A free-standing-type design for cathodes of rechargeable Li-O2 batteries

A novel free-standing type cathode of rechargeable Li-O-2 battery composed of only Co3O4 catalyst and Ni foam current collector was designed and realized by a simple chemical deposition reaction. The carbon and binder are no longer necessary for the air electrode. The new air electrode was found to yield obviously higher specific capacity and improved cycle efficiency than the conventional carbon-supported one with almost the highest discharge voltage (2.95 V), the lowest charge voltage (3.44 V), the highest specific capacity (4000 mAh g(cathode)(-1)) and the minimum capacity fading among the Li-O-2 batteries reported to date. During its discharge process, the discharge products would deposit at the surface and in the pores of the free-standing catalysts. The improved performance was attributed to the abundant available catalytic sites of the particularly structured air electrode, the intimate contact of the discharge product with the catalyst, the effective suppression of the volume expansion in the electrode during subsequent deposition/decomposition of the discharge products, the good adhesion of the catalyst to the current collector, and the open pore system for unrestricted access of the reactant molecules to and from active sites of the catalysts. Furthermore, EIS study pointed out the intrinsic distinction resulting in the different performance between the new electrode and the conventional carbon-supported electrode. The new free-standing type electrode represents a critical step toward developing high-performance Li-O-2 batteries.