Realizing the Synergy of Interface and Dual-Defect Engineering for Molybdenum Disulfide Enables Efficient Sodium-Ion...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Defects in electrocatalysts are crucial for charge storage and transfer in energy systems.
• Developing advanced materials for efficient sodium-ion batteries is essential.

Purpose of the Study:

• To synthesize a novel bimetallic sulfide/oxide composite with enhanced electrochemical properties.
• To investigate the role of engineered defects and heterojunctions in improving sodium storage.

Main Methods:

• A two-step synthesis involving mixing MoO3 nanobelts and Co-PAA, followed by selective etching.
• Fabrication of a coaxial carbon-coated composite electrode.
• Electrochemical testing of the electrode in sodium-ion half and full cells.
• Characterization using DFT, electrochemical kinetics, in situ Raman, and ex-situ XRD.

Main Results:

• The composite exhibited dual defects (interlayer and sulfur vacancies) and MoO2/MoS2-/CoS heterojunctions.
• The carbon coating provided high conductivity and structural stability.
• The electrode achieved high reversible capacity (158.3 mAh g^-1 at 10 A g^-1) and excellent cycle stability (0.04% decay per cycle).
• A full cell demonstrated a reversible capacity of 128.1 mAh g^-1 after 600 cycles at 1 A g^-1, comparable to state-of-the-art Na-ion cells.

Conclusions:

• Engineered defects and heterojunctions significantly boost electron and ion transport.
• The developed material offers a promising pathway for high-performance sodium-ion batteries.
• Understanding the sodium storage mechanism is crucial for future material design.