Porous Mo2C-Mo3N2 heterostructure/rGO with synergistic functions as polysulfides regulator for high-performance lithium sulfur batteries

Abstract

Shuttle effect of lithium polysulfides (LiPSs) is among the critical obstacles hampering development of lithium-sulfur batteries. Herein, we present a porous Mo2C-Mo3N2 heterostructure/rGO host and the Mo2C-Mo3N2 heterostructure combines the merits of high adsorption Mo2C and high catalytic Mo3N2 so as to achieve rapid anchoring-diffusion-conversion of LiPSs across the Mo2C-Mo3N2 heterointerface. The Mo2C-Mo3N2 heterointerface boosts the trapping efficiency and conversion to Li2S of LiPSs. rGO provides fast paths for electron transport as well as serves as a protective layer to prevent the structure from being damaged during cycling. Density functional theory (DFT) calculation shows that Mo2C has stronger adsorption ability for Li2S4 than Mo3N2 and Mo3N2 has better reaction kinetic characteristics. Experimentally, Mo2C-Mo3N2/[email protected] electrode respectively shows outstanding rate capability. At high sulfur loadings (3.4 and 5.0 mg cm−2), the capacity retention values are 78%, and 70% at 0.5C after 300 cycles. Mo2C-Mo3N2/rGO sulfur electrodes shows high Li+ diffusion coefficient of 4.56 × 10-7 cm2 s−1, which benefits from the accelerated conversion of LiPSs at interface. Our results reveal the critical role of anchoring-diffusion-conversion of LiPSs in terms of inhibiting the shuttle effect.