Advanced In Situ Electrochemical Induced Dual-Mechanism Heterointerface toward High-Energy Aqueous Zinc-Ion Batteries.

In situ electrochemical activation brings unexpected electrochemical performance improvements to electrode materials, while the mechanism behind is still needed to study deeply. Herein, an in situ electrochemically approach is developed for the activation of heterointerface MnOx /Co3 O4 by inducing Mn-defect, wherein the Mn defects are formed through a charge process that converts the MnOx with poor electrochemical activities toward Zn2+ into high electrochemically active cathode for aqueous zinc-ion batteries (ZIBs). Guided by the coupling engineering strategy, the heterointerface cathode exhibits an intercalation/conversion dual-mechanism without structural collapse during storage/release of Zn2+ . The heterointerfaces between different phases can generate built-in electric fields, reducing the energy barrier for ion migration and facilitating electron/ion diffusion. As a consequence, the dual-mechanism MnOx /Co3 O4 shows an outstanding fast charging performance and maintains a capacity of 401.03 mAh g-1 at 0.1 A g-1 . More importantly, a ZIB based on MnOx /Co3 O4 delivered an energy density of 166.09 Wh kg-1 at an ultrahigh power density of 694.64 W kg-1 , which outperforms those of fast charging supercapacitors. This work provides insights for using defect chemistry to introduce novel properties in active materials for highly for high-performance aqueous ZIBs.

Coupling Engineering of NH4 + Pre-Intercalation and Rich Oxygen Vacancies in Tunnel WO3 Toward Fast and Stable Rocking Chair Zinc-Ion Battery.

Herein, for the first time, a pre-intercalated non-metal ion (NH4 + ) with rich oxygen vacancies stabilized tunnel WO3 is proposed as a new intercalation anode to construct Zn-metal-free rocking-chair ZIBs. With the ethylene glycol additive in the aqueous electrolyte, the Zn2+ solvation structure can be regulated and the side reaction of hydrogen evolution can also be suppressed. Owing to the integrated synergetic modification, a high-rate and ultra-stable aqueous Zn-(NH4 )x WO3 battery can be constructed, which exhibits an improved specific capacity (153 mAh g-1 at 0.1 A g-1 ), excellent rate performance (when the current density increases to 3 A g-1 , the specific capacitance is still 86 mAh g-1 ), and a high cycle stability with 100% capacity retention after 2,200 cycles under 5 A g-1 . Ex situ X-ray diffraction and XPS reveal the reversible insertion/extraction of Zn2+ in (NH4 )x WO3 . The assembled (NH4 )x WO3 //MnO2 rocking-chair ZIBs delivers excellent capacity of 82 mAh g-1 at 0.1 A g-1 , impressive cyclic stability. Additionally, the flexible (NH4 )x WO3 //MnO2 ZIBs can power the electrochromic device-based PANI/WO3 with high color contrast and fast response time. This study provides new insight for developing high-performance rechargeable aqueous ZIBs.

Synergistic Engineering of Defects and Architecture in a Co@Co3O4@N-CNT Nanocage toward Li-Ion Batteries and HER.

The design and synthesis of hollow and porous nanostructured electrode materials is an effective strategy to improve the electrochemical performance of lithium-ion batteries and the hydrogen evolution reaction (HER). Herein, we synthesize hollow and porous Co@Co3O4 nanoparticles embedded in N-doped CNTs (N-CNTs) with rich surface defects through a two-step calcination strategy. The formation mechanism is explored. The influence of oxygen vacancies regulated by the nanoscale Kirkendall effect on the electrochemical performance of the electrode is elucidated. The Co@Co3O4@N-CNTs exhibit remarkable activity for catalyzing the HER with a low onset overpotential of 296 mV (a low Tafel slope of 116.2 mV dec-1), much better than Co3O4@N-CNTs (315 mV for overpotential and 124.2 mV dec-1 for Tafel slope). Significantly, the Co@Co3O4@N-CNTs deliver a high discharge capacity of 990 mA h g-1 after 600 cycles at 0.1 A g-1. Our nanostructure strategy can provide new insights into the strategy for high-rate and highly stable energy storage systems.

