Nanofiber Anodes Research Articles

Constructing High-Performance Carbon Nanofiber Anodes by the Hierarchical Porous Structure Regulation and Silicon/Nitrogen Co-Doping

Due to the rapid development of bendable electronic products, it is urgent to prepare flexible anode materials with excellent properties, which play a key role in flexible lithium-ion batteries. Although carbon fibers are excellent candidates for preparing flexible anode materials, the low discharge specific capacity prevents their further application. In this paper, a hierarchical porous and silicon (Si)/nitrogen (N) co-doped carbon nanofiber anode was successfully prepared, in which Si doping can improve specific capacity, N doping can improve conductivity, and a fabricated hierarchical porous structure can increase the reactive sites, improve the ion transport rate, and enable the electrolyte to penetrate the inner part of carbon nanofibers to improve the electrolyte/electrode contacting area during the charging–discharging processes. The hierarchical porous and Si/N co-doped carbon nanofiber anode does not require a binder, and is flexible and foldable. Moreover, it exhibits an ultrahigh initial reversible capacity of 1737.2 mAh g−1, stable cycle ability and excellent rate of performance. This work provides a new avenue to develop flexible carbon nanofiber anode materials for lithium-ion batteries with high performance.

Hierarchical and Heterogeneous Porosity Construction and Nitrogen Doping Enabling Flexible Carbon Nanofiber Anodes with High Performance for Lithium-Ion Batteries.

With the rapid development of flexible electronic devices, flexible lithium-ion batteries are widely considered due to their potential for high energy density and long life. Anode materials, as one of the key materials of lithium-ion batteries, need to have good flexibility, an excellent specific discharge capacity, and fast charge–discharge characteristics. Carbon fibers are feasible as candidate flexible anode materials. However, their low specific discharge capacity restricts their further application. Based on this, N-doped carbon nanofiber anodes with microporous, mesoporous, and macroporous structures are prepared in this paper. The hierarchical and heterogeneous porosity structure can increase the active sites of the anode material and facilitate the transport of ions, and N-doping can improve the conductivity. Moreover, the N-doped flexible carbon nanofiber with a porous structure can be directly used as the anode for lithium-ion batteries without adding an adhesive. It has a high first reversible capacity of 1108.9 mAh g−1, a stable cycle ability (954.3 mAh g−1 after 100 cycles), and excellent rate performance. This work provides a new strategy for the development of flexible anodes with high performance.

Flexible Porous Silicon/Carbon Fiber Anode for High-Performance Lithium-Ion Batteries.

We demonstrate a cross−linked, 3D conductive network structure, porous silicon@carbon nanofiber (P−Si@CNF) anode by magnesium thermal reduction (MR) and the electrospinning methods. The P−Si thermally reduced from silica (SiO2) preserved the monodisperse spheric morphology which can effectively achieve good dispersion in the carbon matrix. The mesoporous structure of P–Si and internal nanopores can effectively relieve the volume expansion to ensure the structure integrity, and its high specific surface area enhances the multi−position electrical contact with the carbon material to improve the conductivity. Additionally, the electrospun CNFs exhibited 3D conductive frameworks that provide pathways for rapid electron/ion diffusion. Through the structural design, key basic scientific problems such as electron/ion transport and the process of lithiation/delithiation can be solved to enhance the cyclic stability. As expected, the P−Si@CNFs showed a high capacity of 907.3 mAh g−1 after 100 cycles at a current density of 100 mA g−1 and excellent cycling performance, with 625.6 mAh g−1 maintained even after 300 cycles. This work develops an alternative approach to solve the key problem of Si nanoparticles’ uneven dispersion in a carbon matrix.

Carbon Nanofiber Double Active Layer and Co-Incorporation as New Anode Modification Strategies for Power-Enhanced Microbial Fuel Cells.

