NbP-NbO Heterostructures with Engineered Built-In Electric Fields for Accelerated Lithium Polysulfide Conversion

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Lithium polysulfides (LiPSs) pose challenges in lithium-sulfur (Li-S) batteries due to sluggish conversion kinetics.
• Effective regulation of LiPSs is crucial for improving Li-S battery performance and energy density.

Purpose of the Study:

• To design and investigate a novel NbP-NbO heterostructure catalyst for regulating LiPSs.
• To enhance the conversion kinetics of LiPSs in Li-S batteries.
• To evaluate the electrochemical performance of a cathode utilizing the NbP-NbO/C@S heterostructure.

Main Methods:

• Density functional theory (DFT) calculations to understand the electronic structure and catalytic mechanism.
• Galvanostatic intermittent titration (GIT) to study activation energy and concentration gradients.
• In situ electrochemical impedance spectroscopy (EIS) to analyze kinetic barriers and transport limitations.

Main Results:

• The NbP-NbO heterostructure generates a built-in electric field, inducing electron flow and lowering the LiPS reduction energy barrier.
• DFT calculations confirmed accelerated LiPS conversion kinetics due to electron redistribution.
• The NbP-NbO/C@S cathode demonstrated a high specific capacity (1463.6 mAh g^-1 at 0.2 C), excellent cycling stability, and superior rate capability (704.9 mAh g^-1 at 5 C).

Conclusions:

• The NbP-NbO heterostructure effectively regulates LiPSs and enhances conversion kinetics.
• The developed cathode material shows significant potential for high-performance Li-S batteries.
• A practical pouch cell achieved a high energy density of 403 Wh kg^-1, indicating viability for real-world applications.