Tungsten Nitride/Carbon Cloth as Bifunctional Electrode for Effective Polysulfide Recycling

The inevitable dissolution, diffusion, and migration of polysulfides cause an irreversible loss of active material, leading to poor cyclic performance in lithium sulfur batteries. Herein, a freestanding tungsten nitride nanorod/carbon cloth (WN/CC) interlayer is prepared by hydrothermal growth to function as both current collector and physicochemical barrier to soluble lithium polysulfides (Li₂S_x). The cells containing a dual-functional interlayer deliver a significantly improved initial discharge capacity of 1337 mAh g^-1 with a reversible capacity of 814.2 mAh g^-1 after 500 cycles at 100 mA g^-1. The enhanced electrochemical performance is attributed to the highly adsorptive WN nanorods grown on conductive CC to entrap polysulfides, leading to effective recycling of active materials. The density functional theory (DFT) calculations prove important roles of the WN (200) surface in entrapping polysulfides through their strong adsorption energies (3.21-4.67 eV) with Li₂S_x and S₈. The potential of the dual-functional WN/CC composite interlayer in improving the electrochemical performance of lithium sulfur batteries has not been reported previously.