High‐Performance,Stretchable, Wire‐Shaped Supercapacitors

A general approach toward extremely stretchable and highly conductive electrodes was developed. The method involves wrapping a continuous carbon nanotube (CNT) thin film around pre‐stretched elastic wires, from which high‐performance, stretchable wire‐shaped supercapacitors were fabricated. The supercapacitors were made by twisting two such CNT‐wrapped elastic wires, pre‐coated with poly(vinyl alcohol)/H₃PO₄ hydrogel, as the electrolyte and separator. The resultant wire‐shaped supercapacitors exhibited an extremely high elasticity of up to 350 % strain with a high device capacitance up to 30.7 F g⁻¹, which is two times that of the state‐of‐the‐art stretchable supercapacitor under only 100 % strain. The wire‐shaped structure facilitated the integration of multiple supercapacitors into a single wire device to meet specific energy and power needs for various potential applications. These supercapacitors can be repeatedly stretched from 0 to 200 % strain for hundreds of cycles with no change in performance, thus outperforming all the reported state‐of‐the‐art stretchable electronics.     

Elastic and Wearable Wire‐Shaped Lithium‐Ion Battery with High Electrochemical Performance

A stretchable wire‐shaped lithium‐ion battery is produced from two aligned multi‐walled carbon nanotube/lithium oxide composite yarns as the anode and cathode without extra current collectors and binders. The two composite yarns can be well paired to obtain a safe battery with superior electrochemical properties, such as energy densities of 27 Wh kg^?1 or 17.7 mWh cm^?3 and power densities of 880 W kg^?1 or 0.56 W cm^?3, which are an order of magnitude higher than the densities reported for lithium thin‐film batteries. These wire‐shaped batteries are flexible and light, and 97 % of their capacity was maintained after 1000 bending cycles. They are also very elastic as they are based on a modified spring structure, and 84 % of the capacity was maintained after stretching for 200 cycles at a strain of 100 %. Furthermore, these novel wire‐shaped batteries have been woven into lightweight, flexible, and stretchable battery textiles, which reveals possible large‐scale applications.     

Flexible and Stretchable Lithium‐Ion Batteries and Supercapacitors Based on Electrically Conducting Carbon Nanotube Fiber Springs

The construction of lightweight, flexible and stretchable power systems for modern electronic devices without using elastic polymer substrates is critical but remains challenging. We have developed a new and general strategy to produce both freestanding, stretchable, and flexible supercapacitors and lithium‐ion batteries with remarkable electrochemical properties by designing novel carbon nanotube fiber springs as electrodes. These springlike electrodes can be stretched by over 300 %. In addition, the supercapacitors and lithium‐ion batteries have a flexible fiber shape that enables promising applications in electronic textiles.     

Dual‐Doped Molybdenum Trioxide Nanowires: A Bifunctional Anode for Fiber‐Shaped Asymmetric Supercapacitors and Microbial Fuel Cells

A novel in situ N and low‐valence‐state Mo dual doping strategy was employed to significantly improve the conductivity, active‐site accessibility, and electrochemical stability of MoO₃, drastically boosting its electrochemical properties. Consequently, our optimized N‐MoO_3?x nanowires exhibited exceptional performances as a bifunctional anode material for both fiber‐shaped asymmetric supercapacitors (ASCs) and microbial fuel cells (MFCs). The flexible fiber‐shaped ASC and MFC device based on the N‐MoO_3?x anode could deliver an unprecedentedly high energy density of 2.29 mWh cm^?3 and a remarkable power density of 0.76 μW cm^?1, respectively. Such a bifunctional fiber‐shaped N‐MoO_3?x electrode opens the way to integrate the electricity generation and storage for self‐powered sources.     

