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In recent years, the automotive industry has made significant progress in integrating multifunctional sensors to improve vehicle performance, safety, and efficiency. As the number of integrated sensors keeps increasing, there is a growing interest in alternative energy sources. Specifically, self‐powered sensor systems based on energy harvesting are drawing much attention, with a main focus on sustainability and reducing reliance on typical batteries. This paper demonstrates the use of triboelectric nanogenerators (TENGs) in a computer mouse for efficient energy harvesting and in automobile braking systems for safety applications using SrBi2Ta2O9 (SBTO) perovskite, blended PDMS composite operating in free‐standing mode with an interdigitated patterned aluminum electrode. This self‐powered sensor is capable of distinguishing between normal and abnormal braking patterns using digital signal processing techniques. It is noteworthy that the addition of 15% wt. of the SBTO in PDMS composite‐based TENG delivered 13.5 V, 45 nA, and an output power of 0.98 µW. This new combination of energy harvesting and safety applications enables real‐time monitoring and predictive maintenance in the automotive industry. [ABSTRACT FROM AUTHOR]

Li-CO2 batteries with unique reaction pathways and high theoretical capacity are powerful tools for addressing greenhouse issues. Thus, it is critical and urgent to develop highly active catalysts for the cathodes of Li-CO2 batteries to promote both CO2 reduction (CRR) and evolution reactions (CER). Herein, La0.8Sr0.2NixCu1–xO3 perovskite is in situ synthesized on multiwalled carbon nanotubes (LSNC/MWCNTs) paper as cathodes of Li-CO2 batteries. The morphology, structure, and electrochemical performance of the as-prepared cathodes are investigated systematically, as well as the reaction products and reversible reaction mechanism. As a result, the Li-CO2 batteries constructed with La0.8Sr0.2Ni0.7Cu0.3O3 (N7C3)/MWCNTs cathode exhibit remarkable electrochemical properties, showcasing a large specific capacity of 16.90 mAh cm–2 at a high specific current of 0.07 mA cm–2, a low overpotential of 0.76 V after 15 cycles rate test, and good cycling stability, maintaining a low overpotential throughout the 500 h of discharge–charging at 0.02 mA cm–2 with a cutoff capacity of 0.1 mAh cm–2 (50 cycles). The superior electrochemical performance of the N7C3/MWCNTs cathodes is attributed to the high Ni3+ content and a large amount of oxygen vacancies caused by the tuning of the atomic ratio on B-sites of perovskite crystals. The results of this work would provide an easy design option for the free-standing cathodes of Li-CO2 batteries and will inspire more original high-performance metal–air batteries. [ABSTRACT FROM AUTHOR]

This text provides an overview of John Rawls's concept of political liberalism and its implications for pluralist societies. Rawls argues that in societies with diverse and reasonable comprehensive views, a political conception of justice is necessary to address conflicts over fundamental issues. He emphasizes the importance of social cooperation, well-ordered societies, and the acceptance of diverse conceptions of the common good. The text also discusses the distinction between comprehensive and political conceptions of justice, the need for a political conception in pluralist societies, and the challenges of maintaining a distinction between essentials and ordinary policy. It concludes by suggesting that political liberalism represents a realistic utopia. [Extracted from the article]

Developing thermoelectric films without substrates—free-standing films—eliminates substrate-induced effects on performance and meets the flexibility requirements of emerging wearable thermoelectric applications. This study investigates Gallium-doped Zinc Oxide (GZO), composed of abundant and non-toxic elements, to fabricate a substrate-free GZO film via 3D printing and compares its structural, chemical, and thermoelectric properties with those of a substrate-constrained GZO film produced through chemical deposition. Both films exhibited uniform crystal structures and phase purity; however, the substrate-constrained film displayed additional diffraction peaks, suggesting potential substrate interactions. The 3D-printed free-standing film effectively eliminated the tensile stresses observed in the substrate-constrained film. FE-STEM analysis revealed nanostructures with homogeneous elemental distribution in both films, though the substrate-constrained film showed discontinuities, such as pores, likely caused by post-deposition annealing treatment. XPS analysis highlighted differences in chemical states and elemental compositions between the films, influenced by fabrication methods, substrate-induced stresses, and surface energy mismatches. The free-standing GZO film developed through 3D printing exhibited a more balanced incorporation of Zn and O, as it was not subject to substrate or post-deposition annealing constraints. Consequently, it demonstrated a 14 % increase in electrical conductivity and a 91 % improvement in the Seebeck coefficient compared to the substrate-constrained film, resulting in a higher room-temperature power factor of 261 nW/m·K2. These findings underscore the potential of 3D-printed free-standing GZO films to advance thermoelectric applications, offering a promising alternative to overcome the challenges of substrate-constrained films and further drive innovation in the field.

Free-standing electrode materials provide many desirable properties for electrochemical energy storage devices due to their light weight, good conductive capacity, excellent mechanical strength, high energy/power density and extraordinary electrochemical stability. Particularly, carbonaceous matrix nanomaterials, such as graphene materials, carbon nanotubes, carbon nanofibers, carbon papers and carbon cloths, play important roles in the free-standing electrodes, including serving as conducting network skeleton, loading electrochemically active material, enhancing mechanical toughness and flexibility, and preventing the structural damage during charge/discharge processes. In this review, we give a systematic overview of the state-of-the-art research progress on carbonaceous matrixes-based free-standing electrode materials for electrochemical energy storage, from synthesis methods, structural design, to important applications in flexible energy storage devices including lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, lithium-oxygen batteries, and supercapacitors for each class of matrix-based electrode materials. In particular, the structure design strategies utilizing the advantages of free-standing matrixes to address the existing issues and improve the electrochemical and mechanical performance of energy storage devices are discussed in detail. At the end, we also discuss the challenges and demonstrate the prospective for the future development of such materials for advanced flexible energy storage devices.

