Hexagonal CoSe₂ nanosheets: rational design towards stable sodium-ion storage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) are a viable alternative to lithium-ion batteries (LIBs) due to sodium's abundance and cost-effectiveness.
• Challenges in SIBs include poor cycling stability and low rate performance, primarily due to the larger ionic size of Na+ impacting ion diffusion and material integrity.

Purpose of the Study:

• To develop a high-performance anode material for SIBs that overcomes the limitations of sodium-ion diffusion and structural degradation.
• To investigate the electrochemical properties of a novel 2D hexagonal CoSe2 embedded in N-doped carbon (2DH-CoSe2@NC) for SIB applications.

Main Methods:

• Fabrication of 2D hexagonal CoSe2 nanosheets within a nitrogen-doped carbon matrix (2DH-CoSe2@NC) via solvothermal synthesis and gas-phase selenation.
• Electrochemical characterization of the 2DH-CoSe2@NC anode in SIBs, including rate performance and long-term cycling stability tests.
• Assembly and testing of SIB full cells using 2DH-CoSe2@NC as the anode.

Main Results:

• The 2DH-CoSe2@NC anode exhibited excellent rate capability and cycling durability in SIBs.
• After 2600 cycles at 5 A g-1, a stable reversible capacity of 516.2 mAh g-1 was maintained with near 100% coulombic efficiency.
• Full cells (2DH-CoSe2@NC∥NVP) demonstrated a significant reversible capacity of 364.8 mAh g-1 at 1 A g-1.

Conclusions:

• The unique architecture of 2DH-CoSe2@NC provides synergistic effects that significantly enhance electrochemical performance for SIBs.
• The developed material shows great promise for high power-density SIB applications due to its remarkable stability and capacity.
• This work presents a viable strategy for designing advanced anode materials for next-generation sodium-ion energy storage systems.