A Highly Elastic and Reversibly Stretchable All‐Polymer Supercapacitor

Multiple stretchability has never been demonstrated as supercapacitors because the hydrogel used cannot fully recover after being heavily deformed. Now, a highly reversibly stretchable all‐polymer supercapacitor was fabricated using a developed double network hydrogel (DN hydrogel) as electrolyte and pure polypyrrole (PPy) as electrode. The DN hydrogel provides excellent mechanical properties, which can be stretched up to 500 % many times and then restore almost 100 % of the original length. To fabricate the fully recoverable stretchable supercapacitor, we annealed a free‐standing pure conducting polymer film as electrode so that the electrodes induced retardance is minimized. The as‐fabricated DN hydrogel/pure conducting polymer supercapacitors can be perfectly recovered from 100 % strain with almost no residual deformation left and the electrochemical performance can be maintained even after 1000 stretches (but not bending).     

An Intrinsically Stretchable and Compressible Supercapacitor Containing a Polyacrylamide Hydrogel Electrolyte

Stretchability and compressibility of supercapacitors is an essential element of modern electronics, such as flexible, wearable devices. Widely used polyvinyl alcohol‐based electrolytes are neither very stretchable nor compressible, which fundamentally limits the realization of supercapacitors with high stretchability and compressibility. A new electrolyte that is intrinsically super‐stretchable and compressible is presented. Vinyl hybrid silica nanoparticle cross‐linkers were introduced into polyacrylamide hydrogel backbones to promote dynamic cross‐linking of the polymer networks. These cross‐linkers serve as stress buffers to dissipate energy when strain is applied, providing a solution to the intrinsically low stretchability and compressibility shortcomings of conventional supercapacitors. The newly developed supercapacitor and electrolyte can be stretched up to an unprecedented 1000 % strain with enhanced performance, and compressed to 50 % strain with good retention of the initial performance.     

Realizing both High Energy and High Power Densities by Twisting Three Carbon‐Nanotube‐Based Hybrid Fibers

Energy storage devices, such as lithium‐ion batteries and supercapacitors, are required for the modern electronics. However, the intrinsic characteristics of low power densities in batteries and low energy densities in supercapacitors have limited their applications. How to simultaneously realize high energy and power densities in one device remains a challenge. Herein a fiber‐shaped hybrid energy‐storage device (FESD) formed by twisting three carbon nanotube hybrid fibers demonstrates both high energy and power densities. For the FESD, the energy density (50 mWh cm^?3 or 90 Wh kg^?1) many times higher than for other forms of supercapacitors and approximately 3 times that of thin‐film batteries; the power density (1 W cm^?3 or 5970 W kg^?1) is approximately 140 times of thin‐film lithium‐ion battery. The FESD is flexible, weaveable and wearable, which offers promising advantages in the modern electronics.     

Self‐Healable Electrically Conducting Wires for Wearable Microelectronics

Electrically conducting wires play a critical role in the advancement of modern electronics and in particular are an important key to the development of next‐generation wearable microelectronics. However, the thin conducting wires can easily break during use, and the whole device fails to function as a result. Herein, a new family of high‐performance conducting wires that can self‐heal after breaking has been developed by wrapping sheets of aligned carbon nanotubes around polymer fibers. The aligned carbon nanotubes offer an effective strategy for the self‐healing of the electric conductivity, whereas the polymer fiber recovers its mechanical strength. A self‐healable wire‐shaped supercapacitor fabricated from a wire electrode of this type maintained a high capacitance after breaking and self‐healing.     

Sodium‐Doped Mesoporous Ni2P2O7 Hexagonal Tablets for High‐Performance Flexible All‐Solid‐State Hybrid Supercapacitors

A simple hydrothermal method has been developed to prepare hexagonal tablet precursors, which are then transformed into porous sodium‐doped Ni₂P₂O₇ hexagonal tablets by a simple calcination method. The obtained samples were evaluated as electrode materials for supercapacitors. Electrochemical measurements show that the electrode based on the porous sodium‐doped Ni₂P₂O₇ hexagonal tablets exhibits a specific capacitance of 557.7 F g^?1 at a current density of 1.2 A g^?1. Furthermore, the porous sodium‐doped Ni₂P₂O₇ hexagonal tablets were successfully used to construct flexible solid‐state hybrid supercapacitors. The device is highly flexible and achieves a maximum energy density of 23.4 Wh kg^?1 and a good cycling stability after 5000 cycles, which confirms that the porous sodium‐doped Ni₂P₂O₇ hexagonal tablets are promising active materials for flexible supercapacitors.     