The development of wearable devices requires flexible batteries that can be bent and folded. However, deficiencies in material flexibility, conductivity, and other aspects can affect the performance of a flexible electrode. One-dimensional nanofibers possess high specific surface area, high conductivity, and a 3D network structure that enables them to buffer stress and strain. Consequently, they hold significant potential in the field of electrochemical energy storage as flexible electrode materials. In this study, we utilized polyvinylpyrrolidone (PVP) as a template to form a supramolecular polymer (PNDS) through hydrogen bonding between 1,4,5,8-naphthalene tetracarboxylic acid (NTCA) and 3,3′-diaminobenzidine (DAB) monomers. Through core–shell electrospinning and carbonization, PNDS precursors were used to prepare polybis-(benzimidazobenzophenanthroline-dione) (BBB)-based carbon nanofibers featuring a core–shell structure. The BBB polymer, featuring a continuous aromatic ring structure, undergoes conversion into a highly graphitic carbon skeleton upon carbonization at 1000 °C. This transformation enhances the conductivity of flexible electrodes, improves the current collection effect under high currents, and ensures stability in the charge–discharge cycle. The iron-containing polymers within the shell layer ultimately transform into iron oxide and iron carbide nanoparticles encapsulated within the carbon fibers, compensating for the lower specific capacity characteristic of pure carbon materials. Serving as a SIB flexible anode, the specific capacity can achieve 250 mAh g–1 after 950 cycles at 0.2 A g–1, with negligible attenuation throughout the cycling process. This study demonstrates that BBB-based carbon nanofibers featuring core–shell structures exhibit excellent electrochemical performance while retaining flexibility, presenting clear advantages over traditional electrodes characterized by complicated processes and limited active substance content. [ABSTRACT FROM AUTHOR]

The NASICON-structured Na3MnZr(PO4)3 compound is a promising high-voltage cathode material for sodium-ion batteries (SIBs). In this study, an easy and scalable electrospinning approach was used to synthesize self-standing cathodes based on Na3MnZr(PO4)3 loaded into carbon nanofibers (CNFs). Different strategies were applied to load the active material. All the employed characterization techniques (X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), and Raman spectroscopy) confirmed the successful loading. Compared to an appositely prepared tape-cast electrode, Na3MnZr(PO4)3/CNF self-standing cathodes demonstrated an enhanced specific capacity, especially at high C-rates, thanks to the porous conducive carbon nanofiber matrix. Among the strategies applied to load Na3MnZr(PO4)3 into the CNFs, the electrospinning (vertical setting) of the polymeric solution containing pre-synthesized Na3MnZr(PO4)3 powders resulted effective in obtaining the quantitative loading of the active material and a homogeneous distribution through the sheet thickness. Notably, Na3MnZr(PO4)3 aggregates connected to the CNFs, covered their surface, and were also embedded, as demonstrated by TEM and EDS. Compared to the self-standing cathodes prepared with the horizontal setting or dip–drop coating methods, the vertical binder-free electrode exhibited the highest capacity values of 78.2, 55.7, 38.8, 22.2, 16.2, 12.8, 10.3, 9.0, and 8.5 mAh/g at C-rates of 0.05C, 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, and 20C, respectively, with complete capacity retention at the end of the measurements. It also exhibited a good cycling life, compared to its tape-cast counterpart: it displayed higher capacity retention at 0.2C and 1C, and, after cycling 1000 cycles at 1C, it could be further cycled at 5C, 10C, and 20C. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) have demonstrated remarkable development potential and commercial prospects. However, in the current state of research, the development of high-energy-density, long-cycle-life, high-rate-performance anode materials for SIBs remains a huge challenge. Free-standing flexible electrodes, owing to their ability to achieve higher energy density without the need for current collectors, binders, and conductive additives, have garnered significant attention across various fields. In this work, we designed and fabricated a free-standing three-dimensional flexible Nb2O5@WS2@C carbon nanofiber (CNF) anode based on a hybrid adsorption–intercalation–conversion mechanism of sodium storage, using electrospinning and hydrothermal synthesis processes. The hybrid structure, aided by synergistic effects, releases the advantages of all materials, demonstrating a superior rate performance (288, 248, 211, 158, 90, and 48 mA h g−1 at the current density of 0.2, 0.5, 1, 2, 5, and 10 A g−1, respectively) and good cycling stability (160 mA h g−1 after 200 cycles at 1 A g−1). This work provides certain guiding significance for future research on hybrid and flexible anodes of SIBs. [ABSTRACT FROM AUTHOR]

Here, a novel fabrication method for making free‐standing 3D hierarchical porous carbon aerogels from molecularly engineered biomass‐derived hydrogels is presented. In situ formed flower‐like CaCO3 molecularly embedded within the hydrogel network regulated the pore structure during in situ mineralization assisted one‐step activation graphitization (iMAG), while the intrinsic structural integrity of the carbon aerogels was maintained. The homogenously distributed minerals simultaneously acted as a hard template, activating agent, and graphitization catalyst. The decomposition of the homogenously distributed CaCO3 during iMAG followed by the etching of residual CaO through a mild acid washing endowed a robust carbon aerogel with high porosity and excellent electrochemical performance. At 0.5 mA cm−2, the gravimetric capacitance increased from 0.01 F g−1 without mineralization to 322 F g−1 with iMAG, which exceeds values reported for any other free‐standing or powder‐based biomass‐derived carbon electrodes. An outstanding cycling stability of ~104% after 1000 cycles in 1 M HClO4 was demonstrated. The assembled symmetric supercapacitor device delivered a high specific capacitance of 376 F g−1 and a high energy density of 26 W h kg−1 at a power density of 4000 W kg−1, with excellent cycling performance (98.5% retention after 2000 cycles). In combination with the proposed 3D printed mold‐assisted solution casting (3DMASC), iMAG allows for the generation of free‐standing carbon aerogel architectures with arbitrary shapes. Furthermore, the novel method introduces flexibility in constructing free‐standing carbon aerogels from any ionically cross‐linkable biopolymer while maintaining the ability to tailor the design, dimensions, and pore size distribution for specific energy storage applications. [ABSTRACT FROM AUTHOR]

The current and future energy demands require high‐performance batteries with stable long‐term cycling, high capacities, and fast‐charging capabilities. In recent years, niobate compounds have gained significant research interests due to their attractive properties suited for battery applications. In this work, cobalt niobate, CoNb2O6, was synthesized via a simple and scalable solid‐state mechanochemical method through high‐energy ball milling, mechanical treatment (pellet formation), and calcination at 900 °C. The resulting product is a pure, columbite‐type (orthorhombic) cobalt niobate based on XRD findings. Electrochemical testing in a half‐cell against Li/Li+ of the as‐prepared free‐standing cobalt niobate anode material revealed a highly reversible process of lithiation (discharge) and delithiation (charge), with increasing pseudocapacitive behavior at higher scan rates. At 0.1 A g−1, the observed initial discharge capacity was about 900 mAh g−1. The synthesized CoNb anode material displayed an impressive rate performance, which involved increased stability at elevated current densities. During prolonged cycling tests, the anode material displayed extremely stable cycling vs Li/Li+, even at 2 A g−1, delivering a specific capacity of 700 mAh g−1 in the initial cycle, followed by a relatively constant capacity of 150 mAh g−1 throughout the majority of 5000 cycles completed. Post‐mortem analysis illustrated the reversibility of the cobalt niobate anode material and confirmed the growth and partial breakdown of the SEI film. With the results obtained from this work, cobalt niobate is full of potential as an anode material for Li‐ion battery applications. [ABSTRACT FROM AUTHOR]

