Search

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]

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 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]

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]

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]

Biomass materials with great advantages of wide accessibility, low cost and environmental benignity have favorable application prospects as Si anodes for lithium-ion batteries (LIBs). In order to alleviate the volume effect and improve the conductance of Si, we fabricated a conductive copper ion-reinforced sodium alginate (SA) aerogel based free-standing Si anode (Si@CNTs/Alg-Cu-II) containing silicon nanoparticles, sodium alginate aerogel, carbon nanotubes and Cu nanoparticles, via a simple, low-cost and sustainable process (under 1 × 10−1 Pa, 1 °C/min to 200 °C holding for 1 h). In the irregular lamellar porous aerogel, silicon particles with good dispersion are bound by macromolecular chains of SA via dynamic hydrogen bonds and subsequently restrained in the porous aerogel to release volume stress. The in situ generated Cu particles and well-dispersed carbon nanotubes (CNTs) construct the conductive network around Si particles to improve the electrical conductivity of the electrode. This unique structure delivers a capacity of 835.6 mAh/g after 100 cycles at 0.1 A/g based on the total mass of Si@CNTs/Alg-Cu-II composite (Si content of 25.62%). Moreover, it also shows outstanding stability under high current density (a capacity retention of 84.1% after 100 cycles at 0.5 A/g). The sustainable preparation method and excellent electrochemical performance of Si@CNTs/Alg-Cu-II provide a new strategy to develop high-performance free-standing Si-based anodes for LIBs. • Cu ion-reinforced sodium alginate aerogel was designed as a free-standing Si anode. • The in situ reduced Cu particles and CNTs construct the conductive network around Si. • The electrode delivers a capacity of 835.6 mAh/g after 100 cycles at 0.1 A/g. • The electrode exhibits an outstanding stability with a capacity retention of 84.1%. • The fabrication process is truly green and environmental friendly. [ABSTRACT FROM AUTHOR]

[Display omitted] Flexible electrode plays a key role in flexible energy storage devices. The SnTe/C nanofibers membrane (SnTe/CNFM) with excellent mechanical flexibility has been successfully synthesized for the first time through electrospinning, and it demonstrates outstanding electrochemical performance as free-standing anode for lithium/sodium-ion batteries. The SnTe/CNFM electrode delivers a discharge capacity of 526.7 mAh g−1 at 1000 mA g−1 after 1000 cycles in lithium-ion half-cells and a discharge capacity of 236.5 mAh g−1 at 500 mA g−1 after 80 cycles in lithium-ion full-cells with a LiFePO 4 cathode. Not only that, it shows a discharge capacity of 182.7 mAh g−1 at 200 mA g−1 after 200 cycles in sodium-ion half-cells and a high discharge capacity of 207.0 mAh g−1 at 500 mA g−1 after 50 cycles in sodium-ion full-cells with a Na 0.44 MnO 2 cathode. Moreover, the prepared SnTe/CNFM exhibits good mechanical flexibility. The SnTe/CNFM can still return to its original state without any breakage after bending, curling, folding and kneading. These results indicate that SnTe/CNFM is expected to become one of the promising free-standing anodes for lithium/sodium-ion batteries. [ABSTRACT FROM AUTHOR]

• Free-standing Si/rGO film was prepared using lyotropic liquid crystallinity of GO. • Si is embedded into interlayers of graphene to form an ordered layer-to-layer stacking structure. • Dispersion of Si was quantitatively described via zeta potential with average particle size. • Si/rGO film shows a high discharge capacity of 1727.2 mAh/g with superior cycling stability. Silicon (Si) is regarded as the most promising anode candidate for the next high energy density lithium ion batteries (LIBs) owing to its highest theoretical specific capacity and low lithiation potential. However, the practical application of Si-based materials is severely limited due to their enormous volume expansion, which leads to the breakdown of the electrode structure and shortens the cycle life. Herein, we successfully fabricated a free-standing graphene encapsulated silicon nanospheres (Si/rGO) film through homogenizing nano-Si in the lyotropic liquid crystallinity of graphene oxide (GO), followed by coating on the PET substrate and hot pressing technology. For the first time during the preparation process, the dispersion of nano-Si in deionized water was quantitatively characterized through real-time measurements of zeta potential and average particle size. Benefiting from the highly ordered layer-to-layer stacking and dense framework, the as-prepared Si/rGO film shows a high initial discharge capacity of 1727.2 mAh/g at 200 mA/g and superior cycling stability (1024.2 mAh/g over 200 cycles). This straightforward and easy-to-implement method can be used for industrial-scale production through continuous feeding. [ABSTRACT FROM AUTHOR]

Rationally engineered anode materials with high specific capacities and rate capability are essential for lithium-ion batteries (LIBs). In this paper, a free-standing anode composed of Co3S4 nanosheets arrays and carbon cloth (abbreviated Co3S4@CC) was fabricated for high performance LIBs. The three-dimensional (3D) porous carbon cloth could not only improve the conductivity but also boost Li + transfer and increase contact area for reactions. Besides, the porous thin Co3S4 nanosheets possessing strong interaction with carbon cloth by formation of C–S bond and high surface area could facilitate the mitigation of volume expansion and reduction of Li + diffusion distance, coupling with efficient contact with electrolytes during cycling process. As expected, the freestanding Co3S4@CC anode presents pseudocapacitance-dominated storage behavior with a very high specific capacity of 847 mAh g − 1 at 250 mA g − 1 after 100 cycles and good rate capability for LIBs. This work provides an approach for designing metal sulfides with high capacities and rate capability for LIBs, especially flexible LIBs. Resulting from strong interaction of porous Co3S4 nanosheets and carbon cloth, coupling with enhanced pseudocapacitance-storage, Co3S4/CC anode presents a high reversible capacity and good rate performance. Moreover, Co3S4 was directly grown on carbon cloth without any binders and conductive carbon, saving costs and preparation process of the electrode, which is beneficial to the development of metal sulfides in other applications, including catalysis and flexible batteries. [ABSTRACT FROM AUTHOR]