A Method for Oscillation Errors Restriction of SINS Based on Forecasted Time Series.

Continuity, real-time, and accuracy are the key technical indexes of evaluating comprehensive performance of a strapdown inertial navigation system (SINS). However, Schuler, Foucault, and Earth periodic oscillation errors significantly cut down the real-time accuracy of SINS. A method for oscillation error restriction of SINS based on forecasted time series is proposed by analyzing the characteristics of periodic oscillation errors. The innovative method gains multiple sets of navigation solutions with different phase delays in virtue of the forecasted time series acquired through the measurement data of the inertial measurement unit (IMU). With the help of curve-fitting based on least square method, the forecasted time series is obtained while distinguishing and removing small angular motion interference in the process of initial alignment. Finally, the periodic oscillation errors are restricted on account of the principle of eliminating the periodic oscillation signal with a half-wave delay by mean value. Simulation and test results show that the method has good performance in restricting the Schuler, Foucault, and Earth oscillation errors of SINS.

Fiber-based flexible all-solid-state asymmetric supercapacitors for integrated photodetecting system.

Integrated nanodevices with the capability of storing energy are widely applicable and have thus been studied extensively. To meet the demand for flexible integrated devices, all-solid-state asymmetric supercapacitors that simultaneously realize energy storage and optoelectronic detection were fabricated by growing Co3 O4 nanowires on nickel fibers, thus giving the positive electrode, and employing graphene as both the negative electrode and light-sensitive material. The as-assembled integrated systems were characterized by an improved energy storage, enhanced power density (at least by 1860 % enhanced) by improving the potential window from 0-0.6 V to 0-1.5 V, excellent photoresponse to white light, and superior flexibility of both the fiber-based asymmetric supercapacitor and the photodetector. Such flexible integrated devices might be used in smart and self-powered sensory, wearable, and portable electronics.

In situ electrochemically activated V2O3@MXene cathode for a super high-rate and long-life Zn-ion battery.

The development of a high specific capacity and stable vanadium-based cathode material is very attractive for aqueous zinc-ion batteries (ZIBs). Herein, an in situ electrochemically oxidized cathode is fabricated based on a V2O3@MXene cathode for Zn-ion storage. V2O3@MXene undergoes a phase transition to Zn3(OH)2V2O7·2H2O and ZnyVOz on the first charge, thus allowing for the subsequent insertion/de-insertion of zinc ions, which can be regulated by the amount of H2O in the electrolyte. The MXene in the composite was also beneficial to electron transfer and cycling stability. V2O3@MXene delivered a high capacity of 450 mA h g-1 at 0.2 A g-1, ultra-high-rate performance and cycling stability as well as high energy density.

Copper-doped layered Fe2VO4 nanorods for aqueous zinc-ion batteries.

Zinc-ion batteries (ZIBs) have attracted an increasing attention as a potential low-cost, environmentally friendliness, and high-safety energy storage system. Among them, transition metal vanadates with high oxidation state vanadium have great potential in ZIBs cathode research due to their high theoretical capacity. However, many vanadate particles still inevitably suffer from low ion mobility, low electrical conductivity and stability. Cation doping or compositing is an effective pathway capable of enhancing electrical conductivity. In this work, layered Cu-Fe2VO4 porous nanorods are obtained by introducing Cu2+ into MIL-88A(Fe) (a metal-organic framework; MIL stands for materials from Institute Lavoisier) and further ion-exchanged with NH4VO3, exhibiting excellent zinc storage properties as an cathode. The existence of oxygen vacancies and the change of electronic structure caused by Cu2+ substituting part of Fe2+ enhanced the conductivity and electron transfer rate. It delivers a reversible discharge capacity of 237 mAh/g at 0.3 A/g and a satisfactory high rate capacity of 126 mAh/g after 30 cycles at 5 A/g, and stable cycling performance (198 mAh/g after 1000 cycles at 1 A/g). Furthermore, the energy density can reached to 230.97 Wh kg-1 at 208.6 W kg-1. The assembled quasi-solid-state ZIBs maintain a high capacitance retention of 75% after 8000 cycles at 1 A/g.

