Edge Electron Effect Induced High-Entropy SEI for Durable Anode-Free Sodium Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Anode-free sodium metal batteries offer high energy density but suffer from unstable sodium metal growth and consumption.
• Achieving stable cycling and high Coulombic efficiency is crucial for practical applications.

Purpose of the Study:

• To develop a strategy for uniform sodium deposition and reduced electrolyte consumption in anode-free sodium metal batteries.
• To enhance the stability and cycling life of these energy storage systems.

Main Methods:

• Utilizing ordered zinc flower edges on an aluminum substrate to induce a high-entropy solid electrolyte interphase (SEI).
• Investigating the electronic properties and facet characteristics of zinc using theoretical and experimental methods.
• Analyzing the composition and structure of the SEI layer and its effect on sodium nucleation and growth.

Main Results:

• The zinc flower edges facilitated the formation of a thin, inorganic-rich, high-entropy SEI layer (18 nm).
• This SEI layer promoted uniform sodium deposition with high density nucleation (7.36 × 10^13 N cm^-2) and controlled growth (3 mAh cm^-2, 22 µm).
• Anode-free sodium batteries achieved ultrahigh initial Coulombic efficiency (97.05%) and maintained 86% capacity over 90 cycles with high cathode loading (32 mg cm^-2).
• Anode-less pouch batteries demonstrated excellent durability with 99% capacity retention after 600 cycles.

Conclusions:

• Ordered zinc edges effectively regulate sodium deposition by forming a beneficial SEI layer.
• This approach significantly improves the stability, efficiency, and cycling life of anode-free sodium metal batteries.
• The findings present a promising pathway for developing high-performance sodium-based energy storage devices.