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Vanadium nitride is a typical pseudocapacitive material that has attracted much attention among electrode materials as a result of its high theoretical capacity and wide voltage window. Nevertheless, its poor rate capability, cycling stability, and dissolution in alkaline electrolytes have restricted its practical applications. In this work, these problems are addressed by utilizing melamine-assisted pyrolysis and a dual-carbon composite strategy. A structurally controllable clustered shuttle vanadium-MOF is selected as the precursor. By subjecting it to high-temperature pyrolysis, melamine-derived carbon is coated on the surface of the vanadium-MOF, resulting in the formation of vanadium nitride-doped carbon electrode materials. Interestingly, they have a capacity of 407.5 F g−1 at a current density of 0.5 A g−1, with a capacity retention of 82.02% and a Coulombic efficiency of 80.59% after 10 000 cycles at a current density of 3 A g−1. When assembled into a device, the device shows a power density of 775 W kg−1 and an energy density of 39.29 W h kg−1. It is worth noting that the energy density reaches 15.82 W h kg−1 when the maximum power density of 3, 875 W kg−1 is attained. These anode materials have broad applications in energy storage systems, providing an innovative approach to developing new materials. [ABSTRACT FROM AUTHOR]

Rare earth element doped bimetallic oxides are a new technology for improving the electrochemical performance of electrode materials. In this study, 0.5% La-NiMoO4 flower-like structured nanomaterials were directly grown on nickel-based surfaces through a fast and simple room temperature stirring method. The characterization methods such as SEM and TEM confirmed that the prepared product has a three-dimensional nanoflower-like structure, and also demonstrated that the prepared 0.5% La-NiMoO4 nanoflower material was successfully doped with rare earth elements. We also conducted electrochemical tests on the material, and the results showed that at a reaction time of 16 h, the 0.5% La-NiMoO4 flower-like structure exhibited excellent electrochemical performance. At a current density of 2 A g-1, the specific capacitance was 2100 F g-1. After 5500 cycles of charging and discharging at a current density of 1 A g-1, the capacitance retention rate was 99.8%. A 0.5% La-NiMoO4/Ni//Fe2O3/Ni asymmetric supercapacitor device was assembled using 0.5% La-NiMoO4 as the positive electrode and Fe2O3 as the negative electrode. At a current density of 15 A g-1 and a working window voltage of 1.8 V, the power density of the asymmetric device was 8000 W kg-1 (energy density 56.5 W h kg-1). At a current density of 5 A g-1, the device underwent 5000 cycles of charge and discharge, and the capacitance retention rate was 89.5%. The 0.5% La-NiMoO4 electrode material prepared in this study through a simple, fast, environmentally friendly method exhibits good electrochemical performance, making it a potential electrode material for development. [ABSTRACT FROM AUTHOR]

Multi-component metal sulfide heterostructures possess a modulated electronic structure, abundant active sites and various morphology features, which are kinetically beneficial for fast electron/ion transport to enhance the energy storage performance. Herein a novel NiMoS4@Co9S8/Ni3S2 core–shell heterostructure is designed and constructed, which consists of Co9S8/Ni3S2 heterogeneous hollow nanotubes as the core and NiMoS4 nanospheres as the shell. The hierarchical NiMoS4@Co9S8/Ni3S2 array has the merits of each component and exhibits excellent electrochemical performance due to the synergistic effect. When examined as the supercapacitor electrode, an area specific capacitance of 9.61 F cm−2 was provided at a current density of 2 mA cm−2. In addition, the assembled asymmetric supercapacitor device achieves superior properties regarding high energy density of 0.44 mW h cm−2 at a power density of 2.30 mW cm−2 and good durability with 82.67% capacitance retention over 5000 cycles. This work sheds light on the design and construction of multi-component heterostructure with well-defined hollow core–shell morphology, which is an effective strategy to fabricate electrode materials for high performance energy storage devices. [ABSTRACT FROM AUTHOR]