Oxygen Vacancy-Enriched Bi2SeO5 Nanosheets with Dual Mechanism for Ammonium-Ion Batteries.

Ammonium ions feature a light molar mass and small hydrated radius, and the interesting interaction between NH4+ and host materials has attracted widespread attention in aqueous energy storage, while few studies focus on high-performance NH4+ storage anodes. Herein, we present a high-performance inset-type anode for aqueous ammonium-ion batteries (AIBs) based on Bi2SeO5 nanosheets. A reversible NH4+/H+ co-intercalation/deintercalation accompanied by hydrogen bond formation/breaking and a conversion reaction mechanism in layered Bi2SeO5 is proposed according to ex situ characterizations. Accordingly, the optimized Bi2SeO5 anode has a high reversible capacity of 341.03 mAh g-1 at 0.3 A g-1 in 1 M NH4Cl electrolyte and an impressive capacity retention of 86.7% after 7000 cycles at 3 A g-1, which is related to the existence of oxygen vacancies that enhance ion/electron transfer and promote the formation of hydrogen bonds between NH4+ and the host material. When the rocking-chair ammonium-ion battery is assembled using a MnO2 cathode, the device delivers an ultrahigh capacity of 140.73 mAh g-1 at 0.15 A g-1 and energy density of 207.13 Wh kg-1 at the power density of 2985.07 W kg-1. This work provides a promising strategy for designing high-performance anodes for next-generation AIBs.

Metal organic framework derived P-doping CoS@C with sulfide defect to boost high-performance asymmetric supercapacitors.

Cobalt sulfide (CoS) is a promising battery-type material for electrochemical energy storage. However, the poor conductivity and slow charge transfer kinetics as well as the deficiency of electrochemically active sites seriously limit their applications. Herein, a class of the P-doping induced hexagonal CoS nanosheets with S defects (P-CoS1-x) derived from Co-based metal organic frameworks (MOFs) supported on carbon nanotube film (CNT) is designed and prepared. The density functional theory (DFT) simulations show the higher conductivity of the P-CoS1-x electrode than CoS. Taking advantage of the synergistic effects of the high conductive P-CoS nanosheets with rich S defects and the flexible CNT, the P-CoS1-x/CNT electrode exhibits a high reversible capacity of 4.3F cm-2, remarkable rate capability, and outstanding long-term cyclability. Impressively, the flexible asymmetric supercapacitor (ASC) based on P-CoS1-x//CoS@PPy achieves a satisfying energy density of 0.18 mWh cm-2 and high bending stability. The electrocatalytic result suggests that the P-CoS1-x possesses the lowest overpotential and the smallest Tafel slope. This vacancy engineering strategy also provides a new insight into active materials and should be beneficial for the design of the next generation of energy storage devices.

Defect engineering of P doped Fe7S8 porous nanoparticles for high-performance asymmetric supercapacitor and oxygen evolution electrocatalyst.

Transition metal sulfides are promising battery-type materials for electrochemical energy storage and a great electrocatalyst for oxygen evolution reaction (OER). However, the poor conductivity and sluggish reaction kinetic as well as the deficiency of electrochemically active sites hinder the practical application of FexSy. Herein, we design Fe7S8 porous nanoparticles with surface phosphate ions and enriched sulfur-vacancies (P-Fe7S8), which is reported as a new high-specific-capacity material for asymmetric supercapacitor. Benefiting from the merits of substantially improved electrical conductivity and increased active sites, the optimized P-Fe7S8 negative electrode delivers ultra-high specific capacitance of 804.7F/g at 0.4 mA. Moreover, the assembled NiS//P-Fe7S8 ASC presents an impressive specific capacitance of 335.9F/g at 1.2 A/g, a high energy density of 134.8 Wh/kg at a power density of 1042.1 W/kg, and great flexibility under different bending angles. Furthermore, the one-step vulcanization process is provided with universal applicability for the synthesis of NixFe1-xS bimetallic sulfide. With the synergy effect produced by the bimetal, the Ni0.5Fe0.5S hollow porous nanoparticles exhibit the remarkable activity of oxygen evolution reaction with a low overpotential of 174 mV at 10 mA cm-2 and Tafel slope of 41 mV dec-1. This simple method provides new insight into the synthesis of novel multifunctional metal sulfide nanomaterials.

