Geometrically Defined Nanochannels Resolve the Interplay of Mass Transport and Product Deposition in Lithium-Oxygen Batteries.

The discharge process at the positive electrode in lithium-oxygen batteries (LOBs) involves coupled O2 transport, electrochemical generation of LiO2 intermediates, and subsequent Li2O2 deposition that progressively restricts O2 transport. In practical porous electrodes, geometric complexity obscures this interplay and hinders mechanistic understanding. Here, these processes were spatially separated and analyzed by employing an anodic aluminum oxide (AAO) positive electrode with one-dimensional nanochannels as a model reaction field. The results reveal that the deposition location of Li2O2 reflects the travel distance of dissolved LiO2 intermediates from the electrode. Furthermore, even partial accumulation of discharge products on the order of tens of nanometers can significantly restrict O2 transport and lead to early attainment of the discharge cutoff. This study provides a framework to reinterpret complex electrode reactions using a simplified AAO reaction field and offers guidelines for achieving high capacity in LOBs.