Search

1H NMR and DSC on [EMIm+][FSI−] confined in Si-templated carbons revealed a wider freezing temperature range, as compared to the neat IL, due to ions in interaction with the mesopore walls remaining mobile even if the IL in pore center is frozen.

Hierarchical micro/mesoporous carbons obtained by template carbonization were investigated by nitrogen adsorption/desorption and gave a type IV isotherm with a H1 hysteresis loop closing perfectly near P/P0 = 0.6. When using the 2D-NLDFT theory to calculate the pore size distribution (PSD) from the adsorption branch of the isotherms, while assuming slit pores with a heterogeneous rough surface (2D–HS–SLIT model), an unexpected artifact was observed ca. 3.5 nm. Recognizing that the H1 hysteresis loop is usually related to the adsorption in materials with cylindrical pores, where in general it is recommended to use the desorption branch for the pore size analysis, we have applied the 2D–HS–SLIT model to the adsorption isotherm up to P/P0 = 0.2 and a cylindrical pore model to the desorption isotherm down to P/P0 = 0.2. Interestingly, the application of this dual shape pore model to hierarchical micro/mesoporous carbons of various mesopore sizes and oxygenated surface functionalities shows an excellent fit with the experimental isotherms, while the mesopore peak in the PSDs is narrower, and the previously labeled artifact is eliminated. It is noteworthy that the cumulative surface area values are significantly larger than when applying the 2D–HS–SLIT model, what is due to the larger surface area of cylindrical than slit-shaped mesopores.

Flexible three-dimensional interconnected carbon nanotubes on the carbon cloth (3D-CNTs/CC) were obtained through simple magnesium reduction reactions. According to the Nernst equation, the cell voltage based on these pure carbon electrodes without any additives could reach 1.5 V due to the higher di-hydrogen evolution over potential in neutral 3.5 M LiCl electrolytes. In order to improve the electrochemical performance of the electrodes, 3D-CNTs/CC electrodes covered with polyaniline barrier layer (3D-PANI/CNTs/CC) were prepared by in situ electropolymerization using interfacial engineering method. The assembled symmetric supercapacitors display a broadened voltage of 1.8 V, high areal capacitance of 380 mF cm−2, outstanding areal energy density of 85.5 μWh cm−2 and 84% of its initial capacitance after 20 000 charge-discharge cycles. This work demonstrated that the interface engineering strategy provides a promising way to improve the energy density of carbon-based aqueous supercapacitors by widening the voltage and boosting the capacitance simultaneously.

Quasi-solid-state fiber-shaped aqueous supercapacitors (FSASs) are regarded as one of the most promising candidates for high-performance energy storage devices of wearable consumer electronics, due to outstanding cycle stability, high safety and decent mechanical flexibility. The dominated obstacle facing current FSASs system is their quite limited energy density, which is the consequence of insufficient active sites of electrodes, and narrow operating voltage window of electrolyte. In the light of the outlined issues, a novel symmetric FSAS comprising surface-wrinkled and N-doped reduced graphene oxide (rGO) fiber (NRGF) electrodes matched with concentrated “water-in-salt” gel polymer electrolyte (GPE, 8.96 M) was reported in this work. Benefit from the one-dimensional porous microstructure of NRGF and improved hydration energy of GPE, the assembled FSAS has delivered a widely broadened voltage window of 0–2.2 V, an ultrahigh energy density of 25.6 μWh cm−2 (22.7 mWh cm−3) and an outstanding cycling stability for over 20,000 cycles. The electrochemical performance of this FSAS can be well-maintained even under different deformation conditions or after numerous bending cycles. Interestingly, the as-fabricated FSAS can also deliver high energy density from 8.4 μWh cm−2 to 36.6 μWh cm−2 in a temperature range of -20-70 °C, exhibiting a great potential for wide-temperature aqueous energy device.

