Tailoring mixed geometrical configurations in amorphous catalysts to activate oxygen electrode reactions of lithium-oxygen batteries

Abstract

Constructing well-designed catalysts by manipulating geometrical and electrical structures is regarded as effective strategies for high-performance lithium-oxygen chemistry. However, the high activity and stability of catalysts cannot be always realized simultaneously, which is apt to result in high overpotentials and poor cycling life. Herein, we elaborately construct an amorphous lanthanum-nickel-iron based oxide/hydroxide (a-LNFO) with mixed geometrical configurations of edge- and face-shared octahedra, which exhibits decent catalytic activity and excellent stability. The disordered structure endows randomly arranged terminal and bridging forms and ample oxygen vacancies, exposing massive active sites. Besides, the introduction of Ni3+ with eg orbital occupancy of 1 benefits to the favorable covalency of metal–oxygen bond, which results in the accelerated electron transport and appropriate bond strength between the catalyst and oxygen–containing intermediates, boosting the intrinsic activities toward oxygen evolution reaction and oxygen reduction reaction. Confirmed by X-ray absorption fine structure, short distance between distorted octahedra centers (Ni and Fe cations) reduces the reaction paths and induces strong electrostatic interactions, efficiently accelerating the reaction kinetics. Simultaneously, increased couples of metal-oxygen bonds in edge- and face-shared octahedra ensure the splendid stability. As a proof of concept, the a-LNFO catalyzed lithium-oxygen battery achieves a high specific discharge capacity of 13,617 mAh/g and superior cycling stability of 435 cycles. This work reveals the positive effect of geometrical configuration transformation from corner-shared octahedra to edge- and face-shared octahedra, which provides a feasible strategy for activating oxygen electrode reactions.