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In this study, an electrospinning method was used to produce highly conductive freestanding carbon nanofibers (CNFs). The freestanding CNFs are compatible with hierarchical growth techniques, such as hydrothermal processes, for the nanostructure engineering of supercapacitor electrodes with enhanced electrochemically active sites. Therefore, the flower-like FeMoO 4 @CNF nanosheets were investigated to improve the electrochemical performance using aqueous and neutral electrolytes (Na 2 SO 4 and K 2 SO 4). The optimized FeMoO 4 @CNF electrode exhibits areal capacitances of 252 and 220 mF·cm−2 at a high current density of 2.5 mA·cm−2 with Na 2 SO 4 and K 2 SO 4 electrolytes, respectively. The wide potential window (1.6 V) of the symmetric supercapacitor delivered maximum energy densities of 22.4 and 19.6 μWh·cm−2 at a power density of 2 mW·cm−2 for Na 2 SO 4 and K 2 SO 4 electrolytes, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1D skin-core multilayer structure was fabricated by a facile template method. • Bicontinuous electron/ion transport during the charge/discharge process. • The large specific surface area and hollow hierarchical porous structure. • Adjusting active layers or sites can obviously improve the capacitive properties. • The maximum energy density of 8.77 Wh kg−1 at a power density of 0.25 kW kg−1. The fast transport of electrons and ions within electrodes is crucial to the final electrochemical properties. Herein, we have developed a unique ultra-long one-dimensional (1D) skin-core multilayer structure based on electrospun carbon nanofibers mainly through a facile Stöber method combined with resorcinol–formaldehyde resin, which not only achieves bicontinuous electron/ion transport during the charge/discharge process, but also provides large surface area for ion adsorption. Particularly, controlling the number of active layers as well as regulating the active sites in layer both can obviously improve capacitive properties. Benefiting from the synergistic effects of the desirable architecture, such the rational-designed skin-core structural carbon nanofibers as supercapacitor electrode can deliver a high specific capacitance up to 255 F g−1 at 0.5 A g−1, favorable rate capability with 89% capacitance retention of initial capacitance at 8 A g−1, and excellent cycling stability with nearly 93% capacity retention after 10,000 cycles at 2 A g−1. Furthermore, the as-assembled symmetric supercapacitor devices also present a maximum energy density of 8.77 Wh kg−1 at 0.25 kW kg−1 and a maximum power density of 3.70 kW kg−1 at 6.74 Wh kg−1. Such skin-core carbon nanofibers provide an effective strategy to design high-performance supercapacitor electrode for the next-generation energy storage devices. [ABSTRACT FROM AUTHOR]

The combination of multiple electrode materials and their reasonable structural design are conducive to the preparation of composite electrodes with excellent performance. In this study, based on carbon nanofibers grown with Ni(OH)2 and NiO (CHO) prepared by electrospinning, hydrothermal growth, and low-temperature carbonization, five transition metal sulfides (MnS, CoS, FeS, CuS, and NiS) were hydrothermally grown on their surfaces, exhibiting that CHO/NiS had the optimal electrochemical properties. Subsequently, the effect of hydrothermal growth time on CHO/NiS revealed that the electrochemical performance of CHO/NiS-3h was optimal, with a specific capacitance of up to 1717 F g−1 (1 A g−1), due to its multistage core–shell structure. Moreover, the diffusion-controlled process of CHO/NiS-3h dominated its charge energy storage mechanism. Finally, the asymmetric supercapacitor assembled with CHO/NiS-3h as the positive electrode demonstrated an energy density of 27.76 Wh kg−1 at a maximum power density of 4000 W kg−1, and it still maintained a power density of 800 W kg−1 at a maximum energy density of 37.97 Wh kg−1, exhibiting the potential application of multistage core–shell composite materials in high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two composite methods of carbon nanofibers and metal compounds are proposed. • Iron carbides are evenly distributed among the carbon nanofibers, resulting in improved electrical and electrochemical properties. • Hierarchical 3D hollow structure of CNF@NiCoS-650 relieve volume expansion and facilitate quick ion diffusion. • The Fe 3 C@CNF-650//CNF@NiCoS-650 hybrid supercapacitor exhibits high energy density. To meet the crucial demand for high-performance supercapacitors, much effort has been devoted to exploring electrode materials with nanostructures and electroactive chemical compositions. Herein, iron carbide nanoparticles are encapsulated into carbon nanofibers (Fe 3 C@CNF-650) through electrospinning and annealing methods. Nickel-cobalt sulfide nanoparticles are hydrothermally grown on electrospun carbon nanofibers (CNF@NiCoS-650). The Faradaic electrochemical reactions of transition metal compounds improve the specific capacitance of the developed electrode. Meanwhile, the electrically conductive framework of carbon nanofibers facilitates Faradic charge transport. In detail, the Fe 3 C@CNF-650 anode and CNF@NiCoS-650 cathode achieve specific capacitances of 1551 and 205 F g−1, respectively, at a current density of 1 A g−1. A hybrid supercapacitor that is fabricated from the Fe 3 C@CNF-650 anode and CNF@NiCoS-650 cathode delivers an energy density of 43.2 Wh kg−1 at a power density of 800 W kg−1. The designed nanostructures are promising for practical supercapacitor applications. [ABSTRACT FROM AUTHOR]

