Polymer-Regulated Solvation and Interphase Engineering for Long-Life and Safe Quasi-Solid-State Anode-Free Sodium...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Anode-free sodium metal batteries (AFSMBs) promise higher energy density than sodium-ion batteries (SIBs) but suffer from short lifespans due to irreversible sodium loss and safety issues.
• Current AFSMBs face challenges with processing highly reactive sodium metal anodes and electrolyte leakage, limiting their practical application.

Purpose of the Study:

• To design and demonstrate long-life quasi-solid-state AFSMBs with enhanced safety and reduced sodium loss.
• To leverage polymer regulation of sodium-ion (Na+) solvation and anode interphase chemistry for improved battery performance.

Main Methods:

• Utilized polyoxymethylene with reduced steric hindrance and weak Na+ chelation to create a weakly solvating, polymer-stabilized, anion-rich Na+ solvation structure.
• Investigated the formation of a robust inorganic-organic dual-layered solid electrolyte interphase (SEI) for smooth sodium metal deposition in quasi-solid-state electrolytes.

Main Results:

• Achieved quasi-solid-state AFSMBs with a lifespan of 500 cycles and 79% capacity retention at a 1 C rate.
• Demonstrated 1.2 Ah pouch cells retaining 81% capacity over 200 cycles, with a volumetric energy density of 340 Wh L⁻¹, surpassing LiFePO4||graphite lithium-ion batteries.
• Confirmed high reliability against nail penetration in ambient conditions at a fully charged state.

Conclusions:

• The developed quasi-solid-state AFSMBs offer a viable pathway to overcome the limitations of traditional sodium metal batteries.
• The polymer-regulated solvation structure and SEI formation are critical for achieving long cycle life, high energy density, and enhanced safety in AFSMBs.