Recently, Li‐ion batteries (LIBs) have attracted extensive attention owing to their wide applications in portable and flexible electronic devices. Such a huge market for LIBs has caused an ever‐increasing demand for excellent mechanical flexibility, outstanding cycling life, and electrodes with superior rate capability. Herein, an anode of self‐supported Fe3O4@C nanotubes grown on carbon fabric cloth (CFC) is designed rationally and fabricated through an in situ etching and deposition route combined with an annealing process. These carbon‐coated nanotube structured Fe3O4 arrays with large surface area and enough void space can not only moderate the volume variation during repeated Li+ insertion/extraction, but also facilitate Li+/electrons transportation and electrolyte penetration. This novel structure endows the Fe3O4@C nanotube arrays stable cycle performance (a large reversible capacity of 900 mA h g−1 up to 100 cycles at 0.5 A g−1) and outstanding rate capability (reversible capacities of 1030, 985, 908, and 755 mA h g−1 at 0.15, 0.3, 0.75, and 1.5 A g−1, respectively). Fe3O4@C nanotube arrays still achieve a capacity of 665 mA h g−1 after 50 cycles at 0.1 A g−1 in Fe3O4@C//LiCoO2 full cells. [ABSTRACT FROM AUTHOR]

Flexible and free-standing electrode materials are prerequisite and key components for next-generation flexible energy storage and conversion devices. However, it is still a chanllenge to fabricate these materials from a continuous, straightforward, and facile method. Herein, we report a flexible composite film with silicon oxides decorated on few-walled carbon nanotubes, which can be continuously fabricated and directly drawn from the hot zone of the reactor. The composite film can be readily used for electrochemical lithium ion storage with high and reversible specific capacity, good rate capability, and excellent cycling performance. These exceptional characteristics make it very promising for flexible energy storage and other emerging applications. A continuous, flexible, and free-standing composite SiO x /CNTs film has been fabricated by the one-step and direct-injection floating catalyst chemical vapor deposition method and utilized for high performance electrochemical lithium ion storage. The materials' very unique and favorable structural and compositional characteristics have resulted in high capacity, excellent rate capability, and good cyclability for lithium ion storage applications. Image 1 [ABSTRACT FROM AUTHOR]

MnO is one of the most attractive anode materials for Li ion batteries (LIBs) due to its high theoretical capacity and low voltage hysteresis. However, its inherent low conductivity and large volume expansion hinder real application. Herein, we construct a flexible freestanding film of MnO quantum dots, N-doped carbon layer and carbon nanotubes by an effective method and demonstrate its direct application as an anode for LIBs. The microstructure observations reveal that well-dispersed MnO quantum dots with the average of 2–5 nm attach tightly on highly conductive carbon nanotube substrates and covered by N-doped carbon layers. Such unique nanocomposite structure provides effective carbon protective layers to accommodate volume change, ensure almost the whole surface of each MnO quantum dots to attend electrochemical reaction, and increases electron conductivity and reduces Li+ diffusion distance. Furthermore, kinetic analysis and characterization tests indicate that capacitive contribution for Li storage in the freestanding film is calculated to be high and further oxidation of Mn2+ to higher valence state upon cycling generates lots of specific capacity, thus endowing it with excellent rate, ultrahigh capacity and outstanding cycling stability. The flexible freestanding anode delivers ultrahigh capacity of 1741mAh g−1 after 120 cycles at 0.1 A g−1, a high-rate capability of 858 mAh g−1 at 3.2 A g−1 after 120 cycles at 0.1 A g−1, and long-term cycling stability with a capacity of 136.5% at 1.0 A g−1 after 1000 cycles. The unique nanostructure design is believed to have great potential in general synthesis of the composite consisted of CNT and oxide quantum dots for energy storage. Image 1 [ABSTRACT FROM AUTHOR]

A facile chemical bath deposition method to grow 10-nm-thick ZnO nanoflakes (NFs) on carbon cloth (CC) was developed; further, free-standing, flexible lithium-ion -battery (LIB) anodes with good electrical contact between current collector and the active substance were prepared. The as-prepared ZnO NFs/CC-based LIB anodes showed a high specific capacity of 1754 mAh g−1 at a current density of 0.1 A g−1, a capacity retention of almost 52.9% at a current density of 2 A g−1, as well as high rate capability. Moreover, the anodes demonstrated a high capacity with reversiblity of approximately 1650 mAh g−1 and only 6% capacity fading at a current density of 0.1 A g−1, even after 100 cycles. These results imply that the synthesized, unique ZnO NFs/CC nanostructures can be employed as high-efficiency anode materials for flexible LIBs. [ABSTRACT FROM AUTHOR]

Freestanding thin film electrodes are competitive candidate materials for high-performance energy stockpile equipment due to their self-supporting structure and because they lack any polymer binder or conductive additive. In our work, a porous carbon nanofiber film (PCNF) electrode has been synthesized via a convenient and low-cost electrospinning approach and the following carbonization and air etching process. The obtained PCNF electrode sample shows a high reversible capacity (1138 mAh g−1 at 0.1 C), remarkable rate capacity (101.2 mAh g−1 at 15 C), and superior cycling stability with a lower capacity decay rate of ~0.013% each cycle upon 1000 cycles (278 mAh g−1 at 5 C). The prominent electrochemical performance of PCNF can be put down to the stable self-supporting conductive structure and the porous feature in each carbon nanofiber, which will significantly promote the transfer tempo of Li-ion and electron and relieve the large volume change during inserting lithium ion. More interestingly, this work exhibits a low-cost and primitive strategy to fabricate thin film anode for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

MoO 2 with low electrical resistivity and high specific capacity as anode for lithium ion batteries is hindered because of its large volume variation during Li + insertion/extraction process, which leads to fast capacity fading. Herein, three-dimensional (3D) core-shell MoO 2 @few-layered MoS 2 covered by S-doped graphene (MO/MS/SG) aerogel has been fabricated through hydrothermal reaction and freeze-drying process together with sulfidation. MoO 2 nanoparticles coated by few-layer MoS 2 can promote good dispersion of MoO 2 nanoparticles and avoid the restacking of MoS 2 . S doping in graphene can increase the defects and active sites. S-doped graphene aerogel as flexible framework and conductive network not only provides the transmission path for ions and electrons, but also maintains the structural integrity of electrode during cycles. Core-shell MoO 2 @few-layer MoS 2 hybrid well-dispersed in S-doped graphene matrix buffers the volume changes during cycles and contributes to high reversible capacity. Free-standing electrode without binder and current collector prevents the separation of electrode materials from current collector during cycles. Benefitting from the unique structures, the MO/MS/SG aerogel as anode for lithium ion battery exhibits high reversible capacities of 683 mAh g −1 at 0.1 A g −1 after 100 cycles and 533 mAh g −1 at 0.5 A g −1 after 350 cycles together with excellent rate capability. This work demonstrates the potential application of the Mo-based materials in lithium ion batteries. [ABSTRACT FROM AUTHOR]

