Solid state; Storage batteries; Zirconium
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d4ta00200h

Solid-state electrolytes (SSEs) have brought significant advancements to secondary battery technology, but phosphides remain relatively unexplored compared to the extensively studied oxides, sulfides, and halides. In this study, we introduce a hierarchical approach for designing a Na-rich phosphide SSE. Starting with Na 3 P, one of the most Na-rich materials, we apply the concept of dilute element compounds, incorporating a small amount of a dopant element to preserve its Na-richness. This leads us to identify Na 7 TaP 4 as a promising candidate. Subsequently, through phase engineering utilizing the inorganic crystal structure database, we pinpoint a superior phase for Na 7 TaP 4 that exhibits significantly enhanced Na diffusion kinetics. Lastly, employing defect engineering, we determine that partial substitution of Ta with Zr or Hf can stabilize Na 7 TaP 4 in the desired phase over the experimentally synthesized phase. This hierarchical approach not only reduces the Na diffusion activation energy of the initial material Na 3 P from 0.67 to 0.25 eV but also increases its band gap from 1.0 to 2.4 eV. These advancements show considerable promise for SSE applications. Furthermore, this design strategy is expected to find broad applicability in the development of SSEs for various types of secondary batteries. A hierarchical approach employing the concepts of dilute element compounds (DECs), phase engineering, and defect engineering for the design of a Na-rich phosphide solid-state electrolyte.