Electrode materials are the key to defining the overall electrochemical performance of energy storage devices and have been an essential hot topic for decades. This study synthesized MnSe-based ZnO composites with MnSe weight ratios (10 and 40%) denoted as ZK-1 and ZK-2 using a simple, cost-effective and economical wet-chemical technique. It investigated their electrochemical characteristics for high-performance hybrid supercapacitors. The comparatively lower resistance of MnSe than that of ZnO (2.40 Ω and 1.45 Ω, respectively) and ZK-2 relative to ZK-1 (1.10 Ω and 0.8 Ω, respectively) give the evident advantages of an improved capacitive energy storage performance owing to their fast faradaic redox reactions due to Mn3+/Mn4+, superior charge storage process, good reversibility and high capacitances of 470 F g−1 and 680 F g−1 at low current rates, respectively. More specifically, at 12 000 cycles, an extraordinarily steady cycling stability of 95.5% was achieved, with a superior energy and power supply of 57.8 W h kg−1 at 13 005 W kg−1 and deficient solution and charge transfer resistance of 1.3 and 6.4 when built as a ZK-2‖AC hybrid supercapacitor. The capacitance, energy and power densities, and low resistance prove the synergistic effect between the MnSe and ZnO nanostructures in a hybrid supercapacitor. Notably, a stable voltage window of 1.75 V in an aqueous solution as an electrolyte boosts the capacitance and power delivery, and thus these seem to be promising electrode materials for advanced hybrid supercapacitors. [ABSTRACT FROM AUTHOR]

Hydrothermal synthesis and annealing process were used to create a honeycomb-structured composite electrode material on nickel foam substrate that contained praseodymium oxide (Pr2O3), cobalt oxide (Co3O4), and reduced graphene oxide (rGO) (named as Pr2O3/Co3O4/rGO/NF). The Pr2O3/Co3O4/rGO/NF (PCGN) composite electrode material was created without the need for a binder and can be employed right away to create a supercapacitor. This honeycomb composite is further grown by the mesh structure of Pr2O3 and Co3O4, which has good electrical conductivity. This nanomorphology not only improves the specific surface area of the material but also facilitates the improvement of electron transfer efficiency. The synthesized electrode material has excellent electrochemical properties due to its special morphology and excellent conductivity, and its performance is better than that of praseodymium oxide and cobalt oxide alone, with a specific capacitance of 3316 F g−1 in the three-electrode system at a current density of 1 A g−1. After forming a symmetrical supercapacitor device, the energy density is 74.8 W h kg−1 and the power density is 300 W kg−1 at 0.5 A g−1. The capacitance retention is 82% even after 35 000 cycles at 2 A g−1. [ABSTRACT FROM AUTHOR]

The porous flower-like microsphere structure composite of gadolinium oxide (Gd2O3), tricobalt tetraoxide (Co3O4) and reduced graphene oxide (rGO) was prepared on the nickel foam (NF) substrate by a hydrothermal synthesis method and annealing process, which can be directly used as an electrode material for supercapacitors without any conductive adhesive or binder. This porous nanostructure not only improves the conductivity of the electrode, but also shortens the migration route of ions and electrons. The innovative electrode of Gd2O3/Co3O4/rGO/NF has a high specific capacitance of 3616 F g−1 (1 A g−1). The supercapacitor is assembled, with a specific capacitance of 442.5 F g−1 (0.5 A g−1) at room temperature (20 °C) and strong multiplicative performance (current density from 0.5 to 20 A g−1, specific capacitance retention of 65.9%). At a power density of 300 W kg−1, the energy density reaches 88.5 Wh kg−1, and the performance stays relatively stable across a large working temperature range of 0 to 60 °C. The specific capacitance is 368.3 F g−1 even at temperatures up to 60 °C and 415.0 F g−1 at temperatures below 0 °C. Even after 40 000 cycles at a high current density of 10 A g−1, the capacity retention is 93.3%, suggesting exceptional cycling stability. This study demonstrates the potential practical application of Gd2O3/Co3O4/rGO/NF electrodes in supercapacitors. [ABSTRACT FROM AUTHOR]

To achieve high-energy density of supercapacitors and maintain their intrinsic high power density, the operating voltage should be extended by assembling high specific capacitance electrode materials into an asymmetric supercapacitor (ASC) device. Herein, an ASC was assembled based on a three-dimensional (3D) interconnected porous carbon framework (PRPC-1K) as a negative electrode and 3D sphere-like nickel nitride (Ni3N) nanosheets as a positive electrode in an aqueous KOH electrolyte. The PRPC-1K was prepared by a simple activation process with biomass poplar root as the carbon precursor, and the Ni3N nanosheets were successfully synthesized via a simple low-temperature hydrothermal and further urea-assisted nitridation process. Due to the unique structures and high capacitive performances of these materials, the Ni3N//PRPC-1K ASC assembled based on these two materials achieved the high energy density of 30.9 W h kg−1 at the high power density of 412 W kg−1 and acceptable electrochemical cycling stability with an 81% retention after 5000 cycles. [ABSTRACT FROM AUTHOR]