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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@FeOx(OH)/iron foam (NQ@FeOx(OH)/IF) hybrid electrode as a highly-efficient anode in Ni/Fe batteries via combining electro-deposition of FeOx(OH) and in situ hydrothermal growth of naphthoquinone. The as-prepared hybrid electrode materials present a 2D nanosheet morphology of FeOx(OH) and a branch/band-like structure of NQ, with the formation of NQ–FeOx(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@FeOx(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@FeOx(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@FeOx(OH)/IF electrode materials paves the way to design and synthesize better iron-based materials for Ni/Fe batteries. [ABSTRACT FROM AUTHOR]

Herein, we report a nanoarchitectured nickel molybdate/carbon fibers@pre-treated Ni foam (NiMoO4/CF@PNF) electrode for supercapacitors. The synthesis of NiMoO4/CF@PNF mainly consists of a direct chemical vapor deposition (CVD) growth of dense carbon fibers (CFs) onto pre-treated Ni foam (PNF) as the substrate, followed by in situ growth of NiMoO4 nanosheets (NSs) on the CF@PNF substrate by means of a hydrothermal process. The NiMoO4/CF@PNF electrode exhibits a high areal capacitance (5.14 F cm−2 at 4 mA cm−2) and excellent cycling stability (97 % capacitance retention after 2000 cycles at 10 mA cm−2). Furthermore, we have successfully assembled NiMoO4 NSs//activated carbon (AC) asymmetric supercapacitors, which can achieve an energy density of 45.6 Wh kg−1 at 674 W kg−1, and excellent stability with 93 % capacitance retention after 2000 cycles at 5 mA cm−2. These superior properties hold great promise for energy-storage applications. [ABSTRACT FROM AUTHOR]

The flexible graphene fiber-based symmetic supercapacitors are usually greatly expected to power small wearable electronics because of their many potential applications. In the present work, the organic electrochemically active material of quinone for asymmetric supercapacitors has been introduced to decorate graphene oxide nanosheets as negative electrodes via a facile hydrothermal self-assembly method. Fortunately, 1,4-naphthoquinone (NQ) is a suitable choice for functionalizing graphene-based materials through noncovalent interactions. Different from conventional quinone based materials, we study naphthoquinone modified electrode materials with satisfactory electrochemical properties, and take the lead in preparing fibrous quinone based electrodes, which are applied to the construction of wearable flexible supercapacitors. As a consequence, the modified NQrGO/CF exhibits an improved capacitance owing to the superposition of capacitance behavior and the synergistic effect of each component. More interestingly, the all-solid asymmetric flexible micro-supercapacitor (AFSC) assembled with NQrGO/CF as the negative electrode, nickel-cobalt hydroxide hybrid graphene-based fiber (NCHrGO/CF) as the positive electrode and PVA/KOH as the gel electrolyte, which has a potential window of 2.0 V, with a maximum energy density of 50.7 Wh kg−1. Moreover, we propose the multiple micro-supercapacitors could be reasonably connected in series or in parallel for the reduction of resistance and the promotion of electrochemical performance to meet the requirements of specific operating voltage and energy output in application. The graphene-based fiber electrode modified with quinone provides more methods and better options for the construction and development of asymmetric flexible micro-supercapacitors. [ABSTRACT FROM AUTHOR]