Fiber-shaped photocapacitors (FPCs) combine functions of energy harvesting and storage in a single device has attracted great attention for their potential applications in portable and wearable electronics. However, the FPCs suffer from the low photochemical-electric energy conversion efficiency and poor cycling stability due to the limitation of the fiber-shaped electrodes. Herein, high crystalline conductive polymer fibers with high electrocatalytic activity and energy storage efficiency for both energy harvest and energy storage are prepared and used as shared electrode to fabricate efficient and stable FPCs. Synergistically, the FPCs fabricated by combining a fiber-shaped dye-sensitized solar cell and a fiber-shaped supercapacitor into one device by sharing one electrode exhibit a remarkable total photochemical-electric energy conversion efficiency up to 5.1%, which is higher than that of reported energy fibers and even close to those of the planar devices in previous reports. Meanwhile, the fabricated FPCs show superior cycling capability for more than 1700 photocharge/galvanostatic discharge cycles (63 days) with efficiency retention of 70.6%. The FPCs woven into the textile can steadily power the ultraviolet photodetector after photocharged in natural sunlight, showing potential in the application of wearable electronics.

Fiber-shaped rechargeable batteries are expected to be the energy storage device as a necessary part of the next generation of wearable electronics. However, their application is severely hindered by the difficulty in manufacture of flexible fiber-shaped electrodes with promising electrochemical performance. Here, we fabricated the unique self-supporting nanotube array of sulfur-doped TiO2 (S TiO2) to obtain flexible fiber-shaped electrode with excellent sodium storage properties. The as-prepared S TiO2 fiber electrode has a high reversible capacity of about 183 mA h g−1 at 40 mA g−1, excellent rate capability (142 mA h g−1 at 80 mA g−1) and stable cycling performance (75% retention over 100 cycles at 80 mA g−1). It is worth noting that a flexible fiber-shaped sodium-ion battery was maintained a high reversible capacity under different bending states. This work offers a novel electrode-fabrication method towards broadenning metallic oxide fiber electrodes application especailly in flexible energy storage devices.

The fiber-shaped dye sensitized solar cell represents a promising flexible power conversion system for next generation wearable electronics due to its facile preparation, lightweight, and good weav...

With the rapid development of wearable electronics, smart devices with fast response to external stimulus are attracting our considerable attention. Among them, multifunctional integrated devices which can integrate many functions in one device and miniaturize their volume are much needed. Herein, single Janus iodine-doped rGO/rGO film(IrGO/rGO) with multi-responsive actuation and high capacitance is developed for smart integrated electronics. When served as multiple-responsive actuator materials including humidity, heat and electricity actuation, the single Janus IrGO/rGO film shows exceptionally large static deformation, fast response bending rate up to 70° per second and highly durable repeatability. While worked as electrodes, IrGO/rGO film based supercapacitors exhibit remarkable electrochemical performances with a specific areal capacitance of 12.4 mF cm−2 at a current density of 0.01 mA cm−2 and capacitance retention of 89.2% after 5000 cycles. Based on these extraordinary properties, a smart mechanical gripper and a multifunctional integrated supercapacitor device with smart stimulus-controlled reversible actuator switches were successfully built using the single IrGO/rGO film as the functional materials, demonstrating the application potential in different kinds of smart multifunctional integrated devices.

Fiber-shaped supercapacitors (FSCs) have great promises in wearable electronics applications. However, the limited specific surface area and inadequate structural stability caused by the weak interfacial interactions of the electrodes result in relatively low specific capacitance and unsatisfactory cycle lifetime. Herein, solid-state FSCs with high energy density and ultralong cycle lifetime based on polyaniline (PANI)/sulfur-doped TiO2 nanotube arrays (PANI/S-TiO2) are fabricated by interfacial engineering. The experimental results and ab initio calculations reveal that S doping can effectively promote the conductivity of titania nanotubes and increase the binding energy of PANI anchored on the electrode surface, leading to a much stronger binding of PANI on the surface of the electrode and excellent electrode structure stability. As a result, the FSCs using the PANI/S-TiO2 electrodes deliver a high specific capacitance of 91.9 mF cm–2, a capacitance retention of 93.78% after 12 000 charge–discharge cycl...

