Cyclic Stability of Two-Way Shape Memory Effect in Aged Ni50.3Ti32.2Hf17.5 Polycrystals after Various Thermomechanical Treatments

In the present paper, the cyclic stability of the high-temperature two-way shape memory effect was studied in high-strength Ni50.3Ti32.2Hf17.5 polycrystals after various thermomechanical treatments-training (thermocycling under stress) and stress-induced martensite aging. The effect of training and stress-induced martensite aging on the microstructure, the two-way shape memory effect, and its cyclic stability was determined. It was found out that both thermomechanical treatments induce the high-temperature two-way shape memory effect at T > 373 K, with a strain of 1.5% in tension. The influence of cyclic tests (up to 100 stress-free cycles of cooling/heating) on the two-way shape memory effect strain, the transformation temperatures, and the microstructure was established. Different degradation mechanisms of the two-way shape memory effect were established after thermocycling and stress-induced martensite aging.

Fabrication of High-Performance Asymmetric Supercapacitors Using Rice Husk-Activated Carbon and MnFe2O4 Nanostructures

To meet the growing demand for efficient and sustainable power sources, it is crucial to develop high-performance energy storage systems. Additionally, they should be cost-effective and able to operate without any detrimental environmental side effects. In this study, rice husk-activated carbon (RHAC), which is known for its abundance, low cost, and excellent electrochemical performance, was combined with MnFe₂O₄ nanostructures to improve the overall capacitance of asymmetric supercapacitors (ASCs) and their energy density. A series of activation and carbonization steps are involved in the fabrication process for RHAC from rice husk. Furthermore, the BET surface area for RHAC was determined to be 980 m² g^-1 and superior porosities (average pore diameter of 7.2 nm) provide abundant active sites for charge storage. Additionally, MnFe₂O₄ nanostructures were effective pseudocapacitive electrode materials due to their combined Faradic and non-Faradic capacitances. In order to assess the electrochemical performance of ASCs extensively, several characterization techniques were employed, including galvanostatic charge -discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. Comparatively, the ASC demonstrated a maximum specific capacitance of ~420 F/g at a current density of 0.5 A/g. The as-fabricated ASC possesses remarkable electrochemical characteristics, including high specific capacitance, superior rate capability, and long-term cycle stability. The developed asymmetric configuration retained 98% of its capacitance even after 12,000 cycles performed at a current density of 6A/g, demonstrating its stability and reliability for supercapacitors. The present study demonstrates the potential of synergistic combinations of RHAC and MnFe₂O₄ nanostructures in improving supercapacitor performance, as well as providing a sustainable method of using agricultural waste for energy storage.

Studies on the Application of Polyimidobenzimidazole Based Nanofiber Material as the Separation Membrane of Lithium-Ion Battery

Aromatic polyimide has good mechanical properties and high-temperature resistance. Based on this, benzimidazole is introduced into the main chain, and its intermolecular (internal) hydrogen bond can increase mechanical and thermal properties and electrolyte wettability. Aromatic dianhydride 4,4'-oxydiphthalic anhydride (ODPA) and benzimidazole-containing diamine 6,6'-bis [2-(4-aminophenyl)benzimidazole] (BAPBI) were synthesized by means of a two-step method. Imidazole polyimide (BI-PI) was used to make a nanofiber membrane separator (NFMS) by electrospinning process, using its high porosity and continuous pore characteristics to reduce the ion diffusion resistance of the NFMS, enhancing the rapid charge and discharge performance. BI-PI has good thermal properties, with a Td5% of 527 °C and a dynamic mechanical analysis Tg of 395 °C. The tensile strength of the NFMS increased from 10.92MPa to 51.15MPa after being hot-pressed. BI-PI has good miscibility with LIB electrolyte, the porosity of the film is 73%, and the electrolyte absorption rate reaches 1454%. That explains the higher ion conductivity (2.02 mS cm^-1) of NFMS than commercial one (0.105 mS cm^-1). When applied to LIB, it is found that it has high cyclic stability and excellent rate performance at high current density (2 C). BI-PI (120 Ω) has a lower charge transfer resistance than the commercial separator Celgard H1612 (143 Ω).

Pivotal Role of the Granularity Uniformity of the WO3 Film Electrode upon the Cyclic Stability during Cation Insertion/Extraction

Delicate design and precise manipulation of electrode morphology has always been crucial in electrochemistry. Generally, porous morphology has been preferred due to the fast kinetic transport characteristics of cations. Nevertheless, more refined design details such as the granularity uniformity that usually goes along with the porosity regulation of film electrodes should be taken into consideration, especially in long-term cation insertion and extraction. Here, inorganic electrochromism as a special member of the electrochemical family and WO₃ films as the most mature electrochromic electrode material were chosen as the research background. Two kinds of WO₃ films were prepared by magnetron sputtering, one with a relatively loose morphology accompanied by nonuniform granularity and one with a compact morphology along with uniform particle size distribution, respectively. Electrochemical performances and cyclic stability of the two film electrodes were then traced and systematically compared. In the beginning, except for faster kinetic transport characters of the 50 W-deposited WO₃ film, the two electrodes showed equivalent optical and electrochemical performances. However, after 5000 CV cycles, the 50 W-deposited WO₃ film electrode cracked seriously. Strong stress distribution centered among boundaries of the nonuniform particle clusters together with the weak bonding among particles induced the mechanical damage. This discovery provides a more solid background for further delicate film electrode design.

Structural Construction of WO3 Nanorods as Anode Materials for Lithium-Ion Batteries to Improve Their Electrochemical Performance

WO₃ nanobundles and nanorods were prepared using a facile hydrothermal method. The X-ray diffraction pattern confirms that the obtained samples are pure hexagonal WO₃. Transmission electron microscope images detected the gap between the different nanowires that made up the nanobundles and nanorods. As the anode materials of lithium-ion batteries, the formed WO₃ nanobundles and WO₃ nanorods deliver an initial discharge capacity of 883.5 and 971.6 mA h g^-1, respectively. Both WO₃ nanostructures deliver excellent capacity retention upon extended cycling. At a current density of 500 mA g^-1, the reversible capacities of WO₃ nanobundle and WO₃ nanorod electrodes are 444.0 and 472.3 mA h g^-1, respectively, after 60 cycles.

