Mitigating Li2S agglomeration in lithium-sulfur batteries with hierarchically structured CNT/Ni-Ni0.85Se sulfur hosts

The development of sulfur host materials with high catalytic activity to tackle the shuttling effect of polysulfides and their slow conversion kinetics is a prospective strategy for improving the performance of lithium-sulfur batteries. However, it may result in excessively thick Li₂S films that cover the entire electrode structure, consequently weakening the functionalization effect of the sulfur host. Herein, we developed a hierarchical structured sulfur host material composed of a three-dimensional composite conductive network of carbon nanotubes and Ni nanoparticles, along with Ni_0.85Se nanosheets grown on its surface. The synergistic effects of hierarchical structure and conductive network accelerate the electron and ion transport, mitigate the volume expansion during lithiation, enhance the conversion kinetics of polysulfides, and importantly prevent the agglomeration of thick Li₂S films, which results in a significant improvement in the electrochemical performance of the sulfur cathode. The developed CC@CNT/Ni-Ni_0.85Se-S exhibits excellent rate performance and long-term stability, achieving a discharge-specific capacity of 965 mA h g⁻¹ at 3 C and maintaining a discharge-specific capacity of 789 mA h g⁻¹ even after 300 cycles at 1 C. Notably, the capacity retention rate is as high as 92.9% for 100 cycles at 0.1 C, even with a high sulfur loading of 4.0 mg mg⁻². This work not only effectively mitigates the agglomeration of Li₂S film but also offers a novel design approach for the practical application of high-energy-density lithium-sulfur batteries.