"Constraining-adsorption-catalysis" effect of WC composite modified separators on polysulfides in high performance lithium-sulfur battery

In recent years, Lithium-sulfur (Li-S) batteries have great potential to replace lithium batteries as one of the new generations of energy storage devices due to their high energy density, environmental friendliness, abundant natural resources and low cost. However, there is a serious polysulfide "shuttle phenomenon" in Li-S batteries, which greatly leads to the loss of battery capacity and the reduction of coulomb efficiency. Based on the above, a novel tungsten carbide (WC)-modified nitrogen-doped carbon nanotubes/nickel composite (N-CNTs/Ni@WC) was synthesized under argon atmosphere in this paper. The carbon nanotubes functioned as physical barriers to inhibit the shuttling of LiPSs, while the highly polar WC and Ni nanoparticles chemically adsorbed the polar LiPSs and simultaneously exerted a catalytic effect to induce Li 2 S deposition and facilitate the redox reaction. In addition, N-CNTs, Ni and WC have high ionic conductivity, in favor of fast lithium-ion transport. Because of these features, Li-S batteries on the basis of modified N-CNTs/Ni@WC separators show a high initial discharge capacity (1139.56 mAh g −1 at 0.5 C current density), high coulomb efficiency (close to 100 % after 500 cycles at 1 C), and low capacity decay rate (0.08 % for 500 cycles with 1 C). In conclusion, this work offers a method for optimizing the preparation and design of materials for lithium-sulfur separators in a reliable way.