Bare Carbon Nanotubes Research Articles

Electrochemical Preparation of Poly(arginine)-Modified Carbon Nanotube Paste Electrode and its Application for the Determination of Pyridoxine in the Presence of Riboflavin: An Electroanalytical Approach

A simple poly(arginine) film-modified carbon nanotube paste electrode (PAMCNTPE) was prepared using cyclic voltammetry (CV). The devised sensor was subjected to field-emission scanning electron microscope (FESEM) and CV characterization. The sensing of 0.1 mM pyridoxine (PY) was upgraded at PAMCNTPE as compared to the bare carbon nanotube paste electrode (BCNTPE). The PAMCNTPE detects the 0.1 mM PY at a specific potential 0.727 V with a current response of 10.68 µA. In the case of BCNTPE, the PY appeared at 0.798 V with a current 2.90 µA. The proposed analytical method was optimized by prime parameters such as the impact scan rate, pH and PY concentration. Under optimal conditions, the concentration of PY is directly proportional to oxidation current (Ipa) in linear range 2–10 µM, and 10–80 µM with a detection limit (LOD) of 9.6 × 10−7 M and limit of quantification (LOQ) of 3.21 × 10−6 M. The simultaneous determination, concentration variation analysis of PY is performed with riboflavin (RF) and interference analysis in detecting PY also examined. The proposed sensor was effectively applied for the determination of PY in natural food supplement with excellent recovery.

Adsorption of uranyl ions from its aqueous solution by functionalized carbon nanotubes: A molecular dynamics simulation study

The adsorption behavior of uranyl ions from aqueous medium on the bare carbon nanotubes (CNTs) and CNTs functionalized with –COO−, –OH or –COOH functional groups is investigated by molecular dynamics simulations. The adsorption of uranyl ions on carboxylate ion functionalized CNT is found to be much more than that in other cases. It is also observed that the extent of adsorption on the carboxylate ion functionalized nanotube increases with the extent of functionalization. On the other hand, the maximum adsorption capacity of the –OH and –COOH functionalized CNTs are almost the same as that of the bare one. Detailed analyses demonstrate that the mode of adsorption in –COO– functionalized CNT is different from bare and –OH/-COOH functionalized CNTs. We have shown that the adsorption of uranyl ions on carboxylate ion functionalized CNTs is energetically favorable. In general, mobility of uranyl ions in the solution has been found to decrease with increasing concentration of the uranyl ions. Greater reduction in diffusivity of the uranyl ions in case of –COO– functionalized CNT as compared to other CNTs further confirms that the mode of adsorption for the carboxylate ion functionalized nanotube is different and corroborates the fact that the –COO– functionalized CNT has more adsorption capacity.

Amperometric enzymatic sensing of glucose using porous carbon nanotube films soaked with glucose oxidase

Glucose oxidase was soaked into a porous carbon nanotube film coating on a platinum disk electrode, then trapped beneath a topcoat of electrodeposition paint. The resulting sensors, operated at a potential of +0.6V (vs. Ag/AgCl), produced a glucose signal that was linear up to 40mM, with a 50μM detection limit. Signal stability over >100h of continuous operation in a flow cell showed the remarkable functional durability of the biosensor, and confirmed that the electropaint coating effectively prevented loss of the enzyme. This performance is deemed to derive from the minimalistic immobilization layer design and the prevention of protein leakage. The immobilization method has a potentially wide scope, in that it may also be applicable in other types of enzymatic biosensor. Graphical abstract Illustration of an enzyme biosensor design that uses glucose oxidase in bare carbon nanotube electrode modifications with electropaint topcoat for amperometric glucose quantification. Immobilization matrix supplementation with extra functional (nano-) materials was unnecessary for high-quality and stable analysis performance.

