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The judicious design of highly electrochemically active materials on 1D fiber substrate to form a hierarchical integrated hybrid structure is an efficient technique to improve the limited cylindrical space and volumetric energy density of fiber‐shaped supercapacitors (FSCs). Herein, a 3D negative electrode, consisting of vertically aligned interconnected mesoporous Co‐N/C leaf‐like structure on 1D MXene‐carbon fiber (Co‐N/C@MX/CF) is prepared by controlling the composition and morphology. At the same time, a 3D positive electrode is also prepared by introducing Mo in NiCo‐LDH anchored on Co‐N/C@MX/CF (Mo‐NiCo‐LDH@Co‐N/C@MX/CF) by electrodeposition method. Benefitting from the systematic hierarchical structures with highly accessible surface area, adequate pore size and easy permeation of electrolyte, both positive and negative electrodes demonstrate highly improved electrochemical performance with areal capacity/capacitance of 0.96 mAh cm−2/4.55 mF cm−2 at a current density of 3.86 mA cm−2, respectively. Furthermore, the fiber‐shaped solid‐state hybrid supercapacitor (FSHSC) based on Mo1.5NiCo‐LDH@Co‐N/C@MX/CF(+)//Co‐N/C0.5@MX/CF(−) is fabricated, exhibiting compelling energy density of 86.72 mWh cm−3 at a power density of 480.30 mW cm−3 with an outstanding capacitance retention of 80.2% after 20000 galvanostatic‐charge‐discharge cycles. This study puts forward a new perspective on the development of highly efficient FSCs for practical application. [ABSTRACT FROM AUTHOR]

In recent years, much effort has been devoted to developing hybrid supercapacitors due to their capability to deliver both high energy and power density. The hybrid approach is advantageous in terms of reinforcing the synergic combination of the properties of different components in a hybrid composite. However, a large kinetic mismatch existing between the fast capacitive and sluggish battery-type electrodes greatly hinders its advancement. In this work, we report the fabrication of a solid-state hybrid supercapacitor (SSHSC) device using metal–organic framework (MOF)-derived cobalt-embedded N-doped carbon nanofibers (Co–N-CNFs) and Co2−xFexP–N–C micropillar arrays grown on Ni foam (Co2−xFexP–N–C/NF) as multi-component hybrid electrodes with improved charge storage kinetics. Such Co–N-CNFs (negative electrode) exhibited a remarkable specific capacitance of 280 F g−1 at a current density of 1 A g−1, while Co2−xFexP–N–C/NF (positive electrode) exhibited a high specific capacity of 345 mA h g−1 at a current density of 1 A g−1 due to the synergistic combinations of different components in a single hybrid composite. The assembled Co2−xFexP–N–C/NF(+)//Co–N-CNFs(−) SSHSC device demonstrated a high specific capacity of 104 mA h g−1 at a current density of 1 A g−1 with a maximum energy density of 84.7 W h kg−1 at a power density of 706 W kg−1. It also exhibited excellent stability and reversibility with a capacity retention of 93% and coulombic efficiency of 99.6% after 10 000 galvanostatic charge–discharge (GCD) cycles. Two SSHSC devices connected in series after being charged could easily light up a red LED bulb. These excellent performances indicate that Co–N-CNFs(−) and Co2−xFexP–N–C/NF(+) materials could be considered as potential electrodes for high energy density storage systems. [ABSTRACT FROM AUTHOR]

Hollow‐structured FexCo2−xP, FexCo3−xO4, and Prussian blue analogue (FeCo‐PBA) microbuilding arrays on Ni foam (NF) are derived from Co‐based metal–organic frameworks (Co‐MOF) using a simple room temperature and post‐heat‐treatment route. Among them, FexCo2−xP/NF shows excellent bifunctional catalytic activities by demonstrating very low oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) overpotentials of 255/114 mV at a current density of 20/10 mA cm−2 respectively, whereas FexCo3−xO4/NF and FeCo‐PBA/NF demand higher overpotentials. Remarkably, for water electrolysis, FexCo2−xP/NF requires only 1.61 V to obtain 10 mA cm−2. In contrast to water electrolysis, urea electrolysis reduces overpotential and simultaneously purifies the urea‐rich wastewater. The urea oxidation reaction at the FexCo2−xP/NF anode needs just 1.345 V to achieve 20 mA cm−2, which is 140 mV less than the 1.48 V potential required for OER. Moreover, the generation of H2 through urea electrolysis needs only 1.42 V to drive 10 mA cm−2. [ABSTRACT FROM AUTHOR]

