Boosting the kinetics with graphene quantum dots (GQDs)-decorated NiCo2O4 nanosheets towards high-performance Li-O2 batteries

Abstract

The performance of energy-dense lithium-oxygen batteries depend primarily on the electrocatalytic activity and architecture of the oxygen electrodes. However, highly catalytically active cathode materials such as metal oxides suffer from insufficient electronic conductivity, resulting in restricted kinetics and O2/e−/Li+ three-phase reaction regions. In this study, we design and fabricate a free-standing and lightweight cathode with graphene quantum dots (GQDs) modified NiCo2O4 (NCO) nanosheets array anchored on 3D graphene foam (GF). The potential electrocatalytic activity of metal oxide materials can be fully excited by electronic conductivity compensation, and the triple-phase reaction regions are expanded from the NCO/GF interface to the entire surface of NCO. As a result, the cathode can deliver a discharge capacity as high as 7672 mAh g−1, cacaulated based on the whole mass of the entire cathode, and can sustain more than 500 cycles with a high energy efficiency of over 78.5%. These findings demonstrate that the GQDs@NCO@GF cathode has remarkable potential for applications in lithium-oxygen batteries, and the cathode structure design scheme and GQDs modification strategy can be further applied to other high-efficiency catalysts.