Mixed Ionic-Electronic Conductor of Perovskite Li(x)La(y)MO(3-)(delta)toward Carbon-Free Cathode for Reversible Lithium-Air Batteries

Mixed ionic-electronic conductors (MIECs) can play a pivotal role in achieving high energies and power densities in rechargeable batteries owing to their ability to simultaneously conduct ions and electrons. Herein, a new strategy is proposed wherein late 3d transition metals (TMs) are substituted into a perovskite Li-ion conductor to transform it into a Li-containing MIEC. First-principles calculations show that perovskite Li(x)La(y)MO(3)with late 3d TMs have a low oxygen vacancy formation energy, implying high electron carrier concentrations corresponding to high electronic conductivity. The activation barriers for Li diffusion in LixLayMO3(M = Ti, Cr, Mn, Fe, and Co) are below 0.411 eV, resulting in high Li-ion conductivity. The designed perovskites of Li(0.34)La(0.55)MnO(3-)(delta)experimentally prove to have high electronic (2.04 x 10(-3)S cm(-1)) and Li-ion (8.53 x 10(-5)S cm(-1)) conductivities, and when applied in a carbon-free cathode of a Li-air cell, they deliver superior reversibility at 0.21 mAh cm(-2)over 100 charge/discharge cycles while avoiding the degradation associated with carbonaceous materials. This strategy enables the effective design of Li-conducting MIEC and reversible Li-air batteries.