δ‐Manganese dioxide (δ‐MnO2) is a 2D material which possesses distinct properties and features due to its unique atomic structure and has already been utilized in numerous disciplines recently, especially in the field of magnetism, energy storage, magnetic resonance imaging, biocatalysts, and fluorescence sensing. Keeping an eye on the huge potential of this 2D material, we report our recent discovery of single‐step synthesis of MnO2 nanosheets via bottom‐up laser crystallization (of aqueous KMnO4 solution) and top‐down sonochemical exfoliation of bulk MnO2 powder. The successful synthesis of δ‐MnO2 nanosheets has been proved through the observation of characteristic Raman peaks at 173 and 634 cm−1 and characteristic X‐ray diffraction peaks. The optical band gap was found to be 1.64 and 1.45 eV for both methods. We also demonstrated that 2D‐MnO2 is a prominent candidate material for ammonia sensing and strain sensing. δ‐MnO2 powder, when employed as cathode material in Li‐ion batteries, results in a stable voltage of ˜0.5 V and in contrast, gives ˜1 V when used in Li‐S batteries and the attained voltage is stable even for >5 h. New methods of synthesis of δ‐MnO2 and its hybrids with graphene will lead to future generation devices, it is expected. [ABSTRACT FROM AUTHOR]

In these experiments, Ti, Si and glass carbon substrates were selected to prepare ultra-thin polycrystalline diamond films by microwave plasma chemical vapor deposition (MPCVD) using CH4/H2 as the reaction source. The overall morphology, surface morphology, composition and stress state of the prepared diamond films were characterized and analyzed by SEM, Raman and a profilometer. The results show that only diamond films grown on glass carbon substrate can be automatically peeled off to form a complete free-standing film. The crystal surface of the film grains is clear, and the film thickness is only 10 μm. Raman spectra reveal that thin films have strong sharp diamond characteristic peaks, and that the calculated residual stress is the lowest, which is −0.2161 GPa. It is expected to provide an effective new technique for the one-step growth and stripping of ultra-thin self-supported CVD diamond films.

Abstract The current and future energy demands require high‐performance batteries with stable long‐term cycling, high capacities, and fast‐charging capabilities. In recent years, niobate compounds have gained significant research interests due to their attractive properties suited for battery applications. In this work, cobalt niobate, CoNb2O6, was synthesized via a simple and scalable solid‐state mechanochemical method through high‐energy ball milling, mechanical treatment (pellet formation), and calcination at 900 °C. The resulting product is a pure, columbite‐type (orthorhombic) cobalt niobate based on XRD findings. Electrochemical testing in a half‐cell against Li/Li+ of the as‐prepared free‐standing cobalt niobate anode material revealed a highly reversible process of lithiation (discharge) and delithiation (charge), with increasing pseudocapacitive behavior at higher scan rates. At 0.1 A g−1, the observed initial discharge capacity was about 900 mAh g−1. The synthesized CoNb anode material displayed an impressive rate performance, which involved increased stability at elevated current densities. During prolonged cycling tests, the anode material displayed extremely stable cycling vs Li/Li+, even at 2 A g−1, delivering a specific capacity of 700 mAh g−1 in the initial cycle, followed by a relatively constant capacity of 150 mAh g−1 throughout the majority of 5000 cycles completed. Post‐mortem analysis illustrated the reversibility of the cobalt niobate anode material and confirmed the growth and partial breakdown of the SEI film. With the results obtained from this work, cobalt niobate is full of potential as an anode material for Li‐ion battery applications.

Abstract δ‐Manganese dioxide (δ‐MnO2) is a 2D material which possesses distinct properties and features due to its unique atomic structure and has already been utilized in numerous disciplines recently, especially in the field of magnetism, energy storage, magnetic resonance imaging, biocatalysts, and fluorescence sensing. Keeping an eye on the huge potential of this 2D material, we report our recent discovery of single‐step synthesis of MnO2 nanosheets via bottom‐up laser crystallization (of aqueous KMnO4 solution) and top‐down sonochemical exfoliation of bulk MnO2 powder. The successful synthesis of δ‐MnO2 nanosheets has been proved through the observation of characteristic Raman peaks at 173 and 634 cm−1 and characteristic X‐ray diffraction peaks. The optical band gap was found to be 1.64 and 1.45 eV for both methods. We also demonstrated that 2D‐MnO2 is a prominent candidate material for ammonia sensing and strain sensing. δ‐MnO2 powder, when employed as cathode material in Li‐ion batteries, results in a stable voltage of ˜0.5 V and in contrast, gives ˜1 V when used in Li‐S batteries and the attained voltage is stable even for >5 h. New methods of synthesis of δ‐MnO2 and its hybrids with graphene will lead to future generation devices, it is expected.

