Flexible solid-state supercapacitors provide a promising energy-storage alternative for the rapidly growing flexible and wearable electronic industry. Further improving device energy density and ...developing a cheap flexible current collector are two major challenges in pushing the technology forward. In this work, we synthesize a nitrogen-doped graphene/MnO2 nanosheet (NGMn) composite by a simple hydrothermal method. Nitrogen-doped graphene acts as a template to induce the growth of layered δ-MnO2 and improves the electronic conductivity of the composite. The NGMn composite exhibits a large specific capacitance of about 305 F g–1 at a scan rate of 5 mV s–1. We also create a cheap and highly conductive flexible current collector using Scotch tape. Flexible solid-state asymmetric supercapacitors are fabricated with NGMn cathode, activated carbon anode, and PVA–LiCl gel electrolyte. The device can achieve a high operation voltage of 1.8 V and exhibits a maximum energy density of 3.5 mWh cm–3 at a power density of 0.019 W cm–3. Moreover, it retains >90% of its initial capacitance after 1500 cycles. Because of its flexibility, high energy density, and good cycle life, NGMn-based flexible solid state asymmetric supercapacitors have great potential for application in next-generation portable and wearable electronics.
A facile, general, and highly efficient approach to obtain azobenzene (azo)-containing molecularly imprinted polymer (MIP) microspheres with both photo- and thermoresponsive template binding ...properties in pure aqueous media is described for the first time, which involves the first synthesis of “living” azo-containing MIP microspheres with surface-immobilized alkyl halide groups via atom transfer radical precipitation polymerization (ATRPP) and their subsequent modification via surface-initiated atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm). The successful grafting of poly(NIPAAm) (PNIPAAm) brushes onto the obtained MIP microspheres was confirmed by FT-IR, SEM, water dispersion stability and static contact angle studies, and template binding experiments. The introduction of PNIPAAm brushes onto the azo-containing MIP microspheres significantly improved their surface hydrophilicity and imparted thermoresponsive properties to them, leading to their pure water-compatible and thermoresponsive template binding properties. In addition, the binding affinity of the imprinted sites in the grafted azo-containing MIP microspheres was found to be photoresponsive toward the template in pure water, and this photoregulation process proved to be highly repeatable under photoswitching conditions.
The SDSM was employed for downscaling of daily mean temperature of 32 meteorological stations (1954–2014) and future scenarios were generated up to 2100. The data were daily NCEP/NCAR reanalysis data ...and the daily mean climate model outputs for the RCP2.6, RCP4.5, and RCP8.5 scenarios from the MRI of Japan. Periodic features were obtained by wavelet analysis. The results showed the following. (1) The pattern of change and the numerical values of the air temperature could be reasonably simulated, with the average R2 between observed and generated data being 0.963 for calibration and 0.964 for validation. (2) All scenarios projected increases of different degrees of temperature in all seasons, except for spring in the 2020s. Annually, the most remarkable changes in the 2020s, 2050s, and 2080s were 0.27, 1.00, and 1.84°C, respectively. Seven dominant periods appeared under RCP4.5 and RCP8.5 from 1954 to 2100; however, an additional period appeared under RCP2.6. (3) In future periods, especially the 2020s, decreases in temperature were significantly located in the center of Yunnan under all three scenarios, whereas there were distinct increases in northwest and southeast Yunnan in most future periods. Besides, the RCP8.5 scenario showed the greatest increase in the 2080s.
Display omitted
•Interconnected porous honeycomb hollow carbon spheres (IPHHCSs) were fabricated via a facile strategy.•IPHHCSs enhanced electrochemical reaction kinetics.•The IPHHCS supercapacitor’s ...electrode delivered an outstanding rate capability.•The IPHHCSs/S cathode demonstrated remarkable rate performance and cyclic stability.
The application of hollow carbon spheres in energy storage devices is still hindered by their relatively low electron transmission and ion diffusion kinetics, as well as their insufficient storage sites. Herein, we prepare interconnected porous honeycomb hollow carbon spheres (IPHHCSs) using hard-templating route by increasing the concentration of template spheres and introducing cationic surfactants simultaneously. The as-obtained IPHHCSs show favorable features for ESD, such as large contacted areas between spheres, high specific surface areas (951 m2 g−1), hierarchical porous frameworks with high volume of mesopores, and rich N-doping (3.36%), achieving a lower interface-resistance between spheres, more ion-storage sites, and developed mesoporous channels for rapid ions diffusion. Thus, such a unique carbon architecture endows IPHHCSs a superior rate capability for supercapacitor and lithium-sulfur battery applications. The IPHHCSs supercapacitor’s electrode delivers a high specific capacitance of 295F g−1 at 1 A g−1, an outstanding rate capability (87% capacitance retention from 1 A g−1 to 20 A g−1), with a high cycling life stability (1.2% loss after 10,000 cycles). As for lithium-sulfur batteries, the IPHHCSs/S cathode with sulfur loading of 70% demonstrated an initial reversible capacity of 1160 mAh g−1 at 0.2C and an excellent rate performance with a capacity retention of 53% at 10C. More notably, IPHHCSs/S electrode could also enable a remarkable cyclic stability that possesses a reversible capacity of 285 mAh g−1 at 10C upon 1000 cycles with a low capacity degradation of 0.042% per cycle. Controllable design of interconnected porous HCSs structures could decrease interface-resistance and promote ion diffusion, which can be an effective way for developing high-rate supercapacitors and Li–S batteries.