Highly mesoporous cobalt oxide nanosheets are grown on nickel foam (M-Co 3 O 4 /NF) by a hydrothermal method. Ag nanoparticles with 10–50 nm diameters are uniformly distributed on the surface of the mesoporous Co 3 O 4 nanosheets (Ag/M-Co 3 O 4 /NF) after chemical bath reaction. Moreover, we discovered that the homogeneous distribution of Ag nanoparticles on free-standing, highly mesoporous Co 3 O 4 nanosheets showed the synergistic effect of the high electrocatalyst reactions toward the ORR from Ag and OER from M-Co 3 O 4 . Highly mesoporous Co 3 O 4 nanosheets with a thickness of 10 nm as free-standing cathode for Li-O 2 battery are beneficial to accommodating insoluble discharge products and facilitating oxygen diffusion and electrolyte impregnation. Ag nanoparticles can improve the electrical conductivity of the O 2 electrode and provide a catalytic activity for ORR at the same time. The Ag/M-Co 3 O 4 /NF exhibited a robust catalytic activity as cathode for Li-O 2 batteries with a high reversible capacity of 2471.1 mA h g −1 , a low discharge/charge overpotential, and a cycle life of 124 cycles (under the curtaining capacity of 500 mA h g −1 ). The preliminary results indicate that Ag/M-Co 3 O 4 /NF is an efficient and stable bifunctional cathode for Li-O 2 batteries. [ABSTRACT FROM AUTHOR]

Highly flexible free-standing electrodes for flexible lithium-ion batteries (LIBs) are prepared by casting slurry on a glass substrate and detaching the film after drying. The slurry is composed of lithium cobalt oxide (LiCoO 2 ) as a cathode material and Super-P as a conductive agent. These are currently used in conventional electrode fabricating. The flexible electrode contains the similar constituents and composition to the electrodes in commercial LIBs, but does not include metal foil as a current collector as that limits the flexibility of the LIB. Polyvinylidene fluoride (PVDF) with hexafluoropropylene (HFP) is used as a binder instead of PVDF alone due to its better mechanical properties (tensile stress, strain, and peel-off strength). In order to compensate for the low electronic conductivity of flexible electrodes without metal foil, a carbon nanotube (CNT) is incorporated into the electrode. The flexible electrodes offer great flexibility with the ability to be bent and folded without deforming. The flexible electrode exhibits high overpotential during charging/discharging process and inferior electrochemical performance (rate capability, energy density and cycling stability) to conventional electrodes with metal foil due to the low electronic conductivity but it delivers reasonable performance in a punch cell with an aluminum-deposited PET substrate as a current collector. Using CNT enhances the electrochemical properties of flexible electrodes, but weakens its mechanical strength at the same time. Therefore, the optimum amount of CNT needs to be determined. [ABSTRACT FROM AUTHOR]

Recent attention has been focused on the synthesis and application of flexible lithium-ion battery electrodes for the development of high-performance and durable electronic devices. Herein, we synthesize a novel composites with carbonized cotton covered by graphene/SnO 2 (CGN/SnO 2 ), in which SnO 2 nano-particles grow in-situ on the cotton fibers covered with graphene oxide (CGO) under the following thermal annealing process. The conductivity of the composites and the sizes of the SnO 2 particles in the composites could be expediently adjusted by changing the thermal annealing temperatures. The as-prepared flexible CGN/SnO 2 composites can be directly used as an anode for lithium-ion batteries without the addition of conductive additive, binder and current collector. The CGN/SnO 2 composites prepared at 500 °C have exhibited a good reversible specific capacity (calculated by the weight of whole electrode) of 406 mAh·g − 1 (1.70 mAh·cm − 2 ) after 80 cycles. This work provides an effective way for the metal oxide composed with flexible carbon framework, promising to develop a new portable electrochemical energy-storage electrode. [ABSTRACT FROM AUTHOR]

With the wearable electronics progressing rapidly, the demand for flexible, long-life and low-cost electrodes of Li-ion batteries (LIBs) becomes more and more urgent. Due to the abundant resources and low cost, silica (SiO 2 ), especially the amorphous one, has attracted a lot of interests on the application of anode materials for LIBs. However, SiO 2 still suffer from the poor cycling performance mainly caused by the huge volume change during cycling like other alloy-type materials. Furthermore, it remains a challenge to fabricate the SiO 2 –based flexible electrode. Herein, we propose a facile in situ strategy to fabricate the electrospun robust free-standing SiO 2 /carbon nanofibers (denoted as in-SCNFs) film constructed by N-doped carbon nanofibers encapsulating uniformly amorphous SiO 2 nanoparticles. The in situ synthesized finer SiO 2 nanoparticles in the in-SCNFs are uniformly encapsulated in flexible carbon nanofibers, which can effectively buffer the volume change. Furthermore, the robust in-SCNFs film possesses the excellent mechanical flexibility and strength. So, when served as the free-standing anode of LIBs, the in-SCNFs film exhibits superior cycling performance. A discharge specific capacity of 405 mAh/g can be delivered even after a long-term 1000 cycles at a large current density of 500 mA/g, and the retention is up to 115%. It is an exciting finding that the in-SCNFs film is also a long-life anode of Na-ion batteries (NIBs). The 99% of initial capacity can be kept after 250 cycles at 500 mA/g. To our best knowledge, this is the first report on the application of SiO 2 /C composite for NIBs. These results suggest that the as-fabricated in-SCNFs film can become one promising free-standing long-life anode for LIBs and NIBs. [ABSTRACT FROM AUTHOR]

ABSTRACT Flexible freestanding cotton-graphene (CGN) composites were prepared by a simple immersion and freeze-drying method and a thermal annealing process together. The composites had a constant cotton microstructure covered by graphene. The microstructure and morphology of the composites could be easily adjusted through the variation of the thermal annealing temperatures. Electrochemical tests demonstrated that the annealing temperatures had great effects on the electrochemical performances of the obtained composites. The CGN composite annealed at 700 °C exhibited a reversible capacity of 245.2 mAh/g after 100 cycles. Even after it was bent 1000 times, the CGN composite still maintained its superior electrochemical properties. The results suggest that because of its high flexibility and excellent conductive and electrochemical activities, the CGN composites could be used as lithium-ion battery anode materials on a large scale for corresponding applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44727. [ABSTRACT FROM AUTHOR]

