Durable High Capacity Li-O2 Cathode Composed of Iron-Nitrogen-Doped Mesoporous Core-Shell Carbon Loaded with RuO2 Nanoparticles

Abstract

The reversible lithium oxygen battery has generated a lot of interests for its high energy density. Limitations of oxygen reduction and evolution (ORR/OER) kinetics in aprotic solvents, lack of reversible lithium peroxide deposition/dissolution, and degradation problems have hintered development of Li-O2 technology. There are few reports of durable high capacity cathode performance. Nitrogen-doped mesoporous carbon has been succesfully deployed for ORR in aqueous electrolytes[1]. Here, we report Fe-N-doped hierarchical mesoporous carbon loaded with RuO2 nanoparticles (Fe-N-HCMS-RuO2) for application as a Li-O2 cathode. Promising results are observed with capacity reaching 1/3 the theoretical energy density of Li-O2 (3,500 Wh/kg). The Fe-N-HCMS-RuO2 electrode demonstrates excellent performance which can be attributed to three features of the composite. A well-defined core-shell mesoporous structure provides excellent mass transport and limits the Li2O2 deposition to be dispersed in nanoscale. The Fe-N doping of carbon provides the corrosion resistance, high conductivity, and active sites for favorable interaction with RuO2. Small and amorphous RuO2 provides highly catalytic activity for decomposition of Li2O2. Discharge capacity of 10,000 mAh/g is demonstrated with discharge potential of 2.4 V and recharge potential of 3.6 V maintained at 2 A/g based on total mass of catalyst and carbon support and maintained at 2.5 V and 3.5 V at 1 A/g over 50 cycles.