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• Mg2+ and Mn2+ co-doped Na 3 V 2 (PO 4) 3 is prepared via a simple high temperature solid method. • Mg2+ and Mn2+ co-doping can propel kinetics behavior and enhance electronic conductivity. • The NVP-(MM) 0.01 exhibits an outstanding rate and cycling performance. • Ex-situ XRD revealed that the structure of NVP-(MM) 0.01 is well maintained after 500 cycles at 10 C. In this article, Mg2+ and Mn2+ co-doped Na 3 V 2 (PO 4) 3 cathode material is prepared, which exhibits enhanced rate capability and long-term cyclic stability for sodium-ion batteries. [Display omitted] Na 3 V 2 (PO 4) 3 with open 3D framework structure is perceived as the most potential cathode material for sodium-ion batteries (SIBs). Nevertheless, its electrochemical properties are generally restricted by the larger radius of Na+ and the intrinsic poor electrical conductivity. Herein, we adopt a unique bimetallic doping strategy to prepare Mg2+ and Mn2+ co-doped Na 3 V 2−x (Mg 0.5 Mn 0.5) x (PO 4) 3 [NVP-(MM) x (x = 0, 0.01, 0.02)] through a high temperature solid state reaction. The as-prepared NVP-(MM) 0.01 presents a high initial discharge capacity of 107.7 mA h g−1 at 1 C. Furthermore, NVP-(MM) 0.01 displays a highly rate capability (75.5 mA h g−1 at 15 C) and excellent cycling performance (71 mA h g−1 after 1000 cycles at 20 C). Electrochemical results exhibit that Mg2+ and Mn2+ co-doped with appropriate proportion can enhance the electronic conductivity and sodium storage kinetics process of Na 3 V 2 (PO 4) 3 effectively. Our work provides a novel idea to construct high performance SIBs via a bimetallic co-doped strategy. [ABSTRACT FROM AUTHOR]

• A simple method with preparing the core-shell ZnO/CoO@NiCoS nanoarray with double-layer heterojunction. • The coating of NiCoS and the ZnO/CoO heterojunction nanowires can greatly improve the energy storage capacity of electrodes. • This study provides a novel strategy for the preparation of low-cost, deep-discharge electrodes for supercapacitors. A simple method with preparing the core-shell ZnO/CoO@NiCoS nanoarray with double-layer heterojunction for high-performance supercapacitor. [Display omitted] Hybrid supercapacitors (HSC) with high power density and long cycle life are received more attention in the field of energy storage devices, however, the wide application of HSC is limited by the low energy density owing to the insufficient active sites and poor electronic conductivity of electrode materials. Here, we successfully synthesize the ZnO/CoO@NiCoS nanohybrids with double-layer heterojunction by a three-step method. The conductivity of the as-prepared electrode can be improved by the built-in electric field formed between ZnO and CoO. The coating of amorphous NiCoS can provide sufficient active sites and strengthen the physical/chemical stability of ZnO/CoO nanowires. The obtained ZnO/CoO@NiCoS delivers a high specific capacity of 934 C g−1 (1868 F g−1), which is 5.5 times the pristine ZnO electrode. Furthermore, a HSC with ZnO/CoO@NiCoS shows an improved power density (3987.7 W kg−1), a high energy density of 39.2 Wh kg−1, and an excellent cycling stability (initial capacity retention rate of 81.7% after 6,000 cycles). This study not only proposes an effective strategy for the preparation of low-cost, deep-discharge electrodes for supercapacitors, but also provides a novel method to construct nanomaterials with double-layer heterostructure and built-in electric field. [ABSTRACT FROM AUTHOR]

• The Co 3 O 4 is modified by deposition CoNiS nanowires. • CoNiS improves the chemical stability and electrical conductivity of Co 3 O 4. • Co 3 O 4 @CoNiS exhibits high specific capacity. • Core-shell structure provides more active sites and stable structure. • Co 3 O 4 @CoNiS//NOPC supercapacitor delivers an outstanding cyclic stability. Tricobalt tetroxide (Co 3 O 4) with high theoretical capacity has been considered as a promising material for supercapacitors. However, the poor electrical conductivity and poor capacity retention hinder its further larger-scale application. Besides, a series of metal sulfides shows good thermal stability, mechanical stability and electrical conductivity. Here, hierarchical core-shell nanostructure is successfully synthesized by coating the Co 3 O 4 nanowires with highly conductive CoNiS (Co 3 O 4 @CoNiS) by a facile two-step method of hydrothermal treatment and succeeding electrodeposition. And the core-shell structure presents high electrical conductivity, discharge capacity and good cycle life. The as-prepared Co 3 O 4 @CoNiS exhibited a high specific capacity of 1153.75 C g−1, which is 1.97 times as much as that of Co 3 O 4. Furthermore, an asymmetric supercapacitor (ASC) was assembled by using the N/O co-doped porous carbon (NOPC) as negative electrode and the as-prepared Co 3 O 4 @CoNiS as positive electrode, which showed a high energy density of 46.95 Wh kg−1 at the power density of 400 W kg−1 and an ultra-stable capacity retention with 95.6% for 20,000 cycles. The cyclic stability of similar work is lower than that of our work, which provides a reference for the preparation of electrode materials with long-term cyclic stability. [ABSTRACT FROM AUTHOR]