Design and synthesis of hierarchical, freestanding bowl-like NiCo2O4 as cathode for long-life Li-O2 batteries

Abstract

In this paper, hierarchical, freestanding bowl-like NiCo2O4 growing directly on carbon fiber paper (NiCo2O4@CFPs) are designed and synthesized through a controllable and facile electro-deposition combined with hard template method, and then applied as air electrode for long-life Lithium-O2 batteries. This novel air electrode could deliver a high discharge capacity of 9624.2 mAh g−1, low discharge/charge over-potentials (over-potential gap < 1.0 V), excellent cycleability (∼100 cycles). Moreover, it exhibits extraordinarily rate capability and reversibility. Specifically, amorphous nanosheet-like Li2O2 have been observed as the main discharge products, which might be tailored by the special bowl-like catalyst. The excellent cell performances could be ascribed to the special open structure of the synthesized bowl-like catalyst, which could provide large specific surface area, enough space for accommodating the discharge products and facilitate the transport of oxygen and electrolyte in the Lithium-O2 batteries. This facile, low-cost synthesis approach further sheds light on fabrication of various hierarchical bowl-like air electrodes including metal oxides, metals or their hybrids, and possesses promising applications on metal-air batteries and fuel cells.