The dynamics of three-dimensional (3D) slender systems such as statues, obelisks, monuments, museums, and household objects are highly nonlinear. In this study, a numerical model for rigid blocks in 3D, referred to as the physical model (PM), is developed to explore and view the motion of the slender blocks to base excitations. The model can represent the dynamics of both symmetric and mass-eccentric 3D blocks for unidirectional and bidirectional excitations. Keeping the kinematics of the system in view, the PM is developed as an assemblage of different subsystems in the Simscape Multibody Library. The rigid block supported by four tiny spheres at the corners is resting on a rigid table. Physical interaction between the table and the rigid body is simulated by introducing a virtual plane characterized by a spring and a damper that follows the visco-elastic Kelvin model. The values of the depth of the virtual plane, parameters of the Kelvin model, and the dimension of the tiny spheres are suitably chosen for such interaction. Adequately large values for kinetic and static friction are used in the virtual plane to prevent the body from sliding during its rocking motion. The motion of the table is described by choosing the inertial reference frame with origin at a fixed point and another parallel frame fixed with the tabletop. The response of the rigid body is described by the asymmetric Euler sequence. A third set of the frame, i.e. the body-fixed reference with the origin at the centre of mass of the corresponding symmetric body is introduced by a Bushing joint. A calculated amount of mass-eccentricity is generated by adding very small square blocks to the side-faces of the 3D symmetric block. The response of mass eccentric systems to trigonometric base excitations applied in-plane and out-of-plane of the eccentricity is computed using the PM, and a comparison of the same to the results derived analytically confirms the adequacy of the model. In the sequel, representative case studies are presented and interpreted to uncover the complex dynamics of the mass eccentric rocking systems. The PM can also serve as the basis of analyzing and viewing the motion of blocks with arbitrary geometry. [ABSTRACT FROM AUTHOR]

[Display omitted] • The flexible free-standing antibacterial NP-Ag ribbon is fabricated. • The NP-Ag can rapidly release Ag+ in 24 h to damage bacterial membrane. • The NP-Ag can realize rapid antibacterial efficacy in vivo. • The good biosafety in vivo due to the long-term stable Ag+ release of NP-Ag. The biomedical field has the potential to significantly benefit from the use of flexible free-standing Ag nanostructures due to their outstanding mechanical and antibacterial properties. However, the intricate process of synthesizing these nanostructures, as well as the potential toxicity of nanostructured Ag, pose significant challenges. This study used a facile etching method to synthesize the free-standing nanoporous Ag (NP-Ag) ribbons with a homogeneous and bicontinuous three-dimensional ligament structure. The free-standing NP-Ag ribbons demonstrated stable mechanical performance and excellent flexibility when subjected to various deformation states on artificial fingers. Additionally, the NP-Ag ribbons exhibited remarkable antibacterial capacity with rates of 99.81 ± 0.14% against Escherichia coli , 96.11 ± 1.49% against Staphylococcus aureus , and 95.37 ± 1.24% against methicillin-resistant Staphylococcus aureus. The antibacterial mechanism of NP-Ag is attributed to the rapid release of Ag ions (Ag+) in 24 h, causing damage to the bacterial membrane. Moreover, the in vivo results demonstrate that the NP-Ag ribbons provide rapid antibacterial efficacy and are biosafe due to the long-term stable Ag+ release of NP-Ag. The development of these free-standing flexible NP-Ag ribbons offers a new avenue for wearable antibacterial applications. [ABSTRACT FROM AUTHOR]

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Implementing high‐performance silicon (Si) anode in actual processing and application is highly desirable for next‐generation, high‐energy Li‐ion batteries. However, high content of inactive matrix (including conductive agent and binder) is often indispensable in order to ensure local conductivity and suppress pulverization tendency of Si particles, which thus cause great capacity loss based on the mass of whole electrode. Here, we designed an accordion‐structured, high‐performance electrode with high Si content up to 95%. Si nanoparticles were well anchored into the interlayer spacings of accordion‐like graphene arrays, and free‐standing electrode was prepared via a simple filtration process without any binder. Conductive accordion framework ensures strong confinement effect of Si nanoparticles and also provides direct, non‐tortuous channels for fast electrochemical reaction kinetics. As a consequence, the accordion Si electrodes exhibit ultrahigh, electrode‐based capacities up to 3149 mAh g−1 (under Si content of 91%), as well as long‐term stability. Also, the accordion electrode can bear extreme condition of over‐lithiation and maintains stable in full‐cell test. This design provides a significant stride in high Si content toward realistic, high‐performance electrodes. [ABSTRACT FROM AUTHOR]

The NASICON-structured Na3MnZr(PO4)3 compound is a promising high-voltage cathode material for sodium-ion batteries (SIBs). In this study, an easy and scalable electrospinning approach was used to synthesize self-standing cathodes based on Na3MnZr(PO4)3 loaded into carbon nanofibers (CNFs). Different strategies were applied to load the active material. All the employed characterization techniques (X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), and Raman spectroscopy) confirmed the successful loading. Compared to an appositely prepared tape-cast electrode, Na3MnZr(PO4)3/CNF self-standing cathodes demonstrated an enhanced specific capacity, especially at high C-rates, thanks to the porous conducive carbon nanofiber matrix. Among the strategies applied to load Na3MnZr(PO4)3 into the CNFs, the electrospinning (vertical setting) of the polymeric solution containing pre-synthesized Na3MnZr(PO4)3 powders resulted effective in obtaining the quantitative loading of the active material and a homogeneous distribution through the sheet thickness. Notably, Na3MnZr(PO4)3 aggregates connected to the CNFs, covered their surface, and were also embedded, as demonstrated by TEM and EDS. Compared to the self-standing cathodes prepared with the horizontal setting or dip–drop coating methods, the vertical binder-free electrode exhibited the highest capacity values of 78.2, 55.7, 38.8, 22.2, 16.2, 12.8, 10.3, 9.0, and 8.5 mAh/g at C-rates of 0.05C, 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, and 20C, respectively, with complete capacity retention at the end of the measurements. It also exhibited a good cycling life, compared to its tape-cast counterpart: it displayed higher capacity retention at 0.2C and 1C, and, after cycling 1000 cycles at 1C, it could be further cycled at 5C, 10C, and 20C.

Sodium-ion batteries (SIBs) have demonstrated remarkable development potential and commercial prospects. However, in the current state of research, the development of high-energy-density, long-cycle-life, high-rate-performance anode materials for SIBs remains a huge challenge. Free-standing flexible electrodes, owing to their ability to achieve higher energy density without the need for current collectors, binders, and conductive additives, have garnered significant attention across various fields. In this work, we designed and fabricated a free-standing three-dimensional flexible Nb2O5@WS2@C carbon nanofiber (CNF) anode based on a hybrid adsorption–intercalation–conversion mechanism of sodium storage, using electrospinning and hydrothermal synthesis processes. The hybrid structure, aided by synergistic effects, releases the advantages of all materials, demonstrating a superior rate performance (288, 248, 211, 158, 90, and 48 mA h g−1 at the current density of 0.2, 0.5, 1, 2, 5, and 10 A g−1, respectively) and good cycling stability (160 mA h g−1 after 200 cycles at 1 A g−1). This work provides certain guiding significance for future research on hybrid and flexible anodes of SIBs.