Study of field emission properties of pure graphene-CNT heterostructures connected via seamless interface

Vertically aligned carbon nanotubes (CNTs) have proven to be one of the best materials for use as an efficient field emitter. To further improve their efficiency as well as long-term use in practical devices, it is necessary to reduce the quantum resistance originating from the interface between electrode and emitters and the entanglement of the CNTs in a bundle texture. Thus, the incorporation of graphene at the bottom of CNT bundles via a seamless carbonaceous interface can easily solve this bottleneck. In this work we have demonstrated for the first time, growth and field emission properties of pure seamless graphene-CNT heterostructures and pure seamless graphene-vertically patterned oriented CNTs heterostructures (SGVCNTs) on Si/SiO2 substrates in contrast to the bare CNT mats and few-layer graphene structures without using any tedious post transfer processes. It was observed that seamless SGVCNTs show better field emission performance in terms of higher current density (236 mA cm−2), lowered turn-on field (0.45 V μm−1) and threshold field (1.931 V μm−1 @100 mA cm−2), and improved field enhancement factor (β ∼ 41 315) which is improved ∼4 fold when compared to a bare CNT mat. The significant improvement of the field emission performance of SGVCNTs is mainly attributed to the low resistive seamless C–C covalent carbonaceous interface, the higher number of emitter sites and patterned vertical orientation that leads to long-term stability of the field emitter with minimal loss up to 32 h. This finding could provide an important solution for carbonaceous material based field emitters for real phase device applications.

Polyluminol Modified Carbon Nanotube Electrodes for Electrochemical Capacitors

Luminol exhibits electrochemical redox activity when electropolymerized on various substrates, and has been used for electrocatalysis and biosensors [1, 2]. This electrochemical behavior is due to the presence of different amine functional groups within the polymer structure. Recent studies have shown that introducing amine groups on a carbon surface improves the charge storage capacity and the conductivity of the obtained material [3]. Our work aims to leverage the electrochemical properties of polyluminol (Plum) for electrochemical capacitors (ECs). Firstly, the Plum was synthesized using a chemical approach and characterized using spectroscopic methods and electrochemical analyses. Secondly, the polymer was deposited on carbon nanotubes (CNT) to enhance the charge storage capacity for ECs. The chemical composition of the polymer was found to be a mixture of benzoid and quinoid segments, bonded via secondary (NH) or tertiary amine (=N-) groups, respectively. Such functionalities facilitated chemical, thermal, and electrochemical stability of the polymer. The composite electrode material was obtained by in-situ chemical polymerization of Plum on CNT. Morphological analyses of CNT confirmed the increase of the Plum thickness on CNT with polymerization time, reaching a saturation point of 6.5 nm. In addition, a 4x increase of charge storage capacity with good electrode stability was observed compared to bare CNT over a potential window of 1.2 V as seen in figure 1. Study of the redox reaction kinetics revealed a mostly capacitive contribution of the polymer on CNT. This work showed the successful surface modification and engineering of CNT using a simple and effective fabrication method, which is suitable for large-scale fabrication of composite electrode materials for ECs. G.-F. Zhang and H.-Y. Chen, Analytica Chimica Acta, 419, 25 (2000).A. Sassolas, L. J. Blum and B. D. Leca-Bouvier, Sensors and Actuators B: Chemical, 139, 214 (2009).N. Phattharasupakun, J. Wutthiprom, P. Suktha, N. Ma and M. Sawangphruk, Journal of The Electrochemical Society, 165, A609 (2018). Figure 1

Sensitive and Selective Electrochemical Resolution of Tyrosine with Ascorbic Acid through the Development of Electropolymerized Alizarin Sodium Sulfonate Modified Carbon Nanotube Paste Electrodes

AbstractAn approachable and a selective electrocatalytic investigation of tyrosine (TR) with ascorbic acid (AA) in phosphate buffer solution (PBS) was done using a sensitive Poly Alizarin sodium sulfonate modified Carbon nanotube paste electrode (PASSMCNTPE). The morphological and elemental studies on PASSMCNTPE and bare carbon nanotube paste electrode (BCNTPE) were resolute through field emission scanning electron microscopy (FESEM) and energy dispersive X‐ray spectroscopy (EDX). The PASSMCNTPE shows excellent sensitivity, selectivity, stability, repeatability, and reproducibility for the electrochemical characterization of TR through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The prepared sensor provides an elevated current response towards TR as compared to the BCNTPE. A plot of the anodic peak current of TR and the concentration of TR was obtained linearly in the range 1.4×10−4 M to 2×10−4 M with the limit of detection (LOD) 7.8×10−7 M and the limit of quantification (LOQ) 26×10−7 M respectively. The equipped sensor was also helpful for the quantitative and qualitative analysis of TR moiety in a pharmaceutical drug as a real sample.

