Mesopore-Controlled Surface Utilization in Carbon Aerogel Positive Electrodes in Lithium–Oxygen Batteries

Abstract

High-capacity positive electrode development for lithium–oxygen batteries (LOBs) requires porous carbon materials with proportional pore-size distribution and sufficiently large pore volumes. This study synthesized carbon aerogels (CAs) with different pore structures via catalyst concentration and activation time tuning, and examined their performance as LOB positive electrodes. The samples are labeled as CAX, where X denotes the molar ratio of resorcinol-to-sodium carbonate catalyst. CA200, with a peak mesopore radius of 9.2 nm, delivered the highest discharge capacity of 11.4 mAh cm–2, despite commercial activated carbon possessing larger specific surface areas (SSAs). This result highlights the pivotal role of mesopores in enabling micropores to act as effective reaction sites. Subsequent CO2 activation in CA100 and CA200 enlarged their SSAs and mesopore volumes while preserving their mesopore sizes. The discharge capacity was raised to 19.2 mAh cm–2 for activated CA200. However, the surface-area-normalized capacity did not scale proportionally with micropore growth, indicating that further refinement of pore architecture is required to maximize micropore utilization. Overall, these findings demonstrate the synergistic interplay between mesopores and micropores that governs discharge capacity, thereby offering design guidelines for high-capacity activated carbon-based positive electrodes with tailored mesoporous architectures for LOBs.