Performance Deficiency Improvement of CNT-Based Strain Sensors by Magnetic-Induced Patterning

As one of the most promising candidates, ubiquitous cycling degradation seriously affects the accuracy of carbon nanotube (CNT)-based sensors, and the reason for which is still unclear. Herein, the cycling degradation mechanism of CNT-based strain sensors has been detected by comparatively investigating the difference between the sensing behavior of CNT- and silver nanowire (Ag-NW)-based sensors, from which the microcrack-disconnection and unfolding-tunneling effects have been clarified as the sensing mechanism for Ag-NWs and CNT-based strain sensors, respectively. Furthermore, sliding and unfolding behaviors resulting from the weak interaction between CNTs have been proven to cause degradation. Correspondingly, a creative magnetically induced patterning method is proposed by utilizing magnetic nanoparticles as obstacles to prevent the CNTs from relative sliding. Benefiting from the advantageous factor, the performance deficiency of the CNT-based sensor has been overcome, and the sensitivity was significantly improved up to 5.2 times with accurate human activity detection. The competitive sensing performance of the CNTs demonstrates the reference value of the deficiency mechanism and solution scheme obtained in this study.

The Controllable Ratio of the Polyaniline-Needle-Shaped Manganese Dioxide for the High-Performance Supercapacitor Application

The nanohybrid development of metal oxide/conducting polymer as an energy storage material is an active research area, because of the device stability, conductive behavior, and easy fabrication. Herein, needle-like MnO₂ was coupled with polyaniline fabricated through chemical polymerization followed by the hydrothermal process. The characterization results show that MnO₂/polyaniline exhibited a needle-like morphology. Different characterization techniques such as X-ray diffraction patterns and scanning electron microscopy confirmed the formation of the MnO₂/polyaniline nanohybrids. The electrochemical performance, including cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), specific capacitance (C_sp), and cyclic stability, was examined using a three-electrode assembly cell. The optimized electrode displayed a C_sp of 522.20 F g^-1 at a current load of 1.0 A g^-1 compared with the other electrodes. The developed synergism during MnO₂/polyaniline fabrication provided enhanced conductive channels and stability during the charge-discharge process.

Direct-Chemical Vapor Deposition-Enabled Graphene for Emerging Energy Storage: Versatility, Essentiality, and Possibility

The direct chemical vapor deposition (CVD) technique has stimulated an enormous scientific and industrial interest to enable the conformal growth of graphene over multifarious substrates, which readily bypasses tedious transfer procedure and empowers innovative materials paradigm. Compared to the prevailing graphene materials (i.e., reduced graphene oxide and liquid-phase exfoliated graphene), the direct-CVD-enabled graphene harnesses appealing structural advantages and physicochemical properties, accordingly playing a pivotal role in the realm of electrochemical energy storage. Despite conspicuous progress achieved in this frontier, a comprehensive overview is still lacking by far and the synthesis-structure-property-application nexus of direct-CVD-enabled graphene remains elusive. In this topical review, rather than simply compiling the state-of-the-art advancements, the versatile roles of direct-CVD-enabled graphene are itemized as (i) modificator, (ii) cultivator, (iii) defender, and (iv) decider. Furthermore, essential effects on the performance optimization are elucidated, with an emphasis on fundamental properties and underlying mechanisms. At the end, perspectives with respect to the material production and device fabrication are sketched, aiming to navigate the future development of direct-CVD-enabled graphene en-route toward pragmatic energy applications and beyond.

Combining Surface Holistic Ge Coating and Subsurface Mg Doping to Enhance the Electrochemical Performance of LiNi0.8Co0.1Mn0.1O2 Cathodes

Nickel-rich layered cathode LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) is the most promising cathode material due to its high specific capacity and lower cost than lithium cobalt oxides. However, NCM811 suffers from structural instability and capacity degradation during charge-discharge cycles. Herein, we report a strategy to construct a conductive network by employing a holistic Ge coating, which interconnects Mg-doped NCM811 particles. Dopant Mg ions, serving as a "pillar" in the Li slab of NCM811, substantially enhance the structural reversibility. The Ge particles are not only coated on the electrode surface but also enter into the electrode pores to form a multidimensional conductive structure, which improves the conductivity of the electrode and slows down the interface side reaction, thus minimizing the irreversible loss of NCM811 upon long cycling. The modified NCM811 electrode delivers a high discharge capacity (∼204 mAh g^-1 at 0.1C), excellent rate performance (∼155 mAh g^-1 at 10C), and high capacity retention (83% after 200 cycles) even at 4.4 V. Additionally, a cylindrical full battery with graphite/modified NCM811 undergoes 1000 cycles with 86% capacity retention at 2C.

Magnetically Recovered Co and Co@Pt Catalysts Prepared by Galvanic Replacement on Aluminum Powder for Hydrolysis of Sodium Borohydride

Magnetically recovered Co and Co@Pt catalysts for H₂ generation during NaBH₄ hydrolysis were successfully synthesized by optimizing the conditions of galvanic replacement method. Commercial aluminum particles with an average size of 80 µm were used as a template for the synthesis of hollow shells of metallic cobalt. Prepared Co⁰ was also subjected to galvanic replacement reaction to deposit a Pt layer. X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, and elemental analysis were used to investigate catalysts at each stage of their synthesis and after catalytic tests. It was established that Co⁰ hollow microshells show a high hydrogen-generation rate of 1560 mL·min^-1·g_cat^-1 at 40 °C, comparable to that of many magnetic cobalt nanocatalysts. The modification of their surface by platinum (up to 19 at% Pt) linearly increases the catalytic activity up to 5.2 times. The catalysts prepared by the galvanic replacement method are highly stable during cycling. Thus, after recycling and washing off the resulting borate layer, the Co@Pt catalyst with a minimum Pt loading (0.2 at%) exhibits an increase in activity of 34% compared to the initial value. The study shows the activation of the catalyst in the reaction medium with the formation of cobalt-boron-containing active phases.

Molecular Crowded ″Water-in-Salt″ Polymer Gel Electrolyte for an Ultra-stable Zn-Ion Battery

Recently, the use of a gel polymer electrolyte for the development of robust, flexible, quasi-solid, ultra-stable, high-performance zinc-ion batteries (ZiBs) as an alternative to lithium-ion batteries has attracted widespread attention. However, the performance of ZiBs is limited due to the lack of suitable gel electrolytes. Herein, a ″water-in-salt″ (WiS)-based hydrophilic molecular crowded polymer gel electrolyte and binder free V₂O₅@MnO₂ cathode are introduced to augment the durability, flexibility, safety, and electrochemical performance of ZiBs. The ″free water trapping″ capability of the WiS-based cross-linked molecular crowded polymer electrolyte provides an extended electrochemical stability window (ESW) of the device. The quasi-solid-state ZiB delivers ∼422 mAh g^-1 discharge capacity and shows excellent cycling stability as high as ∼79.83% retention of the initial capacity after 5000 cycles. The durable, flexible, and ultra-stable ZiB with the polymer gel electrolyte performs well under various severe conditions where both the battery safety and energy density are of high priority. This work demonstrates a new approach and application for the development of durable, flexible, ultra-stable, quasi-solid-state ZiBs.

