Sequential Catalysis of Defected-Carbon and Solid Catalyst in Li–O₂ Batteries

Abstract

Lithium–oxygen batteries show great promise as energy storage devices but suffer from high overpotential, which is a major cause of poor cycle stability. To reduce the overpotential, catalysis on a carbon-based cathode is crucial. This work examines the sequential catalysis of a carbon-based cathode containing basal defects and Ru nanoparticles. A new type of carbon cathode is fabricated by dispersing Ru nanoparticles onto a highly mesoporous carbon framework of mainly single-walled curved graphene, which has abundant basal defects but few edge sites. This novel cathode exhibits unique sequential catalysis by forming two distinct morphologies of lithium peroxide in the discharge process. These two morphologies are decomposed at different potentials during charging. A comprehensive analysis, including in situ differential electrochemical mass spectrometry, reveals that the low and high-potential charging plateaus are induced by two different catalytic mechanisms derived from basal defects and Ru nanoparticles, respectively. Interestingly, these two mechanisms do not interfere with each other but act sequentially, reducing the overpotential and thus enhancing the cycle stability.