Co-doped carbon nanofiber mats can be prepared by the addition of cobalt acetate to the polyacrylonitrile/DMF electrospun solution. Wastewater obtained from food industries was utilized as the anolyte as well as microorganisms as the source in single-chamber batch mode microbial fuel cells. The results indicated that the single Co-free carbon nanofiber mat was not a good anode in the used microbial fuel cells. However, the generated power can be distinctly enhanced by using double active layers of pristine carbon nanofiber mats or a single layer Co-doped carbon nanofiber mat as anodes. Typically, after 24 h batching time, the estimated generated power densities were 10, 92, and 121 mW/m2 for single, double active layers, and Co-doped carbon nanofiber anodes, respectively. For comparison, the performance of the cell was investigated using carbon cloth and carbon paper as anodes, the observed power densities were smaller than the introduced modified anodes at 58 and 62 mW/m2, respectively. Moreover, the COD removal and Columbic efficiency were calculated for the proposed anodes as well as the used commercial ones. The results further confirm the priority of using double active layer or metal-doped carbon nanofiber anodes over the commercial ones. Numerically, the calculated COD removals were 29.16 and 38.95% for carbon paper and carbon cloth while 40.53 and 45.79% COD removals were obtained with double active layer and Co-doped carbon nanofiber anodes, respectively. With a similar trend, the calculated Columbic efficiencies were 26, 42, 52, and 71% for the same sequence.

High-performance, flexible, binder-free silicon–carbon anode for lithium storage applications

The development of flexible Li-ion batteries (LiBs) is important for applications in wearable devices, display systems, intelligent communication, and other electronics fields. Herein, we report a flexible, binder-free, silicon@silica@carbon nanofiber (Si@SiO2@CNF) anode fabricated by a scalable electrospinning method and a novel “pre-oxidation–slicing–carbonization” process. Si nanoparticles (Si NPs) uniformly dispersed within the CNFs were coated with layers of SiO2, leading to the formation of core–shell-structured silicon@silica (Si@SiO2). Due to the introduction of the SiO2 coating, aggregation of the Si NPs was effectively inhibited, and the change in volume of the Si NPs could be confined within the CNFs during cycling, resulting in enhanced structural and cycling stability. Furthermore, the interconnected conductive CNFs further increased the overall conductivity, leading to improved rate performance. More importantly, the novel “pre-oxidation–slicing–carbonization” process ensures the integrity of the edge of the electrode film. The fiber film obtained by electrospinning can be used directly as a freestanding, binder-free anode material, which significantly simplifies the fabrication process and reduces the cost. The Si@SiO2@CNF composite retains excellent performanceof 903.7 mAh g−1 beyond 100 cycles at 100 mA g−1, and a remarkable rate capacity of 634.6 mAh g−1 after 300 cycles. The proposed facile and scalable synthesis means that this novel, flexible, and binder-free Si/C anode should have practical applications in next-generation, flexible, binder-free Li-ion batteries.

Effective toxicity assessment of synthetic dye in microbial fuel cell biosensor with spinel nanofiber anode

Textile dyes are one of the most commonly found contaminants in wastewater requiring their insitu real-time monitoring and biotreatment. In the present study, two different microbial fuel cells with plain and magnesium ferrite coated stainless steel mesh (PBS/SS and PBS/MF-SS) bioanodes were tested for the simultaneous biosensing and biotreatment of three different concentrations of Ponceau BS dye with mixed microbial community as biological sensing elements. The study revealed the direct correlation of added toxicant and the performance of microbial fuel cell biosensor and observed an almost perfect linear fit for concentration vs. voltage output graph corroborating the potential of microbial fuel cell as a toxicity detector. The cyclic voltammetry confirmed the bioactivity of microbial fuel cell reactor with reference to the unacclimated system. In addition, the cyclic voltammetry analysis of microbial fuel cells at different dye concentration suggested its promising toxicity sensing potential. Electrochemical Impedance Spectroscopy data confirmed that biofouling affected the internal resistances of microbial fuel cells. In addition, the effect of extended run-time (of a year) on the performance of microbial fuel cell was established by comparing the voltage outputs of this study with our previous work. As compared to the previous study, the voltage output for microbial fuel cells with plain and magnesium ferrite coated stainless steel mesh showed a decline by nearly 53% and 41% respectively suggesting the fouling of system. The lesser drop in the performance for microbial fuel cell with modified electrode showed the potential of modified electrode in more efficient electron transfer in the long run. The results conclude that the microbial fuel cell biosensor provides a quick and effective approach for real-time monitoring of hazardous and recalcitrant contaminants such as dyes in environmental samples; nevertheless, fouling of the system is a significant impediment to the long-term practical implementation of microbial fuel cells.