To simplify the fabrication of electrode in batteries and improve the electrochemical performance, free-standing films composed of N-doped carbon incorporated TiO 2 hierarchical nanofibers were prepared via electrospinning followed by heat-treatment under a nitrogen atmosphere in this study. It is found that hierarchical nanofibers were formed at 700 °C or above due to the phase transformation and the presence of carbon matrix. The as-prepared film was tested as an anode in lithium-ion batteries and sodium-ion batteries. Electrochemical results demonstrate a high rate performance (180 mAh g −1 at 5 A g −1 in lithium ion batteries) and excellent cycle stability can be achieved in lithium-ion batteries as well as in sodium-ion batteries. This self-standing film is binder free and thus promising for scale-up applications for lithium-ion batteries and sodium-ion batteries with easy fabrication and satisfactory electrochemical performance. [ABSTRACT FROM AUTHOR]

It is necessary to build flexible and free-standing materials for flexible/wearable electronics in high-performance lithium-ions batteries. Herein, we design and fabricate a flexible and free-standing 3 D carbon/MoO 2 composite through a facile immersing method followed by an annealing process. The carbon framework is supported by non-woven cotton totally covered by graphene sheets. The nanosized MoO 2 particles were uniformly anchored on cotton fibers and graphene sheets. The structure has several advantages, such as an interconnected 3D electronically conductive network, plenty of channels for electrolyte solution cross, and more active points for the electrode reaction. Compared with cotton/MoO 2 (C/MoO 2 ) without graphene sheets, the CGN/MoO 2 composite (cotton covered by graphene/MoO 2 ) showed much better thermal stability and excellent cycling performance. The proposed synthesis process paves a new way as promising electrode materials for high power battery applications such as roll-up displays and wearable devices. [ABSTRACT FROM AUTHOR]

A facile strategy is designed for the fabrication of flexible and free-standing ternary CoSnO 3 /graphene/carbon nanotubes (CoSnO 3 /GN/CNTs) composite papers through a simple filtration, followed by annealing process. The CoSnO 3 /GN/CNTs composite papers with high flexibility and tailorability can be easily fabricated. The CoSn(OH) 6 nanoparticles/graphene oxide/carbon nanotubes (CoSn(OH) 6 /GO/CNTs) composite papers obtained by a simple filtration method are transformed into CoSnO 3 /GN/CNTs composite papers after a thermal treatment process. In this unique composite structure, CoSnO 3 nanoparticles (nanocubes and nanoboxes) are embedded homogenously into the 3D framework of graphene and carbon nanotubes, respectively, in which offers not only a 3D conductive network and a dual restriction on the aggregation of CoSnO 3 nanoparticles, but also accommodates the large volume expansion of CoSnO 3 nanoparticles. When used directly as binder- and conductive agent-free anodes for lithium-ion batteries, the CoSnO 3 /GN/CNTs composite papers exhibit superb electrochemical properties including extraordinary reversible capacities, superior rate capabilities and stable cycle performances compared to CoSnO 3 nanoparticles and GN/CNTs paper, suggesting a new pathway for the rational engineering of anode materials. [ABSTRACT FROM AUTHOR]

As one of binary transition metal oxides, NiCo 2 O 4 (NCO) suffers from several problems like self–agglomeration and drastic volume change when used as an anode for lithium–ion batteries (LIBs). Herein, we propose a facile one–step hydrothermal method combined with heat treatment to prepare a hierarchical micro–nano hydrangea–like NiCo 2 O 4 /V 2 O 3 composite array (denoted as NCO/VO) on a nickel foam substrate as a free–standing anode for LIBs. The V 2 O 3 is introduced to form a composite structure with NCO, improving the electronic and ionic conductivity of the electrode. The synergistic effect of porosity, composite structure and micro–nano architecture offers the electrode excellent electrochemical performance. The specific capacity of the as–prepared electrode is 1155.6 mA h g−1 after 200 cycles under the current density of 100 mA g−1, with a retention ratio of 91.02 %. When the current density rises to 1000 mA g−1, it delivers a specific capacity of 750 mA h g−1, showing excellent rate performance. This work demonstrates that NCO/VO–NF is a promising candidate anode for next–generation LIBs. [Display omitted] • A first–time synthesis of NiCo 2 O 4 –V 2 O 3 composite arrays on nickel foam by a facile method. • The unique hierarchical micro–nano hydrangea–like morphology. • Improved electrochemical performances as an anode for LIBs by introducing V 2 O 3. [ABSTRACT FROM AUTHOR]

A flexible, free-standing, and light-weight LiMnTiO 4 /MWCNT electrode has been prepared by vacuum filtration method for the first time. The as-prepared flexible LiMnTiO 4 /MWCNT electrode possesses a three-dimensional braiding structure in which LiMnTiO 4 particles are well embedded in the twining CNT networks. The novel LiMnTiO 4 /MWCNT electrodes show tensile strength of 1.34 MPa and 2.04 MPa, when the percentages of MWCNTs reach to 30% and 50%, respectively. This novel flexible electrode exhibits a superior electrochemical property, especially at rate capability and cycling stability. The LiMnTiO 4 /MWCNT electrode can deliver capacity of 161 mAh g −1 (86.4% retention) after 50 cycles at 0.5C rate. Since the high conductivity from MWCNT networks, the LiMnTiO 4 /MWCNT electrode can still maintain a capacity of 77 mAh g −1 at 5C rate, which is much higher than that of the conventional electrode fabricated by slurry casting method on Al foil. The features of free-standing, light-weight, and excellent electrochemical performance indicate the potential of using the LiMnTiO 4 /MWCNT cathode in new-generation flexible lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: Silicon is a remarkable candidate for lithium‐ion battery anodes, due to the highest theoretical specific capacity, low working potential, and abundance on earth. However, the volume of Si changes ≈300 % during the lithiation–delithiation cycling, leading to pulverization and poor electrical contact between Si and the current collector, resulting in fast fading capacity. To overcome these problems, we develop a novel free‐standing anode by encapsulating Si nanoparticles into a lightweight, flexible, and conductive graphene network by utilizing a facile freeze‐drying strategy. The Si nanoparticles are tightly anchored on the ultrathin and flexible graphene sheets, which can serve as mechanical support, electrical network, and buffer layer for Si. This free‐standing aerogel exhibits superior electrochemical performance, and the specific capacity is 617 mA h g−1 after 50 cycles at a current density of 0.8 A g−1, 4 times that of a traditional Si electrode on Cu foil fabricated by a typical slurry method. [ABSTRACT FROM AUTHOR]

