Cobalt-decorated carbon nanotube bottlebrushes for boosting polysulfide conversion in lithium-sulfur batteries

Developing superhierarchical carbon materials with multiple levels of structural hierarchy including porous structure, hybrid skeleton and/or topological morphology, is highly desirable to fulfill the demands of complex catalytic reactions in electrochemical energy storage and conversion systems. Herein, a class of hierarchical porous cobalt-decorated carbon nanotube bottlebrushes (Co/CNTBs) have been developed by controllably grafting hairy CNTs from the surface of a hybrid CNT backbone with Co nanoparticles as catalytic sites. The well-defined bottlebrush-like topology with hierarchically porous structure provides efficiently accessible surfaces/interfaces and highly conductive networks, while the Co-decorated hybrid skeleton promotes the reaction kinetics of sulfur redox conversion. As a result, an excellent rate capability of 707 mA h g−1 at 10 C and long-term cycling stability can be achieved for lithium-sulfur (Li-S) cells with Co/CNTBs-functionalized separators. Remarkably, the Li-S cell with Co/CNTBs-functionalized separator can deliver a high areal capacity of 4.81 mA h cm−2 after 100 cycles at 0.1 C with a sulfur loading of 6.72 mg cm−2. These findings may shed light on the facile in situ grafting strategy for the fabrication of high-performance superhierarchical carbon hybrids towards numerous challenging applications.