Search

• MnO 2 /CNF/Ag nanofabric electrodes are developed for flexible supercapacitors. • The brittle issue in the CNF electrode is greatly improved by an Ag incorporation. • The optimized MnO 2 /CNF/Ag electrode has a specific capacitance of 184 F/g at 1 A/g. • An energy density of 16.3 Wh/kg and a power density of 400 W/kg was achieved. • A capacitance retention rate of 87 % was demonstrated when subjected to bending. Flexible supercapacitors are gaining increasing popularity due to their potential in powering portable, wearable, and lightweight electronic devices. In this study, we have successfully developed a high-performance flexible electrode for quasi-solid-state supercapacitors by incorporating Ag into carbon nanofibers (CNF) through electrospinning, and growing MnO 2 as an active material on the electrode using an in-situ redox method. The Ag and MnO 2 co-decorated CNF electrode offers several advantages over conventional CNF electrodes, including an enlarged reaction area, higher charge storage capacity, and improved resistance to brittleness issues. Among all the quasi-solid-state supercapacitors tested, the MnO 2 -decorated electrode with an optimized Ag incorporation exhibited the highest specific capacitance of 184 F/g at a current density of 1 A/g, representing a remarkable 17-fold increase compared to the reference CNF electrode. Furthermore, the Ag and MnO 2 co-decorated electrode demonstrated an energy density of 16.3 Wh/kg and a power density of 400 W/kg at the same current density. Notably, the electrode exhibited excellent flexibility, with a capacitance retention rate of 87 % when subjected to bending with a curvature ranging from 5 to 1.25 cm. Our results suggest that the Ag and MnO 2 co-decorated CNF electrode holds great promise for flexible energy storage applications. [Display omitted] [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]

Nowadays, materials that possess high activity and natural oxygen vacancy have garnered significant attention as potential electrode materials for supercapacitors. In this study, we successfully prepared the Hf 6 Ta 2 O 17 (HTO) nanofibres (NFs) with an orthorhombic superlattice structure using the electrospinning technique and sintering process. The characterization results indicate that the HTO NFs synthesized at 750 °C show good micro nanostructures and outstanding electrochemical properties. To enhance its energy storage performance, additional oxygen vacancies (OVs) were introduced through a carbothermal treatment under an Ar atmosphere. Although longer reduction reaction times can produce more OVs, the integration of grain boundaries and the growth of grain size caused by large annealing times may limit its electrochemical performance. Therefore, the HTO NFs treated for 1 h (HTO/C-1) exhibited the maximum C s of 925 F·g−1 at 1 A·g−1 with a larger voltage window of 2.1 V. Furthermore, a symmetric supercapacitor fabricated by two reduced HTO NFs electrodes and 1 M Na 2 SO 4 solution, recorded as r-HTO NFs//r-HTO NFs. The device demonstrated excellent energy density of 73.3 Wh·kg−1 (at power density of 1050 W·kg−1) and a long cycling life (81.8% retained after 5000 cycles). These results suggest that the optimized reduction process can provide appropriate oxygen vacancies in HTO NFs, thereby effectively enhancing its performance. [Display omitted] • The Hf 6 Ta 2 O 17 (HTO) nanofibres (NFs) are synthesized by electrospinning method. • The micro nanostructures and electrochemical property of HTO NFs can be designed by controlling the synthesis temperature. • The carbothermal treatment carried under Ar atmosphere is used to improve the amount of oxygen vacancies of HTO NFs. • The HTO NFs treated of 1 h (HTO/C-1) presents excellent capacitance of 925 F·g−1 at 1 A·g−1. • The r-HTO NFs//r-HTO NFs device shows high energy density of 73.3 Wh·kg−1 at power density of 1050 W·kg−1. [ABSTRACT FROM AUTHOR]

Designing cathode and anode materials that can accommodate capacity and rate performance is a significant challenge in developing lithium-ion capacitors (LICs). Herein, we synthesize a unique N/S dual-doped hierarchical porous carbon (NSC) under the effect of pore distribution modification and heteroatom doping. The nanosheet shape and pore distribution of NSC are highly adjustable, while it demonstrates a reversible capacity that is tens of times more than that of unaltered pristine active carbon. Meanwhile, the prepared glycerol-engineered polyacrylonitrile nanofiber (GPN) form a fast conducting network in the presence of glycerol and carbon nanotubes (CNTs) and exhibit a 300% higher capacity compared to pure polyacrylonitrile nanofibers at 5 A g−1. On this premise, the constructed highly stable LIC (NSC//GPN x @CNTs) can achieve an energy density of 131.48 Wh kg−1 and have an excellent capacity retention rate (93.5%) over 10,000 cycles at a high current density (5 A g−1). This work may lead to new avenues for the preparation of heteroatom-doped porous carbon and redefine the electrode matching of highly stable LICs. [Display omitted] • Highly tunable pore distribution and nanosheet shape of porous carbon. • The cathode nanofibers exhibit high electrical conductivity. • The LIC achieves high energy density and high power density simultaneously. [ABSTRACT FROM AUTHOR]