Recent Advances in Nanoscale Based Electrocatalysts for Metal-Air Battery, Fuel Cell and Water-Splitting Applications: An Overview

Metal-air batteries and fuel cells are considered the most promising highly efficient energy storage systems because they possess long life cycles, high carbon monoxide (CO) tolerance, and low fuel crossover ability. The use of energy storage technology in the transport segment holds great promise for producing green and clean energy with lesser greenhouse gas (GHG) emissions. In recent years, nanoscale based electrocatalysts have shown remarkable electrocatalytic performance towards the construction of sustainable energy-related devices/applications, including fuel cells, metal-air battery and water-splitting processes. This review summarises the recent advancement in the development of nanoscale-based electrocatalysts and their energy-related electrocatalytic applications. Further, we focus on different synthetic approaches employed to fabricate the nanomaterial catalysts and also their size, shape and morphological related electrocatalytic performances. Following this, we discuss the catalytic reaction mechanism of the electrochemical energy generation process, which provides close insight to develop a more efficient catalyst. Moreover, we outline the future perspectives and challenges pertaining to the development of highly efficient nanoscale-based electrocatalysts for green energy storage technology.

In-Situ Synergistic 2D/2D MXene/BCN Heterostructure for Superlative Energy Density Supercapacitor with Super-Long Life

The 2D/2D layered materials are gaining much-needed attention owing to the unprecedented results in supercapacitors by their robust structural and electrochemical compatibility. Here, a facile scalable synthesis of 2D/2D MXene/boron carbon nitride (BCN) heterostructure through no residue direct pyrolysis is reported. The process allows the in-situ growth of BCN nanosheets unravelling the surfaces of MXene synergistically that provide an interconnected conductive network with wide potential window, augmented proportion of Ti sites at elevated temperature removing terminal groups enabling high pseudocapacitive activity and impressive stability. As a result, the as-assembled MXene/BCN electrode records a high specific capacitance of 1173 F g^-1 (1876 C g^-1 ) at 2 A g^-1 and an energy density of 45 Wh kg^-1 . Further, the fabricated solid-state device exhibits an ultra-high cyclability of 100% capacitive retention after 100 000 cycles. This will be an epitome for future 2D/2D heterostructures with commendable electrochemical properties as an expedient solution for energy storage applications.

Interconnected MoS2 on 2D Graphdiyne for Reversible Sodium Storage

In this study, graphdiyne (GDY) was first reported as a substrate material for sodium-ion batteries (SIBs). The creative hybridization of GDY and molybdenum disulfide (MoS₂) endows the composite with unique heterostructural and morphological advantages that boost the charge transport rate and enhance the battery discharge properties. Electrochemical results indicated that the MoS₂@GDY anode displays a considerable discharge capacity of up to 328 mAh g^-1 at 1000 mA g^-1. A capacity retention of 93% even at testing current back to 200 mA g^-1 suggests superior rate characteristics. An outstanding stable cyclic performance of 217 mAh g^-1 is obtained at a high testing density. The attractive results not only demonstrate that GDY could be used not only as an effective conductive substrate to prevent the host material from agglomerating in the electrochemical process but also provide a novel design for fabricating efficient electrode materials for future energy-storage systems.

Insights into the Critical Role of Abundant-Porosity Supports in Polyethylenimine Functionalization as Efficient and Stable CO2 Adsorbents

The emerging polyethylenimine (PEI)-functionalized solid adsorbents have witnessed significant development in the implementation of CO₂ capture and separation because of their decent adsorption capacity, recyclability, and scalability. As an indispensable substrate, the importance of selecting porous solid supports in PEI functionalization for CO₂ adsorption was commonly overlooked in many previous investigations, which instead emphasized screening amine types or developing complex porous materials. To this end, we scrutinized the critical role of different commercial porous supports (silica, alumina, activated carbon, and polymeric resins) in PEI impregnation in this study, taking into account multiple perspectives. Hereinto, the present results identified that abundant larger pore structures and surface functional groups were conducive to loading a considerable amount of PEI molecules. Various supports after PEI functionalization had great differences in adsorption capacities, amine efficiencies, and the corresponding optimal temperatures. In addition, more attention was paid to the role of porous supports in long-term stability during the consecutive adsorption-regeneration cycles, while N₂ and CO₂ purging as regeneration strategies, respectively. Especially, CO₂-induced degradation due to urea species formation was specifically recognized in a SiO₂-based adsorbent, which would induce serious concerns in CO₂ cyclic capture. On the other side, we also confirmed that adopting conventional porous supports, for example, HP20, could achieve superior adsorption performance (above 4 mmol CO₂/g) and cyclic stability (around 1% loss after 30 cycles) rather than the ones synthesized through complex approaches, which ensured the availability and scalability of PEI-functionalized CO₂ adsorbents.

A comparative study on the electrochemical capacitor performance of 1T/2H hybridized phase and 2H pure phase of MoS2nanoflowers

The 1T/2H hybridized and 2H pure phases of MoS₂nanoflowers were synthesized in a one-step hydrothermal process with the molybdenum source as sodium molybdate dihydrate and the sulfur source as thiourea. The as-prepared 1T/2H hybridized and 2H pure phases of MoS₂were investigated using a thermogravimetry\differential thermal analysis, powder x-ray diffraction, field emission scanning electron microscopy, and energy-dispersive x-ray spectroscopy. The obtained 1T/2H hybridized phases of MoS₂were confirmed by the Raman spectroscopy. The electrochemical characteristics of MoS₂electrodes were examined using cycle voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The electrodes are based on the 1T/2H hybridized phases MoS₂with specific capacitance (C_p) of 555.4 F g^-1at current densities (C_d) of 0.5 A g^-1, capacity retention ratio of 85% after 10 000 cycles were observed that could be a strong potential electrode material for supercapacitors application.

Colorless to Multicolored, Fast Switching, and Highly Stable Electrochromic Devices Based on Thermally Cross-Linking Copolymer

Transparent-to-colored electrochromic devices exhibit promising application prospects and have gained popularity. Herein, two triphenylamine derivatives TPA-OCH₃ and TPA-CN with styryl moieties and different donor or acceptor units were designed and synthesized to further prepare solvent-resistant thermally cross-linking polymer P(TPA-OCH₃) and P(TPA-CN) without any additional initiator. P(TPA-OCH₃) and P(TPA-CN) possess two pairs of redox peaks, and P(TPA-OCH₃) shows a lower onset oxidation potential compared to P(TPA-CN) because of the pendent donor unit. Correspondingly, both polymers exhibit multicolored changes from the neutral colorless state to noticeable oxidized colors under different potentials. Furthermore, the thermally cross-linking copolymer P(TPA-OCH₃-co-TPA-CN) was obtained by TPA-OCH₃ and TPA-CN (the molar ratio is 2:1) and presents outstanding electrochromism with four color changes (colorless-orange-blue-purple) due to the multistep redox process of TPA-OCH₃ and TPA-CN units. It is more intriguing that the electrochromic device based on the copolymer films possesses a high optical contrast of 57.8% at 680 nm, fast switching time (0.52 and 0.66 s), and robust cyclic stability over 30 000 cycles with very little decay. Therefore, the thermally cross-linking copolymer is a promising candidate material for high-performance transmittive electrochromic devices, such as smart windows, sunglasses, and E-papers.