The vertical graphene with hierarchical three-dimensional network architecture is a promising substrate for high energy and power density Li-ion battery due to its large surface area, inherent three-dimensional network and excellent ion transport property. Three dimensional vertical graphene (3DVG) is synthesized via plasma enhanced chemical vapor deposition (PECVD) using cost-effective and environment-friendly natural oil of M. alternifolia as precursor. The MoS 2 nanosheets are then anchored on free-standing 3DVG by hydrothermal method to make the binder free MoS 2 @3DVG anode of a Li-ion battery. The MoS 2 @3DVG electrodes deliver an enhanced capacity of 670 mAh g −1 with the capacity retention of 99% after 30 cycles at 100 mA g −1 , much better than that of the reference sample of MoS 2 @3DG (550 mAh g −1 at 100 mA g −1 ) which uses 3D planar graphene. Superior performance of the vertical graphene based electrode is attributed to the unique hierarchical structure and densely packed reactive edges of the as-synthesized 3DVG. The versatility of plasma-assisted natural precursor based vertical graphene as functional nano-structured substrate for MoS 2 , as active material, for advanced energy storage devices is demonstrated. [ABSTRACT FROM AUTHOR]

This work presents a novel binder-free nitrogen-doped carbon paper electrode (NCPE), which was derived from a N-rich polypyrrole (PPy)/cellulose-chopped carbon filaments (CCFs) composite, for Li–O 2 batteries. The fabrication of NCPE involved cheap raw materials ( e.g., Cladophora sp. green algae) and easy operation ( e.g., doping N by a carbonization of N-rich polymer), which is especially suitable for large-scale production. The NCPE exhibited a bird's nest microstructure, which could provide the self-standing electrode with considerable mechanic durability, fast Li + and O 2 diffusion, and enough space for the discharge product deposition. In addition, the NCPE contained N-containing function groups, which may promote the electrochemical reactions. Furthermore, binder-free architecture designs can prevent binder-involved parasitic reactions. A Li–O 2 cell with the NCPE displayed a cyclability of more than 30 cycles at a constant current density of 0.1 mA/cm 2 . The 1st discharge capacity for a cell with the NCPE reached 8040 mAh/g at a current density of 0.1 mA/cm 2 , with a cell voltage around 2.81 V. A cell with the NCPE displayed a coulombic efficiency of 81% on the 1st cycle at a current density of 0.2 mA/cm 2 . These results represent a promising progress in the development of a low-cost and versatile paper-based O 2 electrode for Li–O 2 batteries. [ABSTRACT FROM AUTHOR]

Developing scalable, simple and low-cost synthesis approach for Si nanoparticles and fabricating Si/carbon composites with specific microstructure to improve the Li storage ability are of great significance for practical application of Si-based Li-ion battery anode. In this report, we employed a facile method to synthesize Si nanoparticles via acid-etching Al-Si alloy powder. The etching process was fully investigated. The as-synthesized Si nanoparticles (∼10 nm) were further embedded into graphene sheets to form a flexible, free-standing paper with “sandwich-like” structure. The Si/graphene paper was directly applied as anode for Li-ion batteries without adding any binder and conductive additive. The graphene sheets not only increase the conductivity of Si material, but also function as a flexible scaffold for strains/stresses release and volume expansion during charge/discharge cycling process, resulting in much higher cycling stability (1500 mAh g −1 after 100 cycles at a current density of 100 mA g −1 with Coulombic efficiency >99%) compared to the native Si nanoparticles. It provides a scalable Si nanoparticles synthesis approach and a promising high-performance Si/graphene anode material. [ABSTRACT FROM AUTHOR]

• Variation of Young's modulus of Ga in the process of discharge (lithiation) was measured. • Self-healing ability of EGaIn to automatic repair the cracks resulted from charge/discharge. • The CNF/CNT@EGaIn NPs anode is free-standing, flexible and binder-free. Gallium-based liquid metals are considered as potential anode materials for lithium-ion batteries owing to their self-healing, non-poisonous advantages, as well as high theoretical capacity. However, due to the alloying/dealloying reaction mechanism to store lithium, Gallium-based alloys face huge volume change resulted in poor cycle life. Furthermore, the poor wettability of liquid metals on many kinds of substrates (carbon materials, stainless steel, etc.) and their strong ability to form alloys with many metallic current collectors (Cu, Al foil) make them hard to be designed into electrode with excellent electrochemical performance. One objective of this paper is to investigate Young's modulus of Ga discharged to different cut-off potentials, in order to gain a further understanding of mechanical property attenuation of Ga in the process of lithiation. Moreover, a three-dimensional (3D) free-standing electrode is fabricated by confining Ga-based liquid metal, EGaIn, in the matrix of carbon nanofibers/carbon nanotubes paper (CNF/CNT@EGaIn NPs). The network structure provides effective pathways for electrons and ions, as well as enough space to contain the volume expansion of EGaIn. The dense CNT layer plays a further role on preventing EGaIn from shedding of the conductive substrates. Obtained CNF/CNT@EGaIn NPs exhibits a good ionic/electronic conductivity and mechanical stability, delivers capacity of 351 mAh g−1 at 1.6 A g−1 and remains a reversible capacity of ∼420 mAh g−1 after 100 cycles at 800 mA g−1. This work could provide valuable insights into the development of Ga-based liquid metal anodes. [ABSTRACT FROM AUTHOR]

Free-standing, flexible, paper-like Fe 2 O 3 /graphene/carbon nanotubes (Fe 2 O 3 /GCNTs) ternary hybrid film with a three-dimensional hierarchical structure is synthesized through a simple filtration and a subsequent reduction process. The Fe 2 O 3 particles are densely anchored onto the GCNTs conducting network, which serves as an ideal host for fast and efficient lithium storage. The layered GCNTs network not only withstands the huge stresses caused by Fe 2 O 3 expansion/extraction but prevents the agglomeration of Fe 2 O 3 upon continuous charging/discharging. The as-synthesized Fe 2 O 3 /GCNTs hybrid film is directly used as an anode for both half and full lithium-ion cells. Electrochemical measurement results indicate a high reversible capacity and a good rate capability can be realized on the hybrid when tested in half cell system. Furthermore, the prepared anode also shows favorable operation in full cell system comprising LiCoO 2 cathode. These superior electrochemical performances of the hybrid film can be ascribed to the unique micro-structure, surface properties, and the strong synergistic effects among the individual component. [ABSTRACT FROM AUTHOR]