The hurdle of fabricating asymmetric supercapacitor (ASC) devices using a faradic cathode and a double layer anode is challenging due to the required large amount of active mass of anodic material compared to that of the cathodic material during mass balancing due to the large difference in capacitance values of the two electrodes. Here, the problem is addressed by engineering a negative electrode that furnishes an ultrahigh capacitance. An in situ developed metal–organic framework (MOF)‐based thermal treatment is adopted to grow highly porous N‐doped carbon nanotubes (CNTs) containing submerged Co nanoparticles over nano‐fibrillated electrospun hollow carbon nanofibers (HCNFs). The optimized CNT@HCNF‐1.5 furnishes an ultrahigh capacitance approaching 712 F g–1 with excellent rate capability. The capacitance reported from this work is the highest for any carbonaceous material reported to date. The CNT@HCNF‐1.5 is further used to fabricate symmetric supercapacitors (SSCs), as well as ASC devices. Remarkably, both the SSC and ASC devices furnish incredible performances in all aspects of SCs, such as a high energy density, long cycle life, and high rate capability, displaying decent practical applicability. The energy density of the SSC device reaches as high as 20.13 W h kg–1, whereas that of ASC approaches 87.5 W h kg–1. [ABSTRACT FROM AUTHOR]

The microstructure, electrical and electrochemical properties of MXene/aromatic poly(ether amide) (PEA)‐derived hybrid carbon nanofibers (HCNFs) as high‐performance free‐standing supercapacitor electrode materials are reported. For this purpose, a series of HCNFs are fabricated by sequential methods of electrospinning of PEA solutions, dip‐coating (1–10 cycles) of as‐spun PEA nanofibers into MXene aqueous dispersion, and heat‐treatment of MXene‐coated PEA nanofibers for carbonization. The structural analyses of HCNFs reveal that MXene nanosheets are uniformly deposited on PEA‐derived and nitrogen self‐doped CNFs and that they are accumulated with increasing the number of dip‐coating cycles. Accordingly, the electrical conductivity increases from 3.94 S cm−1 for PEA‐derived neat CNF to 15.74 S cm−1 for HCNF10 (10 dip‐coating cycles) due to the increase in the content of electrically conductive MXene nanosheets. On the other hand, the electrochemical performance is measured to be the highest in HCNF7 (7 dip‐coating cycles) owing to a trade‐off effect of ion barrier function and high electrical conductivity of MXene nanosheets to porous CNF webs. For a symmetric supercapacitor setup of two self‐standing HCNF7 electrodes, outstanding electrochemical properties of specific capacitance of 66.7–179.3 F g−1, power density of 1000–10 000 W kg−1, and energy density of 52.7–91.2 Wh kg−1 are attained at current densities of 1–10 A g−1. [ABSTRACT FROM AUTHOR]

