NMR Insights into Pore Architecture and Li + Accessibility for Optimized Energy Density in Li‐O 2 Batteries

Abstract

Lithium-oxygen batteries have gained prominence in recentyears due to their potential advantages over conventionallithium-ion batteries, including higher energy density, costeffectivenessand environmental sustainability. To fully exploitthese advantages, it is essential to understand the interplaybetween porous carbon electrode materials and electrolytes inthese devices. This study presents a nuclear magnetic resonanceinvestigation of the confined LiTFSI (lithiumbis(trifluoromethanesulfonyl)imide) - TEGDME (tetraethyleneglycol dimethyl ether) electrolyte within carbonaceous materialswith different pore sizes. Three carbon materials (microporous,mesoporous, and hierarchical) were synthesized from the sameprecursor to ensure equivalent surface chemistry, which wasverified by X-ray photoelectron spectroscopy. The dynamicsand distribution of solvent and Li ions in the different poreswere studied by 1H and 7Li, 1D and 2D exchange, NMRspectroscopy. It was found that the accessibility of Liþ withinthe pores of the carbonaceous material depends not only ontheir size but also on their size distribution. The knowledgegained from this study can contribute to the design of theappropriate pore size distribution, which could optimize theelectrolyte utilization and consequently increase the energydensity of lithium-oxygen batteries.