Similar to graphene, transition metal oxide nanosheets have attracted a lot of attention recently owning to their unique structural advantages, and demonstrated promising chemical and physical properties for various applications. However, the synthesis of transition metal oxide nanosheets with controlled size and thickness remains a great challenge for both fundamental study and applications. The present work demonstrates a facile solvothermal synthesis of ultra-large (over 100 μm) VO 2 (B) nanosheets with an exceptionally small thickness of only 2–5 nm corresponding to 3–8 layers of (001) planes. It can be readily transferred into V 2 O 5 with well retained nanosheet structures when calcined, which exhibit remarkable rate capability and great cycling stability. Specifically, the as-synthesized vanadium pentoxide nanosheets deliver a specific discharge capacity of 141 mA h g −1 at a current density of 0.1 A g −1 , which is 96% of its theoretical capacity (147 mA h g −1 ) for one Li + ion intercalation/removal per formular within a voltage window of 2.5–4 V. Even at an extreme-high current density of 5 A g −1 , it still can exhibit a high specific discharge capacity of 106 mA h g −1 . It is worthy to note that the V 2 O 5 nanosheets electrode can retain 92.6% of the starting specific discharge capacity after 500 discharge/charge cycles at the current density of 1.5 A g −1 . [ABSTRACT FROM AUTHOR]

Carbon nanotube films (CNT-1 and CNT-2) were fabricated in a vertical CVD gas flow reactor with water sealing. CNT-1 films consist of ordered crystalline carbon nanotubes, while CNT-2 are defective carbon nanotube films. The films are flexible and transferrable and can be used as binder-free anodes for lithium-ion batteries (LIB). Electrochemical measurements show that CNT-2 possess a reversible capacity of 452 mA h g −1 under a current density of 30 mA g −1 , which is higher than that of CNT-1 (375 mA h g −1 ) under the same current density. In addition, the CNT-2 shows a reversible capacity of 107.9 mA h g −1 after 500 cycles at a current density of 3000 mA g −1 , while 82.1 mA h g −1 for CNT-1 under the same condition. Good correlations between morphological factors, defective structure and electrochemical performance are observed. [ABSTRACT FROM AUTHOR]

Continuous free-standing Carbon Nanotubes (CNTs)/Titanium oxide (TiO 2 ) composite films were fabricated in a vertical CVD gas flow reactor with water sealing by the One-Step Chemical Vapor Deposition (CVD) approach. The composite films consist of multiple layers of conductive carbon nanotube networks with titanium oxide nanoparticles decorating on carbon nanotube surface. The as-synthesized flexible and transferrable composite films show excellent electrochemical properties, when the content of tetrabutyl titanate is 19.0 wt.%, which can be promising as binder-free anodes for Lithium-Ion Battery (LIB) applications. It demonstrates remarkably high rate capacity of 150 mAh g −1 , as well as excellent high rate cyclic stability over 500 cycles (current density of 3000 mA g −1 ). Such observations can be attributed to the relatively larger surface area and pore volume comparing with pristine CNT films. Great potentials of CNTs/TiO 2 composite films for large-scale production and application in energy devices were shown. [ABSTRACT FROM AUTHOR]

Premixed flame configuration is considered as an effective method for the synthesis of carbon materials. In this work, flexible single-walled carbon nanotube network decorated by carbon-encapsulated Fe 2 O 3 nanoparticles (C@Fe 2 O 3 /SWCNT) membrane was in-situ fabricated via a facile floating catalyst premixed ethanol flame method, and followed by annealing treatment. In this process, low-cost ethanol and ferrocene were used as carbon source and catalyst precursor for the synthesis of C@Fe 2 O 3 /SWCNT, respectively. Benefiting from the interconnected conductive network, the as-fabricated C@Fe 2 O 3 /SWCNT membrane was used as a free-standing anode for lithium-ion batteries. Structural characterization revealed that the ultrafine Fe 2 O 3 nanoparticles homogeneously anchored on the SWCNT network, which facilitates the fast diffusion for electron. Furthermore, the carbon layers uniformly enwrap on Fe 2 O 3 can effectively suppress the aggregation and buffer the volume change of Fe 2 O 3 during the lithiation/delithiation process. Consequently, this material delivered an excellent lithium storage performance with a high reversible capacity of 1294.7 mAh g−1 at 50 mA g−1, and an excellent cyclability of 82.5% retention is obtained after cycles at 2 A g−1. This study provides a novel low-cost and fast method for preparing flexible advanced electrode for next-generation rechargeable batteries. • Free-standing C@Fe 2 O 3 /SWCNT was fabricated via a novel premixed flame. • Low-cost ethanol was used as carbon source for premixed flames. • SWCNT and Fe 2 O 3 synergistically enhance electrical properties of composite anodes. [ABSTRACT FROM AUTHOR]

Free-standing electrodes have attracted extensively attention for their absence of non-electrochemical activity binders, conductive additives, and current collectors. Here, the fordable and flexible ZnSe@carbon nanofibers (ZnSe@CNFs) composites have been synthesized via electrospinning method and subsequent one-step carbonization/selenization process. Benefited by the structural advantage of ZnSe nanoparticles encapsulated inside carbon nanofibers conductive network, this delicate electrode exhibits superior electrochemical performance, including outstanding rate capability and ultra-long cycling life (426.1 mAh g−1 over 3000 cycles at 5 A g−1 with only 0.01% decay per cycle). More importantly, the free-standing electrode could be further applied in pouch cell, which delivers prominent capacity of 448.9 mAh g−1 during 700 cycles at 0.5 A g−1. What's more, this pouch cell successfully lightens the luminescence of the light-emitting diodes (LEDs). Even if we repeatedly fold 30 times at different angle (90°, 180°, and 0°), the pouch cell is still in good agreement with the pristine stage. This design is beneficial to propel the development of free-standing electrode in the aspect of flexible/wearable electronic devices. [Display omitted] • Flexible and free-standing ZnSe@carbon nanofibers electrodes are designed by one-step electrospinning methods. • Outstanding rate capability and ultra-long cycling life over 3000 cycles at 5 A g−1 are achieved. • Ex-situ XRD reveals the internal lithium storage mechanism of ZnSe. • The large-area pouch cell is successfully assembled and operated at different bending angles. [ABSTRACT FROM AUTHOR]