Random poly(3‐hexylthiophene‐co‐3‐cyanothiophene‐co‐3‐(2‐ethylhexyl)thiophene) copolymers with high open‐circuit voltage in polymer solar cells

For the purpose of developing poly(3‐hexylthiophene) (P3HT) based copolymers with deep‐lying highest occupied molecular orbital (HOMO) levels for polymer solar cells with high open‐circuit voltage (V_oc), we report a combined approach of random incorporation of 3‐cyanothiophene (CNT) and 3‐(2‐ethylhexyl)thiophene (EHT) units into the P3HT backbone. This strategy is designed to overcome CNT content limitations in recently reported P3HT‐CNT copolymers, where incorporation of more than 15% of CNT into the polymer backbone leads to impaired polymer solubility and raises the HOMO level. This new approach allows incorporation of a larger CNT content, reaching even lower‐lying HOMO levels. Importantly, a very low HOMO level of ?5.78 eV was obtained, representing one of the lowest HOMO values for exclusively thiophene‐based polymers. Lower HOMO levels result in higher V_oc and higher power conversion efficiencies (PCE) compared to the previously reported P3HT‐CNT copolymers containing only 3‐hexylthiophene and CNT units. As a result, solar cells based on P3HT‐CNT‐EHT(15:15) , which contains 70% of P3HT, 15% of CNT and 15% of EHT, yield a V_oc of 0.83 V in blends with PC₆₁BM while preserving high fill factor (FF) and high short‐circuit current density (J_sc), resulting in 3.6% PCE. Additionally, we explored the effect of polymer number‐average molecular weight (M_n) on the optoelectronic properties and solar cell performance for the example of P3HT‐CNT‐EHT(15:15). The organic photovoltaic (OPV) performance improves with polymer M_n increasing from 3.4 to 6.7 to 9.6 kDa and then it declines as M_n further increases to 9.9 and to 16.2 kDa. The molecular weight study highlights the importance of not only the solar cell optimization, but also the significance of individual polymer properties optimization, in order to fully explore the potential of any given polymer in OPVs. The broader ramification of this study lies in potential application of these high band gap copolymers with low‐lying HOMO level in the development of ternary blend photovoltaics as well as tandem OPV. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1526–1536     

Facile Synthesis of a Furan–Arylamine Hole‐Transporting Material for High‐Efficiency,Mesoscopic Perovskite Solar Cells

A novel hole‐transporting molecule (F101) based on a furan core has been synthesized by means of a short, high‐yielding route. When used as the hole‐transporting material (HTM) in mesoporous methylammonium lead halide perovskite solar cells (PSCs) it produced better device performance than the current state‐of‐the‐art HTM 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD). The F101‐HTM‐based device exhibited both slightly higher J_sc (19.63 vs. 18.41 mA cm^?2) and V_oc (1.1 vs. 1.05 V) resulting in a marginally higher power conversion efficiency (PCE) (13.1 vs. 13 %). The steady‐state and time‐resolved photoluminescence show that F101 has significant charge extraction ability. The simple molecular structure, short synthesis route with high yield and better performance in devices makes F101 an excellent candidate for replacing the expensive spiro‐OMeTAD as HTM in PSCs.     

A Twisted Wire‐Shaped Dual‐Function Energy Device for Photoelectric Conversion and Electrochemical Storage

A wire‐shaped energy device that can perform photoelectric conversion and electrochemical storage was developed through a simple but effective twisting process. The energy wire exhibited a high energy conversion efficiency of 6.58 % and specific capacitance of 85.03 μF cm^?1 or 2.13 mF cm^?2, and the two functions were alternately realized without sacrificing either performance.     