Recent Progress in the Development of Advanced Functionalized Electrodes for Oxygen Evolution Reaction: An Overview

Presently, the global energy demand for increasing clean and green energy consumption lies in the development of low-cost, sustainable, economically viable and eco-friendly natured electrochemical conversion process, which is a significant advancement in different morphological types of advanced electrocatalysts to promote their electrocatalytic properties. Herein, we overviewed the recent advancements in oxygen evolution reactions (OERs), including easy electrode fabrication and significant action in water-splitting devices. To date, various synthetic approaches and modern characterization techniques have effectively been anticipated for upgraded OER activity. Moreover, the discussed electrode catalysts have emerged as the most hopeful constituents and received massive appreciation in OER with low overpotential and long-term cyclic stability. This review article broadly confers the recent progress research in OER, the general mechanistic approaches, challenges to enhance the catalytic performances and future directions for the scientific community.

High-Performance-Based Perovskite-Supported Nanocomposite for the Development of Green Energy Device Applications: An Overview

Perovskite-based electrode catalysts are the most promising potential candidate that could bring about remarkable scientific advances in widespread renewable energy-storage devices, especially supercapacitors, batteries, fuel cells, solid oxide fuel cells, and solar-cell applications. This review demonstrated that perovskite composites are used as advanced electrode materials for efficient energy-storage-device development with different working principles and various available electrochemical technologies. Research efforts on increasing energy-storage efficiency, a wide range of electro-active constituents, and a longer lifetime of the various perovskite materials are discussed in this review. Furthermore, this review describes the prospects, widespread available materials, properties, synthesis strategies, uses of perovskite-supported materials, and our views on future perspectives of high-performance, next-generation sustainable-energy technology.

Unprecedented Electrochromic Stability of a-WO3-x Thin Films Achieved by Using a Hybrid-Cationic Electrolyte

With large interstitial space volumes and fast ion diffusion pathways, amorphous metal oxides as cathodic intercalation materials for electrochromic devices have attracted attention. However, these incompact thin films normally suffer from two inevitable imperfections: self-deintercalation of guest ions and poor stability of the structure, which constitute a big obstacle toward the development of high-stable commercial applications. Here, we present a low-cost, eco-friendly hybrid cation 1,2-PG-AlCl₃·6H₂O electrolyte, in which the sputter-deposited a-WO_3-x thin film can exhibit both the long-desired excellent open-circuit memory (>100 h, with zero optical loss) and super-long cycling lifetime (∼20,000 cycles, with 80% optical modulation), benefiting from the formation of unique Al-hydroxide-based solid electrolyte interphase during electrochromic operations. In addition, the optical absorption behaviors in a-WO_3-x caused by host-guest interactions were elaborated. We demonstrated that the intervalence transfers are primarily via the "corner-sharing" related path (W⁵⁺ ↔ W⁶⁺) but not the "edge-sharing" related paths (W⁴⁺ ↔ W⁶⁺ and/or W⁴⁺ ↔ W⁵⁺), and the small polaron/electron transfers taking place at the W-O bond-breaking positions are not allowed. Our findings might provide in-depth insights into the nature of electrochromism and provide a significant step in the realization of more stable, more excellent electrochromic applications based on amorphous metal oxides.

Dual-Branched Dense Hexagonal Fe(II)-Based Coordination Nanosheets with Red-to-Colorless Electrochromism and Durable Device Fabrication

Highly dense hexagonal Fe(II)-based coordination nanosheets (CONASHs) were designed by dual-branching, at the metal-coordination moieties and the tritopic ligands, which successfully obtained a liquid/liquid interface by the complexation of Fe(II) ions and the tritopic bidentate ligands. The 1:1 complexation was confirmed by titration. The obtained Fe(II)-based nanosheets were fully characterized by small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). A monolayer of the sheets was obtained, employing the Langmuir-Blodgett (LB) method, and the determined thickness was ∼2.5 nm. The polymer nanosheets exhibited red-to-colorless electrochromism because the electrochemical redox transformation between Fe(II) and Fe (III) ions controlled the appearance/disappearance of the metal (ion)-to-ligand charge-transfer (MLCT) absorption. The poor π-conjugation in the tritopic ligands contributed to the highly colorless electrochromic state. A solid-state device, with the robust polymer film, exhibited excellent electrochromic (EC) properties, with high optical contrast (ΔT > 65%) and high durability after repeated color changes for >15 000 cycles, upon applying low-operating voltages (+1.5/0 V).

Addressing Passivation of a Sulfur Electrode in Li-S Pouch Cells for Dramatically Improving Their Cyclic Stability

The effective passivation of a sulfur electrode in Li-S pouch cells is addressed by increasing the discharging cutoff voltage from 1.6 to 2.0 V. This simple method can effectively suppress the generation of solid and insulated Li₂S deposition while reserves the majority of capacity and improves the cyclic stability of Li-S pouch cells. Upon increasing the discharging cutoff voltage from 1.6 to 2.0 V, the Li-S pouch cell loses only 8% of the initial discharge capacity and remarkably promotes the capacity retention rate from 62.4 to 91.6% within 40 cycles at 0.05C. The analysis of electrochemistry and physics of a sulfur cathode demonstrates that the less Li₂S deposition under the discharging cutoff voltage of 2.0 V can ensure fast reaction kinetics in Li-S pouch cells with high areal sulfur loadings and lean electrolyte. The mechanism of the passivation of a sulfur electrode is studied and discussed in detail. This brand new methodology may provide an effective approach to enhance the cyclic stability of a Li-S battery.

