Regulating Sodium Deposition Behavior by a Triple-Gradient Framework for High-Performance Sodium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Sodium metal anodes are crucial for high-energy-density batteries.
• Achieving uniform sodium deposition and preventing dendrite formation remains a significant challenge.
• Existing anode materials often suffer from poor cycling stability and low Coulombic efficiency.

Purpose of the Study:

• To develop an efficient synthesis method for a self-supporting carbon framework (Gra-GC-MoSe2) with tailored properties.
• To investigate the mechanism of sodium deposition regulation within the designed framework.
• To evaluate the electrochemical performance of the modified sodium anode in sodium-ion batteries.

Main Methods:

• Synthesis of a triple-gradient carbon framework (Gra-GC-MoSe2) with controlled sodiophilic sites, pore volume, and electrical conductivity.
• In situ and ex situ characterization techniques.
• Theoretical calculations to understand ion diffusion and deposition mechanisms.
• Electrochemical testing of symmetric and asymmetric cells, and full cells.

Main Results:

• The Gra-GC-MoSe2 framework facilitated uniform sodium deposition from bottom to top, suppressing dendrite formation.
• Gradient distribution of selenium in MoSe2 derivatives enhanced sodiophilicity, while porous nanostructures optimized Na+ diffusion.
• The modified anode (Na@Gra-GC-MoSe2) exhibited high Coulombic efficiency, long cycling life (2000 h in symmetric cells), low polarization, and stable operation at high capacity (10 mAh cm-2).
• A full cell (Na@Gra-GC-MoSe2||Na3V2(PO4)3) demonstrated high energy density and excellent cycling performance.

Conclusions:

• The proposed Gra-GC-MoSe2 framework is a highly effective strategy for regulating sodium deposition.
• This material significantly enhances the stability and performance of sodium metal anodes.
• The findings pave the way for developing safer and more efficient sodium-ion batteries.