Graphitic Carbon Nitride/Carbon Nanotube Cathodes for Non-Aqueous Lithium-Oxygen Batteries

Abstract

Although non–aqueous lithium–oxygen (Li–O2) batteries have been gaining attention in recent years for their potentially high energy density, their actual performances are still inferior to that of state–of–the–art Li–ion batteries. To overcome the high overvoltage, low rate capability, and poor cycle performance, the development of O2 electrode structures and electrocatalysts is of great importance. Herein, a graphitic carbon nitride/carbon nanotube composite (GCN/CNT) was synthesized using a facile annealing method and evaluated as a cathode for non–aqueous Li–O2 batteries, where CNT can provide storage sites for the reactants and products while facilitating electron transfer, and GCN can act as catalytic centers for oxygen reactions.Due to its large surface area, high nitrogen content and synergistic coupling, GCN/CNT (18 wt.% GCN) demonstrated improved activity and stability towards ORR and OER (ΔE = 1.07 V), compared to pure CNT. Consequently, GCN/CNT exhibited lower overpotentials and better cycling stability when applied as a Li–O2 battery cathode. It delivered a specific discharge capacity of 3796 mAh g–1 at a current density of 100 mA g–1, and a relatively stable cycling performance of up to 35 cycles at a limited capacity of 1000 mAh g–1. Moreover, the reversible formation and decomposition of the Li2O2 product after cycling was confirmed in the characterization data (SEM images and XRD patterns). Hence, this GCN/CNT composite could be a promising cathode material in Li–O2 batteries. Figure 1. ORR LSV curves of CNT, Pt/CNT, and GCN/CNT electrodes in an O2−saturated 0.1 M KOH electrolyte at a scan rate of 5 mV s−1 and rotation speed of 1600 rpm Figure 1