Flexible and implantable glucose biosensors are emerging technologies for continuous monitoring of blood-glucose of diabetes. Developing a flexible conductive substrates with high active surface area ...is critical for advancing the technology. Here, we successfully fabricate a flexible and highly sensitive nonenzymatic glucose by using DVD-laser scribed graphene (LSG) as a flexible conductively substrate. Copper nanoparticles (Cu-NPs) are electrodeposited as the catalyst. The LSG/Cu-NPs sensor demonstrates excellent catalytic activity toward glucose oxidation and exhibits a linear glucose detection range from 1 μM to 4.54 mM with high sensitivity (1.518 mA mM−1 cm−2) and low limit of detection (0.35 μM). Moreover, the LSG/Cu-NPs sensor shows excellent reproducibility and long-term stability. It is also highly selective toward glucose oxidation under the presence of various interfering species. Excellent flexing stability is also demonstrated by the LSG/Cu-NPs sensor, which is capable of maintaining 83.9% of its initial current after being bent against a 4-mm diameter rod for 180 times. The LSG/Cu-NPs sensor shows great potential for practical application as a nonenzymatic glucose biosensor. Meanwhile, the LSG conductive substrate provides a platform for the developing next-generation flexible and potentially implantable bioelectronics and biosensors.
Display omitted
•A flexible and highly sensitive LSG/Cu-NPs glucose sensor is successfully fabricated.•Cu nanoparticle catalysts are electrodeposited on a laser-scribed-graphene substrate produced by a DVD drive.•The LSG/Cu-NPs sensor demonstrates a linear glucose detection range from 1 μM to 4.54 mM.•The LSG/Cu-NPs sensor exhibits high sensitivity (1.518 mA mM−1 cm−2) and low limit of detection (0.35 μM).•Excellent flexing stability and interfering resistance are demonstrated by the LSG/Cu-NPs sensor.
•Electropolymerized PANI and PPy serve as cathode for Zn//I battery, respectively.•The PANI shows a micro-nano porous structure while the PPy is dense.•The porous PANI has more excellent ...electrochemical performances than the PPy.•The performance differences are related to the microstructure of the PANI and PPy.•The PANI electrode has a 75.7% capacity retention after 10,000 cycles at 3.5 A g−1.
At present, Zinc-iodine (Zn//I) batteries have attracted much attention due to their high safety and capacity. However, how to suppress the shuttling of polyiodide ions generated during charging processes is still a tricky problem. Herein, polyaniline (PANI) and polypyrrole (PPy) are electro-polymerized on carbon felt (CF) by constant current and used as cathodes for zinc-iodine (Zn//I) batteries. Electrochemical tests of the PANI@CF and PPy@CF electrodes prove that the PANI@CF electrode has a higher capacity, a stronger ability to suppress shuttling of polyiodine ions, and more excellent cyclic stability than the PPy@CF electrode. According to the material characterizations, the differences of both electrodes in electrochemical performances are mainly caused by the microstructures of PANI and PPy in both electrodes. The PANI has a micro-nano porous structure while the PPy is very dense. The porous PANI not only has more channels for the infiltration of electrolyte, but also can provide more active adsorption sites to minimize the shuttling of polyiodide ions to anode, ensuring the excellent performances of the PANI@CF. However, dense PPy seriously hinders the electrolyte diffusion and triggers the formation of an insulating dense iodine film, bringing poor performances to the PPy@CF. Ultimately, the PANI@CF electrodes achieves the most specific capacity of 235.9 mAh g−1 at 0.35 A g−1 (∼1.7 C) and performs out long cycle life with high stability (75.7% capacitiy rention after 10,000 cycles) at 3.5 A g−1 (∼17 C) in Zn//I battery, manifesting the porous PANI@CF electrode is a greatly promising candidate as cathode for Zn//I batteries in actual application.
