Work

A Family of Sodium Solid‐State Electrolytes Based on the NaGa x Al 1‐x Cl 4 Solid Solution

Year: 2026

Type: article

Abstract: ABSTRACT Sodium‐based metal chloride solid electrolytes are promising for sodium solid‐state batteries due to their excellent oxidation stability, which, as shown for Li halides, can coexist with high ionic conductivity. To explore cationic substitution effects, we synthesized NaGa x Al1 ‐x Cl 4 (0 ≤ x ≤ 1) via ball milling and investigated structural and transport properties. X‐ray diffraction and Rietveld refinement confirmed complete solubility between NaAlCl 4 and NaGaCl 4 within the orthorhombic P 2 1 2 1 2 1 space group. Electrochemical impedance spectroscopy revealed a minimal conductivity decrease with increasing Ga 3+ content at first (≈ 1‐3 x 10 −6 S cm −1 for 0 ≤ x ≤ 0.5), but down to 5 × 10 −7 S cm −1 for NaGaCl 4 . Structural analysis linked this trend to bottleneck closure in Na + pathways, increasing activation energy. Despite the reduced conductivity, Ga substitution significantly broadened the electrochemical stability window to 2.12 ‐ 4.86 V vs. Na + /Na, surpassing most sodium halide electrolytes. Ex situ XAS and XPS confirmed the excellent reduction stability. This work improves our understanding of solid electrolytes and of the structure‐property relationship in halide materials. Thereby, it expands the accessible range of cation choices for sodium metal chloride materials with new candidates of interest in light of their excellent electrochemical stability.

Source: Advanced Materials Interfaces

DOI: 10.1002/admi.202600004

Authors: Hao Guo, Matteo Bianchini

Institution: University of Bayreuth

Language: English

Topic: Advanced Battery Materials and Technologies

Subfield: Electrical and Electronic Engineering

Field: Engineering

Domain: Physical Sciences

SDG: Affordable and clean energy

Open Access status: gold

Estimated APC paid: $3,100