Using renewable biomass precursors to develop high-performance carbon electrodes is a promising approach for the advancement of supercapacitors. This work proposes a feasible strategy to prepare self-supporting flexible porous carbon nanofibers by electrospinning and carbonizing the mixture of cuttlefish ink, polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA). The impacts of cuttlefish ink precursor on the structure, elemental composition, and capacitance properties of carbon nanofibers have been studied. Herein, the unique structural advantage of cuttlefish ink can significantly optimize the porous structure of carbon nanofibers. Due to the hierarchical porous structure, large specific surface area, hollow channels and high nitrogen content, the carbon nanofibers offer a high specific capacitance of 364.8 F g−1 at 0.5 A g−1 current density, alongside desirable rate performance and cycle life. Furthermore, the carbon nanofiber electrode performs good mechanical flexibility. The flexible solid-state supercapacitor based on this electrode exhibits 14.1 Wh kg−1 energy density at 0.4 kW kg−1 power density, and 97.8% capacitance retention after 5000 cycles. The favorable capacitive properties make this carbon nanofiber material a potential candidate for supercapacitor electrodes. [Display omitted] • Electrospun porous carbon nanofibers (CPP–CNF) were prepared from cuttlefish ink. • CPP-CNF features hierarchical pores and hollow channels. • CPP-CNF is mechanically flexible with superior capacitive performance. • The flexible supercapacitor achieves high energy density and cycling stability. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li–S) batteries hold great expectations as next-generation advanced capacity storage devices due to their higher theoretical energy density and low cost. Even so, polysulfide shuttles, insulation, and volume expansion of sulfur impede its commercial progress. To suppress these problems, we used electrospinning and self-templating to construct C/Co 9 S 8 hybrid polyhedra-modified carbon nanofibers (denoted as C/Co 9 S 8 –C@S fibers) as sulfur hosts. The quasi-metallic polar Co 9 S 8 strongly bonds and locks polysulfides, and the hollow polyhedra provide sulfur storage space. Moreover, the overall nanofiber forms an interconnected conductive network to assist the transmission of Li+/e− and restrain the escape of the sulfur phase to a certain extent. Compared with C/Co 9 S 8 polyhedra and carbon nanofibers, the C/Co 9 S 8 –C@S fiber delivers excellent adsorption characteristics for polysulfides. As a Li–S battery cathode, the C/Co 9 S 8 –C@S fiber (sulfur content: 87.20 wt%) exhibits an initial specific capacity of 1013.7 mAh g−1 at 0.1 C, displaying a stable capacity of 694.9 mAh g−1 after 150 cycles. Additionally, it shows a high specific capacity of 894.7 mAh g−1 at 1C with a capacity decay of ~0.116% per cycle over 500 cycles. [ABSTRACT FROM AUTHOR]

Supercapacitors are increasingly used in short‐distance electric transportation due to their long lifetime (≈15 years) and fast charging capability (>10 A g−1). To improve their market penetration, while minimizing onboard weight and maximizing space‐efficiency, materials costs must be reduced (<10 $ kg−1) and the volumetric energy‐density increased (>8 Wh L−1). Carbon nanofibers display good gravimetric capacitance, yet their marketability is hindered by their low density (0.05–0.1 g cm−3). Here, the authors increase the packing density of low‐cost, free‐standing carbon nanofiber mats (from 0.1 to 0.6 g cm−3) through uniaxial compression. X‐ray computed tomography reveals that densification occurs by reducing the inter‐fiber pore size (from 1–5 µm to 0.2–0.5 µm), which are not involved in double‐layer capacitance. The improved packing density is directly proportional to the volumetric performances of the device, which reaches a volumetric capacitance of 130 F cm−3 and energy density of 6 Wh L−1 at 0.1 A g−1 using a loading of 3 mg cm−2. The results outperform most commercial and lab‐scale porous carbons synthesized from bioresources (50–100 F cm−3, 1–3 Wh L−1 using 10 mg cm−2) and contribute to the scalable design of sustainable electrodes with minimal 'dead volume' for efficient supercapacitors. [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]