Stretchable fiber-shaped supercapacitors (SFSSs) with high energy density and high-voltage output are becoming increasingly critical for powering wearable electronics. However, challenges still exist in the pursuit of combination of mechanical stretchability and excellent electrochemical performance due to the limitation of the fiber electrode. Here we circumvent these problems by developing a new type of “internal tandem” stretchable fiber-shaped supercapacitors based on high crystalline “all-in-one” polymer fiber. This polymer fiber has the combined properties of high conductivity, high flexibility, high specific capacitance and wide electrochemical window that can simultaneously function as electrical conductive wire and as energy storage electrode in an assembled device. The symmetric assembled tandem SFSS groups (T-SFSSs) are fabricated without the use of metal wire and additional welding connection showing tunable voltage output, tailored capacitance and outstanding stretchablility. The resulting T-SFSS assemblies consisting of 8 serially connected cells display high-voltage output of 12.8 V, ultrahigh energy density of 41.1 μW h cm−2 at power density of 3520 μW cm−2 and remarkable stretchability of up to 400% without obvious capacitance degradation. This work provides a new family of flexible fiber electrode and novel concept designs of flexible power systems that could be threaded or integrated into wearable and portable electronics.

The development of flexible electronics requires the power sources with matchable flexibility, robust mechanic property, as well as high power and energy density that would maintain the durability of flexible electronics during use. Herein, newly designed free-standing N-doped carbon films with hierarchical structure of carbon nanofibers and carbon nanotubes (CNFs/CNTs hybrids) are prepared via a simple electrospinning process. This interconnected hybrid film displays high conductivity and excellent flexibility. As a free-standing and binder-free anode material, the CNFs/CNTs hybrid electrode can achieve a reversible capacity of 1099.5 mAh g −1 at a current density of 0.05 A g −1 with superior rate capabilities and excellent cyclic stability. What's more, utilizing the CNFs/CNTs hybrid film as the electrode, this assembled highly flexible half and full batteries also show attractive performances and can easily light up a group of 12 light emission diodes at flat and various bending positions, making it possible to be applied in the flexible electronic devices.

Flexible supercapacitors have attracted great interest due to outstanding flexibility and light weight. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) fibers have the great potential in using as electrodes for flexible supercapacitors due to the good flexibility. However, the reported conductivity and specific capacitance of these PEDOT: PSS fibers are not very high, which limit their electrochemical performances. In this work, composite fibers of reduced graphene oxide(rGO)-PEDOT: PSS with a highly-wrinkled structure on the surface and pores inside are prepared by wet spinning. The fibers with different ratios of graphene to PEDOT:PSS show a distinctly enhanced conductivity up to ca. 590 S·cm−1 and high strength up to ca. 18.4 MPa. Meanwhile, the composite fibers show an improved electrochemical performances, including a high specific areal capacitance of 131 mF cm−2 and high specific areal energy density of 4.55 μWh·cm−2. The flexible supercapacitors including fiber-shaped supercapacitors and interdigital designed supercapacitors not only could work in different bending states without obvious capacitance decay, but also have small leakage current. The interdigital design can further improve the performances of composite fibers with high capacitance and high utilization compared with traditional parallel connected structure.

