Metal–organic frameworks-derived porous carbon/Co₃O₄ composites for rechargeable lithium–oxygen batteries

Highlights: • We develop porous carbon/Co₃O₄ composites for Li–O₂ batteries. • Porous carbon/Co₃O₄ composites are derived from cobalt-containing MOFs. • Co₃O₄ nanoparticles catalyze both ORR and OER in a rechargeable Li–O₂ system. • The porous structure of the composites realizes a high discharge capacity. • The uniform distribution of Co₃O₄ realizes effective catalytic effects. - Abstract: Lithium–oxygen (Li–O₂) batteries are promising candidates for high-performance energy storage systems because of their tremendous energy density, which significantly exceeds that of conventional Li–ion batteries. Cobalt oxide (Co₃O₄) is considered an effective catalyst for non-aqueous Li-O₂ batteries owing to its excellent oxygen reduction and oxygen evolution reaction activity. However, low electrical conductivity and agglomeration of Co₃O₄ can degrade the electrochemical performance properties. We present a facile method of synthesizing porous carbon/Co₃O₄ composites derived from metal–organic frameworks (MOFs) via post-thermal treatment for use as the cathode in rechargeable Li–O₂ batteries. Use of cobalt-containing MOFs as a sacrificial template produces uniformly distributed Co₃O₄ nanoparticles in the carbonaceous matrix, alleviating the problems of using only Co₃O₄ as the cathode material. As-synthesized porous carbon/Co₃O₄ composites show superior electrochemical performance, for example, a low overpotential and high reversible capacity of about 9850 mA h g⁻¹ at a current density of 100 mA g⁻¹. They also exhibit excellent cyclability up to the 320th cycle, with a limited capacity of 500 mA h g⁻¹ at a current density of 200 mA g⁻¹. The improvement is attributed to the catalytic activity and mesoporous structure of uniformly distributed Co₃O₄ nanoparticles in the carbonaceous matrix.