SnS is an ideal material for supercapacitors because of its unique layered structure and excellent electrochemical performance, but the research of SnS based electrode materials of flexible self-supporting supercapacitors has been rarely exploited. In this study, microsphere like Co doped SnS grown on carbon nanofibers (Co-SnS@CNF) was prepared by electrospinning, hydrothermal method and annealing treatment. Co-SnS@CNF has great flexibility, high specific capacitance, excellent rate performance and cycle stability. Specifically, the specific capacitance is 750 F g−1 at the current density of 1 A g−1. The special microsphere structure with more electrochemical active sites and lower resistance of ion and charge transfer by Co doping are responsible for the superior electrochemical performances. Furthermore, when assembled Co-SnS@CNF as the symmetrical supercapacitor device, the energy density of 20.89 Wh Kg−1 and the power density of 376 W Kg−1 are achieved at the current density of 1 A g−1, while showing ultra-high cycle stability. Therefore, the Co-SnS@CNF offers excellent application potential for flexible self-supporting supercapacitors. • Revealing reasons for the high-performance of the microspherical Co-doped SnS. • The specific capacitance is 750 F g−1 at the current density of 1 A g−1. • The assembled symmetrical device exhibits the ultra-high cycle stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • The free-standing flexible anode electrode were synthesized by electrospinning. • MXene nanosheets improve the conductivity and stability of the anode electrode. • The flexible full-cell exhibits extremely low impedance and excellent cycling stability. Low energy density remains a major obstacle limiting the development and application of flexible sodium-ion batteries (SIB). Thus, this study aimed to eliminate non-active materials in electrodes, which can be a feasible way to increase the energy density of SIBs. An anode made up of flexible, free-standing SnS 2 /Sb 2 S 3 /Ti 3 C 2 T x composite carbon nanofibers (SnSbS/T-M@CNF), a Na 3 V 2 (PO 4) 3 composite carbon nanofibers cathode (NVP@CNF), and composite gel polymer fiber electrolytes (CGPFE) were successfully synthesized through electrospinning. MXene nanosheets improved the electrical conductivity of the SnSbS/T-M@CNF electrode and absorbed sodium sulfide, inhibiting the loss of S during the reaction. Consequently, the SnSbS/T-M@CNF free-standing electrode could be stably cycled for 1000 cycles at a current density of 1 A g−1 and maintained a reversible capacity of 397.6 mAh g−1. Further, the NVP@CNF cathode and CGPFE quasi-solid electrolyte half-cells had an excellent cycle stability and rate performance. The flexible, free-standing SnSbS/T-M@CNF anode and NVP@CNF cathode were assembled into quasi-solid-state full cells to test their application value. The SnSbS/T-M@CNF||CGPFE||NVP@CNF full cell had a very low resistance and could easily power a 3 V LED chest lamp. After 500 cycles, it maintained a discharge capacity of 153 mAh g−1 under a current density of 0.5 A g−1. [ABSTRACT FROM AUTHOR]

• A lithiophilic and conductive interlayer is prepared by electrospinning. • The interlayer can be used as both a Li+ redistributor and a lithiophilic host. • The composite anode has superior performance at ultrahigh current and capacity. Lithium metal battery is strongly deemed as the most promising next-generation energy-storage devices due to its high theoretical energy density. However, uneven lithium deposition and infinite volume change are still the main challenges that significantly hinder their practical applications. Herein, a silicon nanoparticle-decorated carbon nanofibers (Si@CNFs) mat was explored as a novel lithiophilic and conductive interlayer for commercial Li foil. The Si@CNFs interlayer with three-dimensional porous and conductive structure can act as a Li+ redistributor and a lithiophilic host to regulate Li deposition behaviors and buffer the volume changes during the Li plating/stripping processes. The obtained Si@CNFs-Li anodes possess outstanding cycling stability under ultrahigh currents and capacities (e.g. 1800 cycles at 20 mA cm−2/5 mAh cm−2 and 900 cycles at 80 mA cm−2/40 mAh cm−2). This strategy is facile and efficient in inhibiting Li dendrite growth and can be extended to other alkali metal batteries. [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]

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]

