conventional 3D and 2D types when used for miniaturized electronic devices, textile electronics, and implantable medical devices. [1,2] However, compared with other energy storage devices such as batteries, the much lower stored specific energy of 1D supercapacitors limited their practical applications. Since the energy stored in a supercapacitor is proportional to CV 2 (E = 1/2 CV 2 , where C is the capacitance of the device and V is the operating voltage), enhancements in energy density can be achieved by increasing the specific capacitance (C) or widening the operating voltage range (V). [3] Specific capacitance can be improved by the incorporation of electrochemically active nanomaterials (e.g., metal oxides or conducting polymers) into the base electrode materials, such as carbon nanotube (CNT) or graphene assemblies. In comparison, insufficient attention has been paid to improve the voltage range of flexible supercapacitors. This is especially true in fiber-shaped supercapacitors (FSSs), which usually show ideal capacitive behavior only in a relatively small potential window (0.8-1.0 V), [4][5][6][7][8][9][10][11][12][13][14] and consequently deliver limited energy or power densities. An effective approach for addressing this issue is the strategy of asymmetric electrode configuration by coupling different positive and negative electrode materials with well-separated potential windows for achieving a high operating voltage. [15][16][17][18] So far, several papers addressing asymmetric FSS can be found in the literature. A fiber-based flexible all-solid state asymmetric supercapacitor using molybdenum disulfide (MoS 2 )-reduced graphene oxide (rGO)/multiwalled carbon nanotube (MWCNT) and rGO/MWCNT fibers has accomplished a potential window of 1.4 V with high Coulombic efficiency and improved energy density. [19] Cheng et al. reported an asymmetric fiber-shaped supercapacitor based on MnO 2 /conducting polymer/CNT fiber and ordered microporous carbon/ CNT hybrid fiber as positive and negative electrode, respectively, which produced a high energy density of 11.3 mW h cm −3 . [20] Yang et al. fabricated a fiber-shaped asymmetric supercapacitor by using porous NiO/Ni(OH) 2 /PEDOT/contra wire electrode as the positive electrode, and the ordered mesoporous carbon fiber as the negative electrode. The supercapacitor exhibited an output voltage of 1.5 V. [21] Wang et al. used titanium wire/cobalt oxide (Co 3 O 4 ) nanowires and carbon fibers/graphene electrodes to fabricate an asymmetric supercapacitor, which enhanced both stored energy and delivered power by at least 1860% compared with that of the supercapacitor with a potential window The emerging fiber-shaped supercapacitors (FSSs) have motivated tremendous research interest in energy storage devices. However, challenges still exist in the pursuit of combination of excellent electrochemical performance and mechanical stretchability. Here, a core-sheath asymmetric FSS is first made by wrapping gel electrolyte coated carbon nanotube (CNT)@MnO 2 core fiber with CNT@...

The emergence of stretchable electronic devices has attracted intensive attention. However, most of the existing stretchable electronic devices can generally be stretched only in one specific direction and show limited specific capacitance and energy density. Here, we report a stretchable isotropic buckled carbon nanotube (CNT) film, which is used as electrodes for supercapacitors with low sheet resistance, high omnidirectional stretchability, and electro-mechanical stability under repeated stretching. After acid treatment of the CNT film followed by electrochemical deposition of polyaniline (PANI), the resulting isotropic buckled acid treated CNT@PANI electrode exhibits high specific capacitance of 1147.12 mF cm(-2) at 10 mV s(-1). The supercapacitor possesses high energy density from 31.56 to 50.98 μWh cm(-2) and corresponding power density changing from 2.294 to 28.404 mW cm(-2) at the scan rate from 10 to 200 mV s(-1). Also, the supercapacitor can sustain an omnidirectional strain of 200%, which is twice the maximum strain of biaxially stretchable supercapacitors based on CNT assemblies reported in the literature. Moreover, the capacitive performance is even enhanced to 1160.43-1230.61 mF cm(-2) during uniaxial, biaxial, and omnidirectional elongations.

A new and facile vapor deposition method has been developed for the preparation of sol-gel matrix. This method was used to form a titania sol-gel thin film and to immobilize horseradish peroxidase (HRP) on a glassy carbon electrode surface for the production of an amperometric hydrogen peroxide biosensor. This process prevented the cracking of conventional sol-gel-derived glasses. The morphologies of both titania sol-gel and the enzyme membranes were characterized using scanning electron microscopy and proved to be chemically clean, porous, and homogeneous and to have a very narrow particle size distribution. The sol-gel-derived titania-modified electrode retained the enzyme bioactivity and provided for long-term stability of the enzyme in storage. In the presence of catechol as a mediator, the sensor exhibited a rapid electrocatalytic response (less than 5 s), a linear calibration range from 0.08 to 0.56 mM with a detection limit of 1.5 microM and a high sensitivity (61.5 microA mM(-1)) for monitoring of H2O2. Effects of pH and operating potential were also explored for optimum analytical performance by using the amperometric method. The apparent Michaelis-Menten constant of the encapsulated HRP was 1.89 +/- 0.21 mM.

Flexible energy storage electronics have gained increasing attention in recent years, but the simultaneous acquiring of high volumetric and high areal capacities as well as excellent flexibility in order to truly implement wearable and portable electronics in practice remains challenging. Here, a conductive and highly deformable freestanding all‐pseudocapacitive paper electrode (Ti3C2Tx/MnO2 NWs) is fabricated by solution processing of hybrid inks based on Ti3C2Tx MXene and ultralong MnO2 nanowires. The resulting Ti3C2Tx/MnO2 NWs hybrid paper manifests a remarkable areal capacitance of up to 205 mF cm−2 and outstanding volumetric capacitance of 1025 F cm−3. Both the values are highly comparable with, or in most cases much higher than those of previously reported MXene‐based flexible electrodes. The excellent energy storage performance is well maintained with a capacitance retention of 98.38% during 10 000 charge–discharge cycles. In addition, the flexible supercapacitor demonstrates excellent flexibility and electrochemical stability during repeated mechanical bendings of up to 120°, suggesting great potentials for the applications in future flexible and portable electronics.

No abstract

The as-prepared Fe7S8@C exhibits outstanding electrochemical performance as anode materials for LIBs and SIBs owing to the biscuit-like nanostructure and conformal surface coating with carbon.

Sodium-ion batteries (SIBs) have attracted tremendous interest and become a worldwide research hotpot owing to their low cost and abundant resources. To obtain suitable anode materials with excellent performance for SIBs, an effective and controllable strategy is presented to fabricate SnS nanosheets coating on nanohollow cubic CoS /C (CoS /C@SnS ) composites with a hollow structure using Co-metal-organic frameworks as the starting material. As anodes for SIBs, the CoS /C@SnS electrode exhibits ultralong cycle life and excellent rate performance, which can maintain a high specific capacity of 400.1 mAh g even after 3500 cycles at a current density of 10 A g . When used in a full-cell, it also shows enhanced sodium storage properties and delivers a high reversible capacity of 567.3 mAh g after 1000 cycles at 1 A g . This strategy can pave a way for preparing various metal sulfides with fascinating structure and excellent performance for the potential application in energy storage area.

No abstract