Two-dimensional β-cobalt hydroxide phase transition exfoliated to atom layers as efficient catalyst for lithium-oxygen batteries.

Metal-oxygen batteries, especially Li-oxygen batteries (LOBs), have attracted tremendous research attentions in the past decades. It is necessary to design novel cost-effective catalysts in the development of high performance rechargeable LOBs. Herein, we prepare the atom-layered two-dimensional (2D) β -Co(OH) 2 nanosheets (AL- β -Co(OH) 2 ) via phase transition of layered α- Co(OH) 2 nanosheets ( α- Co(OH) 2 ) in a mild wet chemical process. The thickness of AL- β- Co(OH) 2 is less than 1.5 nm. It is the first time of using atom-layered β -Co(OH) 2 in the system of LOBs and this material shows outstanding catalytic performance. The AL- β -Co(OH) 2 nanosheets as electrocatalysts in LOBs can better reduce the over-potential, enhance the specific capacity and improve cycling capability. It demonstrates a high initial capacity 11841 mAh g −1 at a current density of 100 mA g −1 . It displays long cycle stability more than 70 cycles with a capacity restriction of 1000 mAh g −1 . These results suggest that this strategy for designing oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts via exfoliation of materials to atom-layered level could be a promising way to improve the performance of LOBs. [ABSTRACT FROM AUTHOR]