Rubbery wound closure adhesives. I. design,synthesis, characterization,and testing of polyisobutylene‐based cyanoacrylate homo‐ and co‐networks

Novel rubbery wound closures containing various proportions and molecular weights of polyisobutylene (PIB) and poly(2‐octyl cyanoacrylate) [P(OctCA)] for potential clinical use were designed, synthesized, characterized, and tested. Homo‐networks were prepared by crosslinking 3‐arm star‐shaped PIBs fitted with terminal cyanoacrylate groups, [Ø(PIB‐CA)₃], and co‐networks by copolymerizing Ø(PIB‐CA)₃ with OctCA using N‐dimethyl‐p‐toluidine (DMT). Neat Ø(PIB‐CA)₃, and Ø(PIB‐CA)₃/OctCA blends, upon contact with initiator, polymerize within seconds to optically transparent strong rubbery co‐networks, Ø(PIB‐CA)₃‐co‐P(OctCA). Homo‐ and co‐network formation was demonstrated by sol/gel studies, and structures and properties were characterized by a battery of techniques. The T_g of P(OctCA) is 58 °C by DSC, and 75 °C by DMTA. Co‐networks comprising 25% Ø(PIB‐CA)₃ (M_n = 2400 g/mol) and 75% P(OctCA) are stronger and more extensible than skin. Short and long term creep studies show co‐networks exhibit high dimensional stability and <6% creep strain at high loading. When deposited on porcine skin co‐networks yield hermetically‐adhering clear rubbery coatings. Strips of porcine skin coated with co‐networks could be stretched and twisted without compromising membrane integrity. The co‐network is nontoxic to L‐929 mouse fibroblasts. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1640–1651     

Hybrid Fibers Made of Molybdenum Disulfide,Reduced Graphene Oxide,and Multi‐Walled Carbon Nanotubes for Solid‐State,Flexible, Asymmetric Supercapacitors

One of challenges existing in fiber‐based supercapacitors is how to achieve high energy density without compromising their rate stability. Owing to their unique physical, electronic, and electrochemical properties, two‐dimensional (2D) nanomaterials, e.g., molybdenum disulfide (MoS₂) and graphene, have attracted increasing research interest and been utilized as electrode materials in energy‐related applications. Herein, by incorporating MoS₂ and reduced graphene oxide (rGO) nanosheets into a well‐aligned multi‐walled carbon nanotube (MWCNT) sheet followed by twisting, MoS₂‐rGO/MWCNT and rGO/MWCNT fibers are fabricated, which can be used as the anode and cathode, respectively, for solid‐state, flexible, asymmetric supercapacitors. This fiber‐based asymmetric supercapacitor can operate in a wide potential window of 1.4 V with high Coulombic efficiency, good rate and cycling stability, and improved energy density.     

Hole‐Boosted Cu(Cr,M)O2 Nanocrystals for All‐Inorganic CsPbBr3 Perovskite Solar Cells

The all‐inorganic CsPbBr₃ perovskite solar cell (PSC) is a promising solution to balance the high efficiency and poor stability of state‐of‐the‐art organic–inorganic PSCs. Setting inorganic hole‐transporting layers at the perovskite/electrode interface decreases charge carrier recombination without sacrificing superiority in air. Now, M‐substituted, p‐type inorganic Cu(Cr,M)O₂ (M=Ba²⁺, Ca²⁺, or Ni²⁺) nanocrystals with enhanced hole‐transporting characteristics by increasing interstitial oxygen effectively extract holes from perovskite. The all‐inorganic CsPbBr₃ PSC with a device structure of FTO/c‐TiO₂/m‐TiO₂/CsPbBr₃/Cu(Cr,M)O₂/carbon achieves an efficiency up to 10.18 % and it increases to 10.79 % by doping Sm³⁺ ions into perovskite halide, which is much higher than 7.39 % for the hole‐free device. The unencapsulated Cu(Cr,Ba)O₂‐based PSC presents a remarkable stability in air in either 80 % humidity over 60 days or 80 °C conditions over 40 days or light illumination for 7 days.     