A green electrode material with dual conductive networks via electrospinning with carbonization and co-precipitation method is constructed. Nitrogen-based carbon nanofiber network (CCP-N) is used as the inner-conductive, electrochemical-active substrate and flexible skeleton. The Co Ni layered double hydroxide (Co Ni LDH) nanosheets and flower-like nanospheres, which randomly and closely covering the surface of CCP-N, respectively, just as the fungus grow on trunks in nature, is regarded as outer-conductive and active substance collector in order to provide abundant active centers, sufficient reaction interface to advance fast electrolyte ions diffusion and electrons transport. Furthermore, the growth process of Co Ni LDH on CCP-N is observed by controlling growth time and the Co/Ni ratio of the precursor solution. It is found that the optimal Co/Ni ratio was 2:1, while that optimal growth time is 12 h. The specific capacitance of Co Ni LDH@CCP-N electrode reaches 1319.4 F g-1 at 1 A g-1. The assembled asymmetric supercapacitor device (CCP-N @ Co Ni LDH//CCP-N) possesses a high energy density of 48.1 W h kg-1 at power density of 576.8 W kg-1, excellent cycling stability of 82.2% retention after 10,000 cycles. The results clearly indicate the Co Ni LDH@CCP-N materials have enormously potential in energy storage. This work puts forward a novel strategy for the design and fabrication of green and advanced supercapacitors materials with high power density and energy density. [Display omitted] • A dual conductive network is established by electrospinning and co-precipitation. • CCP-N is the inner-conductive and Co Ni LDH nanosheets is the outer-conductive. • The CCP-N @ Co Ni LDH exists multifunctional charge storage principles. • The CCP-N @ Co Ni LDH possesses abundant active sites and high specific surface area. • The CCP-N @ Co Ni LDH//CCP-N delivers excellent energy density and power density. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) have been playing an essential role in addressing the challenges of the flexibility in energy storage devices. However, the unsatisfactory electrochemical performance and poor electrical conductivity are often caused by insufficient physical contact points of CNFs. The design and implementation of unique electrodes are expected to overcome these issues. Here, the N-doped hierarchical porous carbon nanofibers (NCNFs) hollow framework derived from metal-organic frameworks (MOFs) is fabricated, which is decorated with high conductive reduced graphene oxide rGO and single-crystal ZnO nanorod for engineering the binder-free flexible electrodes NCNF@rGO-x@ZnO. The obtained NCNF@rGO-7@ZnO electrode exhibits the desired specific capacitance of 473 F g-1. An assembled hybrid supercapacitor exhibits the high energy density of 35.16 Wh kg-1 at the power density of 747.2 W kg-1, and superior cycling life. Given these advantages, the NCNF@rGO-7@ZnO is selected as the electrode in a flexible and foldable supercapacitor. There is exceptional flexibility and no visible capacitance loss when the supercapacitor bending at different angles. Furthermore, a timer is successfully driven by two supercapacitor devices connected in series. Hence, a flexible binder-free electrode with excellent electrochemical performance can be obtained by engineering the structure into a hollow interconnected architecture and the rational design of materials. [Display omitted] • The design and structural engineering of unique binder-free electrodes are proposed. • The supercapacitor exhibits considerable flexibility and long cycling stability. • The remarkable performance is related to the rational structure design. • A typical ASC device shows the potential practical application. [ABSTRACT FROM AUTHOR]

Potassium-ion batteries (PIBs) have gained substantial research interest for scalable and affordable stationary applications owing to their low cost, natural abundance, and high energy density. However, the large size of potassium (K) ion hampers its diffusion and causes significant strain in conventional electrode materials, resulting in low capacity, poor rate capability, and short lifespan. Herein, we develop a new strategy by confining amorphous tin sulfide (a-SnS) in electrospun porous carbon nanofibers (denoted as a-SnS@pCNFs) to realize the highly reversible potassiation/depotassiation of SnS. The amorphous nature of a-SnS enables a lower activation energy barrier towards structural rearrangement during any possible conversion reaction, which facilitates an increased electrochemical stability. Moreover, the pCNF skeleton not only improves the overall electrical conductivity of a-SnS@pCNFs, but also accommodates the volume variation of the SnS during the repeated cycles of charge/discharge. Combining these benefits of a-SnS and the tailored pore structures in pCNFs, the a-SnS@pCNFs composite delivers a high reversible capacity (∼300 mAh g−1 at 1 A g−1), a remarkable rate capability (∼85.4 mAh g−1 at 10 A g−1) and an ultralong lifespan (2000 cycles at 3 A g−1). This work provides a viable strategy to stabilize the conversion and alloying materials with fast and reversible K-ion storage towards practical applications. Amorphous SnS embedded in electrospun porous carbon nanofibers has been constructed for potassium-ion storage with a high reversible capacity, superior rate capability, and an ultralong lifespan. [Display omitted] • Amorphous SnS was embedded in nitrogen-doped porous carbon nanofibers by electrospinning, vulcanization and carbonization. • The amorphous nature of SnS enables superior structural stability during potassiation/depotassiation. • The nitrogen-doped carbon matrix enables fast potassiation/depotassiation and good electrode integrity. • The a-SnS@pCNFs composite anode has displayed an excellent lifespan at 3 A g−1 for 2000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel NPR structure for electrospun carbon-based electrode by LDW were obtained. • All-in-one AMSC was assembled from versatile nanofiber as electrode and separator. • The solid-state AMSC showed excellent mechanical and electrochemical properties. It is very necessary to design electrodes with satisfactory electrochemical performance and robust mechanical properties for flexible energy storage devices. Herein, a self-supporting electrode with Negative Poisson's Ratio (NPR) structure was fabricated by combining electrospinning and laser direct writing technology, which overcame the limitation that the traditional carbon-based materials cannot be stretched and avoided the integration problem of rigid electrodes and soft substrates in the conventional stretchable devices. Furthermore, a quasi-solid-state asymmetric micro-supercapacitor with NPR structure was assembled by an as-spun separator coated with gel electrolyte and two composite electrodes composed of carbon nanofibers and nanoarrays (CNF@Fe 2 O 3 nanorods and CNF@MnO 2 nanosheets). The apparatus not only reached an extended voltage window of 2 V, but also achieved an area energy density of 26 μWh·cm−2 at a power density of 0.55 mW·cm−2, which was superior to other wearable micro-supercapacitors. [ABSTRACT FROM AUTHOR]

