Li-O2 Cells Based on Hierarchically Structured Porous α-MnO2 Catalyst and an Imidazolium Based Ionic Liquid Electrolyte
ABSTRACT Highly crystalline α-MnO2 is synthesized by facile reduction of KMnO4 in acidic solution. The obtained α-MnO2 exhibits a high specific surface area of about 156 m2g-1 with a hierarchical bimodal porous structure. The TEM analysis confirmed that the α-MnO2 is highly crystalline and exists in the form of nano-rods agglomerated to form the shape of sphere. It is a promising electro-active material that can act as an oxygen reduction catalyst to improve the recharge ability of lithium-oxygen cells. The cell with α-MnO2 as catalyst and commercially available imidazolium-based room temperature ionic liquid with LiClO4 as electrolyte displayed an initial discharge capacity of 900 mAhg-1 which, after prolonged cycling, reached a stable value of about 600 mAhg-1 with a high recharge efficiency (~ 90%) and good capacity retention. Thus α-MnO2 catalyst along with ionic liquid based electrolyte could be an effective combination to obtain improved capacity and durability in a rechargeable lithium-O2 batteries.