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The increasing popularity of wearable electronics has sparked interest in flexible energy harvesters as alternatives to conventional batteries. Flexible magnetoelectric (ME) composites, known for converting ambient magnetic field energy into useable power, are emerging as promising autonomous energy sources for integration into wearable devices. In this study, we prepared flexible (PVDF-AlN)–(NiO–CNF) based ME composites using two different methods: solution-casting and electrospinning techniques. The ME coupling was confirmed by measuring the ferroelectric and magnetic properties of the composite, and it was qualitatively characterized through the ME coupling coefficient. The electrospinning fibers-based ME composite exhibited an optimal value of 10.6 V/cm.Oe, significantly higher than the solution-casting films-based ME composite (1.3 V/cm.Oe) under a 1 kHz AC magnetic field (off-resonance condition). Subsequently, a flexible magneto-mechano-electric (MME) generator was designed using electrospun-derived material, harvesting a sinusoidal wave with a maximum output peak-to-peak voltage of 9.02 V. The generator displayed an optimal DC power density of 97 μW/m2 when exposed to a weak AC magnetic field of 6 Oe at a frequency of 50 Hz. Consequently, it holds great promise as an efficient autonomous power supply for medical sensing and various miniature electronic applications. [ABSTRACT FROM AUTHOR]

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]

The electrospinning technique is employed for the synthesized cobalt ferrite/carbon nanofibers, utilizing iso-propanol as the solvent. The nanofibers prepared are subjected to sintering at three different temperatures. A comprehensive analysis is carried out on the structural, morphological, dielectric, impedance, and electromagnetic shielding effectiveness within the X-band frequency range (8.2–12.4 GHz). The application of the Debye-Scherer formula yielded an estimated crystallite size of 22 nm. The electrical response of cobalt ferrite/carbon nanofibers pellet is characterized by employing impedance spectroscopy. Variations in impedance plane plots are discussed based on frequency dependent relaxation time modulations. The impact of sintering temperature is observed in terms of increased impedance values and modifications in the conduction mechanism. These changes are contributed to distinct hopping carriers' linkages between Fe3+-Fe2+ and Co3+-Co2+ ions. Dielectric studies are elucidated considering cation polarizability, colossal resistivity, and tangent loss. This study revealed notable characteristics of CoFe 2 O 4 /C nanofibers, including colossal resistivity (8.45 × 108 Ωcm), a dielectric constant of 22, and colossal tangent loss. The CoFe 2 O 4 /C nanofibers exhibit a characteristic electromagnetic interference (EMI) shielding performance of 30–35 dB. This remarkable shielding performance is observed in nanofibers with a 3 mm thickness, specifically in sample S1 that underwent sintering at a low temperature. The shielding effectiveness is demonstrated within the X-band frequency range. [ABSTRACT FROM AUTHOR]

The degradation of the cobalt-zinc oxide structure and its poor conductivity during the charge and discharge limit their further applications for lithium ion storage. Herein, ZnCo 2 O 4 @carbon nanofiber composite with nano-fibrous structure is obtained by electrospinning, annealing in argon and low-temperature oxidation to effectively overcome the above issue. The active sites of ZnCo 2 O 4 are evenly dispersed inside the carbon nanofibers, which can effectively avoid its aggregation and improve electrical conductivity. Additionally, the stable nanofibrous structure can maintain structural stability. The composite exhibits superior lithium ion storage capacity when being served as anode electrode. The ZnCo 2 O 4 @carbon nanofiber electrode possesses a high capacity of 1071 mA h g−1 at 0.1 A g−1. Besides, the electrode shows an outstanding rate capability of 505 mA h g−1 at 3 A g−1 and maintain 714 mA h g−1 after 250 cycles when current density is adjusted to 0.2 A g−1 again. Additionally, the electrode has an outstanding long-cycle performance, which remains a capacity of 447.165 mA h g−1 at 0.5 A g−1 after 500 cycles and 421.477 mA h g−1 at 1 A g−1 after 518 cycles. This result demonstrates that ZnCo 2 O 4 @carbon nanofiber composite has potential application prospects in the fields of advanced energy storage. [ABSTRACT FROM AUTHOR]