Stabilized High-Voltage Cathodes via an F-Rich and Si-Containing Electrolyte Additive

High-voltage cathodes provide a promising solution to the energy density limitation of currently commercialized lithium-ion batteries, but they are unstable in electrolytes during the charge/discharge process. To address this issue, we propose a novel electrolyte additive, pentafluorophenyltriethoxysilane (TPS), which is rich in elemental F and contains elemental Si. The effectiveness of TPS has been demonstrated by cycling a representative high-voltage cathode, LiNi_0.5Mn_1.5O₄ (LNMO), in 1.0 M LiPF₆-diethyl carbonate/ethylene carbonate/ethyl methyl carbonate (2/3/5 in weight). LNMO presents an increased capacity retention from 28 to 85% after 400 cycles at 1 C by applying 1 wt % TPS. Further electrochemical measurements combined with spectroscopic characterization and theoretical calculations indicate that TPS can not only construct a robust protective cathode electrolyte interphase via its oxidation during initial lithium desertion but also scavenge the detrimental hydrogen fluoride (HF) present in the electrolyte via its strong combination with the species HF, F^-, and H⁺, highly stabilizing LNMO during the charge/discharge process. These features of TPS provide a new solution to the obstacle in the practical application of high-voltage cathodes not limited to LNMO.

A Facile Surface Preservation Strategy for the Lithium Anode for High-Performance Li-O2 Batteries

Protecting an anode from deterioration during charging/discharging has been seen as one of the key strategies in achieving high-performance lithium (Li)-O₂ batteries and other Li-metal batteries with a high energy density. Here, we describe a facile approach to prevent the Li anode from dendritic growth and chemical corrosion by constructing a SiO₂/GO hybrid thin layer on the surface. The uniform pore-preserving layer can conduct Li ions in the stripping/plating process, leading to an effective alleviation of the dendritic growth of Li by guiding the ion flux through the microstructure. Such a preservation technique significantly enhances the cell performance by enabling the Li-O₂ cell to cycle up to 348 times at 1 A·g^-1 with a capacity of 1000 mA·h·g^-1, which is several times the cycles of cells with pristine Li (58 cycles), Li-GO (166 cycles), and Li-SiO₂ (187 cycles). Moreover, the rate performance is improved, and the ultimate capacity of the cell is dramatically increased from 5400 to 25,200 mA·h·g^-1. This facile technology is robust and conforms to the Li surface, which demonstrates its potential applications in developing future high-performance and long lifespan Li batteries in a cost-effective fashion.

Bioinspired Hydrophobic Cellulose Nanocrystal Composite Films as Organic-Solvent-Responsive Structural-Color Rewritable Papers

Lots of beetles, moths, and birds in the natural world present stunning unique structural colors as well as excellent hydrophobic performances. Herein, a novel bioinspired variable structural-color film with organic-solvent responsiveness and surface hydrophobicity was fabricated. Cellulose nanocrystals (CNCs) provided structural color with left-handed helicity. PEG-PPG-PEG triblock copolymers (PPPTCs) were blended with CNCs, giving rise to the organic-solvent-responsive structural color and wider red-shift window of the reflectance peak. The color of the film could be regulated repeatedly under the stimulus of cyclohexanone with an obvious red shift up to 107 nm, corresponding to a macroscopic color change from blue to yellow. Low-surface-energy compound hexadecyltrimethoxysilane (HDTMS) was covalently grafted on the surface in a one-step method to introduce hydrophobicity, successfully preventing the effect of water on the ordered nanostructure. Based on the bionics principle, the as-prepared CNC/PPPTC nanocomposite films with variable structural colors and hydrophobicity are beneficial to their prospective applications in display screens, rewritable hydrophobic structural-color-changing paper, biomimetic sensors, and so forth.

Excellent Cyclic and Rate Performances of SiO/C/Graphite Composites as Li-Ion Battery Anode

The SiO-based composites containing different carbon structures were prepared from asphalt and graphite by the milling, spray drying, and pyrolysis. In the obtained near-spherical composite particles, the refined amorphous SiO plates, which are coated with an amorphous carbon layer, are aggregated with the binding of graphite sheets. The SiO/C/Graphite composites present a maximum initial charge capacity of 963 mAh g^-1 at 100 mA g^-1, excellent cyclic stability (~950 mAh g^-1 over 100 cycles), and rate capability with the charge capacity of 670 mAh g^-1 at 1,000 mA g^-1. This significant improvement of electrochemical performances in comparison with pristine SiO or SiO/C composite is attributed to the unique microstructure, in which both the graphite sheets and amorphous carbon coating could enhance the conductivity of SiO and buffer the volume change of SiO. The higher pyrolysis temperature causes the denser spherical microstructure and better cycle life. Our work demonstrates the potential of this SiO/C/Graphite composite for high capacity anode of LIBs.

Surfactant-Free Synthesis of Nb2O5 Nanoparticles Anchored Graphene Nanocomposites with Enhanced Electrochemical Performance for Supercapacitor Electrodes

Nb₂O₅/graphene nanocomposites without any surfactant are synthesized by an in situ microwave irradiation technique. Structural and morphological studies revealed that the prepared composites were composed of Nb₂O₅ nanoparticles intercalated into the graphene sheet. The thermal stability of graphene oxide, Nb₂O₅, and Nb₂O₅/graphene nanocomposite was studied by the TGA. The electrochemical properties are assessed by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy analyses. The specific capacitance of Nb₂O₅/graphene nanocomposites is greater (633 Fg⁻¹) than pure Nb₂O₅ nanoparticles (221 Fg⁻¹) and graphene (290 Fg⁻¹) at a current density of 1 Ag⁻¹. The long-term cyclic measurement confirms higher cyclic stability of the nanocomposite with capacitance retention of 99.3% after 5000 cycles without performance degradation. The composites exhibit higher electrochemical conductivity and allow effective ions and charge transport over the entire electrode surface with aqueous electrolyte. The electrochemical study suggests that Nb₂O₅/graphene nanocomposites have the potential to be an effective electrode for superior performance supercapacitor applications.

In Situ Introduction of Li3BO3 and NbH Leads to Superior Cyclic Stability and Kinetics of a LiBH4-Based Hydrogen Storage System

LiBH₄ is a high-capacity hydrogen storage material; however, it suffers from high dehydrogenation temperature and poor reversibility. To tackle those issues, we introduce a new LiBH₄-based system with in situ formed superfine and well-dispersed Li₃BO₃ and NbH as co-reactants. Those are synthesized by the addition of niobium ethoxide [Nb(OEt)₅] to LiBH₄, heat treatment of the mixture, and then hydrogenation, where Li₃BO₃ and NbH are generated from the reaction of Nb(OEt)₅ and LiBH₄. After optimization, the system with a normalized composition of LiBH₄-0.04(Li₃BO₃ + NbH) in molar fraction shows superior hydrogen storage reversibility and kinetics. The initial and main dehydrogenation temperatures of the system are 200 and 90 °C lower than those of the pristine LiBH₄, respectively, and 8.2 wt % H₂ is released upon heating to 400 °C. A capacity of 7.2 wt % H₂, corresponding to a capacity retention of 91%, is sustained after 30 cycles in an isothermal cyclic regime of dwelling at 400 °C for 60 min for dehydrogenation and dwelling at 500 °C and 50 bar H₂ pressure for 20 min for hydrogenation. Such a high cyclic stability for a LiBH₄-based system has never been reported to date. The in situ introduced Li₃BO₃ and NbH have a synergistic catalysis effect on the improvement of the hydrogen storage performance of LiBH₄, showing highly effective bidirectional action on both dehydrogenation and hydrogenation.

