Aluminum-air battery is the promising candidate for the next-generation high-energy density batteries, but inherent limitations make it difficult in practical use. Here we show that silver nanoparticle-mediated silver manganate nanoplate as an oxygen reduction catalyst greatly improves the catalytic activity and chemical stability in alkaline solution. By means of atomic resolved transmission electron microscopy, we find that the formation of stripe patterns on the surface of silver manganate nanoplate originates from the zigzag atomic arrangement of silver and manganese, creating high concentration of dislocations in crystal lattice. This structure can provide abundant active sites for ion adsorption and high electrical conductivity for fast electron transfer kinetics. We also confirm the outstanding performance of our catalyst in flow-based aluminum-air batteries, demonstrating high gravimetric and volumetric energy densities of ~2,552 Wh kgAl−1 and ~6,890 Wh lAl−1 at 100 mA cm−2 and high stability during mechanical recharging process.