Molybdenum dioxides have been investigated in alkali-ion batteries owing to their low electrical resistivity, large interlayer spacing and high theoretical capacity. However, the slow diffusion kinetics lead to the poor electrochemical performance of Molybdenum dioxides. Herein, MoO 2 nanosheets embedded into carbon nanofibers are designed and synthesized by multi-step methods. The composite delivers the high lithium/sodium ion storage performance and stable ion diffusion, ascribed to the synergistic effect of carbon nanofibers and MoO 2 nanosheets. MoO 2 nanosheets are major contributors to the capacity of composite and carbon nanofibers can provide an interconnected three-dimensional conductive and diffusion networks to improve the kinetics process of MoO 2. The proposed synthesis strategy may offer an effective route to construct the high-performance electrodes for the wearable devices. [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]

High-performance electromagnetic (EM) wave absorption property could be achieved by architecture design of nanomaterials. Herein, two layer hybrid Co 0.2 Fe 2.8 O 4 /carbon nanofibers with porous three-dimensional (3D) hierarchical structure were synthesized successfully through facile electrospinning, carbonization and mild chemical treatment. The Co 0.2 Fe 2.8 O 4 particles grew along the carbon nanofibers, forming the enhanced heterogeneous interfaces and high specific areas. As expected, the EM wave absorbent showed an excellent absorbing capability. The composites achieved a maximum reflection loss (RL) of −43.45 dB at 11.1 GHz with thickness of 3.0 mm. More importantly, the effective bandwidth (RL ≤ −10dB) was 5.85 GHz, covering 30% of the entire measured bandwidth. The absorption intensity and bandwidth were superior to other typical CoFe-based composites. The intrinsic mechanism of the absorption revealed that the polarization losses, magnetic losses, magnetic natural resonance and exchanged resonance losses contributed to the high-performance microwave absorption. Moreover, good impedance matching and complex transmission paths that generated from unique porous network also played an important role. This study is expected to guide future exploration on designing and synthesizing high performance EM wave absorbents. [ABSTRACT FROM AUTHOR]

Homogenous ultra-fine SnO 2 /TiO 2 particles encapsulated into carbon nanofibers (SnO 2 /TiO 2 @CNFs) with a uniform and ordered one-dimensional fibrous structure are fabricated through facile electrospinning technique and subsequent heat treatments, which are confirmed by XRD, Raman, TG, SEM, TEM, and XPS analyses. The battery performance reveals that the SnO 2 /TiO 2 @CNFs-1.5:1 (1.5:1 denotes the mole ratio of SnO 2 to TiO 2 in the carbon nanofibers) electrode displays the optimal electrochemical properties among the whole samples, which can deliver the initial charge and discharge specific capacity of 1061.2 and 1494.8 mAh/g with a coulombic efficiency of 71.0% at 100 mA/g, and exhibit a remarkable specific capacity of 766.1 mAh/g after 200 cycles. Moreover, the SnO 2 /TiO 2 @CNFs-1.5:1 electrode displays a high pseudocapacitive contribution of 73.9% at the scan rate of 2 mV/s and the lithium ion diffusion coefficient of approximately 1.20 × 10−15 cm2 s−1. The excellent electrochemical performance of the SnO 2 /TiO 2 @CNFs-1.5:1 electrode is closely correlated with the synergetic effect of the proper amount of TiO 2 that enhances the electrochemical stability of the electrode and provides fractional capacity, and the flexible and conductive carbon nanofiber matrix that accommodates volume changes and increases overall electronic conductivity. The detailed investigations of the as-prepared electrode materials by a facile electrospinning process may pave possible instructions for the next generation SnO 2 -based anodes and other related electrospun anodes for the energy storage device. [ABSTRACT FROM AUTHOR]