Humidity and Heat Dual Response Cellulose Nanocrystals/Poly(N-Isopropylacrylamide) Composite Films with Cyclic Performance

It has been widely reported that cellulose nanocrystals (CNCs) demonstrate a special structural color, which stems from chiral nematic domains. Herein, the humidity and heat dual response nanocomposite films with multilayered helical structure were prepared by self-assembling of CNCs and hydrazone groups modified poly(N-isopropylacrylamide) (PNIPAM) copolymers. Furthermore, glutaraldehyde was involved to act as a chemical linker to improve cyclic stability by forming acylhydrazone bonds. The structural color of the films could be easily regulated by humidity, heat, or the content of modified PNIPAM copolymers. The absorption of water in higher humidity led to volume expansion of the resin, resulting in a red shift for up to 145 nm. In contrast, the resin shrank under the temperature above the lower critical solution temperature of PNIPAM, leading to a blue shift for up to 87 nm. It was notable that the change of color can be easily captured by the naked eyes. Moreover, the films exhibited excellent stability and cyclicity in response to either vapor or liquid water due to the chemical linking between CNCs and resins. The as-prepared CNCs/PNIPAM nanocomposite films with humidity or heat responsibilities are promising in stimuli-responsive sensors, printing industry, surface decorations, and so forth.

Grafting the Charged Functional Groups on Carbon Nanotubes for Improving the Efficiency and Stability of Capacitive Deionization Process

In the capacitive deionization (CDI) process, the degradation of desalting performance is predominantly due to the co-ion expulsion effect and electrode oxidation. To overcome these complications, carbon nanotubes grafted with amine and sulfonic functional groups respectively were prepared and used as the CDI electrodes. The structural characterizations and performance tests confirmed that a uniform functional layer was formed on the surface of the modified electrodes and it enhanced the ion selectivity and wettability of the electrode surface. Moreover, the effects of the functional layer on the electrode stability were investigated by circulating CV tests and desalination tests. The positive shift value of the potential of zero charge (PZC) for the as-prepared electrodes was tested as a quantitative indication for their possible surface oxidation during cyclic tests. Analysis of the PZC variation and desalting performance demonstrated that the excellent desalting stability was achieved by the Cell N-S assembled with the ammoniated CNTs electrode as anode and sulfonated CNTs electrode as cathode. Because the functional layer could preserve the pores system on the modified electrodes and diminish the parasitic reactions that exacerbate the electrode oxidation. This work provides an effective strategy for promoting the electrode performance and prolonging the life of the electrode.

Stabilizing LiCoO2/Graphite at High Voltages with an Electrolyte Additive

The energy density of commercial Li-ion batteries (LIBs) using LiCoO₂ is adversely affected by the limited access to the Li stored in the CoO₂ lattice, which is imposed partially by the instability of carbonate-based electrolytes at potentials higher than 4.5 V. In this work, we report a novel approach to fully utilize these extra Li via simultaneously stabilizing anode and cathode interfaces with a designed additive, 4-propyl-[1,3,2]dioxathiolane-2,2-dioxide (PDTD), which strongly coordinates with Co ions dissolved in electrolytes while decomposing to form protective interphases on both cathode and anode surfaces. The Co ions present in the electrolyte deposit on the anode in the form of a coordination complex with PDTD, avoiding the formation of Co metal that will catalyze the reduction decomposition of the additive-free electrolyte. The presence of PDTD in the electrolyte enables a higher charging potential of 4.45 V for LiCoO₂/graphite cells, which significantly improves the energy density and cycling stability of this cathode chemistry that has already been used extensively in commercial LIBs.

Dual-Purpose 3D Pillared Metal-Organic Framework with Excellent Properties for Catalysis of Oxidative Desulfurization and Energy Storage in Asymmetric Supercapacitor

This study proposes an approach for improving catalysis of oxidative desulfurization (ODS) of diesel fuel under mild reaction conditions and enhancing supercapacitor (SC) properties for storage of a high amount of charge. Our approach takes advantage of a novel dual-purpose cobalt(II)-based metal-organic framework (MOF), [Co(2-ATA)₂(4-bpdb)₄] _n (2-ATA: 2-aminoterephthalic acid and 4-bpdb: N, N-bis-pyridin-4-ylmethylene-hydrazine as the pillar spacer), which is called NH₂-TMU-53. Due to the stability of the used compound, we decided to evaluate the capability of this compound as a novel electrode material for storing energy in supercapacitors, and also to investigate its catalytic capabilities. It is demonstrated that the addition of H₂O₂ as an oxidant enhances the efficiency of sulfur removal, which indicates that NH₂-TMU-53 can efficiently catalyze the ODS reaction. According to the kinetics results, the catalyzed process follows pseudo-first-order kinetics and exhibits 15.57 kJ mol^-1 activation energy. Moreover, with respect to the radical scavenging evaluations, the process is governed by direct catalytic oxidation rather than indirect oxidative attack of radicals. Furthermore, NH₂-TMU-53 was applied as an electrode material for energy storage in SCs. This material is used in the three-electrode system and shows a specific capacitance of 325 F g^-1 at 5 A g^-1 current density. The asymmetric supercapacitor of NH₂-TMU-53//activated carbon evaluates the further electrochemical activity in real applications, delivers the high power density (2.31 kW kg^-1), high energy density (50.30 Wh kg^-1), and long cycle life after 6000 cycles (90.7%). Also, the asymmetric supercapacitor practical application was demonstrated by a glowing red light-emitting diode and driving a mini-rotating motor. These results demonstrate that the fabricated device presents a good capacity for energy storage without pyrolyzing the MOF structures. These findings can guide the development of high-performance SCs toward a new direction to improve their practical applications and motivate application of MOFs without pyrolysis or calcination.

The Enhanced Lithium-Storage Performance for MnO Nanoparticles Anchored on Electrospun Nitrogen-Doped Carbon Fibers

Manganese monoxide (MnO) is a promising anode material in the lithium-ion battery for its high capacity, low operation potential, and environmental benignity. However, its application is impeded by poor rate capability and rapid capacity fading. In this work, a MnO/carbon hybrid material, in which small-sized MnO nanoparticles are tightly anchored on carbon fibers (denoted as MnO@CFs), was prepared by annealing the electrospun precursor fibers at 650 °C. When applied as the anode material of the Li-ion battery, the small size of MnO shortens the Li-ion diffusion path, and the carbon fibers not only greatly improve the conductivity but also efficiently buffer the MnO structure strain during the charge–discharge process, endowing the MnO@CFs electrode with a good rate capability (185 mAh g⁻¹ at 5 A g⁻¹) and cyclic stability (406 mAh g⁻¹ after 500 cycles at 1.0 A g⁻¹).