Transition metal oxides are regarded as promising candidates of anode for next‐generation lithium‐ion batteries (LIBs) due to their ultrahigh theoretical capacity and low cost, but are restricted by their low conductivity and large volume expansion during Li+ intercalation. Herein, we designed and constructed a structurally integrated 3D carbon tube (3D‐CT) grid film with Mn3O4 nanoparticles (Mn3O4‐NPs) and carbon nanotubes (CNTs) filled in the inner cavity of CTs (denoted as Mn3O4‐NPs/CNTs@3D‐CT) as high‐performance free‐standing anode for LIBs. The Mn3O4‐NPs/CNTs@3D‐CT grid with Mn3O4‐NPs filled in the inner cavity of 3D‐CT not only afford sufficient space to overcome the damage caused by the volume expansion of Mn3O4‐NPs during charge and discharge processes, but also achieves highly efficient channels for the fast transport of both electrons and Li+ during cycling, thus offering outstanding electrochemical performance (865 mAh g−1 at 1 A g−1 after 300 cycles) and excellent rate capability (418 mAh g−1 at 4 A g−1) based on the total mass of electrode. The unique 3D‐CT framework structure would open up a new route to the highly stable, high‐capacity, and excellent cycle and high‐rate performance free‐standing electrodes for high‐performance Li‐ion storage. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous zinc-ion batteries (ZIBs) have been widely studied because of its excellent performance, low price and environment-friendly, and the structure design of ZIBs cathode with high capacity and long cycle life have become the focus. PAN solution containing Mn(NO3)2·xH2O was used as a core layer and PAN solution as skin layer by coaxial electrospinning. Due to the concentration gradient diffusion, Mn(NO3)2·xH2O diffused to the cortex. And MCNFs with sebaceous glandular structure on the surface was obtained by carbonization. MnO2 was electrodeposited on its surface, and MnO2@MCNFs cathode with excellent affinity with electrolytes were prepared. The results show that the sebaceous gland structure not only increases the specific surface area of cathode, but also constructs the riveting effect between MCNFs and α-MnO2, which enhances the interface bonding between the substrate and the active material, reduces the shedding of α-MnO2, reduces the interface resistance, and shortens the electron conduction and ion diffusion path. The test shows that the specific capacity of the first cycle of 3% MnO2@MCNFs can reach about 581.16 mAh/g under the current density of 100 mA/g, and the specific capacity of 120 mAh/g can be maintained after 1000 cycles under the high current density of 1 A/g, and the coulomb efficiency is around 99%.

Exploring highly efficient three-dimensional (3D) nanoarchitectures for H2 and O2 evolution reaction (HER and OER) has received tremendous interest. Here, a binder-free free-standing cobalt/bamboo-shaped carbon nanotube/carbon nanofiber (Co/CNT/CNF) film was prepared based on electrospinning, followed by thermal treatment. The synergistic effect between Co cores, CNT shells (5 nm), and CNF skeletons endows the as-prepared Co/CNT/CNF with a 3D porous dendritic nanostructure. Therefore, the unique Co/CNT/CNF film demonstrates prominent HER (overpotential = 129 mV) and OER (overpotential = 162 mV) catalysis behavior at 10 mA cm–2. Meanwhile, the as-prepared Co/CNT/CNF film displays excellent overall water splitting activity as well as durability (at least 40 h both under 10 and 40 mA cm–2). Moreover, the facile electrospinning followed by the thermal treatment approach is economically practical for flexible film production, which has great potential for industrial application in water splitting technology. [ABSTRACT FROM AUTHOR]

The flexible conducting polymer films (FCPs) with fused ring structure is of great significance in the field of flexible electronics, yet their preparation is challenging. The mechanical properties can be improved by introducing boric acid groups to FCPs. Herein, free‐standing poly (1‐naphaneneboronic acid) (PNBA) film with a conductivity of 3 × 10−4 S cm−1 is readily prepared by electrochemical polymerization of 1‐naphaneneboronic acid. The PNBA film exhibits good redox activity and electrochemical stability. Fourier transform infrared spectrum proves that polymerization site of the as‐prepared PNBA occurs at C5 and C8 positions. The UV–Vis spectrum proves that the optical band gap of PNBA is 2.76 eV. In addition, thermal analysis reveals that the polymer displays excellent thermal stability. Fluorescence spectroscopy results show that PNBA film is a good green light‐emitting material. These characteristics indicate that free‐standing flexible PNBA film has potential applications in flexible electronic semiconductors, fluorescent materials and electrochemical sensors. [ABSTRACT FROM AUTHOR]

In order to subdue the obvious problem of uneven electric field distribution on regularly used copper/aluminum current collectors for alkali metal batteries, graphene on porous stainless steel (pSS_Gr) was fabricated using the ion etching technique that is employed as an effective host for lithium and sodium metal anodes. The binder‐free pSS_Gr demonstrated stable Li plating and stripping at areal current and capacity of 6 mA cm−2 and 2.54 mAh cm−2, respectively, for over 1000 cycles with 98% coulombic efficiency (C.E.). Also, in the case of Na metal anode, the host has shown stable performance at 4 mA cm−2 and 1 mAh cm−2 over 1000 cycles with ∼100% C.E.. Further, a full cell composed of Li‐plated pSS_Gr as an anode and LiFePO4 as a cathode is electrochemically tested at 50 mA g−1 current density with stable 100 cycles. [ABSTRACT FROM AUTHOR]

Properly engineered heterojunction photocatalysts warrant a more effective way to facilitate the separation of photoexcited electron-hole pairs and consequently bolster the photocatalytic hydrogen evolution performance. Herein, 3D bicontinuous nanoporous reduced graphene oxide (np-rGO) is served as a free-standing supporting matrix for the anchorage of CdS nanoparticles to obtain the highly efficient photocatalysis system for hydrogen production. The bicontinuous internal ligament and open nanopores in 3D nanoporous heterojunction are conducive to multiple reflecting and scattering of the incident light, leading to improved light absorption and utilization capacity. Moreover, the construction of p-n heterojunction with staggered band alignment is achieved in CdS/np-rGO to accelerate the transport of photo-excited carriers. The constructed CdS/np-rGO p-n heterojunction achieves a corresponding hydrogen generation rate of 2171.23 μmol g−1 h−1, which is 3.6 times in comparison with bare CdS. DFT calculations also indicate the preferable photocatalytic performance of CdS/np-rGO could be assigned to the ideal interfacial charge rearrangement on the heterointerface, which optimizes the H* adsorption kinetic energies and leads to a remarkable enhancement in the charge separation efficiency. It is anticipated this work could provide new sight for making the best usage of sunlight to produce solar fuel. [Display omitted] • 3D free-standing nanoporous heterostructures are prepared. • P-n junction with staggered band alignment promotes charge separation. • Ideal interfacial charge rearrangement optimizes the H* adsorption free energies. [ABSTRACT FROM AUTHOR]

