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Herein, MnO2 nanoflowers are electrodeposited on a self-supported and electroconductive electrode in which 2D Ti3C2Tx nanosheets are encased in carbon nanofibers (MnO2@Ti3C2Tx/CNFs). This improves the conductivity and hydrophilicity of the MnO2 composite electrode. The asymmetric supercapacitor shows a high energy density of 46.4 W h kg−1 and a power density of 4 kW kg−1. [ABSTRACT FROM AUTHOR]

The synthesis of Laser-Induced Graphene (LIG) through the laser ablation process of carbon-containing materials is a rapid and scalable process which enables the production of graphene in a cost-effective manner. In recent years, metal oxide – graphene composite electrodes have gained a lot of importance due to their use in various Energy Storage Devices (ESDs). In our investigation, we manufacture composite electrodes of manganese dioxide (MnO 2) and LIG through a hydrothermal process and use it as electrodes in Flexible Supercapacitors. This method deviates from traditional procedures as it eliminates the requirement for binders in creating composite electrodes, given that MnO 2 can be directly deposited onto the LIG electrodes. The assembled all-Flexible Supercapacitor (FSC), featuring unique LIG-MnO 2 composite electrodes, showcased a remarkable areal capacitance of 66.5 mF cm−2 at 5 mV s−1 scan rate. The device also exhibited a very high areal energy density (2.3 mWh cm−2) and power density (19.7 mW cm−2) at 0.2 mA cm−2 current density. Also, 82 % capacitance retention was observed at the end of 2000 cycles and the device also exhibited a good flexibility during bending tests, as evidenced by an 80 % capacitance retention after 100 bending cycles. [ABSTRACT FROM AUTHOR]

In this work, lignin-based carbon nanofibers (LCNFs) were for the first time served as substrate for in-situ electrodeposition of polyaniline (PANI) and tested as pseudocapacitor. Two LCNFs with different lignin ratios were designed to distinguish their morphology and structural properties. Next, PANI deposition mechanisms on both LCNFs were investigated and the electrochemical performance of the resulting LCNF/PANIs were evaluated. It was found although LCNF2 was composed of less uniform nanofibers due to more presence of lignin in precursor dope, it had higher tensile strength/modulus than LCNF1 (strength: 34.3MPa to 24.2 MPa; Modulus: 2.40 GPa to 1.45GPa) and was more cost-effective. Particularly, the beaded fibers on LCNF2 contributes to the deposition of PANI with higher specific mass capacitance (612.8 F g−1 to 547.0 F g−1). Upon assembling into solid-state supercapacitors, the C m of LCNF2/PANI device was determined to be 229 F g−1 and the maximum energy density was 11.13Wh kg−1 at a power density of 0.08 kW kg−1. This work showed LCNF produced from renewable and low-cost lignin could be directly used as substrate for PANI deposition. Moreover, the composition in spinning dope played an important role in determining the performances of resulting pseudocapacitors. • First attempt to electrochemically deposit polyaniline on Lignin-based carbon fibers. • LCNF/PANI electrodes showed competitive capacitance to other non-renewable carbon-based electrodes. • LCNF/PANIs derived from beaded/non-beaded LCNFs are compared and investigated. • Higher lignin content is a merit when using as pseudocapacitor electrodes. [ABSTRACT FROM AUTHOR]

Lithium-ion supercapacitors (LICs) have received widespread interests because of their high power density, high energy and long life characteristics. The electrodes for LICs play a significant role in enhancing their performance. Therefore, it is of great significance to design and develop high-performance electrode materials for LIC through integrating various materials to make up for each other's disadvantages. Herein, a bimetallic composite nanomaterial with hierarchical structures (CoSn X /CNFM) and a porous carbon nanomaterial with high specific surface area (PCNFM) were obtained through combining electrospinning, anion exchange or alkali etching and subsequent high-temperature carbonization, respectively. The LIC assembled with the pre-lithiated CoSn X /CNFM as anode and the PCNFM as cathode exhibited a high energy density of 41.48 Wh/kg at a power density of 1500 W/kg, and still had an energy density of 28.13 Wh/kg at a high power density of 7500 W/kg, illustrating its high power density and high energy density. Thus, this paper proposes an effective method for designing and manufacturing high-performance LICs. • Nanofibers with uniformly distributed ZIF-67 NPs were prepared in batches by EMAI. • Hierarchical-structured CoSn X /CNFM was prepared by anion exchange and carbonization. • PCNFM with high specific surface area was prepared by etching and carbonization. • A LIC with pre-lithiated CoSn X /CNFM as anode and PCNFM as cathode was assembled. • The assembled LIC had high power density and high energy density. [ABSTRACT FROM AUTHOR]