Fabrication of WO3·2H2O/BC Hybrids by the Radiation Method for Enhanced Performance Supercapacitors

In this study, we described a facile process for the fabrication of tungsten oxide dihydrate/bamboo charcoal hybrids (WO₃·2H₂O/BC) by the γ-irradiation method. The structural, morphological, and electrochemical properties of WO₃·2H₂O/BC hybrids were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. The combination of BC (electrical double layer charge) and WO₃·2H₂O (pseudocapacitance) created a combined effect, which enhanced the specific capacitance and superior cyclic stability of the WO₃·2H₂O/BC hybrid electrode. The WO₃·2H₂O/BC hybrids showed the higher specific capacitance (391 F g⁻¹ at 0.5 A g⁻¹ over the voltage range from −1 to 0 V), compared with BC (108 F g⁻¹) in 6 M KOH solution. Furthermore, the hybrid electrode showed superior long-term performance with 82% capacitance retention even after 10,000 cycles. The experimental results demonstrated that the high performance of WO₃·2H₂O/BC hybrids could be a potential electrode material for supercapacitors.

Multistimulus Responsive Actuator with GO and Carbon Nanotube/PDMS Bilayer Structure for Flexible and Smart Devices

Smart devices with abilities of perceiving, processing, and responding are attracting more and more attentions due to the emerging development of artificial intelligent systems, especially in biomimetic and intelligent robotics fields. Designing a smart actuator with high flexibility and multistimulation responsive behaviors to simulate the movement of creatures, such as weight lifting, heavy objects carrying via simple materials, and structural design is highly demanded for the development of intelligent systems. Herein, a soft actuator that can produce reversible deformations under the control of light, thermal, and humidity is fabricated by combining high photothermal properties of CNT/PDMS layer with the natural hydrophilic GO layer. Due to the asymmetric double-layer structure, the novel bilayer membrane-based actuator showed different bending directions under photothermal and humidity stimulations, resulting in bidirectional controllable bending behaviors. In addition, the actuation behaviors can be well controlled by directionally aligning the graphene oxide onto carbon nanotube/PDMS layer. The actuator can be fabricated into a series of complex biomimetic devices, such as, simulated biomimetic fingers, smart "tweezers", humidity control switches, which has great potential applications in flexible robots, artificial muscles, and optical control medical devices.

A Novel Radiation Method for Preparing MnO₂/BC Monolith Hybrids with Outstanding Supercapacitance Performance

A novel facile process for fabrication of amorphous MnO₂/bamboo charcoal monolith hybrids (MnO₂/BC) for potential supercapacitor applications using γ-irradiation methods is described. The structural, morphological and electrochemical properties of the MnO₂/BC hybrids have been investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. The combination of BC (electrical double layer charge) and MnO₂ (pseudocapacitance) created a complementary effect, which enhanced the specific capacitance and good cyclic stability of the MnO₂/BC hybrid electrodes. The MnO₂/BC hybrids showed a higher specific capacitance (449 F g⁻¹ at the constant current density of 0.5 A g⁻¹ over the potential range from –0.2 V to 0.8 V), compared with BC (101 F g⁻¹) in 1 M of Na₂SO₄ aqueous electrolyte. Furthermore, the MnO₂/BC hybrid electrodes showed superior cycling stability with 78% capacitance retention, even after 10,000 cycles. The experimental results demonstrated that the high performance of MnO₂/BC hybrids could be a potential electrode material for supercapacitors.

In Situ Chelating Synthesis of Hierarchical LiNi1/3 Co1/3 Mn1/3 O2 Polyhedron Assemblies with Ultralong Cycle Life for Li-Ion Batteries

Layered lithium transition-metal oxides, with large capacity and high discharge platform, are promising cathode materials for Li-ion batteries. However, their high-rate cycling stability still remains a large challenge. Herein, hierarchical LiNi_1/3 Co_1/3 Mn_1/3 O₂ polyhedron assemblies are obtained through in situ chelation of transition metal ions (Ni²⁺ , Co²⁺ , and Mn²⁺ ) with amide groups uniformly distributed along the backbone of modified polyacrylonitrile chains to achieve intimate mixing at the atomic level. The assemblies exhibit outstanding electrochemical performances: superior rate capability, high volumetric energy density, and especially ultralong high-rate cyclability, due to the superiority of unique hierarchical structures. The polyhedrons with exposed active crystal facets provide more channels for Li⁺ diffusion, and meso/macropores serve as access shortcuts for fast migration of electrolytes, Li⁺ and electrons. The strategy proposed in this work can be extended to fabricate other mixed transition metal-based materials for advanced batteries.

Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li⁻O₂ Batteries

As a step towards efficient and cost-effective electrocatalytic cathodes for Li⁻O₂ batteries, highly porous hausmannite-type Mn₃O₄ hollow nanocages (MOHNs) of a large diameter of ~250 nm and a high surface area of 90.65 m²·g−1 were synthesized and their physicochemical and electrochemical properties were studied in addition to their formation mechanism. A facile approach using carbon spheres as the template and MnCl₂ as the precursor was adopted to suit the purpose. The MOHNs/Ketjenblack cathode-based Li⁻O₂ battery demonstrated an improved cyclability of 50 discharge⁻charge cycles at a specific current of 400 mA·g−1 and a specific capacity of 600 mAh·g−1. In contrast, the Ketjenblack cathode-based one can sustain only 15 cycles under the same electrolytic system comprised of 1 M LiTFSI/TEGDME. It is surmised that the unique hollow nanocage morphology of MOHNs is responsible for the high electrochemical performance. The hollow nanocages were a result of the aggregation of crystalline nanoparticles of 25⁻35 nm size, and the mesoscopic pores between the nanoparticles gave rise to a loosely mesoporous structure for accommodating the volume change in the MOHNs/Ketjenblack cathode during electrocatalytic reactions. The improved cyclic stability is mainly due to the faster mass transport of the O₂ through the mesoscopic pores. This work is comparable to the state-of-the-art experimentations on cathodes for Li⁻O₂ batteries that focus on the use of non-precious transition materials.