Hydrophilicity and carbon chain length effects on the gas sensing properties of chemoresistive, self-assembled monolayer carbon nanotube sensors.

Here we describe the development of chemoresistive sensors employing oxygen-plasma-treated, Au-decorated multiwall carbon nanotubes (MWCNTs) functionalized with self-assembled monolayers (SAMs) of thiols. For the first time, the effects of the length of the carbon chain and its hydrophilicity on the gas sensing properties of SAMs formed on carbon nanotubes are studied, and additionally, the gas sensing mechanisms are discussed. Four thiols differing in the length of the carbon chain and in the hydrophobic or hydrophilic nature of the head functional group are studied. Transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy are used to analyze the resulting gas-sensitive hybrid films. Among the different nanomaterials tested, short-chain thiols having a hydrophilic head group, self-assembled onto Au-decorated carbon nanotubes were most responsive to nitrogen dioxide and ethanol vapors, even in the presence of ambient humidity. In particular, this nanomaterial was about eight times more sensitive to nitrogen dioxide than bare Au-decorated carbon nanotubes when operated at room temperature. This response enhancement is attributed to the interaction, via strong hydrogen bonding, of the polar molecules tested to the polar surface of hydrophilic thiols. The approach discussed here could be extended further by combining hydrophilic and hydrophobic thiol SAMs in Au-MWCNT sensor arrays as a helpful strategy for tuning sensor response and selectivity. This would make the detection of polar and nonpolar gas species employing low-power gas sensors easier, even under fluctuating ambient moisture conditions.

Determination of Riboflavin at Carbon Nanotube Paste Electrodes Modified with an Anionic Surfactant

AbstractA Sodium lauryl sulfate modified carbon nanotube paste electrode (SLSMCNTPE) was fabricated for the electroanalysis of Riboflavin (RF) in phosphate buffer solution (PBS) at pH, 7.0 by cyclic voltammetry (CV). The electrode was found to be a very sensitive tool for detection of RF; it was shown that SLSMCNTPE yields a high current response towards RF as compared to the bare carbon nanotube paste electrode (BCNTPE). Key parameters were optimized for RF determination. The effects of surfactant concentration, pH, scan rate and concentration of RF on the oxidation peak current values were determined. The RF oxidation peak appeared at −440 mV and reduction peak at −575 mV vs. saturated calomel electrode (SCE). The SLSMCNTPE revealed good repeatability, reproducibility, stability, high electrochemical sensitivity in its voltammetric response and a detection limit of 9.25×10‐8 M.

Design of novel Surfactant Modified Carbon Nanotube Paste Electrochemical Sensor for the Sensitive Investigation of Tyrosine as a Pharmaceutical Drug.

Purpose: The novel sodium dodecyl sulfate modified carbon nanotube paste electrode (SDS/ CNTPE) was used as a sensitive sensor for the electrochemical investigation of L-tyrosine (TY). Methods: The electrochemical analysis of TY was displayed through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The surface morphology of SDS/CNTPE and bare carbon nanotube past electrode (BCNTPE) was reviewed trough field emission scanning electron microscopy (FESEM). Results: The functioning SDS/CNTPE shows a voltammetric response with superior sensitivity towards TY. This study was conducted using a phosphate buffer solution having neutral pH (pH=7.0). The correlation between the oxidation peak current of TY and concentration of TY was achieved linearly in CV method, in the range 2.0×10-6 to 5 ×10-5 M with the detection limit 729 nM and limit of quantification 2.43 μM. The investigated voltammetric study at SDS/CNTPE was also adopted in the examination of TY concentration in a pharmaceutical medicine as a real sample with the recovery of 97% to 98% . Conclusion: The modified electrode demonstrates optimum sensitivity, constancy, reproducibility, and repeatability during the electrocatalytic activity of TY.

Gas Sensing with Iridium Oxide Nanoparticle Decorated Carbon Nanotubes.

The properties of multi-wall carbon nanotubes decorated with iridium oxide nanoparticles (IrOx-MWCNTs) are studied to detect harmful gases such as nitrogen dioxide and ammonia. IrOx nanoparticles were synthetized using a two-step method, based on a hydrolysis and acid condensation growth mechanism. The metal oxide nanoparticles obtained were employed for decorating the sidewalls of carbon nanotubes. Iridium-oxide nanoparticle decorated carbon nanotube material showed higher and more stable responses towards NH3 and NO2 than bare carbon nanotubes under different experimental conditions, establishing the optimal operating temperatures and estimating the limits of detection and quantification. Furthermore, the nanomaterials employed were studied using different morphological and compositional characterization techniques and a gas sensing mechanism is proposed.

