A New Defect-Rich and Ultrathin ZnCo Layered Double Hydroxide/Carbon Nanotubes Architecture to Facilitate Catalytic Conversion of Polysulfides for High-performance Li-S Batteries

Abstract Lithium-sulfur (Li-S) batteries have been long deemed as next generation power supply for portable electronic and vehicle application due to their extremely high theoretical energy and power density. However, the shuttle effect of soluble lithium polysulfides (LiPs) and sluggish Li-S chemistry has severely limited their wide implication. Herein, we designed an ultrathin and vacancy-rich ZnCo-layered double hydroxide (ZnCo-LDH) anchored on CNT substrate (noted as CNT-LDH/Ar). Theoretical calculations and analysis at the experimental level are used to comprehensively explain the mechanism by which the oxygen vacancies (Vo) regulate the catalytic activity and adsorption capacity mechanism. The introduction of CNT not only improves a three-dimensional conductive network, but also exposes more active sites for polysulfide adsorption and conversion. More importantly, our design of Vo endows the material with excellent half-metallicity properties, adsorption capacity and low redox barrier. Benefiting from these properties, the S/CNT-LDH/Ar cathode exhibited excellent rate capability with 524.3 mAh g-1 at 5 C, and maintained an excellent cyclability over 500 cycles at 1.0 C with a capacity fading of only 0.042% per cycle. Most importantly, decent cyclability can be acquired with a remarkably raised sulfur loading up to 5.5 mg cm-2 with the lean electrolyte/sulfur (E/S) ratio of 6 mL g-1.