Symmetry-Engineered Carbon Scaffold for Interface-First Sodium-Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Room-temperature sodium-sulfur (RT Na-S) batteries are promising for large-scale energy storage due to high theoretical energy density and low-cost materials.
• Commercialization is limited by polysulfide shuttling, sluggish kinetics, and dendrite growth in RT Na-S batteries.

Purpose of the Study:

• To design a bifunctional host material that simultaneously addresses polysulfide shuttling and dendrite growth in RT Na-S batteries.
• To develop a stable and high-performance RT Na-S battery using an all-carbon-fiber symmetric cell architecture.

Main Methods:

• Fabrication of a 3D porous oxygen-doped carbon fiber (OCF) framework.
• Implementation of the OCF framework as a bifunctional host in a symmetric all-carbon-fiber cell.
• Electrochemical performance testing, including nucleation overpotential, cycling stability, rate capability, and full cell performance.

Main Results:

• The OCF framework chemically anchors polysulfides, catalyzes redox reactions, and guides uniform sodium nucleation, suppressing shuttling and dendrites.
• Achieved extremely low Na nucleation overpotential (27 mV at 1 mA cm⁻²) and stable, dendrite-free cycling over 3600 hours.
• Demonstrated high specific capacity (753 mAh g⁻¹ after 200 cycles at 0.2 C), excellent long-term stability (≈85% capacity retention after 2000 cycles at 0.5 C), and good rate performance (5 C) in full Na-S cells.

Conclusions:

• The OCF framework provides a generalizable, interface-first design for safe, long-lasting, and low-cost RT Na-S batteries.
• This approach effectively mitigates key challenges of polysulfide shuttling and dendrite formation.
• Enhanced Na⁺ transport and interfacial kinetic stability contribute to the superior battery performance.