Taming polysulfides and facilitating redox: Novel interlayer based on chestnut-like and multi-level structural materials for ultra-stable lithium-sulfur batteries

Owing to high energy density, lithium sulfur (Li–S) battery is regarded as one of the most promising candidates for future energy storage. However, "shuttle effect" and sluggish redox kinetics of lithium polysulfides impede its practical application. Herein, a novel g-C₃N₄/Co-based MOFs derived chestnut-like superstructure (Co/CNT@DCNS) was prepared to act as the component of interlayer through a low-temperature one-step carbonization strategy. The prepared superstructure was constructed by the strong catalysis of 0D Co nanoparticles, high conductivity of 1D CNTs and excellent polysulfides adsorption of 2D defect C_xN_y nanosheets, which could not only ensure the rapid electrons/ions transport and fast redox kinetics, but also provide sufficient spaces for accommodating the volume expansion of active materials. Therefore, the cells with the prepared interlayer exhibited stable performances with an initial capacity of 1348.3 mAhg⁻¹ and an extended cycling stability of 0.04% per cycle during the 1000 cycles at 1C. Even at a high sulfur loading of 3.1 mg cm⁻², a specific capacity of 691.7 mAh g⁻¹ can be maintained after 500 cycles at 0.5C. This work shares a convenient and safe strategy for the synthesis of multi-dimension, dual-functional and stable superstructure interlayer for advanced Li–S batteries.