Space-confined pyrolysis strategy to self-catalyze the growth of carbon nanotube-wrapped Co3O4 electrocatalyst for lithium-O2 batteries

Abstract

Lithium-oxygen batteries (LOBs) are emerging as one of the most powerful candidates for the next-generation green energy-storage devices due to their high theoretical energy density. However, the high polarization and poor cycling stability have hampered their practical applications that heavily depend on the dual-functional cathodes with abundant highly active sites to promote the mass/electron transfer for efficient oxygen reduction and evolution. Herein, a space-confined pyrolysis strategy is proposed by coating a Co-based metal-organic framework composite precursor (ZIF-8 @ZIF-67) with an inorganic SiO2 layer, which efficiently inhibits the precursor loss and nanostructure collapse during the high-temperature carbonization and yields a high-performance carbon nanotube-wrapped Co3O4 electrocatalyst. Thereinto, the Co within the precursor can act as the self-catalyst for the growth of abundant carbon nanotubes, which not only generates more catalytic sites but also improves the electronic conductivity. Systematic investigations reveal that the resultant Co3O4 wrapped with carbon nanotubes (Co3O4/CNTs) possesses significantly improved bifunctional oxygen reduction and evolution activity when compared with the Co3O4 counterpart derived from the traditional direct pyrolysis, which is benefited from the large content of active sites and strong mass/electron transfer capabilities to allow the exceptional rate performance and cycling stability of LOBs. The space-confined pyrolysis strategy described herein may help to exploit the highly efficient electrocatalysts.