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Zinc-based flow batteries have attracted tremendous attention owing to their outstanding advantages of high theoretical gravimetric capacity, low electrochemical potential, rich abundance, and low cost of metallic zinc. Among which, zinc-iron (Zn/Fe) flow batteries show great promise for grid-scale energy storage. However, they still face challenges associated with the corrosive and environmental pollution of acid and alkaline electrolytes, hydrolysis reactions of iron species, poor reversibility and stability of Zn/Zn2+ redox couples. In this work, bromide ions are used to stabilize zinc ions via complexation interactions in the cost-effective and eco-friendly neutral electrolyte. Cyclic voltammetry results reveal that the redox reversibility between Zn and stabilized Zn2+ is greatly improved. The results of spectrum characterization and density functional theory calculation verify that the formation of Zn[Brn(H2O)6-n]2-n (1≤n≤4, n is integer.) ions accounts for the increased electrochemical reversibility of Zn/Zn2+ pairs. Moreover, to overcome the bottleneck of slow kinetics of the coordination interactions between Zn2+ and Br−, ZnBr2 is judiciously selected as the electrolyte additive to promote the complexation process. Adopting K3Fe(CN)6 as the positive redox species to pair with the zinc anode with ZnBr2 modified electrolyte, the proposed neutral Zn/Fe flow batteries deliver excellent efficiencies and superior cycling stability over 2000 cycles (356 hours), shedding light on their great potential for large scale energy storage.

With the ever-growing market of electric vehicles, spent lithium-ion batteries (LIBs) eventually turn into a very challenging issue to both the environment and resource sustainability. Recycling is key step to enable a closed-loop battery industry.

Synthetic confined systems with inner cavity have attracted extensive research interest in many fields, but how to engineer an effective and inexpensive confined microsystem remains a great challen...

Vanadium redox flow batteries (VRFBs) are widely applied in energy storage systems (e.g., wind energy, solar energy), while the poor activity of commonly used carbon-based electrode limits their large-scale application. In this study, the graphene modified carbon felt (G/CF) with a large area of 20 cm × 20 cm has been successfully prepared by a chemical vapor deposition (CVD) strategy, achieving outstanding electrocatalytic redox reversibility of the VRFBs. The decorating graphene can provide abundant active sites for the vanadium redox reactions. Compared with the pristine carbon felt (CF) electrode, the G/CF composite electrode possesses more defective sites on surface, which enhances activity toward VO2+/VO 2 + couple and electrochemical performances. For instance, such G/CF electrode delivered remarkable voltage efficiency (VE) of 88.4% and energy efficiency (EE) of 86.4% at 100 mA·cm−2, much higher than CF electrode by 2.1% and 3.78%, respectively. The long-term cycling stability of G/CF electrode was further investigated and a high retention value of 47.6% can be achieved over 600 cycles. It is demonstrated that this work develops a promising and effective strategy to synthesize the large size of carbon electrode with high performances for the next-generation VRFBs.

The vanadium redox flow battery (VRFB) is one of the promising large-scale energy storage technologies. The electrode is one of the key components of the VRFB, and its design has an important effect on its electrochemical redox kinetics and battery performance. The ideal VRFB electrode material has high catalytic activity, good conductivity, and high stability. Carbon-based electrodes are the most commonly used electrode materials for VRFBs. However, its reaction kinetics and catalytic active sites are low. This paper summarizes the methods of carbon-based electrode modification of the electrochemical performance in VRFBs. Three representative methods including metal/metal oxide modification, nonmetal atom modification, and defect engineering for graphite felt in VRFBs are generally reviewed. First, metal and metal oxides have high catalytic activity, which can enhance the chemical reaction process of vanadium ions and greatly improve the reversibility of the redox reaction of vanadium ions. Then, nonmetal atom modification can generally improve the hydrophilicity of carbon-based electrodes, enhance the adsorption/desorption capacity of vanadium ions, and improve the reaction kinetics. Moreover, defect engineering can lead to the formation of the micropore structure on the surface and increase the specific surface area of the material, thus generating more redox reaction active sites. Finally, the development direction of electrode modification in VRFBs is prospected, and it is expected that this review will provide useful insights into the development of VRFBs.

The identification of synergistic effect of Pt-based alloys on hydrogen evolution reaction (HER) requires a combination of experimental studies and theoretical calculations. Here, we present the construction of uniform PtCo nanoparticles grown on N-doped carbon frameworks via pyrolyzing Pt and Co ions adsorbed polyaniline, whereby the nanostructure of the nanoalloys can be effectively tuned by controlling the calcination temperature. As-prepared PtCo@NC-900 shows the optimal HER performance in 0.5 M H

Component optimization and structure engineering are commonly used strategies to realize high-performance electrocatalysts for sustainable energy technologies. Herein, we successfully synthesized FeCoNi nanoalloys embedded in a hierarchical N-rich carbon matrix (FeCoNi@HNC), which served as an efficient and durable electrocatalyst for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media. Experimental investigations and density functional theory (DFT) calculations revealed that the core-shell structure of FeCoNi@HNC was highly beneficial for tuning the adsorption/desorption of oxygen intermediates on the N-rich carbon shell through electron penetration effects, thereby simultaneously delivering outstanding ORR activity (comparable to Pt/C) and OER activity (superior to IrO2/C). Further, the N-rich carbon shell acted as a barrier to prevent excessive oxidation and dissolution of the FeCoNi alloy nanoparticles, thus imparting FeCoNi@HNC with excellent stability in alkaline electrolytes. A prototype zinc-air battery constructed using FeCoNi@HNC exhibited a maximum power density of 109 mW cm−2 and no obvious increase in the discharge-charge voltage gap over 200 cycles at 5 mA cm−2, vastly superior battery performance to a battery fabricated using Pt/C+IrO2/C catalysts. Results validate FeCoNi@HNC as a very promising earth-abundant electrocatalyst for rechargeable zinc-air batteries and potentially other energy conversion devices that utilize ORR and OER.

