Enhanced Cyclability in Rechargeable Li-O₂Batteries Based on Mn₃O₄Hollow Nanocage/Ketjenblack Catalytic Air Cathode

Mn3O4hollow nanocages (MOHNs) of mean diameter 250 nm and composed of a number of Mn3O4nanoparticles of mean diameter 25 nm are synthesized via a facile template method using C spheres as the hard template and MnCl2as the Mn source. The C sphere templates are prepared by a hydrothermal method using glucose as the C source. The hydrophilic nature of the surface of the C sphere templates allows the adsorption of Mn2+ions, resulting in the MOHNs upon thermal annealing of the Mn-adsorbed C sphere templates in air. The MOHNs possess a crystalline phase and a hollow-cage porous nanostructure with a high specific surface area of 90.65 m2/g and a linear paramagnetic behavior at room temperature. These MOHNs, when combined with ketjenblack (KB) C blacks to form MOHN/KB catalytic air cathodes in nonaqueous Li-O2batteries (LOBs), exhibit a high and stable reversible restrained specific capacity of 600 mAh/g in excess of 50 discharge-charge cycles at a specific current of 400 mA/g. The pure KB air cathode-based LOBs can only sustain ∼ 15 cycles at the same conditions.