Low-cost, high-performance electrodes are highly attractive for practical supercapacitor applications. MnO 2 -deposited carbon nanofiber mats (MnO 2 -CNFMs) are prepared for use as binder-free supercapacitor electrodes. MnO 2 is deposited on the mats in situ by hydrothermally decomposing aqueous KMnO 4 , leading to the formation of nanocrystals of MnO 2 . The MnO 2 -CNFM electrode produced with 38.0 μmol KMnO 4 (this electrode) shows a high specific capacitance of ~171.6 F·g −1 at a scan rate of 5 mV·s −1 . Moreover, a symmetric supercapacitor with the electrode exhibits a specific capacitance of 67.0 F·g −1 , an energy density of 6.0 Wh·kg −1 and a power density of 160 W·kg −1 at a special current of 0.1 A·g −1 . Further, the symmetric supercapacitor displays excellent cycling stability, retains approximately 99% of the capacitance after 1000 cycles. The simplicity and ease of preparation of the MnO 2 -CNFMs as well as their suitability for use in coin-type supercapacitor cells make them ideal for application in cost-effective and high-performance electrodes for supercapacitors. [ABSTRACT FROM AUTHOR]

The composites of transition metal oxide and carbon nanofibers (CNF) are promising electrode materials for supercapacitors in alkali solutions. However, the weak binding and unsatisfactory rate performance limit their application. To improve the weak binding, this study prepared the SiO 2 -modified carbon nanofibers (Si 1 -C) via electrospinning. Then the fully encapsulated CoO-NiO (NiCo@Si 1 -C) was fabricated on Si 1 -C by solvent-thermal and calcination. As is revealed, CNF containing SiO 2 is conducive to forming a full coverage of CoO-NiO coating with a stacked petal structure. More importantly, nano-SiO 2 plays the anchoring role of NiO-CoO and CNF, making the combination more firmly. The NiCo@Si 1 -C delivers a specific capacitance of 518.1 F g−1 at 0.5 A g−1, almost 2.25 times that of NiCo@Si 0 -C (229.9 F g−1 at 0.5 A g−1). When the current density increases to 50 A g−1, it is only 3.9 % lower than the capacitance (497.9 F g−1), which means a high rate performance. Moreover, asymmetric supercapacitor devices are assembled with activated carbon (NiCo@Si 1 -C//AC) with an energy density of 11.7 Wh kg−1, even at a high power density of 14,000.7 W kg−1. [Display omitted] • Nano-SiO 2 plays the anchoring role of NiO-CoO and CNF, making the combination more firmly. • The NiCo@Si 1 -C has a unique all-encapsulated CoO-NiO with a stacked petals structure. • The NiCo@Si 1 -C has ultra-high rate performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-situ incorporation of MnO in the CNF matrix using unique two-step carbonization. • MnO dispersed CNFs show high specific capacitance of 246F g−1 at 0.5 A g−1. • High power density of 5000 W kg−1 (8.7 W h kg−1) was achieved with 97.5 % capacitance retention after 10,000 cycles. Manganese oxides have attracted great interest as promising pseudocapacitive materials due to its low cost, variable oxidation states, and high theoretical capacitance. In this work, we report the in-situ synthesis of MnO-dispersed carbon nanofibers (CNFs) using electrospinning and a unique two-step carbonization technique. While the single-step carbonization resulted in mixed Mn x O y forms, however, by employing a suitable and optimized two-step carbonization, we were able to obtain CNFs assimilated with MnO nanoparticles (MnO-CNFs). The synthesized MnO-CNF electrodes achieved a high specific capacitance of 246 F g−1 at 0.5 A g−1 in a three-electrode system. A symmetric supercapacitor device assembled with these electrodes exhibited remarkable electrochemical performance with a maximum power density of 5000 W kg−1, maximum energy density of 14 W h kg−1, and an excellent cycling stability (97.5% retention after 10,000 cycles). The exceptional electrochemical performance of MnO-CNFs makes them promising electrode materials for practical energy storage applications. [ABSTRACT FROM AUTHOR]