Searching for high specific capacity anode materials with an optimized structure to achieve high energy density, long cycling life-span, and high rate performance for lithium-ion batteries (LIBs) is a pressing assignment. Metal phosphides have aroused much attention, however, enormous volume variations, poor electrical conductivity, and aggregation of nanoparticles hamper their practical applications. Herein, ZnP 2 nanoparticles grown on N, P co-doped carbon nanofibers (ZnP 2 @NPCNFs) composite synthesized by electrospinning and heat treatment is reported to directly act as binder-free anode in LIBs. The 3D self-standing ZnP 2 @NPCNFs featuring good flexibility can not only boost conductivity and alleviate the volumetric fluctuations in the cycling course, but also buffer the agglomeration and pulverization of nanoparticles. Lithium storage of ZnP 2 @NPCNFs electrode obey the conversion reaction mechanism. Besides, the additional lithium intercalation active sites created by the doped-nitrogen and the existence of P C bond along with the space-confined effect of NPCNFs are conjointly beneficial to endow the ZnP 2 @NPCNFs electrode with distinctive electrochemical properties. When assembled as the anode, the ZnP 2 @NPCNFs electrode reached a high reversible capacity of 746 mA h g−1 after 100 cycles at 0.2 A g−1 and 406.49 mA h g−1 after 1000 cycles at 2 A g−1. Electrochemical tests manifest that most of the capacity contribution comes from capacitive process. Moreover, the similar superior electrochemical performances are obtained in the LiFePO 4 //ZnP 2 @NPCNFs full cell. Generally, this study widens researchers' horizons to conceive rational structure of metal phosphides anodes in LIBs with high capacity conservation. [Display omitted] • The electrospinning method was firstly applied to the synthesis of ZnP 2 @NPCNFs. • The P—C bond and nanoconfinement effect are helpful for the performance of LIBs. • The ZnP 2 @NPCNFs anode delivers excellent performance. [ABSTRACT FROM AUTHOR]

Low-cost and simple methods are constantly chased in order to produce less expensive lithium-ion batteries (LIBs) while possibly increasing the energy and power density as well as the volumetric capacity in order to boost a rapid decarbonization of the transport sector. Li alloys and tin-carbon composites are promising candidates as anode materials for LIBs both in terms of capacity and cycle life. In the present paper, electrospinning was employed in the preparation of Sn/SnOx@C composites, where tin and tin oxides were homogeneously dispersed in a carbonaceous matrix of carbon nanofibers. The resulting self-standing and light electrode showed a greatly enhanced performance compared to a conventional electrode based on the same starting materials that are simply mixed to obtain a slurry then deposited on a Cu foil. Fast kinetics were achieved with more than 90% of the reaction that resulted being surface-controlled, and stable capacities of about 300 mAh/g over 500 cycles were obtained at a current density of 0.5 A/g. [ABSTRACT FROM AUTHOR]