The development of high-performance solid-state electrolyte (SSE) films is critical to the practical application of all-solid-state Li metal batteries (ASSLMBs). However, developing high-performance free-standing electrolyte films remains a challenging task. In this work, we demonstrate a novel scalable solvent-free process for fabricating high ceramic content composite solid-state electrolyte (HCCSE) films. Specifically speaking, a mixture of ceramic and polymer is dry mixed, fibered, and calendered into a free-standing porous ceramic film, on which polymer precursor is coated and polymerized to bridge the inorganic ceramic particles, resulting in a flexible HCCSE film with a ceramic content of up to 80 wt.%. High ceramic content not only leads to high ionic conductivity but also brings good mechanical properties; while the organic phase enables electrode electrolyte interfacial stability. When Li10GeP2S12 (LGPS) and polymeric ionic liquid-based solid polymer electrolytes (PIL-SPEs) were used as the inorganic and organic phases, respectively, the room temperature ionic conductivity of the resulted HCCSE reaches 0.91 mS·cm−1. Based on this HCCSE, Li∥Li symmetric battery cycled stably for more than 2,400 h with ultra-low overpotential, and ASSLMBs with different cathodes (LiFePO4 and sulfurized polyacrylonitrile (PAN-S)) present small polarization and decent cyclability at room temperature. This work provides a novel scalable solvent-free strategy for preparing high-performance freestanding composite solid-state electrolyte (CSE) film for room temperature ASSLMBs. [ABSTRACT FROM AUTHOR]

In this study, we introduce a novel method for synthesizing a free-standing, high-aspect-ratio TiO2 nanotubular (TNT) hybrid membrane. The TNT membrane was fabricated using a two-step electrochemical anodization process, incorporating lactic acid as an additive to enhance mechanical properties and growth rate. The membrane was then hybridized with a rubber polymer binder. The high aspect ratio and structural integrity of the TiO2 nanotubular hybrid membrane make it an ideal candidate for improving non-flammable properties when employed as a ceramic separator. Flame retardation tests revealed that the TNT hybrid membrane kept its structural integrity even after prolonged exposure to flame. These findings suggest that this hybrid membrane could be a valuable addition to the field of secondary batteries, offering potential applications in enhancing battery safety and performance.

[Display omitted] Potassium-ion batteries (PIBs) have attracted enormous attention due to the increasing lithium battery cost, but their development is still in the pre-mature stage due to the limited selection of electrodes. Herein, a free-standing current-collector-integrated electrode, composed of mixed-phase WS 2 nanosheets with nitrogen-doped multichannel carbon nanofibers (N -MCNFs) membrane, is reported for high-performance potassium ion batteries anode. Benefiting the unique multichannel carbon nanostructure as a current collector-integrated electrode as well as mixed-phase lamellar structure WS 2 for enhanced potassium ion entry, the 1T/2H-WS 2 / N -MCNFs hybrid current-collector-free anode delivers an outstanding areal capacity of 2.88 mAh cm−2 (corresponding to 411 mAh/g based on the mass of both electrode and current collector) at a current of 0.7 mA cm−2 as well as long-term cycling stability for over 1000 cycles at a high current of 14 mA cm−2, surpassing the current state-of-art PIB anode. It is believed that our findings based on the high energy current collector integrated electrode at high mass loading would boost future research on practical metal ion batteries. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are regarded as the ideal low-cost choice for next-generation large-scale energy storage system. Carbonyl-based organic salt-disodium rhodizonate (Na2C6O6) with high theoretical specific capacity (501 mAh·g−1) is considered as a promising cathode material for SIBs. However, the dissolution of active material in electrolyte and low electronic conductivity lead to rapidly capacity decay and poor rate performance. Herein, a simple method is designed to construct free-standing and flexible Ti3C2Tx Na2C6O6/MXene paper via vacuum-assisted filtration and antisolvent approach. The MXene can form an electronic conductive network, adsorb the active materials, and offer additional active sites for Na storage. The binder-free Na2C6O6/MXene paper delivers excellent electrochemical property with a high rate performance of 231 mAh·g−1 at 1,000 mA·g−1 and a high capacity of 215 mAh·g−1 after 100 cycles. This work provides an attractive strategy for designing high-performance organic electrode materials of SIBs. [ABSTRACT FROM AUTHOR]

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We introduced a new concept to develop a membrane with ultralong hydrogel-functionalized MnO2 nanowires. With its facile and cost-effective synthesis process, this spiral-windable and robust membrane with high separation performance has great potential for its application on an industrial scale to treat oily wastewater under harsh environments. [Display omitted] • A new membrane was constructed with ultralong hydrogel-functionalized MnO 2 nanowires. • The membrane shows high flux, high separation efficiency and low fouling tendency. • A spiral-windable membrane is adaptable for various membrane configurations. • This membrane endures harsh working environments in industry. An ideal membrane for oil/water separation at industrial scale is expected to possess the combined merits of excellent separation performance, sound mechanical flexibility, and high durability under harsh environments. In response to these challenging requirements, we came up with a new concept to design the membrane constructed with ultralong hydrogel-functionalized MnO 2 nanowires. The super-oleophobic nanowires form highly open and tight pore structures within the membrane, which endows its high permeation flux (2800 L h−1 m−2 bar−1), high oil/water separation efficiency (>99 %) and low fouling tendency for separating emulsified oil from water. Furthermore, the brittleness problem of MnO 2 materials is collectively resolved due to the high aspect ratio and surface functionalization of the hydrogel-functionalized MnO 2 nanowires. This results in the new membrane with extraordinary mechanical flexibility and potential for spiral-wound membrane modules, which are highly desired in industrial applications due to a lower footprint and lower capital cost. The new membrane also demonstrates high durability under harsh environments with non-neutral pH values or high salinities. Given its facile synthesis process and inexpensive materials, this spiral-windable and durable membrane with high separation performance has the great potential to be applied at industrial scale for oily wastewater treatment under harsh environments. [ABSTRACT FROM AUTHOR]

