In situ self-boosting catalytic synthesizing free-standing N, S rich transition metal sulfide/hierarchical CNF-CNT architectures enable high-performance lithium-sulfur batteries

Abstract

Advanced hierarchical carbon-based hybrid (CH) nanostructures, typical carbon nanotubes/carbon nanofibers hybrid (CNT-CNF), with rationally tailored components, structures, and chemistries, have been widely dedicated to potential energy storage and conversion applications. Here we report a facile methodology for the synthesis of precise hierarchical heteroatom-doped carbon hybrid/transition metal sulfide (CNF-CNT/TMS) nanostructure assemblies with novel in-situ formed TMSs as the catalysts for secondary CNTs growth via a self-boosting catalytic pyrolysis. The key to in situ growth of CNT arrays is obtaining small high active TMS nanocatalysts and sufficient supply of carbon sources originated from polystyrene. Such special structure provides abundant active sites, beneficial for the application of N, S codoped CNF-CNT/TMS hybrid film in the electrochemistry without introducing extra dopants. As a proof-of-concept application, the representative CNF-CNT/Co9S8 hybrid was exploited as a conductive and catalytic membrane reactor in a lithium–sulfur (Li-S) battery. This unique architecture can achieve a maximized synergistic effect of electron/ion transport, polysulfide entrapment and catalytic conversion, which enables significant enhancement in electrochemical performance of Li-S batteries. As anticipated, the Li-S battery exhibits ultrastable long-life (over 1000 cycles, with an ultralow decay of 0.034% per cycle) and high-rate performance (6 C). Moreover, at high loading of sulfur of 3.7 mg cm−2, stable cycling performance with high capacity retention can still be achieved after long-term tests. This work also presents a facile and effective strategy in the development of complex hierarchical carbon nanostructure, which may be a competitive candidate in other energy storage and conversion system.