Lithium-Ion Batteries: Charged by Triboelectric Nanogenerators with Pulsed Output Based on the Enhanced Cycling Stability

The triboelectric nanogenerator (TENG) has been used to store its generated energy into lithium-ion batteries (LIBs); however, the influences of its pulse current and high voltage on LIB polarization and dynamic behaviors have not been investigated yet. In this paper, it is found that LIBs based on the phase transition reaction of the lithium storage mechanism [LiFePO₄ (LFP) and Li₄Ti₅O₁₂ (LTO) electrodes] are more suitable for charging by TENGs. Thus, the enhanced cycling capacity, Coulombic efficiency (nearly 100% for LTO electrode), and energy storage efficiency (85.3% for the LFP-LTO electrode) are successfully achieved. Moreover, the pulse current has a positive effect on the increase of the Li-ion extraction, reducing the charge-transfer resistance ( R_ct) for all studied electrodes as well (LFP, LiNi_0.6Co_0.2Mn_0.2O₂, LTO, and graphite). The excellent cyclability, high Coulombic, and energy storage efficiencies demonstrated the availability of storing pulsed energy generated by TENGs. This research has provided a promising analysis to obtain an enhanced charging methodology, which provides significant guidance for the scientific research of the LIBs.

Self-Assembly of Silicon@Oxidized Mesocarbon Microbeads Encapsulated in Carbon as Anode Material for Lithium-Ion Batteries

The utilization of silicon/carbon composites as anode materials to replace the commercial graphite is hampered by their tendency to huge volumetric expansion, costly raw materials, and complex synthesis processes in lithium-ion batteries. Herein, self-assembly method is successfully applied to prepare hierarchical silicon nanoparticles@oxidized mesocarbon microbeads/carbon (Si@O-MCMB/C) composites for the first time, in which O-MCMB core and low-cost sucrose-derived carbon shell not only effectively enhance the electrical conductivity of the anode, but also mediate the dramatic volume change of silicon during cycles. At the same time, the carbon can act as "adhesive", which is crucial in enhancing the adhesive force between Si and O-MCMB in the composites. The as-obtained Si@O-MCMB/C delivers an initial reversible capacity of 560 mAh g^-1 at 0.1 A g^-1, an outstanding cyclic retention of 92.8% after 200 cycles, and respectable rate capability. Furthermore, the synthetic route presented here is efficient, less expensive, simple, and easy to scale up for high-performance composites.

Neutral pH Gel Electrolytes for V2O5·0.5H2O-Based Energy Storage Devices

Gel electrolytes are considered to be promising candidates for the use in supercapacitors. It is worthy to systematically evaluate the internal electrochemical mechanisms with a variety of cations (poly(vinyl alcohol) (PVA)-based Li⁺, Na⁺, and K⁺) toward redox-type electrode. Herein, we describe a quasi-solid-state PVA-KCl gel electrolyte for V₂O₅·0.5H₂O-based redox-type capacitors, effectively avoiding electrochemical oxidation and structural breakdown of layered V₂O₅·0.5H₂O during 10 000 charge-discharge cycles (98% capacitance retention at 400 mV s^-1). With the gel electrolyte, symmetric V₂O₅·0.5H₂O-reduced graphene oxide (V₂O₅·0.5H₂O-rGO) devices exhibited a volumetric capacitance of 136 mF cm^-3, which was much higher than that of 68 mF cm^-3 for PVA-NaCl and 45 mF cm^-3 for PVA-LiCl. Additionally, hybrid full cells of activated carbon cloth//V₂O₅·0.5H₂O-rGO delivered an energy density of 102 μWh cm^-3 and a power density of 73.38 mW cm^-3 over a wide potential window of 2 V. The present study provides direct experimental evidence for the contribution of PVA-KCl gel electrolytes toward quick redox reactions for redox-type capacitors, which is also helpful for the development of neutral pH gel electrolytes for energy storage devices.

Constructing a Protective Interface Film on Layered Lithium-Rich Cathode Using an Electrolyte Additive with Special Molecule Structure

Phenyl vinyl sulfone (PVS) as a novel electrolyte additive is used to construct a protective interface film on layered lithium-rich cathode. Charge-discharge cycling demonstrates that the capacity retention of Li(Li_0.2Mn_0.54Ni_0.13Co_0.13)O₂ after 240 cycles at 0.5 C between 2.0 and 4.8 V (vs Li/Li⁺) reaches about 80% by adding 1 wt % PVS into a standard (STD) electrolyte, 1.0 M LiPF₆ in EC/EMC/DEC (3/5/2 in weight). This excellent performance is attributed to the special molecular structure of PVS, compared to the additives that have been reported in the literature. The double bond in the molecule endows PVS with preferential oxidizability, the aromatic ring ensures the chemical stability of the interface film, and the sulfur provides the interface film with ionic conductivity. These contributions have been confirmed by further electrochemical measurements, theoretical calculations, and detailed physical characterizations.

Highly Efficient Storage of Pulse Energy Produced by Triboelectric Nanogenerator in Li3V2(PO4)3/C Cathode Li-Ion Batteries

Triboelectric nanogenerator (TENG) has been considered as a new type of energy harvesting technology, which employs the coupling effects of triboelectrification and electrostatic induction. One key factor having limited its application is the energy storage. In this work, a high performance Li3V2(PO4)3/C material synthesized by low-cost hydrothermal method followed with subsequent annealing treatment was studied to efficiently store the power generated by a radial-arrayed rotary TENG. Not only does the Li3V2(PO4)3/C exhibit a discharge capacity of 128 mAh g(-1) at 1 C with excellent cyclic stability (capacity retention is 90% after 1000 cycles at a rate of 5 C) in Li-ion battery, but also shows outstanding energy conversion efficiency (83.4%) compared with the most popular cathodic materials: LiFePO4 (74.4%), LiCoO2 (66.1%), and LiMn2O4 (73.6%) when it was charged by high frequency and large current electricity directly from by TENG.

Rechargeable Sodium-Ion Battery: High-Capacity Ammonium Vanadate Cathode with Enhanced Stability at High Rate

Sodium-ion battery (NIB) cathode performance based on ammonium vanadate is demonstrated here as having high capacity, long cycle life and good rate capability. The simple preparation process and morphology study enable us to explore this electrode as suitable NIB cathode. Furthermore, density functional theory (DFT) calculation is envisioned for the NH4V4O10 cathode, and three possible sodium arrangements in the structure are depicted for the first time. Relevant NIB-related properties such as average voltage, lattice constants, and atomic coordinates have been derived, and the estimated values are in good agreement with the current experimental values. A screening study shows ammonium vanadate electrodes prepared on carbon coat onto Al-current collector exhibits a better electrochemical performance toward sodium, with a sustained reversible capacity and outstanding rate capability. With the current cathode with nanobelt morphology, a reversible capacity of 190 mAh g(-1) is attained at a charging rate of 200 mA g(-1), and a stable capacity of above 120 mAh g(-1) is retained for an extended 50 cycles tested at 1000 mA g(-1) without the addition of any expensive electrolyte additive.