The role of Photovoltaic technologies integrated or attached to the building envelope is crucial in managing the building energy demand. In this paper, the performance of PV technologies with the mounting methods of Building integrated and Free-standing (Building attached) is discussed for six different climate zone of the country. A PVGIS program proposed with three PV cell technologies (Crystalline Silicon, Copper indium diselenide, Cadmium Telluride) is used to evaluate monthly energy generation potential and losses of the 2 kWp grid-connected PV system at the latitude and 90°. A 2 kWp PV system is chosen for Economic Weaker Section (EWS) housing schemes depending upon the roof area. From the evaluation, the performance parameter has been estimated. A new parameter Energy Deviation (ED), is proposed to choose the best PV technology in terms of performance. The results of ED agree with the parameters Performance Ratio (PR) and Capacity Factor (CF) defined under the IEC Standard 61724. The potential generation of PV technologies at 90° varies from 41% (Warm and Humid) to 64% (Cold and Sunny) when compared with the latitude. In case of Cold and Sunny and Cold and Cloudy at 90°, the generation performance of Copper indium diselenide is found better in Building integrated and Free-standing mounting methods, respectively. For the remaining zones, Cadmium Telluride technology shows better results. The Percentage loss in the system is found to be minimum in the case of Cold and Sunny, varies between 17% and 25%, and maximum is found for Warm and Humid and varies between 23.2% and 33.4% for the proposed PV technologies. The grid feed-in energy from these EWS houses for all the technologies and climatic zones is found above 45%. It is seen that the combined energy generation from the envelopes (Roof, walls, and facades) makes the houses energy plus in nature. The study has important implications for the government to promote the building integrated Photovoltaic policies in the country.

Abstract Background Evidence is emerging for the use of overground lower limb robotic exoskeletons in the rehabilitation of people with spinal cord injury (SCI), with suggested benefits for gait speed, bladder and bowel function, pain management and spasticity. To date, research has focused on devices that require the user to support themselves with a walking aid. This often precludes use by those with severe trunk, postural or upper limb deficits and places the user in a suboptimal, flexed standing position. Free-standing exoskeletons enable people with higher level injuries to exercise in an upright position. This study aimed to evaluate the feasibility of therapy with a free-standing exoskeleton for those with SCI, and to determine the potential health-related benefits of this intervention. Methods This 12-week intervention study with 12-week waitlist control and 12-week follow up, provided people with SCI scoring

Lithium-ion batteries (LIBs) have been used in many fields, such as consumer electronics and automotive and grid storage, and its applications continue to expand. Several studies have attempted to improve the performance of LIBs. In particular, the use of high-capacity silicon and tin as anodes has been widely studied. Although anodes composed of silicone and tin have high theoretical capacities, poor electrical conductivity and considerable volume expansion of such anodes deteriorate the LIB performance. Thus, Li4Ti5O12 (LTO), a zero-strain material, has attracted much attention with high cycle stability and rate capability through improved electrical conductivity. However, LTO has the disadvantages of a low electrical conductivity (10−8 to 10−13 S cm−1) and moderate Li+ ion diffusion coefficient (10−9 to 10−16 cm2 s−1). In this study, the flexible and free-standing composite films were fabricated using only LTO and multi-walled carbon nanotube(CNT) with high electrical conductivity and ion diffusivity. The prepared LTO/CNT films showed a higher charge/discharge capacity than the theoretical capacity of the LTO electrode. [ABSTRACT FROM AUTHOR]

[Display omitted] The design and discovery of free-standing hybrid electrode materials with large absolute capacity and high cycling stability for energy storage become desirable and are still challenging. In this work, we demonstrate that the hybrid supercapacitor (HSC) device is assembled by 3D core–shell hierarchical nanorod arrays of Ni 3 S 2 @NiCoP nanocomposite for the first time. The Ni 3 S 2 @NiCoP nanocomposite is successfully synthesized through a facile stratagem containing hydrothermal process and the subsequent electrodeposition method. The 3D architecture of Ni 3 S 2 @NiCoP hybrid electrode composed of vertically aligned "hyperchannel" 1D Ni 3 S 2 nanorods and highly conductive interconnected 2D nanosheets of NiCoP is beneficial to fast electron transfer kinetics, thus leading to enhancing the ionic and electronic conductivity, kinetics of redox reaction, and synergistic behavior of active species. The fabricated HSC device with Ni 3 S 2 @NiCoP electrode delivers outstanding areal capacity of 109 µAh cm−2 at a current density of 1 mA cm−2, brilliant energy density of 74.9 Wh kg−1 at a power density of 700 W kg−1, and prominent cyclic performance of 92% capacity retention even after 144-h floating test. This work demonstrates that the core–shell hierarchical nanorod arrays of Ni 3 S 2 @NiCoP can be viewed as one of the novel battery-type electrode materials for high-performance HSCs. [ABSTRACT FROM AUTHOR]

The carbon nanofiber-based all-solid-state supercapacitors hold great promise in powering portable electronics, while the low specific capacitance and intrinsic fragility have hindered their practical application. Here, flexible N-doped hollow carbon nanofibers (HCNFs) were prepared using poly-(acrylonitrile-co-acrylamide) as a precursor by the coaxial electrospinning method. The leaf-like NiCo2O4 nanosheets are located on the inner and outer walls of the carbon layer via a simple solvothermal method to construct 3D freestanding NiCo2O4/HCNFs electrodes for a flexible all-solid-state supercapacitor. The hollow structure of HCNFs provides both inner and outer surfaces for NiCo2O4 nanosheets and shortens the distance of ion transportation. NiCo2O4/HCNFs possesses an enhanced specific capacitance of 1864.0 F g–1 at 1 A g–1 and a good capacitance retention capability of 91.7% after 5000 times cycling, which is one of the best reported cycling stabilities to date. The symmetrical all-solid-state supercapacitors (ASSCs) were directly prepared with NiCo2O4/HCNFs as an electrode without adding any conductive agents and binders, which have good flexibility and a maximum energy density of 44.3 W h kg–1 at a specific power of 814.8 W kg–1. Five series-connected ASSCs assembled by NiCo2O4/HCNFs can lighten a "DHU" logo composed of 36 light-emitting diodes, indicating their potential application prospect in wearable and portable devices. [ABSTRACT FROM AUTHOR]

