Mechanically Robust Bismuth-Embedded Carbon Microspheres for Ultrafast Charging and Ultrastable Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) require advanced anodes for improved efficiency.
• Current microstructured alloying anodes suffer from poor cyclability and rate capability due to significant volumetric changes and slow kinetics.
• Mechanical degradation and volume swelling (over 252%) limit the performance of existing SIB anodes.

Purpose of the Study:

• To design and develop a novel anode material for high-performance SIBs.
• To overcome the challenges of poor cyclability, rate capability, and mechanical degradation in SIB anodes.
• To enhance the volumetric capacity and charging speed of SIB anodes.

Main Methods:

• Fabrication of densely packed bismuth (Bi) nanoparticles embedded within highly conductive carbon microspheres.
• Characterization of anode properties including mechanical strength, tap density, and volumetric swelling.
• Electrochemical testing for capacity, cyclability, rate capability, and performance at low temperatures.
• Chemo-mechanical simulations to elucidate performance mechanisms.

Main Results:

• The novel Bi-carbon microsphere anode exhibits high mechanical strength (>590 MPa) and limited volume swelling (10.9%).
• Achieved a high volumetric capacity of 908.3 mAh cm^-3 and ultrafast chargeability (200 A g^-1).
• Demonstrated outstanding cyclability (>12,000 cycles) and stable performance at -30 °C.
• A full cell utilizing this anode retained >80% capacity after 600 cycles at 36 C, with a 126 C rate capability.

Conclusions:

• The developed bismuth-carbon microsphere anode effectively addresses mechanical degradation and kinetic limitations in SIBs.
• This design offers a promising pathway for durable, fast-charging, and high-capacity anodes for next-generation SIBs.
• The study provides insights into the mechanisms governing the superior electrochemical and mechanical performance.