Hybrid Fibers Made of Molybdenum Disulfide,Reduced Graphene Oxide,and Multi‐Walled Carbon Nanotubes for Solid‐State,Flexible, Asymmetric Supercapacitors

One of challenges existing in fiber‐based supercapacitors is how to achieve high energy density without compromising their rate stability. Owing to their unique physical, electronic, and electrochemical properties, two‐dimensional (2D) nanomaterials, e.g., molybdenum disulfide (MoS₂) and graphene, have attracted increasing research interest and been utilized as electrode materials in energy‐related applications. Herein, by incorporating MoS₂ and reduced graphene oxide (rGO) nanosheets into a well‐aligned multi‐walled carbon nanotube (MWCNT) sheet followed by twisting, MoS₂‐rGO/MWCNT and rGO/MWCNT fibers are fabricated, which can be used as the anode and cathode, respectively, for solid‐state, flexible, asymmetric supercapacitors. This fiber‐based asymmetric supercapacitor can operate in a wide potential window of 1.4 V with high Coulombic efficiency, good rate and cycling stability, and improved energy density.     

An All‐Solid‐State Fiber‐Shaped Aluminum–Air Battery with Flexibility,Stretchability, and High Electrochemical Performance

Owing to the high theoretical energy density of metal–air batteries, the aluminum–air battery has been proposed as a promising long‐term power supply for electronics. However, the available energy density from the aluminum–air battery is far from that anticipated and is limited by current electrode materials. Herein we described the creation of a new family of all‐solid‐state fiber‐shaped aluminum–air batteries with a specific capacity of 935 mAh g⁻¹ and an energy density of 1168 Wh kg⁻¹. The synthesis of an electrode composed of cross‐stacked aligned carbon‐nanotube/silver‐nanoparticle sheets contributes to the remarkable electrochemical performance. The fiber shape also provides the aluminum–air batteries with unique advantages; for example, they are flexible and stretchable and can be woven into a variety of textiles for large‐scale applications.     

An All‐Solid‐State Fiber‐Shaped Aluminum–Air Battery with Flexibility,Stretchability, and High Electrochemical Performance

Owing to the high theoretical energy density of metal–air batteries, the aluminum–air battery has been proposed as a promising long‐term power supply for electronics. However, the available energy density from the aluminum–air battery is far from that anticipated and is limited by current electrode materials. Herein we described the creation of a new family of all‐solid‐state fiber‐shaped aluminum–air batteries with a specific capacity of 935 mAh g^?1 and an energy density of 1168 Wh kg^?1. The synthesis of an electrode composed of cross‐stacked aligned carbon‐nanotube/silver‐nanoparticle sheets contributes to the remarkable electrochemical performance. The fiber shape also provides the aluminum–air batteries with unique advantages; for example, they are flexible and stretchable and can be woven into a variety of textiles for large‐scale applications.     

Flexible,Stretchable, and Rechargeable Fiber‐Shaped Zinc–Air Battery Based on Cross‐Stacked Carbon Nanotube Sheets

The fabrication of flexible, stretchable and rechargeable devices with a high energy density is critical for next‐generation electronics. Herein, fiber‐shaped Zn–air batteries, are realized for the first time by designing aligned, cross‐stacked and porous carbon nanotube sheets simultaneously that behave as a gas diffusion layer, a catalyst layer, and a current collector. The combined remarkable electronic and mechanical properties of the aligned carbon nanotube sheets endow good electrochemical properties. They display excellent discharge and charge performances at a high current density of 2 A g⁻¹. They are also flexible and stretchable, which is particularly promising to power portable and wearable electronic devices.     

Strong and Robust Polyaniline‐Based Supramolecular Hydrogels for Flexible Supercapacitors

We report a supramolecular strategy to prepare conductive hydrogels with outstanding mechanical and electrochemical properties, which are utilized for flexible solid‐state supercapacitors (SCs) with high performance. The supramolecular assembly of polyaniline and polyvinyl alcohol through dynamic boronate bond yields the polyaniline–polyvinyl alcohol hydrogel (PPH), which shows remarkable tensile strength (5.3 MPa) and electrochemical capacitance (928 F g^?1). The flexible solid‐state supercapacitor based on PPH provides a large capacitance (306 mF cm^?2 and 153 F g^?1) and a high energy density of 13.6 Wh kg^?1, superior to other flexible supercapacitors. The robustness of the PPH‐based supercapacitor is demonstrated by the 100 % capacitance retention after 1000 mechanical folding cycles, and the 90 % capacitance retention after 1000 galvanostatic charge–discharge cycles. The high activity and robustness enable the PPH‐based supercapacitor as a promising power device for flexible electronics.