Bottom-Up Synthesis and Mechanical Behavior of Refractory Coatings Made of Carbon Nanotube-Hafnium Diboride Composites.

We use aligned carbon nanotube (CNT) forests as scaffolds to deposit hafnium diboride (HfB2) and fabricate millimeter-thick ultrahigh-temperature composite coating. HfB2 has a melting temperature of 3250 °C, which makes it an attractive candidate for applications requiring operation in extreme environments. Compared to typical refractory HfB2 processing, which requires temperatures exceeding 1500 °C, we use conformal HfB2 chemical vapor deposition (CVD) to coat CNT forests at a low temperature of 200 °C. During this process, nanometer-thin HfB2 films grow on the CNT surface and uniformly fill tall CNT forests, thus transforming nanometer film deposition to a scalable HfB2 coating technology. The conformal HfB2 coating process uses static (S-) CVD, where the precursor is fed into a closed system, enabling highly conformal coating and economically efficient utilization of the HfB2 precursor reaching 85%. The modulus and compressive strength of the composites are measured using flat-punch indentation of micropillars having various coating thickness. Filling the CNTs with HfB2 strengthens their node morphology and effectively enhances the mechanical properties. We study the nonlinear behavior of the material to extract a unique modulus value that describes the stress-strain response at any applied compression. At the highest HfB2 coating thickness of 45 nm, the solid fraction is increased from 2% for the bare CNTs to 36% for the composite; the modulus and strength reach 107 and 1.5 GPa, respectively. An analytical model is used to explain the mechanism of the measured structure-mechanical property scaling. Finally, the process is used to fabricate CNT-HfB2 films having 1.7 mm height, a centimeter square area, and only 5.8 × 10-6 nm/nm thickness gradient to demonstrate the potential for scalability.

Removal of Cr(VI) by magnetic Fe/C crosslinked nanoparticle for water purification: rapid contaminant removal property and mechanism of action.

In this study, a novel method based on the magnetic Fe/C crosslinked nanoparticles (MNZVI/CNTs-OH) is reported for the effective removal of Cr(VI) in aqueous solutions. Parameters that influence the effectiveness of the nanoparticles, such as pH, temperature, reaction time, and particle dosage, was analyzed. It was found that MNZVI/CNTs-OH particles exhibit significantly higher activity toward Cr(VI) removal than bare NZVI, carbon nanotubes (CNTs), and other synthetic nanomaterials. Under optimized conditions, the removal efficiency of Cr(VI) by MNZVI/CNTs-OH is up to 98% with an initial contaminant concentration of 50 mg/L, and chromium content in the residue up to 48 mg/g. Physical characterizations, including Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and TG-TD measurements, provide insights into the working mechanism of Cr(VI) purification. Our findings suggest that immobilization of MNZVI onto carbon nanotubes increase the covalent bond property, while crosslinked nanoparticles (NPs) provide the electron transfer passage from the NZVI surface and improves the dispersity of the MNZVI, thus enhancing the performance. These results demonstrate the potential of the MNZVI/CNTs-OH nanoparticles for the rapid and efficient treatment of Cr(VI)-containing wastewater.

Vapor-Assisted Ex-Situ Doping of Carbon Nanotube toward Efficient and Stable Perovskite Solar Cells.

Single-walled carbon nanotubes (CNTs) has been considered as a promising material for a top electrode of perovskite solar cells owing to its hydrophobic nature, earth-abundance, and mechanical robustness. However, its poor conductivity, a shallow work function, and nonreflective nature have limited further enhancement in power conversion efficiency (PCE) of top CNT electrode-based perovskite solar cells. Here, we introduced a simple and scalable method to address these issues by utilizing an ex-situ vapor-assisted doping method. Trifluoromethanesulfonic acid (TFMS) vapor doping of the free-standing CNT sheet enabled tuning of conductivity and work function of the CNT electrode without damaging underneath layers. The sheet resistance of the CNT sheet was decreased by 21.3% with an increase in work function from 4.75 to 4.96 eV upon doping of TFMS. In addition, recently developed 2D perovskite-protected Cs-containing formamidium lead iodide (FACsPbI3) technology was employed to maximize the absorption. Because of the lowered resistance, better energy alignment, and improved absorption, the CNT electrode-based PSCs produced a PCE of 17.6% with a JSC of 24.21 mA/cm2, VOC of 1.005 V, and FF of 0.72. Furthermore, the resulting TFMS-doped CNT-PSCs demonstrated higher thermal and operational stability than bare CNT and metal electrode-based devices.

