Carbon nanotube-supported polyimide nanoarrays as sulfur host with physical/chemical polysulfide-traps for Li-S batteries

Lithium-sulfur (Li-S) batteries have been regarded as the most promising next-generation energy storage devices due to their large specific capacity and high energy density. However, their practical implementation is still subjected to the insulation of sulfur and discharge products, serious shuttle effect, and large volume expansion of sulfur during the discharge/charge processes. Herein, polyimide nanoarrays functionalized carbon nanotubes (PI@CNT) were proposed as a sulfur host with the incorporation of additional carbon nanotubes (CNTs) conductive networks. The as-preformed polyimide nanoarrays on the surface of CNTs expose sufficient adsorption sites for sulfur loading. PI@CNT chemically bind lithium polysulfides (LiPS) via the polar Li-N bonding interaction and physically confine LiPS in the network. Meanwhile, the intertwined frameworks can bear the volume expansion of sulfur and maintain the electrode integrity. The PI@CNT/CNT/S cathode exhibits the sulfur loading as high as 70 wt% and shows the cycling stability with a capacity retention of 67% after 300 cycles at 1 C. Furthermore, the additional incorporation of CNTs can form continuous electron transfer paths, thereby promoting the rate capability. This work integrated the polar polymer host and conductive networks with robust LiPS trapping and fast conversion, and would propose a new paradigm for designing high-performance sulfur cathodes.

Automated summary

This study successfully designed a high-performance sulfur cathode by integrating polyimide nanoarrays and conductive networks formed by carbon nanotubes, which can efficiently trap LiPS and enable fast conversion. The PI@CNT/CNT/S cathode has a sulfur loading as high as 70% and maintains a capacity retention of 67% after 300 cycles.