Battery-type hollow Prussian blue analogues for asymmetric supercapacitors.

Hollow/porous nanomaterials are widely applicable in various fields. The last few years have witnessed increasing interest in the nanoscale Kirkendall effect as a versatile route to fabricate hollow/porous nanostructures. The transformation of Cu-Co Prussian blue analogue (CuCo-PBA) and FeFe-PBA nanocubes into CuO/Co3O4 and Fe2O3 nanoframes is based on two types of nanoscale Kirkendall effect, which are related to solid-solid interfacial oxidation and solid-gas interfacial reaction, respectively. Both CuO/Co3O4 and Fe2O3 nanoframe electrodes exhibit high reversible discharge capacity, good rate performance and long cycling stability. Moreover, an asymmetric supercapacitor (ASC) is assembled by using CuO/Co3O4 as a cathode and Fe2O3 as an anode, respectively. The ASC can be operated in a wide potential range of 1.4 V with a large specific capacity of 181.8 F g-1, a high energy density of 48.77 W h kg-1 (at 751.2 W kg-1), an outstanding power density of 3657.8 W kg-1 (at 32.9 W h kg-1) and a good capacity retention (73.68%) after 6000 galvanostatic charge-discharge cycles, together with excellent flexibility. The ASC in series can power a LED and work stably under water conditions, delivering excellent practicability.

Co@N-CNT/MXenes in situ grown on carbon nanotube film for multifunctional sensors and flexible supercapacitors.

The rapid development of human-machine interfaces and artificial intelligence is dependent on flexible and wearable soft devices such as sensors and energy storage systems. One of the key factors for these devices is the design of a flexible electrode with high sensitivity, fast response time, and a wide working range. Here, we report the fabrication of strain sensors and all-solid-state flexible supercapacitors using Co@N-CNT/MXenes as an electrode material. The manufactured sensor shows a high tensile range (strain up to 200%) and high stability. The resistance change caused by the fingers touching the sensor can be used to transmit the Morse code information. Flexible supercapacitors serving as power supply demonstrate excellent cycling stability (85 000 cycles) and coulombic efficiency (99.7%) for their high surface area and pseudocapacitance. A self-powered integrated system composed of the strain sensor and flexible supercapacitor is fabricated and operates stably in a wide strain sensing test range. Moreover, the flexible solar-charging self-powered integrated system could be attached to the human body for stable human motion detection. This study clearly shows that appropriate selection of a single functional material to enable it to be used in multi-functional sensors and supercapacitors can simplify the process and reduce the cost of manufacturing wearable devices.

A multifunctional supercapacitor based on 2D nanosheets on a flexible carbon nanotube film.

The manufacture of multifunctional and high-performance wearable supercapacitors (SCs) requires a new class of flexible electrodes with high conductivity, high mechanical stability, good water-proof ability and self-healable capability. Herein, we report a stretchable and self-healable SC based on a MoS2/PEDOT/CNT electrode. The specific capacitance of the SC could be retained up to 81.98% even after the 21st breaking/healing cycle. Furthermore, a sheet-type asymmetric supercapacitor (ASC) based on a MoS2/PEDOT/CNT positive electrode and SnS2/CNT negative electrode is constructed, and it exhibits high performance with an extended potential window of 1.7 V, areal capacitance of 103.76 mF cm-2 at 1.5 mA cm-2, and outstanding stability with no capacitance degradation under a wide range of bending conditions. The ASC is sealed by polyimide films, and it shows high electrochemical stability in hot water and under high speed centrifugation conditions, indicating good water-proof ability and wearability. The as-prepared ASC is also encapsulated in elastic films to provide 225% stretchability. The ASC devices packaged in all these ways exhibit high capacitance retention (>90%) under various bending and dynamic conditions.