Mn3O4-Anchored Carbon-Nanotube Based Asymmetric Supercapacitor

A facile route to anchor pseudocapacitive materials on multi-walled Carbon Nanotubes (CNTs) to realize high-performance electrode materials for Asymmetric Supercapacitors (ASCs) is achieved. The anchoring process is achieved after direct decomposition of metal-hexacyanoferrate complexes on the CNT surface. Transmission electron microscopy (TEM) analysis reveals that the nanoparticles (NPs) are discretely attached over CNT surface without forming a uniform layer, thus making almost entire NP surface available for electrochemical reactions. Accordingly, CNT-Mn3O4 nanocomposite cathode shows significantly improved capacitive performance as compared to bare CNT electrode, validating the efficacy of designing the composite electrode. With CNT-Fe3O4 nanocomposite as paired anode, the hybrid ASC delivers a specific capacitance of 135.2 F/g at a scan rate of 10 mV/s within a potential window of 0-1.8V in the aqueous electrolyte and retains almost 100% of its initial capacitance even after 15000 cycles.

SnO2 Nanowires on Carbon Nanotube Film as a High Performance Anode Material for Flexible Li-ion Batteries

Today, Li-ion batteries (LIBs) are the most common rechargeable batteries used in electronic devices. SnO2 with theoretical specific capacity of 782 mAh/g is among the best anode materials for LIBs. In this report, Three-dimensional SnO2 nanowires (NWs) on carbon nanotube (CNT) thin film (SnO2 / CNT) is fabricated using a combination of vacuum filtration and thermal evaporation techniques. The resulting 3D heterostructure SnO2/CNT was characterized by X-ray diffraction, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). This fabricated SnO2/CNT electrode has been tested as a flexible and binder-free anode for LIB, which exhibits high initial discharge/charge capacity of 4.8/2.25 mAh/cm2 at a current density of 0.25 A/g, much larger than discharge/charge capacity of bare CNT film (2.2/0.3 mAh/cm2). Relatively high areal capacity of 1.23 mAh/cm2 has been achieved for the fabricated LIB with SnO2/CNT electrode after 20 cycles, proposing this material as a high performance flexible LIB anode material.

Influence of the morphological structure of carbon nanotubes on the viscoelasticity of PMMA‐based nanocomposites

ABSTRACTThe rheological behavior of polymeric nanocomposites provides major determination for their processability. In this work, three carbon nanotubes (CNTs) with varied geometries were adopted as nanofiller and then were introduced into poly(methyl methacrylate) (PMMA) matrix with different loadings (0.07–1.0 wt %). The different preparation routine led to varied CNTs dispersion states, on which the shear viscosity and the compressibility of their melts were proved to be sensitive. The technology for the preparation of their nanocomposites played a crucial role in controlling their rheological behavior. With melting blended bare CNTs, the dynamic shear viscosity of PMMA/CNTs increased with the increase of CNTs content, accompanied by aggregated CNTs in which no polymer matrix was entrapped. With the help of surface modification and pre‐mixing, well dispersed CNTs were obtained and a rather low aggregation rate ca. 0.029% was revealed. The well dispersed CNTs with an organic layer which was constructed by small molecules and presented lower viscosity. Such CNTs led to no remarkable clusters within polymer host and played the role of lubricant with an increased‐mobility layer, which can be reflected from the weighted relaxation time spectra. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46444.