• The novel free-standing Mo 2 C quantum dots/CNFs for KIBs is first investigated. • Impressive long-term stability with the capacity fading ratio of 0.026% per cycle. • Hybrid potassium-ion capacitors presents a high energy/power density. Potassium ion batteries (KIBs) have attracted worldwide attention on account of low cost and abundance of resources, and potentially high energy density. However, the development of KIBs is blocked by the sluggish reaction kinetics and the instability electrode materials caused by repetitive intercalation/deintercalation of large ions size of K+. Herein, the novel flexible and free-standing Mo 2 C/NCNFs anode for KIBs, in which the Mo 2 C quantum dots are inlaid in N-doped carbon nanofibers, is synthesized via a simple electrospinning route. The rationally designed structure with Mo 2 C quantum dots uniformly embedded in NCNFs can not only facilitate to accelerate the K+ reaction kinetics but also potentially alleviated the expansion and pulverization of Mo 2 C during the long-term cycling process. Furthermore, the N doping carbon nanofibers can provide a highway for K+ ions and electrons transport, while the whole electrode also offers a free-standing electrode without the addition of conductive agents and adhesives, facilitating to promote energy density of batteries. As a result, the Mo 2 C/NCNFs as anode for KIBs demonstrate impressive long-term stability with the capacity fading ratio of only 0.026% per cycle until 1000 cycles at 1.0 A g−1. More importantly, Mo 2 C/NCNFs as anode for hybrid potassium-ion capacitors (KICs) deliver a high energy/power density of 88.2 W h kg−1/629.9 W kg−1, as well as excellent capacity retention of about 80.4% after 1000 cycles. The versatile strategy, excellent cycling stability and ultra-robust flexibility make the Mo 2 C/NCNFs a great prospect for application in the field of alkali metal ion batteries, electrocatalyst and flexible wearable devices. [ABSTRACT FROM AUTHOR]

[Display omitted] One-dimensional (1D) electrospun carbon nanofibers functionalized with NiCo 2 S 4 nanoparticles have been synthesized and exhibits excellent performance as a low-cost, lightweight, flexible and binder-free cathode for aqueous Ni-Zn batteries. • Electrospun carbon nanofibers functionalized with NiCo 2 S 4 nanoparticles are synthesized. • The CNF@NiCo 2 S 4 electrode is lightweight, flexible and binder-free. • The CNF@NiCo 2 S 4 exhibits excellent performance for aqueous Ni-Zn batteries. • The quasi-solid-state CNF@NiCo 2 S 4 //Zn battery is also fabricated with polymer electrolyte. Aqueous nickel-zinc (Ni-Zn) batteries hold great promise for large-scale energy storage systems. However, traditional Ni-based cathode electrodes are generally consist of none capacity contribution additives and heavy current collectors, resulting in a low percentage of the active materials. In this regard, developing lightweight, flexible and binder-free cathode electrodes for aqueous Ni-Zn batteries is highly desirable. Herein, for the first time, we develop a simple electrospinning technique to synthesize the one-dimensional (1D) electrospun carbon nanofibers functionalized with ternary NiCo 2 S 4 nanoparticles (denoted as CNF@NiCo 2 S 4) as a lightweight, flexible and binder-free electrode for aqueous Ni-Zn batteries. Based on the self-standing CNF@NiCo 2 S 4 film as cathode, the as-fabricated aqueous CNF@NiCo 2 S 4 //Zn battery exhibits a high capacity of 0.32 mAh cm−2 and 35.9 mAh cm−3 at a current density of 2 mA cm−2, and good rate performance (0.21 mAh cm−2 at 20 mA cm−2) and long-term cycling stability (83% capacity retention at 10 mA cm−2 after 2000 cycles). More importantly, a quasi-solid-state CNF@NiCo 2 S 4 //Zn battery is also fabricated, which also displays an impressive energy density of 362.3 Wh kg−1, indicating the potential towards practical applications. Impressively, the volumetric energy density of CNF@NiCo 2 S 4 //Zn battery are 58.2 mWh cm−3 (liquid) and 45.4 mWh cm−3 (quasi-solid-state), which are much larger than the values of other reported Ni-Zn batteries. Theses results indicate the self-standing CNF@NiCo 2 S 4 film is promising for for next generation electronic applications. [ABSTRACT FROM AUTHOR]