Simultaneous Improvement on Strength, Modulus, and Elongation of Carbon Nanotube Films Functionalized by Hyperbranched Polymers.

Carbon nanotube (CNT) buckypapers, or films, have the potential for wide applications because of their unique properties. Neat buckypapers or pristine CNT (PCNT) films have relatively large elongation but low strength and low modulus due to the weak interaction between CNTs. Chemical modifications of PCNT films can significantly strengthen the interaction between CNTs, resulting in high strength and high modulus but usually accompanied by low elongation. Here, we report the functionalization of pristine CNT films by thiol-ended hyperbranched polymers (THBP-n) via a thiol-ene click reaction that can introduce simultaneous improvements on the strength, modulus, and elongation to the PCNT film by 689, 812, and 32.4%, respectively. The high thiol content of THBP-n enables the formation of a network with a high degree of cross-linking between carbon nanotubes, which provides high-efficiency load transfer that increases the tensile strength and modulus of the resulting films and at the same time a compressible hyperbranched structure that allows for deformation and slip between CNTs and consequently improved elongation. The main factors affecting the mechanical performance of the functionalized CNT film are also investigated.

A high performance asymmetric supercapacitor based on in situ prepared CuCo2O4 nanowires and PPy nanoparticles on a two-ply carbon nanotube yarn.

One-dimensional supercapacitors (SCs) are of great interest for future wearable electronics, but improvement in both high capacitance and high flexibility is still a challenge. Herein, we fabricate a high performance yarn asymmetric SC (ASC) using in situ prepared CuCo2O4 nanowires and polypyrrole (PPy) nanoparticles on the surface of a two-ply carbon nanotube (CNT) yarn. The parallel-shaped yarn ASC not only shows outstanding redox pseudocapacitance, including a high areal capacitance (59.55 mF cm-2), specific energy density (20 µW h cm-2) and power density (5.115 mW cm-2), but also exhibits good flexibility because of its well maintained capacitance during repeated dynamic bending states. The capacitance retention still remains 80.1% under 8000 cycles, suggesting relatively good reversibility and stability.

Fabrication of hollow nanorod electrodes based on RuO2//Fe2O3 for an asymmetric supercapacitor.

In this work, hollow RuO2 nanotube arrays were successfully grown on carbon cloth by using a facile two-step method to fabricate a binder-free electrode. The well-aligned electrode displays excellent electrochemical performance. By using RuO2 hollow nanotube arrays as the positive electrode and Fe2O3 as the negative electrode, a flexible solid-state asymmetric supercapacitor (ASC) has been fabricated which exhibited excellent electrochemical performance, such as a high capacitance of 4.9 F cm-3, a high energy density of 1.5 mW h cm-3 and a high power density of 9.1 mW cm-3. In addition, the two-electrode SC shows high cycling stability with 97% capacitance retention after 5000 charge-discharge cycles. These excellent electrochemical performances are ascribed to the unique hollow structural design of electrodes, which can shorten the ion diffusion length, provide a fast ion transport channel, and offer a large electrode/electrolyte interface for the charge-transfer reaction. The structural design and the synthesis approach are general and can be extended to synthesizing a broad range of materials systems.

A dynamic stretchable and self-healable supercapacitor with a CNT/graphene/PANI composite film.

Conventional flexible supercapacitors can work under consecutive bending, folding and even twisting without performance degradation. Nevertheless, these devices can hardly be used under large tensile strain. Flexible stretchable and healable supercapacitors are highly desired due to their many potential applications in electric devices. However, it is challenging to fabricate supercapacitors that can withstand stretchability and self-healability. Herein, we report a stretchable and self-healable supercapacitor based on a carbon nanotube@graphene@PANI nanowire film. The supercapacitor possesses high energy density from 36.3 to 29.4 µW h cm-2 with the corresponding power density changing from 0.17 to 5 mW cm-2 at a current from 0.1 to 3 mA, and the highest capacitive performance can reach up to 261.5 mF cm-2. In terms of the bending test, the supercapacitor can operate under different static bending angles and dynamic bending conditions with different bending frequencies, and the capacitance was merely affected. Moreover, the supercapacitor can sustain a tensile strain up to 180% and 80.2% capacitance retention after the 10th healing cycle. This novel design integrating all stretchable and healable components provides a pathway toward the next generation of wearable energy devices in modern electronics.