Rolled-up fiber scrolls with outer omnidirectional porous and inner hierarchical porous structure have been fabricated as electrodes of fiber-shaped supercapacitors (FSCs) by polymerizing polyaniline (PANi) nanopillars onto hierarchical 3D interconnected porous N-doped carbon nanofibers scrolls (PANi-HCNFs). The as-prepared fiber-shaped PANi-HCNFs electrode materials used for all solid-state FSCs display excellent electrochemical performance with a high specific capacitance of 339.3 F g−1 (85.1 mF cm−1) and specific mass energy density of 11.6 Wh kg−1 (areal energy density of 4.28 μWh cm−2). Meanwhile, PANi-HCNFs show good cycling stability with capacity retention of 74.2% after 3000 cycles at 0.5 A g−1. The superior electrochemical performance can be attributed to the combining of PANi nanopillars array on the 3D interconnected conducting network with the outer omnidirectional porous and inner hierarchical porous composite structure. This unique composite structure can provide high specific surface area, enabling the effective transport of electrolyte to the inner region of the composite fiber. The backbones of N-doped carbon nanofibers form abundant interconnected conductive network and offer multiple electronic transfer paths. Meanwhile, introducing nanostructured PANi nanopillars array into the carbon matrix can improve higher energy density and provide better cycling stability.

Three-dimensional (3D) flexible electrodes of stringed hollow nitrogen-doped (N-doped) carbon nanospheres as graded sulfur reservoirs and conductive frameworks were elaborately designed via a combination of the advantages of hollow structures, 3D electrodes and flexible devices. The as-prepared electrodes by a synergistic method of electrospinning, template sacrificing and activation for Li–S batteries without any binder or conductive additives but a 3D interconnected conductive network offered multiple transport paths for electrons and improved sulfur utilization and facilitated an easy access to Li+ ingress/egress. With the increase of density of hollow carbon spheres in the strings, the self-supporting composite electrode reveals an enhanced synergistic mechanism for sulfur confinement and displays a better cycling stability and rate performance. It delivers a high initial specific capacity of 1422.6 mAh g−1 at the current rate of 0.2C with the high sulfur content of 76 wt.%, and a much higher energy density of 754 Wh kg−1 and power density of 1901 Wh kg−1, which greatly improve the energy/power density of traditional lithium–sulfur batteries and will be promising for further commercial applications.

Fiber-shaped supercapacitors (FSCs) have great promises in wearable electronics applications. However, the limited specific surface area and inadequate structural stability caused by the weak interfacial interactions of the electrodes result in relatively low specific capacitance and unsatisfactory cycle lifetime. Herein, solid-state FSCs with high energy density and ultralong cycle lifetime based on polyaniline (PANI)/sulfur-doped TiO

Recently, fiber-shaped yarn supercapacitors (YSCs) have attracted extensive attention due to their merits of small volume, high flexibility and potential to be woven in textiles for future wearable electronics. PEDOT:PSS possesses properties of high-redox capacitance, high conductivity and high intrinsic flexibility, so PEDOT:PSS yarn electrodes are quite promising in the field of YSCs. However, to the best of our knowledge, twisted yarns based on wetspun PEDOT:PSS fibers for fiber-shaped YSCs have not been reported. Herein, we develop a new coagulation bath with CaCl2 in aqueous solution for preparing meter-long PEDOT:PSS fibers. The PEDOT:PSS fibers with good mechanical properties can be easily woven, sewed, knotted and braided as the YSC electrode. The PEDOT:PSS fiber-based YSCs show a high areal capacitance of 119 mF cm−2 and areal energy density of 4.13 μW h cm−2. Meanwhile, the all-solid-state YSCs are flexible and robust enough to tolerate the long-term and repeated bending without an obvious capacitance drop.

Porous network-like FeOOH/ carbonized bacterial cellulose (FeOOH/CBC) nanocomposite was successfully prepared and used as adsorbent of organic dyes. The phases, morphology, structure and adsorptive properties of FeOOH/CBC nanocomposite were characterized by XRD, FI-IR, SEM, TEM, BET and UV–vis. The adsorption equilibrium of as-prepared FeOOH/CBC nanocomposite for methyl orange (MO) was achieved within one hour, with the maximum adsorption capacity for MO reaching 107.68 mg/g at pH 6.0 and 30 °C. As-prepared FeOOH/CBC nanocomposite maintains high adsorption activities after four times of adsorption and desorption, accompanying the removal rate for MO is up to 60% in 10 min.