• Hierarchical porous carbon (HPC) is obtained with three-dimensional (3D) structure. • The HPC with highly fluffy 3D continuous network is found as an ideal support. • HPC-supported MnO 2 nanofibers composite is achieved as a supercapacitor material. • The as-prepared MnO 2 @HPC composite has 3D interpenetrating network structure. • The MnO 2 @HPC composite presents excellent electrochemical performance. For improving the conductivity of porous carbon and the utilizations of its pore structures, a hierarchical porous carbon (HPC) had been developed with highly fluffy three-dimensional (3D) continuous network structure. Using the HPC as a support, a novel MnO 2 @HPC composite with 3D interpenetrating network structure was prepared as electrode material of supercapacitor via simple hydrothermal method. When the hydrothermal reaction temperature was 100°C, the MnO 2 nanofibers (∼5 nm) were uniformly grown on and within the fluffy 3D porous network of the HPC, forming a composite with interpenetrating network structure. The as-prepared composite (MnO 2 @HPC-100) exhibited the characteristics of both electric double-layer capacitance and pseudo-capacitance, which had a high specific capacity of 368 F g−1 at a current density of 0.5 A g−1 and 186 F g−1 at 10 A g−1 (50.5% retention). In addition, the asymmetric supercapacitor device was assembled with a relatively high energy density of 88.2 Wh Kg−1 at a power density of 162 W Kg−1. The device had a high capacity retention rate of 95% after 10000 cycles, and the coulomb efficiency was stable at 99.7%, showing the excellent stability of the composite. Therefore, the MnO 2 @HPC-100 composite has great application prospects in energy storage. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon-based materials have emerged as promising anode candidates for lithium-ion capacitors (LICs) owing to the advantages of high electronic conductivity and environmental benignity. However, further development of carbonaceous anodes has been greatly hindered by the sluggish kinetics and insufficient cycling stability. Herein, mesopore-rich N-doped carbon nanofibers (MNCNF) membranes are designed as a free-standing anode material to achieve ultra-high rate and ultra-long lifespan Li storage performance. The interconnected network with rich mesopore volume, high doping level of pyridinic/pyrrolic N, and expanded interlayer spacing affords the as-fabricated MNCNF anode abundant active sites, promoted electronic conductivity and superior diffusion kinetics. With prominent merits of pore and defect engineering, MNCNF anode manifests extraordinary Li storage performance in terms of ultra-high rate capability (139 mA h g−1 at 50 A g−1) and ultra-long cycling stability (370 mA h g−1 after 10000 cycles at 10 A g−1). More importantly, LICs by using MNCNF as anodes deliver a high energy density of 165 Wh kg−1 and an ultra-high power density of 132 kW kg−1, together with a high capacitance retention of 84% after 20000 cycles. This study demonstrates the combination of pore and defect engineering for boosting Li storage performance and holds great promise for practical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of high-energy lithium-ion and sodium-ion capacitors (LICs and SICs) is still a challenge due to the kinetics mismatch between the insertion/deinsertion anode and adsorption/desorption cathode. Here, high-level N/P-doped Sn-carbon nanofibers (Sn-NP-CNFs) were fabricated via an electrospinning technique followed by pre-oxidization and carbonization. The N/P-doping increased the defects and carbon interlayer distance to inhibit the precipitation and volume expansion of the Sn and improve the Li/Na-adsorption, resulting in an ultrahigh pseudocapacitance and rate capability of the Sn-NP-CNF. An advanced LIC and SIC were composed of an activated carbon cathode and a Sn-NP-CNF anode. The LIC and SIC displayed ultrahigh energy densities (186.0 Wh kg−1 and 134.6 Wh kg−1) and power densities (20.0 kW kg−1 achieved at 22.2 Wh kg−1) with superior energy retentions (83.7% and 79.8% after 10,000 cycles at 5.0 A g−1). [ABSTRACT FROM AUTHOR]

Hybrid Li-ion capacitors (LICs) are a new kind of electrochemical energy storage device with high energy and power densities. In this work, phosphorus-doped TiO 2 /phosphorus-doped carbon nanofibers (PTO/PC NFs) are fabricated through a simple electrospinning method with disodium hydrogen phosphate as a phosphorus source. Differing from the PTO prepared by hydrothermal method, sol-gel method or calcining treatment at phosphorous atmosphere. The P-doping evenly distributed in PTO/PC NFs and PTO nanoparticles are embedded in PC, which improves the conductivity, structure stability and Li+ ions diffusion of TiO 2. As a result, the PTO/PC NFs anode shows high capacities of 329 and 150 mA h g−1 (0.1 and 2 A g−1), long cycle life (201 mA h g−1 after 1000 cycles at 1 A g−1, 69 mA h g−1 after 1000 cycles at 5 A g−1), and superior pseudocapacitance (87%, 2 mV s−1). Furthermore, the LICs assembled with PTO/PC NFs anode and AC cathode show outstanding capacity of 35 F g−1 at a current density of 0.1 A g−1, high energy density of 72 Wh kg−1 at the power density of 250 W kg−1, and cycle stability (54%, 10 000 cycles, 1 A g−1). This suggests that PTO/PC NFs is a potential anode material for high-performance LICs. Image 1 • P-doped TiO 2 /P-doped C nanofibers (PTO/PC NFs) are fabricated by electrospinning. • The PTO/PC NFs exhibited good conductivity, stability and Li+ ions diffusion. • The PTO/PC anode showed high capacity, long cycle life and high pseudocapacitance. • LIC assembled with PTO/PC NFs anode showed a high energy density and power density. [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]