Unveiling the Electrocatalytic Activity of 1T'-MoSe₂ on Lithium-Polysulfide Conversion Reactions

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries offer high energy density but are hindered by lithium polysulfide (LiPS) dissolution and shuttling.
• Existing two-dimensional (2D) materials for Li-S batteries have limited active sites, primarily at their edges.

Purpose of the Study:

• To explore phase transformation in a 2D material to create more active sites for LiPS redox reactions.
• To investigate the potential of phase-transformed MoSe2 as an electrocatalyst for Li-S batteries.

Main Methods:

• Theoretical calculations to predict phase transformation and LiPS adsorption in MoSe2.
• Experimental characterization using microscopic and spectroscopic techniques to confirm phase transformation and adsorption.
• Electrochemical evaluation of phase-transformed MoSe2 in Li-S battery cathodes.

Main Results:

• Phase transformation from 2H to 1T' phase in MoSe2 was shown to activate basal planes for LiPS adsorption.
• Experimental evidence confirmed the transformation mechanism and LiPS adsorption capabilities of 1T'-MoSe2.
• 1T'-MoSe2 demonstrated strong electrocatalytic activity for LiPS reduction and oxidation.

Conclusions:

• Phase transformation is an effective strategy to enhance the electrocatalytic activity of 2D materials for Li-S batteries.
• 1T'-MoSe2 cathode hosts enable superior cycling performance (>250 cycles), minimal capacity loss (0.15%/cycle), and high Coulombic efficiency (99.6%).