Methoxychlor and its metabolite HPTE inhibit rat neurosteroidogenic 3α-hydroxysteroid dehydrogenase and retinol dehydrogenase 2.

Methoxychlor is primarily used as an insecticide and it is widely present in the environment. The objective of the present study was to investigate the direct effects of methoxychlor and its metabolite hydroxychlor (HPTE) on rat neurosteroidogenic 3α-hydroxysteroid dehydrogenase (AKR1C14) and retinol dehydrogenase 2 (RDH2) activities. Rat AKR1C14 and RDH2 were cloned and expressed in COS-1 cells, and the effects of methoxychlor and HPTE on these enzymes were measured. HPTE was more potent to inhibit AKR1C14 and RDH2 activities than methoxychlor, with IC50 values of 2.602 ± 0.057 µM and 20.473 ± 0.049 µM, respectively, while those of methoxychlor were over 100 µM. HPTE competitively inhibited AKR1C14 and RDH2 when steroid substrates were used, while it showed a mode of mixed inhibition on these enzymes when NADPH/NAD+ were used. We elucidated the binding mode of methoxychlor and HPTE to the crystal structure of AKR1C14 by molecular docking and found that HPTE had higher affinity with the enzyme than methoxychlor. In conclusion, HPTE is more potent than methoxychlor to inhibit both AKR1C14 and RDH2.

Flexible Asymmetric Threadlike Supercapacitors Based on NiCo2 Se4 Nanosheet and NiCo2 O4 /Polypyrrole Electrodes.

Flexible threadlike supercapacitors with improved performance are needed for many wearable electronics applications. Here, we report a high performance flexible asymmetric all-solid-state threadlike supercapacitor with a NiCo2 Se4 positive electrode and a NiCo2 O4 @PPy (PPy: polypyrrole) negative electrode. The as-prepared electrodes display outstanding volume specific capacitance (14.2 F cm-3 ) and excellent cycling performance (94 % retention after 5000 cycles at 0.6 mA) owing to their nanosheet and nanosphere structures. The asymmetric all-solid-state threadlike supercapacitor expanded the stability voltage window from 0-1.0 V to 0-1.7 V and exhibits high volume energy density (5.18 mWh cm-3 ) and superior flexibility under different bending conditions. This study provides a scalable method for fabricating high performance flexible supercapacitors from easily available materials for use in wearable and portable electronics.

In Situ Grown Fe2O3 Single Crystallites on Reduced Graphene Oxide Nanosheets as High Performance Conversion Anode for Sodium-Ion Batteries.

Electrochemical conversion reactions of metal oxides provide a new avenue to build high capacity anodes for sodium-ion batteries. However, the poor rate performance and cyclability of these conversion anodes remain a significant challenge for Na-ion battery applications because most of the conversion anodes suffer from sluggish kinetics and irreversible structural change during cycles. In this paper, we report an Fe2O3 single crystallites/reduced graphene oxide composite (Fe2O3/rGO), where the Fe2O3 single crystallites with a particle size of ∼300 nm were uniformly anchored on the rGO nanosheets, which provide a highly conductive framework to facilitate electron transport and a flexible matrix to buffer the volume change of the material during cycling. This Fe2O3/rGO composite anode shows a very high reversible capacity of 610 mAh g-1 at 50 mA g-1, a high Coulombic efficiency of 71% at the first cycle, and a strong cyclability with 82% capacity retention after 100 cycles, suggesting a potential feasibility for sodium-ion batteries. More significantly, the present work clearly illustrates that an electrochemical conversion anode can be made with high capacity utilization, strong rate capability, and stable cyclability through appropriately tailoring the lattice structure, particle size, and electronic conduction channels for a simple transition-metal oxide, thus offering abundant selections for development of low-cost and high-performance Na-storage electrodes.