Mesoporous boron-doped onion-like carbon as long-life oxygen electrode for sodium–oxygen batteries

Abstract

Metal–oxygen batteries are thought to be the ultimate energy storage solution due to their high specific energy. We report here on the synthesis of mesoporous boron-doped onion-like carbon (B-OLC) microspheres and their application in rechargeable sodium–oxygen (Na–O₂) batteries. Low overpotential, high specific capacity (over 10 200 mA h g⁻¹), enhanced rate capability (∼7500 mA h g⁻¹ at 0.6 mA cm⁻²) and excellent cyclability (up to 125 cycles) can be achieved by using B-OLC based electrodes in Na–O₂ batteries. The critical role of surface chemistry on the morphology and composition of products is studied and the optimum performance of Na–O₂ batteries with B-OLC based electrodes is attributed to the synergistic effects arising from the combination of catalytic activity and the uniquely mesoporous carbon nanoarchitecture. This study indicates that mesoporous B-OLC demonstrated intriguing properties and great potential applications as effective metal-free bifunctional catalysts for Na–O₂ batteries and encourages the development of heteroatom-doped carbon materials for performance improvement of metal–oxygen batteries.