Efficient Capacitive Deionization Using Thin Film Sodium Manganese Oxide

More energy efficient desalination methods are needed to address global water scarcity. Capacitive deionization (CDI) is an emerging electrochemical desalination technology that could outperform other desalination technologies if new electrode materials were developed with high salt sorption capacity and efficiency. In this paper, we report on the desalination performance of thin-film sodium manganese oxide (NMO). We deposit thin-film MnO via atomic layer deposition (ALD), and electrochemically convert the MnO to NMO in NaCl(aq). Charge storage capacity is tuned with NMO thickness, and the relationship between charge storage capacity and reversible salt sorption is probed. NMO coated electrodes exhibit increases in charge storage capacity up to 170 times higher than uncoated electrodes. Electrochemical quartz crystal microbalance (EQCM) measurements reveal that thin-film NMO leads to the efficient electrochemical removal of Na+ ions. A hybrid CDI (HCDI) cell comprised of NMO-coated carbon nanotube (CNT) cathode and Ag nanoparticle-decorated CNT anode yields a ∼20-fold improvement in charge storage over bare CNT electrodes. The HCDI cell has an anomalously high reversible charging efficiency, which we study using ab initio modeling and EQCM. This is the first CDI report using thin film NMO, and the high desalination efficiency we identify promises to facilitate the development of HCDI devices with enhanced performance.

Charge calculation studies done on a single walled carbon nanotube using MOPAC

Dipole symmetry of induced charges on DWNTs are required for their application as a nanomotor. Earlier a molecular dynamics analysis was performed for a double-walled carbon-nanotube based motor driven by an externally applied sinusoidally varying electric field. One of the ways to get such a system is chemical or end functionalization, which promises to accomplish this specific and rare configuration of the induced charges on the surface of the carbon nanotube (CNT). CNTs are also a promising system for attaching biomolecules for bio-related applications. In an earlier work, ab initio calculations were done to study the electronic and structural properties of the groups –COOH, –OH, –NH2 and –CONH2 functionalized to an (8, 0) SWNT. The systems were shown to have a very stable interaction with the CNTs. The exterior surface of the SWNT is found to be reactive to NH2 (amidogen). In this work, charge calculations are done on a CNT using MOPAC, which is a semi empirical quantum chemistry software package. As a first step, we calculate the effect of NH2 functionalization to a (5,0) SWNT of infinite length. The symmetric charge distribution of the bare SWNT is observed to be disturbed on addition of a single NH2 in the close proximity of the SWNT. A net positive and opposite charge is observed to be induced on the opposite sides of the nanotube circumference, which is, in turn, imperative for the nanomotor applications. The minimum and maximum value of the charge on any atom is observed to increase from − 0.3 to 0.6 and from − 0.3 to − 1.8 electronic charge as compared to the bare SWNT. This fluctuation of the surface charge to larger values than bare CNT, can be attributed to the coulomb repulsion between NH2 and the rest of the charge on the surface which results into minimizing the total energy of the system. No such opposite polarity of charges are observed on adding NH2 to each ring of the SWNT implying addition of a single amidogen to be the most appropriate configuration to produce a DWNT configuration suited to act like a nanomotor.

An Ultraflexible Silicon-Oxygen Battery Fiber with High Energy Density.

To satisfy the rapid development of portable and wearable electronics, it is highly desired to make batteries with both high energy densities and flexibility. Although some progress has been made in recent decades, the available batteries share critical problems of poor energy storage capacity and low flexibility. Herein, we have developed a silicon-oxygen battery fiber with high energy density and ultra-high flexibility by designing a coaxial architecture with a lithiated silicon/carbon nanotube hybrid fiber as inner anode, a polymer gel as middle electrolyte and a bare carbon nanotube sheet as outer cathode. The fiber showed a high energy density of 512 Wh kg-1 and could effectively work after bending for 20 000 cycles. These battery fibers have been further woven into flexible textiles for a large-scale application.

An Ultraflexible Silicon–Oxygen Battery Fiber with High Energy Density

AbstractTo satisfy the rapid development of portable and wearable electronics, it is highly desired to make batteries with both high energy densities and flexibility. Although some progress has been made in recent decades, the available batteries share critical problems of poor energy storage capacity and low flexibility. Herein, we have developed a silicon–oxygen battery fiber with high energy density and ultra‐high flexibility by designing a coaxial architecture with a lithiated silicon/carbon nanotube hybrid fiber as inner anode, a polymer gel as middle electrolyte and a bare carbon nanotube sheet as outer cathode. The fiber showed a high energy density of 512 Wh kg−1 and could effectively work after bending for 20 000 cycles. These battery fibers have been further woven into flexible textiles for a large‐scale application.