Rechargeable zinc-ion batteries have received increasing attention because of their cost effectiveness, eco-friendliness, and high capacity. However, they suffer from poor rate capacities and low ...lifespans because of the uncontrolled formation of zinc dendrite on the zinc metal anode. Although replacing the zinc metal negative electrode could fundamentally solve the dendritic problem, it may lead to the lack of anodic Zn2+ source to sustain the charge carriers during charge-discharge. Here, by adopting a pre-zincation electrode treatment, we demonstrate a novel zinc-ion hybrid supercapacitor (ZIS) by using GNS/CNT@MnO2 electrode and activated carbon electrode as the positive and negative electrode, respectively. The ZIS exhibits a high specific energy of 41.5 Wh kg−1 and excellent cycle stability. It retains over 81% of its initial capacitance and near 100% coulombic efficiency after 10000 cycles at 2 A g−1. We also create a Flexible Quasi-Solid-State Zinc-ion Hybrid Supercapacitor (FQSSZIS) by using a ZnSO4/MnSO4-xanthan gel electrolyte and cheap graphite paper current collectors. The obtained device exhibits excellent flexibility, good cycling stability, and a high energy density of 3.13 mWh cm−3 with a power density of 7 mW cm−3. The pre-zincation approach exhibits great potential for exploring zinc-ion energy storage devices without zinc metal electrodes.
Display omitted
•We report a pre-zincation method to treat both electrodes for Zn2+ supercapacitor.•The electrode pre-treatment effectively enhances the specific capacity.•Eliminating the Zn metal solves the dendrite problem in Zn2+ supercapacitor.•A high performance flexible quasi-solid-state hybrid supercapacitor is achieved.
•Vertically ordered polyvinyl alcohol (PVA) hydrogel is prepared through simply repeated freezing-thawing process.•Polyaniline (PANI) grows from the bottom up within the vertical PVA hydrogel ...template by electro-polymerization.•PVA hydrogel improves the utilization rate of PANI during energy storage process.•PANI@PVA hydrogel electrode performs out long cycle life (15,000) at 5 mA cm−2.
Recently, polyaniline@polyvinyl alcohol (PANI@PVA) composite materials are favored by many researchers due to the synergistic properties of conductive PANI and flexible PVA. Although PANI@PVA composite materials have been studied widely as electrodes for flexible supercapacitors, it is still a challenge to prepared PANI@PVA hydrogel electrodes with long cycle life. In this work, vertically ordered PANI@PVA hydrogel electrodes with an excellent stability were fabricated via electropolymerizing PANI within a template of vertically ordered PVA hydrogel for the first time. In brief, vertically ordered PVA hydrogel coating on a graphite paper collector was prepared through a repeated freezing-thawing method. Then PANI grew within the template of the vertical PVA hydrogel by electro-polymerization. When using the vertically ordered PANI as electrodes, PVA not only worked as gel electrolyte, but also provided support for excellent mechanical flexibility and durability of the electrodes. The vertical PANI@PVA electrode performed a much longer cyclic life (80% retention after 15,000 cycles) than a pure PANI electrode (80% retention after 3,000) and a disordered PANI@PVA electrode (80% retention after 4,300 cycles), benefiting from the vertical structure supported by the PVA hydrogel. Furthermore, asymmetric flexible supercapacitors (AFSCs) had been fabricated with the vertical PANI@PVA hydrogel anodes and activated carbon cathodes. The AFSCs showed excellent flexibility, high area capacity of 244 mC cm−2 at 1 mV s−1 (with a specific capacitance of 244 mF cm−2 for a voltage of 1.0 V), and superior cyclic stability with a capacitance retention of 80% after 7,000 cycles. These results strongly prove that using the polyaniline electropolymerized within a template of vertically ordered PVA as electrodes of flexible supercapacitors has a great potential in actual application.
For lithium metal batteries (LMBs), the elevated operating temperature results in severe capacity fading and safety issues due to unstable electrode–electrolyte interphases and electrolyte solvation ...structures. Therefore, it is crucial to construct advanced electrolytes capable of tolerating harsh environments to ensure stable LMBs. Here, we proposed a stable localized high-concentration electrolyte (LHCE) by introducing the highly solvating power solvent diethylene glycol dimethyl ether (DGDME). Computational and experimental evidence discloses that the original DGDME-LHCE shows favorable features for high-temperature LMBs, including high Li+-binding stability, electro-oxidation resistance, thermal stability, and nonflammability. The tailored solvated sheath structure achieves the preferred decomposition of anions, inducing the stable (cathode and Li anode)/interphases simultaneously, which enables a homogeneous Li plating–stripping behavior on the anode side and a high-voltage tolerance on the cathode side. For the Li||Li cells coupled with DGDME-LHCE, they showcase outstanding reversibility (a long lifespan of exceeding 1900 h). We demonstrate exceptional cyclic stability (∼95.59%, 250 cycles), high Coulombic efficiency (>99.88%), and impressive high-voltage (4.5 V) and high-temperature (60 °C) performances in Li||NCM523 cells using DGDME-LHCE. Our advances shed light on an encouraging ether electrolyte tactic for the Li-metal batteries confronted with stringent high-temperature challenges.
PDF