This study investigates the synthesis and application of boron nitride quantum dot (BNQD) covalently bonded reduced graphene oxide (rGO) hybrid materials as a novel electrode material for supercapacitors. Because of the p-doping as well as the enhanced hydrophilicity and interfacial bonding force enabled by the hybridization of amine-functionalized boron nitride quantum dot (A-BNQD) with rGO via the chemical coupling reaction, the A-BNQD/rGO shows improved charge carrier density, wettability of electrolyte, and durability. As a result of the synergistic effects, the A-BNQD/rGO as a supercapacitor electrode shows much higher specific capacitance compared to those of rGO and raw BNQD/rGO at a current density of 1 A g−1. Further, the A-BNQD/rGO shows high cycling stability, maintaining almost 94.38%, even after 10,000 cycles due to the enhanced interfacial bonding force between the A-BNQD and rGO. Besides, the fabricated symmetric supercapacitor exhibits high specific capacitance (90 F g−1@1 A g−1), an energy density (12.5 Wh kg−1@0.5 kW kg−1), and good cycling stability. This result suggested that the fabricated A-BNQD/rGO has great potential as electrode materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Transition-metal-based layered triple hydroxides (LTHs) are evolving as potential positrode candidates for high-performance supercapacitors; however, their phase stabilization is still critical. Alongside, the availability of limited negatrodes pushes research toward exploring novel alternatives in order to minimize performance limitation issues in the fabricated supercapacitors. Herein, a facile strategy for stabilizing freestanding MnCuCo-LTH-based positrode possessing intermingled nanodisk-needle-like morphology is reported. Alongside, novel high-surface-area negatrodes based on Mn 1 Fe 2 S 2 exhibiting porous microthorn-like morphology are also optimized. MnCuCo_LTH and Mn 1 Fe 2 S 2 exhibit remarkably high specific capacities of ∼494 mAh g -1 (∼2540 F g -1 ) and ∼429 mAh g -1 (∼1546 F g -1 ), respectively, at 1 A g -1 . The fabricated quasi-solid-state supercapacitor equipped with a poly(vinyl alcohol) (PVA)-KOH gel electrolyte displays a high specific capacity of ∼144 mAh g -1 and a specific capacitance of ∼325 F g -1 at 1 A g -1 . The ultrahigh energy cum power traits of ∼105 Wh kg -1 (1 A g -1 ) and ∼8370 W kg -1 (at 10 A g -1 ) establish an asymmetric supercapacitor as a high-performance energy storage device. This device shows an appreciably high cycling life with a capacitance retention of ∼93% after 10 000 consecutive cycles, at 10 A g -1 . This approach provides a neoteric foresight for developing high-performance advanced energy storage devices equipped with cheaper and eco-friendly components.

Fabrication of hierarchical nanosheet arrays of 1T phase of transition-metal dichalcogenides is indeed a critical task, but it holds immense potential for energy storage. A single-step strategy is employed for the fabrication of stable 1T-Mn x Mo 1- x S 2- y Se y and MoFe 2 S 4- z Se z hierarchical nanosheet arrays on carbon cloth as positive and negative electrodes, respectively. The flexible asymmetric supercapacitor constructed with these two electrodes exhibits an excellent electrochemical performance (energy density of ≈69 Wh kg -1  at a power density of 0.985 kW kg -1 ) with ultralong cyclic stability of ≈83.5% capacity retention, after 10 000 consecutive cycles. Co-doping of the metal and nonmetal boosts the charge storage ability of the transition-metal chalcogenides following enrichment in the metallic 1T phase, improvement in the surface area, and expansion in the interlayer spacing in tandem, which is the key focus of the present study. This study explicitly demonstrates the exponential enhancement of specific capacity of MoS 2 following intercalation and doping of Mn and Se, and Fe 2 S 3 following doping of Mo and Se could be an ideal direction for the fabrication of novel energy-storage materials with high-energy storage ability., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)