Ultrathin Porous NiCo2O4 Nanosheets for Lithium-Oxygen Batteries: An Excellent Performance Deriving from an Enhanced Solution Mechanism

Lithium-oxygen batteries are of interest for long-range electric vehicles owing to their high theoretical energy density. However, the poor cycling performance and low round-trip efficiency deriving from the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics severely impede their practical application. Ingenious design of cathode catalysts is imperative to overcome these challenges. Here, we report ultrathin porous NiCo2O4 nanosheets with abundant oxygen vaccines as an efficient cathode catalyst toward both OER and ORR for Li-O-2 batteries. From combined theoretical calculation with experimental results, a unique enhanced solution mechanism is proposed in the ether-based electrolyte system. Benefiting from the porous 2D architecture of the cathode and the hierarchical toroidal products, the Li-O-2 batteries using NiCo2O4 cathodes deliver a high discharge capacity of 16 400 mAh g(-1) at 200 mA g(-1) and an excellent cycling performance up to 150 cycles with a restricted capacity of 1000 mAh g(-1).