In this study, in-situ carbon coating technology was used to embed the sulfide-loaded MXene in the carbon nanofibers through electrospinning to improve the sulfide conductivity and ion transfer rate. Polyacrylonitrile (PAN) with a high carbon conversion rate was used as carbon nanofiber, while polyvinylpyrrolidone (PVP) with a low carbon conversion rate was used as a pore-forming sacrificial agent. PAN–PVP-based porous carbon nanofibers (PCNF) with good meso/macropore structure were prepared via a thermally induced phase separation process. FeCo 2 S 4 nanoparticles and ultra-thin Ti 3 C 2 T x MXene were uniformly fixed in PCNF in situ, and a flexible hybrid film was prepared as the electrode material of supercapacitors (FeCo 2 S 4 /MXene/PCNF). The FeCo 2 S 4 /MXene/PCNF hybrid membrane inherits a three-dimensional pore structure and hierarchical PCNF nanostructure. It can provide continuous channels for the rapid electrolyte diffusion, thereby obtaining electrochemically active FeCo 2 S 4 nanoparticles. Moreover, carbon nanofibers can act as a conductive core for providing effective electron transport for the rapid Faraday redox reaction of the FeCo 2 S 4 sheath or as a buffer matrix for reducing local volume expansion/contraction during long-term cycling. Therefore, the optimized FeCo 2 S 4 /MXene/PCNF hybrid membrane has excellent cyclic stability, which fundamentally solves the problems of poor sulfide conductivity and cyclic stability. [Display omitted] [ABSTRACT FROM AUTHOR]

Porous carbonized electrospun nanofibers with limited nanopores realize a high-loading sulfur cathode in a lean-electrolyte lithium-sulfur cell featuring excellent dynamic and static electrochemical stabilities. [Display omitted] • A selective decomposition method is adopted to explore the effect of nanoporosity. • A fibrous carbon network with low nanoporosity might be an ideal cathode substrate. • A lean-electrolyte lithium-sulfur cell features a high-loading sulfur cathode. • The high-loading sulfur cathode attain high energy density and capacity retention. • The high-loading sulfur cathode exhibits dynamic/static electrochemical stability. High-performance sulfur cathodes characterized by high loading and content of active material and stable electrochemical properties with a lean electrolyte hold the key to realizing lithium-sulfur batteries with a high energy density. In this study, we present high-loading polysulfide cathodes using a series of carbon nanofibers that are generated from the carbonized electrospun nanofibers (CENFs). We fabricate the CENFs with similar porous fibrous skeleton decorating with tunable nanoporosity that allows us to explore the effect of nanoporosity on the electrochemical characteristics of the high-loading polysulfide cathodes. The CENF-polysulfide cathode made with non-nanoporous CENFs attains a high sulfur content of 71 wt% and loading of 14.4 mg cm−2, both of which exceed sulfur cathodes reported in the literature (<60 wt% and <3 mg cm−2). The high-loading CENF-polysulfide cathodes attain high reversible discharge capacities of 802 and 670 mA h g−1, high capacity retention rates of 82% after 200 cycles, and a long shelf life of 3 months at C/20 and C/10 rates, respectively. The cells further demonstrate high areal energy density values of 23.6 and 18.6 mW h cm−2 in a cell with a low electrolyte-to-sulfur ratio of 4 µL mg−1 at C/20 and C/10 rates. Therefore, our results demonstrate that the porous CENFs with limited nanopores prevent the rapid consumption of electrolyte and enable high-loading polysulfide cathodes to maintain high electrochemical efficiency and stability. [ABSTRACT FROM AUTHOR]

In this work, we prepared network-structured carbon nanofibers using polyacrylonitrile blends (PAN150 and PAN85) with different molecular weights (150,000 and 85,000 g mol−1) as precursors through electrospinning/hot-pressing methods and stabilization/carbonization processes. The obtained PAN150/PAN85 polymer nanofibers (PNFs; PNF-73, PNF-64 and PNF-55) with different weight ratios of 70/30, 60/40 and 50/50 (w/w) provided good mechanical and electrochemical properties due to the formation of physically bonded network structures between the blended PAN nanofibers during the hot-processing/stabilization processes. The resulting carbonized PNFs (cPNFs; cPNF-73, cPNF-64, and cPNF-55) were utilized as anode materials for supercapacitor applications. cPNF-73 exhibited a good specific capacitance of 689 F g−1 at 1 A g−1 in a three-electrode set-up compared to cPNF-64 (588 F g−1 at 1 A g−1) and cPNF-55 (343 F g−1 at 1 A g−1). In addition, an asymmetric hybrid cPNF-73//NiCo2O4 supercapacitor device also showed a good specific capacitance of 428 F g−1 at 1 A g−1 compared to cPNF-64 (400 F g−1 at 1 A g−1) and cPNF-55 (315 F g−1 at 1 A g−1). The cPNF-73-based device showed a good energy density of 1.74 W h kg−1 (0.38 W kg−1) as well as an excellent cyclic stability (83%) even after 2000 continuous charge–discharge cycles at a current density of 2 A g−1. [ABSTRACT FROM AUTHOR]