Cells coordinate their activity and regulate biological processes in response to chemical signals. Mimicking natural processes, control over the formation of artificial supramolecular materials is of high interest for their application in biology and medicine. Supramolecular material that can form in response to chemical signals is important for the development of autonomously responsive materials. Herein, a supramolecular hydrogel system is reported enabling in situ generation of hydrogelators in response to a specific chemical signal. Using self-immolative chemistry, spatial control over the formation of supramolecular hydrogel material and structured free-standing hydrogel objects via providing H 2 O 2 locally is demonstrated. In addition, a hybrid system is developed enabling in situ generation of the H 2 O 2 by the action of an enzyme and glucose, providing an extra handle for the development of an intelligent soft material. This generic design should enable the use of various (chemical)stimuli that can be obtained via coupling different stimuli and various chemical and/or biological markers and appears a versatile approach for the design of smart artificial soft materials that can find application in theranostic purposes., (© 2024 Wiley‐VCH GmbH.)

Free-standing micro-supercapacitor (MSC) devices without substrate or current collectors are promising for practical applications. However, it is still difficult to prepare high-performance free-standing MSC devices because of the requirement of optimized active sites, conductivity, ion diffusion, controlled patterns, moisture susceptibility, etc. Here, it is proposed that the optimization of oxygen level on graphene is promising to solve these requirements because of the balance of sp 2 and sp 3 hybridization. Using the medium-oxidized graphene, the flexible, conductive, hydro-stable, easy-processing film can be facilely obtained, which facilitates the preparation of free-standing MSC electrodes. After constructing with gel electrolyte, the free-standing MSC device shows a high capacitance of 898.4 mF cm -2 using aqueous-gel electrolyte and 383.6 mF cm -2 using ion-gel electrolyte with mass loading of ca. 10 mg cm -2 . Correspondingly, the MSC device can achieve a landmark energy density of 42.6 µWh cm -2 at 0.85 mW cm -2 (7.1 mWh cm -3 at 141.7 mW cm -3 ). The advantages of high performance, facile preparation, and low inactive components make the free-standing MSC device promising for practical applications., (© 2024 Wiley‐VCH GmbH.)

Free-standing reduced graphene oxide (RGO) hydrogel was synthesized through two-stepped hydrothermal reduction treatment of aqueous graphene oxide (GO) suspension. GO with high interface affinity for overlapping of cross-linking graphene sheets contributes to forming steady-state RGO hydrogel. RGO hydrogel shows higher B band/G band intensity ratio than GO suspension in Raman spectrum analysis, indicating well-restored hexagonal carbon rings with the enhanced crystal structure. Free-standing RGO hydrogel could be directly acted as supercapacitor electrode without using any substrate material. The specific capacitance decreases from 253.9 to 92.3 F g−1 in 1.0 M Na2SO4 electrolyte and from 275.3 to 125.9 F g−1 in 1.0 M KOH electrolyte when the current density increased from 0.3 to 4.0 A g−1, presenting the capacity retention of 36.4% and 45.7% respectively. Free-standing RGO hydrogel presents specific capacitance in alkaline KOH electrolyte rather than neutral Na2SO4 electrolyte. KOH electrolyte with superior ionic diffusion coefficient of hydroxyl ion leads to higher current response and electrical double-layer capacitance performance. The capacitance retention ratio of 97.8% at 4.0 A g−1 in 1.0 M KOH electrolyte after 1000 charge-discharge cycles presents superior cycling stability. Accordingly, free-standing RGO hydrogel applied well as superior supercapacitor electrode presents the promising energy storage application. [ABSTRACT FROM AUTHOR]

By tactfully utilizing the different chemical characteristics of Bi and Ni element in the electrodeposition process, this work successfully designs a novel free-standing NiO/Bi@Bi 2 O 3 hybrid electrode with dual electroactive components (NiO and Bi@Bi 2 O 3) and hierarchically porous structure. After co-electrodeposition, the porous Bi metal as a conductive skeleton can effectively improve the electrical conductivity of the electrode. Moreover, Bi 2 O 3 and NiO have synergistic effects by modifying the electronic structure. The newly developed bimetallic NiO/Bi@Bi 2 O 3 hybrid electrode exhibits high volumetric capacitance value of 1166.67 F cm−3, which is attributed to the dual advantages of structure and composition. This work provides a new idea for the design of high-performance transition metal oxide-based electrodes. [ABSTRACT FROM AUTHOR]

A novel binder, PTMSP to synthesize flexible free-standing electrodes without any current collector supporting was reported for the first time, and the batteries assembled with the PTMSP binder demonstrated outstanding discharge capacity and cycling stability. [Display omitted] • A flexible free-standing electrode without any current collector was successfully constructed by using PTMSP as the binder. • The PTMSP binder has a certain universal performance which shows an excellent performance in various electrode materials. • Owing to the advantage of using electrodes without current collector, the discharge capacity has theoretically increased. As a crucial component of the electrode, the binder greatly impacts battery performance. Herein, we report a novel binder, poly[1-(trimethylsilyl)-1-propyne] (PTMSP), which enables the construction of flexible free-standing electrodes for high performance lithium-ion batteries. The free-standing electrodes based on the PTMSP binder demonstrate remarkable cycling performance in various electrode materials, including LFP, S, and LTO, demonstrating significant potential for market application. [ABSTRACT FROM AUTHOR]

The development of smart negative electrode materials with high capacitance for the uses in supercapacitors remains challenging. Although several types of electrode materials with high capacitance in energy storage have been reported, carbon-based materials are the most reliable electrodes due to their high conductivity, high power density, and excellent stability. The most common complaint about general carbon materials is that these electrode materials can hardly ever be used as free-standing electrodes. Free-standing carbon-based electrodes are in high demand and are a passionate topic of energy storage research. Electrospun nanofibers are a potential candidate to fill this gap. However, the as-spun carbon nanofibers (ECNFs) have low capacitance and low energy density on their own. To overcome the limitations of pure CNFs, increasing surface area, heteroatom doping and metal doping have been chosen. In this review, we introduce the negative electrode materials that have been developed so far. Moreover, this review focuses on the advances of electrospun nanofiber-based negative electrode materials and their limitations. We put forth a future perspective on how these limitations can be overcome to meet the demands of next-generation smart devices.