Halide Heterogeneous Structure Boosting Ionic Diffusion and High-Voltage Stability of Sodium Superionic Conductors

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• Solid-state sodium-ion batteries (SSSBs) require superionic Na+ conductors (SSCs) with high conductivity, electrochemical stability, and deformability.
• Heterogeneous structures offer a promising strategy to enhance SSC properties beyond traditional structural optimization.

Purpose of the Study:

• To develop a new class of halide heterogeneous structure electrolytes (HSEs) by exploiting structural variance.
• To achieve high Na+ conductivity and excellent electrochemical and mechanical properties for SSSBs.

Main Methods:

• Construction of halide heterogeneous structures combining high-coordination (UCl3-type) and amorphous low-coordination phases.
• Characterization of Na+ conductivity, electrochemical stability, deformability, and SSSB performance.
• Analysis of ion conduction mechanisms within the crystalline bulk, amorphous regions, and interfaces.

Main Results:

• The developed halide HSEs exhibit the highest Na+ conductivity (2.7 mS cm-1 at RT) among halide SSCs.
• Synergistic ion conduction and amorphization effects were elucidated.
• SSSBs utilizing HSEs demonstrate stable cycling performance with 91.0% capacity retention after 100 cycles.

Conclusions:

• Halide heterogeneous structure electrolytes are a promising pathway for advanced solid-state sodium-ion batteries.
• The synergistic effects in HSEs lead to enhanced ionic conductivity and battery performance.
• The developed HSEs show excellent potential for practical SSSB applications due to their stability and deformability.