Bimetallic carbides have aroused wide attention for energy-storage applications recently. In this work, one-dimensional Fe 2 MoC/CNFs (Fe 2 MoC/C nanofibers) are successfully synthesized via a facile electrospinning method for the first time. To obtain the most integrated structure between the Fe 2 MoC nanoparticles and carbon nanofibers, we explore the optimal heating rate during the carbonization treatment. Fe 2 MoC/CNFs exhibits an integrated one-dimensional structure under 800 °C with a heating rate of 5 °C/min. As revealed in the experimental results, Fe 2 MoC/CNFs possesses a high specific surface area of 196.9 m2/g, a high specific capacitance of 347.8 F/g at the current density of 1 A/g, an excellent rate capability of 91% capacitance retention from 1 A/g to 40 A/g, and shows superior cycling stability with the capacitance retention of about 85.6% and Coulombic efficiency of about 100% after 5000 cycles. An asymmetric supercapacitor coin-cell device using Fe 2 MoC/CNFs as the positive electrode displays an energy density of 14.5 Wh/kg at a power density of 300 W/kg and an outstanding cycling life of 93% retention after 5000 cycles. The impressive electrochemical performance indicates that the Fe 2 MoC/CNFs composite is a promising material for efficient supercapacitors. Image 1 • Fe 2 MoC nanofibers can be prepared via a facile electrospinning method. • Fe 2 MoC/CNFs-5 exhibits a superior rate capability and cycle stability. • ASC coin-cell device shows a promising energy and power density. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) were directly synthesized on the surface of 304 stainless steel (SS) mesh by a facile one-step ethanol flame synthesis method under a controllable temperature of ∼850 °C, as well as the γ-Fe 2 O 3 particles. The resulted CNFs/Fe 2 O 3 /SS mesh electrode is used to assemble a symmetric supercapacitor (SC) with redox active acidic electrolyte, and it exhibits a large area specific capacitance (C a) up to 2412.6 mF cm−2 at a current density of 3 mA cm−2, and a high energy density of 14.57 mW h cm−3 at a power density of 65.22 mW cm−3. The electrodes also show high cyclic stability, and the specific capacitance retention remains to be 93.55% after 1000 charge-discharge cycles. An asymmetric SC is assembled using the CNFs/Fe 2 O 3 /SS as cathode and the WO 3 /Ti mesh as anode, respectively. It also possesses a high energy density of 9.08 mW h cm−3 at a power density of 70.33 mW cm−3 in a potential window of 0–1.5 V. Their high capacitive performance and good cyclic stability in the acidic electrolyte containing Fe2+/Fe3+ additive could be due to the intrinsic functionalized CNFs produced by the flame deposit method and the reaction balance of the ferric species between the electrode and the electrolyte during the electrochemical process. The facile fabrication method and superior performance of the CNFs/Fe 2 O 3 /SS mesh make it promising electrodes for high-performance SCs with specific electrolyte. [ABSTRACT FROM AUTHOR]

• NPCNFs/PANI with Integrated architecture has been well designed. • 3D continuous and conductive network can reduce internal resistance effectively. • Large surface areas and hierarchical porosity decrease the ion diffusion length. • The all-solid-state flexible device exhibits desirable electrochemical properties. Electrode materials with rationally designed architecture are crucial to achieve high-performance supercapacitors. However, there is still a great challenge for integrating the features of large accessible surface areas, fast electron/ion transport kinetics and favorable mechanical flexibility within a single electrode. Herein, we propose a facile approach to fabricate high-performance freestanding carbon-based electrode of polyaniline modified nitrogen-doped hierarchical porous carbon nanofibers, which effectively combine the merits of highly conductive electrospun carbon nanofibers with hierarchical porous structure, suitable nitrogen content as well as pseudocapacitive materials. Benefiting from the well-designed architecture, the as-assembled symmetric all-solid-state flexible device exhibits a high specific capacitance of 260 F g−1 at 0.5 A g−1 and high rate capability with a capacitance retention of 60% at 16 A g−1. Furthermore, the device also displays a desirable energy density of 8.9 Wh kg−1 with power density of 0.27 kW kg−1 and excellent cycling stability with 80.1% capacitance retention after 10,000 charge-discharge cycles at 2 A g−1. Eventually, the as-designed composite electrodes open up new avenues for facile construction of high-performance supercapacitor electrodes. [ABSTRACT FROM AUTHOR]