ИСТИНА

Today lithium-air batteries (LAB) are among the most attractive electrochemical energy storage systems thanks to extremely high theoretical gravimetric energy, which can potentially reach 1 kWh per kg at a cell level1. However, practical applications of LABs are now hindered by a low round-trip efficiency, caused by slow kinetics of oxygen reduction reaction (ORR) on discharge, oxygen evolution on charge and a variety of side reactions occurring on positive electrodes2. Specifically, LAB operation includes nonconductive solid discharge product formation inside pores of highly dispersed positive electrode. This product mainly consists of Li2O2. The deposition is rather complex multistep process both from chemical point of view and the crystallization mechanism versatility. Depending on the discharge conditions and, especially, on which solvent is used, different growth mechanisms occur giving rise to quiet different morphologies. Among them spherulites composed of thin platelets of Li2O2 are typical3. Their progressive growth can destruct electrode material, and, in addition, can restrict battery rechargeability in case if the crystals loose the contact with electrode surface. Here we report on recent progress in studying processes of lithium peroxide precipitation. Using electronic paramagnetic resonance spectroscopy we found that lithium superoxide disproportionation rate in acetonitrile is 30 times higher than in MeCN that leads to different regimes of cathode’s pore blocking during discharge of Li-O2 cell in these electrolytes. The pore filling was studied by electron microscopy and small-angle neutron scattering. Near-ambient pressure X-ray photoelectron spectroscopy revealed that MeCN-based electrolytes are unstable under Li-O2 battery operation conditions.