Sulfur Doped Hollow Carbon Nanofiber Anodes for Fast-Charging Potassium-Ion Storage

Sulfur Doped Hollow Carbon Nanofiber Anodes for Fast-Charging Potassium-Ion Storage

Porous Fe2O3 nanorod-decorated hollow carbon nanofibers for high-rate lithium storage

Transition metal oxides (TMOs) are considered as promising anode materials for lithium-ion batteries in comparison with conventional graphite anode. However, TMO anodes suffer severe volume expansion during charge/discharge process. In this respect, a porous Fe2O3 nanorod-decorated hollow carbon nanofiber (HNF) anode is designed via a combined electrospinning and hydrothermal method followed by proper annealing. FeOOH/PAN was prepared as precursors and sacrificial templates, and porous hollow Fe2O3@carbon nanofiber (HNF-450) composite is formed at 450 °C in air. As anode materials for lithium-ion batteries, HNF-450 exhibits outstanding rate performance and cycling stability with a reversible discharge capacity of 1398 mAh g−1 after 100 cycles at a current density of 100 mA g−1. Specific capacities 1682, 1515, 1293, 987, and 687 mAh g−1 of HNF-450 are achieved at multiple current densities of 200, 300, 500, 1000, and 2000 mA g−1, respectively. When coupled with commercial LiCoO2 cathode, the full cell delivered an outstanding initial charge/discharge capacity of 614/437 mAh g−1 and stability at different current densities. The improved electrochemical performance is mainly attributed to the free space provided by the unique porous hollow structure, which effectively alleviates the volume expansion and facilitates the exposure of more active sites during the lithiation/delithiation process.Graphical abstractPorous Fe2O3 nanorod-decorated hollow carbon nanofibers exhibit outstanding rate performance and cycling stability with a high reversible discharge capacity.

Construting stable 2 × 2 tunnel-structured K1.28Ti8O16@N-doped carbon nanofibers for ultralong cycling sodium-ion batteries

• A novel 2 × 2 tunnel-structured K 1.28 Ti 8 O 16 @N-doped carbon nanofibers are prepared. • The electrode exhibits excellent long cycle performance. Sodium-ion batteries (SIBs) are one of the most potential candidates for large-scale energy storage due to the low cost and eco-friendliness, however, a stable and reversible anode is urgently developed. In this work, a novel 2 × 2 tunnel-structured K 1.28 Ti 8 O 16 @N-doped carbon nanofibers (KTO@N CNFs) anode is successfully synthesized via simple electrospinning and subsequent thermal treatment with urea acted as the additional convenient nitrogen source. In-situ X-ray diffraction (XRD) measurement confirms the intercalation reaction mechanism and robust structure during Na + insertion/extraction. This composite material exhibits a reversible capacity of 116.4 mAh g − 1 at a current density of 100 mA g − 1 after 1000 cycles. More impressively, even at a high current density of 1 A g − 1 , the battery delivers capacity retention of 98.4 mAh g − 1 after 5000 cycles. The excellent electrochemical performance is attributed to the adequate 2 × 2 tunnel structure and the nano-confinement of N-doped nanofibers on K 1.28 Ti 8 O 16 nanocrystals, which offers enough diffusion paths and enhance the ionic diffusion of sodium ions. This work provides a facile strategy to synthesis stable, reversible, and long-cycle anode for sodium-ion batteries.

Fast-Charging Nonaqueous Potassium-Ion Batteries Enabled by Rational Construction of Oxygen-Rich Porous Nanofiber Anodes.

