Flash Joule Heating: A Promising Method for Preparing Heterostructure Catalysts to Inhibit Polysulfide Shuttling in Li-S Batteries.

ABSTRACT

The "shuttle effect" issue severely hinders the practical application of lithium-sulfur (Li-S) batteries, which is primarily caused by the significant accumulation of lithium polysulfides in the electrolyte. Designing effective catalysts is highly desired for enhancing polysulfide conversion to address the above issue. Here, the one-step flash-Joule-heating route is employed to synthesize a W-W2C heterostructure on the graphene substrate (W-W2C/G) as a catalytic interlayer for this purpose. Theoretical calculations reveal that the work function difference between W (5.08 eV) and W2C (6.31 eV) induces an internal electric field at the heterostructure interface, accelerating the movement of electrons and ions, thus promoting the sulfur reduction reaction (SRR) process. The high catalytic activity is also confirmed by the reduced activation energy and suppressed polysulfide shuttling by in situ Raman analyses. With the W-W2C/G interlayer, the Li-S batteries exhibit an outstanding rate performance (665 mAh g-1 at 5.0 C) and cycle steadily with a low decay rate of 0.06% over 1000 cycles at a high rate of 3.0 C. Moreover, a high areal capacity of 10.9 mAh cm-2 (1381.4 mAh g-1) is obtained with a high area sulfur loading of 7.9 mg cm-2 but a low electrolyte/sulfur ratio of 9.0 µL mg-1.