Enabling 100C Fast-Charging Bulk Bi Anodes for Na-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Developing high-performance alloying anodes for sodium-ion batteries is hindered by slow ion diffusion and material degradation.
• Existing strategies often rely on expensive nanomaterials or complex surface modifications.

Purpose of the Study:

• To design bulk bismuth (Bi) anodes for sodium-ion batteries that achieve ultrafast charging and high energy storage without nanomaterials.
• To investigate the structural evolution and sodium-ion storage mechanisms in bulk Bi anodes.

Main Methods:

• Electrochemical cycling of bulk Bi anodes in a glyme-based electrolyte.
• Characterization of the electrode structure evolution during cycling.
• First-principles calculations to verify structural origins and properties.

Main Results:

• Bulk Bi anodes transformed into a porous nanostructure during cycling, facilitating high sodium-ion diffusivity.
• The Na-Bi half-cell demonstrated a capacity of 379 mAh g⁻¹ at 20C (7.7 A g⁻¹) over 3500 cycles.
• Exceptional capacity retention of 94% and 93% was observed at 80C and 100C, respectively.

Conclusions:

• A rational strategy for designing bulk Bi anodes offers a pathway to superior electrochemical properties for sodium-ion batteries.
• The study provides fundamental insights into fast-charging anode mechanisms and guidelines for future battery material development.
• This approach enables high capacity, fast kinetics, and long cycling stability without advanced nanomaterials.