Practical applications of carbon anodes in high-power potassium-ion batteries (PIBs) were hampered by their limited rate properties, due to the sluggish K+ transport kinetics in the bulk. Constructing convenient ion/electron transfer channels in the electrode is of great importance to realize fast charge/discharge rates. Here, cross-linked porous carbon nanofibers (inner porous carbon nanotubes and outer soft carbon layer) modified with oxygen-containing functional groups were well designed as anodes to realize robust de-/potassiation kinetics. The novel anode delivered excellent rate capabilities (107 mAh g-1 at 20 A g-1 and 78 mAh g-1 at 40 A g-1) and superior cycling stability (76% capacity retention after 14,000 cycles at 2 A g-1). In situ XRD measurement, in situ Raman spectra, and galvanostatic intermittent titration verified its surface-dominated potassium storage behavior with fast de-/potassiation kinetics, excellent reversibility, and rapid ion/electron transport. Moreover, theoretical investigation revealed that the carboxyl groups in the carbon offered additional capacitive adsorption sites for K+, thus significantly enhancing the reversible capacity. Surprisingly, a full cell using the anode and perylene-3,4,9,10-tetracarboxylic dianhydride cathode achieved an outstanding power density of 23,750 W kg-1 and superior fast charge/slow discharge performance.

Stability Enhancement of Pbo-Based Anodes through Facile Encapsulation in Carbon Nanofibers for Li-Ion Batteries

Lead (II) Oxide (PbO)-embedded Carbon Nanofiber (CNF) anodes for lithium-ion batteries were prepared via the electrospinning method. While lead-based materials have several advantages over conventional graphite, including higher theoretical capacity and low cost, deleterious performance loss due to degradation caused by volume expansion remains as its main limitation. The use of carbon as an additive has been shown to stabilize the cycling performance and utilizing carbon nanostructures, namely nanofibers, can further substantially improve performance by accommodating volume change during lithiation/de-lithiation upon cycling as well as of batteries through capacity retention over several cycles. In this report, significant enhancement of battery performance in terms of specific capacity and cyclability is made using the prepared PbO/CNF anodes. The PbO particles were effectively embedded into the CNF, which significantly suppressed mechanical degradation of the electrode due to volume expansion and retained the PbO particles over numerous cycles and at high current. The PbO/CNF anode exhibits a high specific capacity of 375 mAh g-1 at a current of 200 mA g-1 (corresponding to ~1.2C) over 250 cycles compared 245 mAh g-1 for CNF, high current capability, and markedly improved stability, indicating its potential as an alternative to conventional graphite anodes.

High Current Production of Shewanella Oneidensis with Electrospun Carbon Nanofiber Anodes is Directly Linked to Biofilm Formation**

AbstractWe study the current production of Shewanella oneidensis MR‐1 with electrospun carbon fiber anode materials and analyze the effect of the anode morphology on the micro‐, meso‐ and macroscale. The materials feature fiber diameters in the range between 108 nm and 623 nm, resulting in distinct macropore sizes and surface roughness factors. A maximum current density of (255 71) μA cm−2 was obtained with 286 nm fiber diameter material. Additionally, micro‐ and mesoporosity were introduced by CO2 and steam activation which did not improve the current production significantly. The current production is directly linked to the biofilm dry weight under anaerobic and micro‐aerobic conditions. Our findings suggest that either the surface area or the pore size related to the fiber diameter determines the attractiveness of the anodes as habitat and therefore biofilm formation and current production. Reanalysis of previous works supports these findings.

Catalytic graphitization of bacterial cellulose–derived carbon nanofibers for stable and enhanced anodic performance of lithium-ion batteries

Bacterial cellulose (BC) produced through microbial fermentation has emerged as a viable precursor for carbon nanofibers (CNF) anode used in lithium-ion batteries. However, the low capacity and fading behavior of BC-derived CNFs render their usage in its pure form. Tuning the microstructure of CNFs in such cases plays an essential role in overcoming these negative ramifications and improves battery performance. In this study, the fermentation media used for BC production is modified by the addition of an iron catalyst, which can induce graphitization in the derived CNFs. Pure BC and catalyst-incorporated BC are pyrolyzed at 900 °C and 1800 °C to obtain CNFs, and the properties of derived CNFs are compared for understanding the role of incorporated catalyst. The structural, morphological, and electrochemical properties of CNFs are analyzed through X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, impedance spectroscopy, galvanostatic charge-discharge studies, and cyclic voltammogram studies. By possessing a higher graphitic content, catalyst-incorporated BC–derived CNFs exhibit an enhanced rate performance with a reversible capacity of 529 mAh g−1 after 100 continuous charge/discharge cycles at a current density of 0.2C.