Abstract: Rice paper (RP) is thermally carbonized in nitrogen to prepare three-dimensionally porous carbon films, which are used for the first time as both a free-standing active anode material and a current collector of a cathode (LiFePO4 here) for lithium-ion batteries. The latter is fabricated through a one-step co-sintering of a Li–Fe–P–O precursor top layer supported on the rice paper. The rate and cycling performances of both these electrodes are found to be rather good or even better than the traditional electrodes due to the three-dimensionally porous structure of the RP-derived carbon. We also design and fabricate an RP-based full cell constructed with the above mentioned anode and cathode together with an RP membrane as the separator. Without using traditional metallic current collectors and separator membranes, such a cell exhibits reversible cycling performance. [Copyright &y& Elsevier]

Abstract: Free-standing and flexible V2O5 films have been prepared by the filtration of ultra-long nanowires synthesized through the hydrothermal technique. In order to improve the conductivity of the films, multiwalled carbon nanotubes (MWCNTs) were added to the V2O5 nanowires to form an integrated web-like structure. The structure of the V2O5 nanowires was investigated with X-ray diffraction and transmission electron microscopy. The possible use of these films as a cathode for lithium ion batteries was also investigated. The free-standing and flexible film electrodes exhibited good rate capability and excellent cycling performance, with a capacity of 140mAh/g, even after 50 cycles at 1.7°C in a voltage range of 2.5–4.0V. The superior reversible lithium storage capability can be attributed to the fully reversible phase transitions of α-V2O5 through to δ-LiV2O5, good lithium diffusion in V2O5, and increased electronic conductivity and electrolyte diffusion from the incorporated MWCNT web. [Copyright &y& Elsevier]

The application of the SiO 2 anodes for flexible and free-standing lithium-ion batteries (LIBs) is restricted by the weaknesses of SiO 2 nanoparticles, such as agglomeration, huge volume expansion and rapid capacity fading during charge/discharge cycles. Herein, the PVP-grafted-silica@carbon nanofibers (PVP-g-SiO 2 @CNF) flexible free-standing anode with high capacity and long cycle stability is successfully fabricated by PVP-grafted-SiO 2 , electrospinning and subsequent heat treatment. PVP modifies the interface between SiO 2 nanoparticles and electrospinning solution to prevent the nanoparticles from aggregation, which makes them are uniformly encapsulated in nanofibers. The uniform structure is beneficial to enhance the interface contact between SiO 2 and Li+, and alleviate volume expansion during lithiation. Furthermore, PVP introduces mesoporous into carbon nanofibers, facilitating the transports of ions and electrons to attain high-rate performance. As a flexible free-standing anode material for LIBs, PVP-g-SiO 2 @CNF achieves high reversible capacity, high-rate capacity and superior cycle stability (440 mAh g−1 at 0.1 A g−1 after 200 cycles), especially 89% capacity retention after 180° bending deformation. Consequently, enhanced capacity and cycle stability for flexible free-standing anode are available through PVP-grafted interface modification and electrospinning. This work is the first to use PVP-grafted interface modification and electrospinning to synthesize flexible free-standing anode for LIBs. PVP-grafted modifies the interface between SiO 2 nanoparticles and electrospinning solution to prevent SiO 2 nanoparticles from aggregation before and after electrospinning, and mesoporous is introduced into carbon nanofibers, which make the anode exhibit excellent cycling and lithium storage performance. [Display omitted] • Uniform and mesoporous SiO 2 @CNF is available by PVP-grafted interface modification. • PVP-g-SiO 2 @CNF exhibits smooth surface with uniformly embedded SiO 2 nanoparticles. • By means of thermal decomposition of PVP, mesoporous is introduced into CNF. • PVP-g-SiO 2 @CNF anode presents increased reversible capacity and cycle stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Free-standing Sb@PC anode materials was fabricated via a facile "L-B-L" method using commercial cotton cloth as template. • The ultrafine Sb nanoparticles were uniformly embedded in the 3D interleaved porous carbon network. • The as-prepared Sb@C composite exhibited a high reversible Li-ion storage capacity and high-rate capability. The free-standing Sb@C anode composites has been fabricated via a controllable "layer-by-layer" (L-B-L) assembly method. As an anode for lithium-ion batteries (LIBs), the as-prepared electrode exhibits remarkable electrochemical performance with a high capacity of 600 and 525 mAh g−1 at 200 and 500 mA g−1 after 300 and 400 cycles, respectively. Such excellent lithium storage properties are primarily benefited from the ultrafine Sb nanoparticles uniformly embedded in the 3D interleaved porous carbon network, which not only provides a fast conductive network but inhibits the volume expansion and agglomeration of Sb during the discharge/charge process. The alloy-model reaction mechanism and outstanding reversibility of the Sb@C anode were systematically investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous nitrogen-doped Sn/C fibers (P-Sn/C-N Fs) film are fabricated using green, high-nitrogen folic acid as nitrogen source. • The P-Sn/C-N Fs film as a free-standing electrode for lithium ion batteries exhibits outstanding electrochemical performance. • After-cycled P-Sn/C-N Fs electrode still maintains structural integrity. The key to the development of wearable electronic equipment lies in the design of flexible batteries, in which the electrodes with outstanding mechanical behavior are quite important. Herein, porous nitrogen-doped Sn/C fibers (P-Sn/C-N Fs) film has been successfully synthesized via simple electrospinning and subsequent calcination process in which folic acid and polymethylmethacrylate (PMMA) play the role of introducing nitrogen and forming pores, respectively. The introduction of nitrogen improves the electronic conductivity of the material, and the presence of porous structure increases the specific surface area. More importantly, when the P-Sn/C-N Fs film is used directly as a free-standing electrode for lithium ion batteries, it exhibits outstanding electrochemical performance. The P-Sn/C-N Fs film exhibits a discharge capacity of 712.1 mAh g−1 at 500 mA g−1 after 500 cycles. Even at the high current density of 5 A g−1, it displays a high discharge capacity of 429.1 mAh g−1 after 1000 cycles. These findings indicate that the P-Sn/C-N Fs film has the potential to be applied as free-standing anode materials for lithium ion batteries. [ABSTRACT FROM AUTHOR]

