Improved electrochemical performance of the FeOx(OH)/IF electrode via in situ surface modification with organic naphthoquinone molecules

Abstract

An organic–inorganic hybrid is a promising electrode material for aqueous batteries due to its larger potential in improving electrochemical performance. Herein, we designed and prepared a naphthoquinone@FeO_x(OH)/iron foam (NQ@FeO_x(OH)/IF) hybrid electrode as a highly-efficient anode in Ni/Fe batteries via combining electro-deposition of FeO_x(OH) and in situ hydrothermal growth of naphthoquinone. The as-prepared hybrid electrode materials present a 2D nanosheet morphology of FeO_x(OH) and a branch/band-like structure of NQ, with the formation of NQ–FeO_x(OH) interfaces. Such an interface structure is revealed to have more electron active sites, with increased electron delocalization caused by the aromatic ring structure, thereby enhancing the transport of the electrons in the electrode materials. Thus, a superior electrochemical performance of the NQ@FeO_x(OH)/IF electrode was received, with a large areal capacity of ∼2.23 mA h cm⁻² and a favorable rate capability of 1.09 mA h cm⁻² at 40 mA cm⁻². Besides, the NQ@FeO_x(OH)/IF anode was coupled with the NiCo₂O₄ cathode to assemble a Ni/Fe battery, as a result, an admirable energy density of 235.2 W h kg⁻¹ and a maximum power density of 5.4 kW kg⁻¹ were obtained. The study on high-performance NQ@FeO_x(OH)/IF electrode materials paves the way to design and synthesize better iron-based materials for Ni/Fe batteries.