A Review of Recent Advancements in Electrospun Anode Materials to Improve Rechargeable Lithium Battery Performance

Although lithium-ion batteries have already had a considerable impact on making our lives smarter, healthier, and cleaner by powering smartphones, wearable devices, and electric vehicles, demands for significant improvement in battery performance have grown with the continuous development of electronic devices. Developing novel anode materials offers one of the most promising routes to meet these demands and to resolve issues present in existing graphite anodes, such as a low theoretical capacity and poor rate capabilities. Significant improvements over current commercial batteries have been identified using the electrospinning process, owing to a simple processing technique and a wide variety of electrospinnable materials. It is important to understand previous work on nanofiber anode materials to establish strategies that encourage the implementation of current technological developments into commercial lithium-ion battery production, and to advance the design of novel nanofiber anode materials that will be used in the next-generation of batteries. This review identifies previous research into electrospun nanofiber anode materials based on the type of electrochemical reactions present and provides insights that can be used to improve conventional lithium-ion battery performances and to pioneer novel manufacturing routes that can successfully produce the next generation of batteries.

Lithium Polymer Batteries: Porous SnO2/C Nanofiber Anodes and LiFePO4/C Nanofiber Cathodes with a Wrinkle Structure for Stretchable Lithium Polymer Batteries with High Electrochemical Performance (Adv. Sci. 17/2020)

Lithium Polymer Batteries: Porous SnO₂/C Nanofiber Anodes and LiFePO₄/C Nanofiber Cathodes with a Wrinkle Structure for Stretchable Lithium Polymer Batteries with High Electrochemical Performance (Adv. Sci. 17/2020)

Growth of carbon nanofibers through chemical vapor deposition for enhanced sodium ion storage

Innovation of carbon anodes plays a significant role in the commercialization of Sodium-ion batteries. In this work, we report hybrid carbon nanofibers synthesized by a facile chemical vapor deposition method and explore their application potential as anode for sodium ion storage. The designed hybrid carbon nanofibers have diameters of 50−150 nm and show linear and spiral structures. Impressively, the carbon nanofibers anode exhibits good electrochemical performance with a high initial Coulombic efficiency of 87.6 % and excellent cycling stability with a capacity retention of 75.4 % at the 100th cycle. The improved Na-ion storage performance is attributed to the carbon nanofiber structure with considerable defect concentration and shortened transfer length for ions and electrons. Moreover, the fibrous structure is interconnected with cross-linked pores, contributing to good mechanical stability and reduced contact resistance. Our work may provide valuable inspiration for developing advanced electrodes for advanced alkali ion energy storage.

Porous SnO2/C Nanofiber Anodes and LiFePO4/C Nanofiber Cathodes with a Wrinkle Structure for Stretchable Lithium Polymer Batteries with High Electrochemical Performance.

Stretchable lithium batteries have attracted considerable attention as components in future electronic devices, such as wearable devices, sensors, and body‐attachment healthcare devices. However, several challenges still exist in the bid to obtain excellent electrochemical properties for stretchable batteries. Here, a unique stretchable lithium full‐cell battery is designed using 1D nanofiber active materials, stretchable gel polymer electrolyte, and wrinkle structure electrodes. A SnO2/C nanofiber anode and a LiFePO4/C nanofiber cathode introduce meso‐ and micropores for lithium‐ion diffusion and electrolyte penetration. The stretchable full‐cell consists of an elastic poly(dimethylsiloxane) (PDMS) wrapping film, SnO2/C and LiFePO4/C nanofiber electrodes with a wrinkle structure fixed on the PDMS wrapping film by an adhesive polymer, and a gel polymer electrolyte. The specific capacity of the stretchable full‐battery is maintained at 128.3 mAh g−1 (capacity retention of 92%) even after a 30% strain, as compared with 136.8 mAh g−1 before strain. The energy densities are 458.8 Wh kg−1 in the released state and 423.4 Wh kg−1 in the stretched state (based on the electrode), respectively. The high capacity and stability in the stretched state demonstrate the potential of the stretchable battery to overcome its limitations.