In this study, we have successfully prepared a free-standing Si/void/rGO yolk–shell structured electrode via the electrostatic self-assembly using protonated chitosan. When graphene oxide (GO) is dispersed in water, its carboxyl and hydroxyl groups on the surface are ionized, resulting in the high electronegativity of GO. Meanwhile, chitosan monomer contains -NH2 and -OH groups, forming highly electropositive protonated chitosan in acidic medium. During the electrostatic interaction between GO and chitosan, which results in a rapid coagulation phenomenon, Si/SiO2 nanoparticles dispersed in GO can be uniformly encapsulated between GO sheets. The free-standing Si/void/rGO film can be obtained by freeze-drying, high-pressure compression, thermal reduction and HF etching technology. Our investigation shows that after 200 charge/discharge cycles at the current density of 200 mA·g−1, the specific discharge capacity of the free-standing electrode remains at 1129.2 mAh·g−1. When the current density is increased to 4000 mA·g−1, the electrode still has a specific capacity of 469.2 mAh·g−1, showing good rate performance. This free-standing electrode with a yolk–shell structure shows potential applications in the field of flexible lithium-ion batteries. [ABSTRACT FROM AUTHOR]

High energy density and low-cost anode materials are essential for lithium-ion batteries (LIBs). Herein, we proposed a strategy that combined electrospinning technique with water bath method to prepare a free-standing nanorod structured ZnO@carbon nanofiber (ZnO@CNF) composite film directly used anode material of LIBs. The resulting ZnO@CNF film offers a hierarchical nanorod arrays structure that can promote fast redox reaction kinetics and maintain the structural integrity of active material. Moreover, 3D conducting carbon fiber matrix enhances transportation and diffusion rate of electron and Li+. ZnO@CNF composite delivers stable cycle stability with a high specific capacity of 535 mAh g−1 after 150 cycles. Even up to 1000 mA g−1, the ZnO@CNF maintains a capacity of 425 mAh g−1. The good electrochemical performance of ZnO@CNF electrode could be attributed to the synergistic effect of the unique nanorod arrays structures and conductive network. Schematic illustration of the preparation process of ZnO@CNF. Image 1 • A ZnO@CNF composite was prepared by electrospinning technique. • 3D vertical ZnO nanorod promotes fast redox reaction kinetics. • Carbon fiber constructs a transportation and diffusion path for electron and Li+. • The ZnO@CNF film exhibits good cycling and rate capability for the Li-ion batteries. [ABSTRACT FROM AUTHOR]

Potassium-ion batteries (PIBs) are in the spotlight as a possible alternative to lithium-ion batteries. Graphitic carbons are promising anode materials for PIBs due to their low-plateau potential that is beneficial for the realization of high-voltage full cells. However, inferior cycling stability hinders their practical application. Herein, highly graphitized carbon nanofibers (HG-CNFs) as a free-standing electrode are served as the anode for PIBs. The HG-CNFs exhibits a reversible capacity of 200 mAh g−1 at the plateau potential below 0.2 V (76% of total capacity) and superior rate performance with a depotassiation capacity of 226 mAh g−1 at 35 C. Moreover, the capacity decay of HG-CNFs is less than 0.008% per cycle during 400 cycles, which is superior to those of most other graphitic carbons. The excellent electrochemical performance of HG-CNFs is attributed to its merits of free-standing fibrous networks and graphitic structure with rational defects that alleviate the volume expansion incurred by K+ intercalation. • Highly graphitized carbon nanofibers as a free-standing electrode was prepared. • The interconnected networks improve the integrity and buffer the volume expansion. • The HG-CNFs exhibits a capacity of 200 mAh g−1 at the plateau potential below 0.2 V. • The HG-CNFs shows outstanding cycling performance in K-ion half-cells. [ABSTRACT FROM AUTHOR]

Herein, the three-dimensional free-standing nano-silicon @ soft carbon embedded in graphene scaffold composite is prepared to boost the lithium storage property of the silicon anode. For the aspect of "single", the own volume expansion is relieved by the encapsulated soft carbon layer and the soft carbon layer can suppress the repeated formation of solid electrolyte interface films onto the "single" silicon nanoparticle (SNP). Moreover, the soft carbon layer possesses alternating amorphous and crystalline regions to provide the rapid lithium-ion diffusion channel. On the side of "monolithic", the 3D free-standing graphene-scaffold loading with evenly distributed SNPs eliminates collisions between SNPs during the charging/discharging cycles, and endows the 'monolithic' electrode with excellent electronic conductivity, fast lithium-ion diffusion pathway and high SNPs content. Thus, the above composite anode exhibits superior specific capacity, cycling performance and rate performance, such as around 2600 mA h g−1 (8.34 mA h cm−2) of specific capacity at a current density of 0.2 A/g and almost no capacity attenuation after 100 cycles. The design thinking (from 'single' to 'monolithic') paves a new avenue towards high-performance anodes of silicon and transition metal oxides. Image 1 • The performance of silicon anode is enhanced from "single" to "monolithic". • Soft carbon layer is encapsulated on silicon particles. • Silicon particles are uniformly dispersed on 3D free-standing graphene scaffold. • The electrode shows outstanding cycling performance and capacity. [ABSTRACT FROM AUTHOR]

Abstract: The desire for practical utilization of rechargeable lithium batteries with high energy density has motivated attempts to develop new electrode materials and battery systems. Here, without additional binders we present a simple vacuum filtration method to synthesize nitrogen and sulfur codoped graphene (N,S-G) blocking layer, which is ultra-lightweight, conductive, and free standing. When the N,S-G membrane was inserted between the catholyte and separator, the lithium-selenium (Li-Se) batteries exhibited a high reversible discharge capacity of 330.7 mAh g−1 at 1 C (1 C = 675 mA g−1) after 500 cycles and high rate performance (over 310 mAh g−1 at 4 C) even at an active material loading as high as ~ 5 mg cm−2. This excellent performance can be ascribed to homogenous dispersion of the liquid active material in the electrode, good Li+-ion conductivity, fast electronic transport in the conductive graphene framework, and strong chemical confinement of polyselenides by nitrogen and sulfur atoms. More importantly, it is a promising strategy for enhancing the energy density of Li-Se batteries by using the catholyte with a lightweight heteroatom doping carbon matrix. [ABSTRACT FROM AUTHOR]