Grain-refining Co0.85Se@CNT cathode catalyst with promoted Li2O2 growth kinetics for lithium-oxygen batteries

Abstract

Highly active cathode catalysts for efficient formation/decomposition of Li2O2 are essential for the performance improvement of lithium-oxygen batteries (LOBs). In this study, a grain-refining Co0.85Se catalyst with a lattice spacing of 2.69 Å of (101) plane closely matching with the (100) plane (2.72 Å) of Li2O2 was applied for high-performance LOBs. Highly (101) plane exposed Co0.85Se@CNT was synthesized by a simple one-pot hydrothermal method. The Co0.85Se with the lattice matching effect not only led to the efficient conversion and polarized growth of Li2O2, but also prevented the formation of byproducts. Density functional theory (DFT) calculations reveal that Co0.85Se (101) plane has the intrinsic catalytic ability to generate/decompose Li2O2 during ORR/OER process, due to its homogeneous electron distribution, suitable adsorption energy, and promoted Li2O2 growth kinetics. As a consequence, the (101) plane highly exposed Co0.85Se@CNT-80 electrode exhibited remarkable cycle stability over 2400h at 100 mA/g and 290 cycles at 500 mA/g, which is about 2 times longer than other electrodes.