Synthesis of mesoporous carbons and reduced graphene oxide and their influence on the cycling performance of rechargeable Li-O2 batteries

In the lithium-oxygen (Li-O2) cell, the porous structure of the cathode is an important issue as well as challenge for its task of accommodating discharge products and providing free paths for oxygen. Clogging of pores and degradation of materials at the cathode affect the discharge rates and cycling performance of Li-O2 cell. Based on the study of five synthesized nanostructured porous carbons, namely, 2-D ordered mesoporous carbon C-15, 3-D ordered mesoporous carbons C-16 and C-16B with larger pores, hollow core mesoporous shell carbon (HCMSC), and reduced graphene oxide (rGO), we found that the type and pore structure of the carbon significantly affect the electrochemical performance of the cell. Both C-15 and rGO cathodes demonstrate good cell cycleability, while the HCMSC, with its interesting bimodal pore system, is not favorable for further improving cycling performance. The C-16B has similar morphology and electrolyte wettability of C-16. However, the former possesses larger pores, and such porosity significantly improves the cell cycleability up to 44 cycles, corresponding to an extended operation life of 850 h.