Fast Sodium Storage with Ultralong Cycle Life for Nitrogen Doped Hollow Carbon Nanofibers Anode at Elevated Temperature

AbstractSodium ion batteries have been suffering low reversible capacity, poor rate, and less cycling reliability upon sodiation/desodiation. To address those formidable issues, electrospinning combined with hard template route is adopted here to collect loofah‐like nitrogen‐doped hollow carbon nanofibers (NHCNFs) derived from sustainable and low‐cost resources, that is, renewable acrylic yarn. NHCNFs render a remarkable reversible capacity of 143 mAh g−1 for 5000 cycles at a current density of 10 A g−1 at ambient temperature. More importantly, NHCNFs possesses an impressive capability in tackling the elevated temperature environment, affording an admirable reversible capacity of 156 mAh g−1 at a high rate of 15 A g−1 even after 10 000 cycles under 50 °C. These superior performances could be attributed to the combination of the following factors: delicately designed microstructure with hollow bead‐like channels, pseudocapacitive behavior and accelerated kinetics. Such an excellent attribute enables loofah‐like NHCNFs to be a promising low‐cost and environment‐friendly anode for sodium ion rechargeable batteries.

Multidimensional jagged SnSb/C/DLC nanofibers fabricated by AP-PECVD method for Li-ion battery anode

The atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) method has been shown to have dramatic effects on the morphology and structure of nanomaterials. For the sake of solving the capacity decline caused by alloy expansion and improving the electrode performance of SnSb/C nanofiber anodes in Li-ion batteries, the self-designed AP-PECVD device was first used to deposit large numbers of diamond-like carbon (DLC) nanoparticles on nanofibers to construct a special 3D structure. Interestingly, after the AP-PECVD and carbonization treatment, we found that most DLC nanoparticles had a single crystal structure and nanofibers reacted with a high energy hydrogen plasma to generate a special jagged morphology. The special jagged grooves provided an excellent channel for the Li ions’ insertion/extraction, and the 3D structure provided a buffer space for the volume expansion of SnSb alloy during the electrochemical cycle. Compared with the SnSb/C nanofibers, SnSb/C/DLC nanofibers exhibited a much better electrochemical performance with a high reversible capacity of 583.54 mAh g−1 at the 100th cycle, and excellent rate capability. This paper proved that the AP-PECVD device can successfully deposit a DLC nanoparticle layer and the construction of nanofiber morphology was a valid method to improve the electrochemical properties of the nanofiber anode in Li-ion batteries.

The electrochemical storage mechanism of an In2S3/C nanofiber anode for high-performance Li-ion and Na-ion batteries

There are only a handful of reports on indium sulfide (In2S3) in the electrochemical energy storage field without a clear electrochemical reaction mechanism. In this work, a simple electrospinning method has been used to synthesize In2S3/C nanofibers for the first time. In lithium-ion batteries (LIBs), the In2S3/C nanofiber electrode can not only deliver a high initial reversible specific capacity of 696.4 mA h g-1 at 50 mA g-1, but also shows ultra-long cycle life with a capacity retention of 80.5% after 600 cycles at 1000 mA g-1. In sodium-ion batteries (SIBs), the In2S3/C nanofibers electrode can exhibit a high initial reversible specific capacity (393.7 mA h g-1 at 50 mA g-1) and excellent cycling performance with a high capacity retention of 97.3% after 300 cycles at 1000 mA g-1. The excellent electrochemical properties mainly benefited from In2S3 being encapsulated by a carbon matrix, which buffers the volume expansion and significantly improves the conductivity of the composite. Furthermore, the structural evolution of In2S3 during the first lithiation/delithiation and sodiation/desodiation processes has been illustrated by ex situ XRD. The results confirm that the reaction mechanism of In2S3 in both LIBs and SIBs can be summarized as conversion reactions and alloying reactions, which provide theoretical support for the development of In2S3 in the field of electrochemistry.