Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li–O(2) Batteries

As a step towards efficient and cost-effective electrocatalytic cathodes for Li–O(2) batteries, highly porous hausmannite-type Mn(3)O(4) hollow nanocages (MOHNs) of a large diameter of ~250 nm and a high surface area of 90.65 m(2)·g(−1) were synthesized and their physicochemical and electrochemical properties were studied in addition to their formation mechanism. A facile approach using carbon spheres as the template and MnCl(2) as the precursor was adopted to suit the purpose. The MOHNs/Ketjenblack cathode-based Li–O(2) battery demonstrated an improved cyclability of 50 discharge–charge cycles at a specific current of 400 mA·g(−1) and a specific capacity of 600 mAh·g(−1). In contrast, the Ketjenblack cathode-based one can sustain only 15 cycles under the same electrolytic system comprised of 1 M LiTFSI/TEGDME. It is surmised that the unique hollow nanocage morphology of MOHNs is responsible for the high electrochemical performance. The hollow nanocages were a result of the aggregation of crystalline nanoparticles of 25–35 nm size, and the mesoscopic pores between the nanoparticles gave rise to a loosely mesoporous structure for accommodating the volume change in the MOHNs/Ketjenblack cathode during electrocatalytic reactions. The improved cyclic stability is mainly due to the faster mass transport of the O(2) through the mesoscopic pores. This work is comparable to the state-of-the-art experimentations on cathodes for Li–O(2) batteries that focus on the use of non-precious transition materials.