P-P Orbital Interaction Enables Single-Crystalline Semimetallic β-MoTe 2 Nanosheets as Efficient Electrocatalysts for Lithium-Sulfur Batteries.

The practical implementation of lithium-sulfur batteries (LSBs) has been impeded by the sluggish redox kinetics of lithium polysulfides (LiPSs) and shuttle effect of soluble LiPSs during charge/discharge. It is desirable to exploit materials combining superior electrical conductivity with excellent catalytic activity for use as electrocatalysts in LSBs. Herein, we report the employment of chemical vapor transport (CVT) method followed by an electrochemical intercalation process to fabricate high-quality single-crystalline semimetallic β-MoTe 2 nanosheets, which are utilized to manipulate the LiPSs conversion kinetics. The first-principles calculations prove that β-MoTe 2 could lower the Gibbs free-energy barrier for Li 2 S 2 transformation to Li 2 S. The wavefunction analysis demonstrates that the p-p orbital interaction between Te p and S p orbitals accounts for the strong electronic interaction between the β-MoTe 2 surface and Li 2 S 2 /Li 2 S, making bonding and electron transfer more efficient. As a result, a β-MoTe 2 /CNT@S-based LSB cell can deliver an excellent cycling performance with a low capacity fade rate of 0.11% per cycle over 300 cycles at 1C. Our work might not only provide a universal route to prepare high-quality single-crystalline transition-metal dichalcogenides (TMDs) nanosheets for use as electrocatalysts in LSBs, but also suggest a different viewpoint for the rational design of LiPSs conversion electrocatalysts.