Highly mesoporous C nanofibers with graphitized pore walls fabricated via ZnCo2O4-induced activating-catalyzed-graphitization for long-lifespan lithium-ion batteries

Transition metals (TMs), e.g. Fe, Co, and Ni, are normally unsuitable for the fabrication of highly porous C materials with graphitized C layers since in situ formed carbides on the surface of the TMs impede their catalytic graphitization effect. In this paper, we report on highly mesoporous sponge-like C nanofibers (SLCNFs) with graphitized pore-walls fabricated through novel activating-catalyzed-graphitization using ZnCo2O4 as a source of ZnO and metallic Co. During the carbonization, the ZnO functions as an in situ activating agent to provide O species to oxidize the inert Co3C to active Co; the original transient "amorphous C/Co-graphite/Co3C" process induced by the metallic Co can be translated into a cyclic "amorphous C/Co-graphite/Co3C-COx/Co" system, to fabricate a sponge-like well-interconnected mesoporous structure. This gives SLCNFs a high reversible capacity (900 mA h g(-1) at 0.1 A g(-1) after 100 cycles), good rate performance, and excellent super-long-term cycle stability (460 mA h g(-1) at 1.67 A g(-1) after 2000 cycles) when used as the anode of a lithium-ion battery. The usability of SLCNFs as a conductive substrate for sulfur is also demonstrated, indicating their excellent potential for application to energy storage and conversion.