Sodium super ionic conductor (NASICON) based electrode and electrolyte compounds offer new prospect to achieve higher energy/power densities, improved safety, and longer cycle life in sodium ion batteries (SIBs). For many years NASICON compounds have not been regarded as a possible electrode material for SIBs, mainly because, the research was focusing on the electrolyte aspect. However, in recent years NASICON type materials have attracted a great deal of attention as an electrode as well due to their excellent properties, which include high ionic mobility, better safety and improved structural stability. This review for the first time features and consolidates the ion diffusion mechanisms and crystal structures of different explored NASICON materials. It also provides insight into the present challenges to commercialize these materials for developing functional SIBs. We believe that the thorough understanding of the ion diffusion mechanisms and crystal structures of NASICON based materials is necessary to design new electrodes and will be useful to improve the electrochemical performances of SIBs. The advantages/disadvantages of each category of materials are also discussed. Apart from the widely investigated NASICON type cathode and anode materials, the rarely explored electrolyte material is also included for the complete review of this potential material. We believe that our detailed analysis on crystal structure and ion diffusion mechanism presented in this review will provide insights into important progress that are made in NASICON materials and could open up new opportunities for devising battery formulations that would continue to evolve and will also appeal to broad research audience.

In recent decades, redox-active electrolytes have been used in energy storage systems due to high specific capacitance originated from the Faraday reaction of electrode/electrolyte surface. Here, we provide an effective strategy that using H2SO4 as electrolyte with VOSO4 as redox additives to improve the electrochemical performances of the carbon felt (CF) electrode. The function of VOSO4 is that it can serve as a redox-active electrolyte to provide additional specific capacitance. The specific capacitance of 3.30 F cm−2 at 1 mV s−1 can be achieved, which is about 100 times of improved specific capacitance higher than that of the CF electrode tested in pure H2SO4. In addition, it also exhibits unexceptionable cycling stability without any specific capacitance loss after 2000 cycles at 5 mA cm−2. What’s more, a novel all-solid-state supercapacitor is assembled using CF, gel electrolyte and membrane. The as-fabricated supercapacitor delivers a high specific capacitance of 234 mF cm−2 and fabulous cycle stability after 1200 cycles at the current density of 2 mA cm−2. Interestingly, three charged supercapacitors connected in series can light a red light-emitting diode effectively for about 24 min. Hence, such mixed electrolyte and electrode materials will hold great potential for high performance supercapacitor applications.

Iontronics are effective in modulating electrical properties through the electric double layers (EDLs) assisted with ionic migration/arrangement, which are highly promising for unconventional electronics, ionic sensory devices, and flexible interactive interface. Proton conductors with the smallest and most abundant protons (H+) can realize a faster migration/polarization under electric field to form the EDL with higher capacitance. Here, a versatile triboiontronic MoS2 transistor via proton conductor by sophisticated combination of triboelectric modulation and protons migration has been demonstrated. This device utilizes triboelectric potential originated from mechanical displacement to modulate the electrical properties of transistors via protons migration/accumulation. It shows superior electrical properties, including high current on/off ratio over 106, low cutoff current (∼0.04 pA), and steep switching properties (89 μm/dec). Pioneering noise tests are conducted to the tribotronic devices to exclude the possible noise interference introduced by mechanical displacement. The versatile triboiontronic MoS2 transistor via proton conductor has been utilized for mechanical behavior derived logic devices and an artificial sensory neuron system. This work represents the reliable and effective triboelectric potential modulation on electronic transportation through protonic dielectrics, which is highly desired for theoretical study of tribotronic gating, active mechanosensation, self-powered electronic skin, artificial intelligence, etc.

Ion exchange membranes play a key role in all vanadium redox flow batteries (VRFBs). The mostly available commercial membrane for VRFBs is Nafion. However, its disadvantages, such as high cost and severe vanadium-ion permeation, become obstacles for large-scale energy storage. It is thus crucial to develop an efficient membrane with low permeability of vanadium ions and low cost to promote commercial applications of VRFBs. In this study, graphene oxide (GO) has been employed as an additive to the Nafion 212 matrix and a composite membrane named rN212/GO obtained. The thickness of rN212/GO has been reduced to only 41 μm (compared with 50 μm Nafion 212), which indicates directly lower cost. Meanwhile, rN212/GO shows lower permeability of vanadium ions and area-specific resistance compared to the Nafion 212 membrane due to the abundant oxygen-containing functional groups of GO additives. The VRFB cells with the rN212/GO membrane show higher Coulombic efficiencies and lower capacity decay than those of VRFB cells with the Nafion 212 membrane. Therefore, the cost-effective rN212/GO composite membrane is a promising alternative to suppress migration of vanadium ions across the membrane to set up VRFB cells with better performances.

Slope protection has always been a major concern in highway construction and later operation. Ecological protection technology is widely used in highway slope, which takes into account functions of protection, ecology, and landscape. Ecological protection technology is mainly to improve the stability of the slope through the combination of supporting structure and plants, and vegetation restoration can reduce the negative impact of highway construction. In this paper, the latest research progress of ecological protection technology was first reviewed to identify the main construction process and types, which revealed the protection mechanism of ecological protection technology. The comprehensive benefits of ecological slope protection technology were analysed from the aspects of air, water circulation, landscape and biodiversity. It has found that ecological protection technology of highway slope mainly forms the atmosphere-plant-soil system. Ecological protection technology of highway slope improved the stability of the slope through the supporting structure and the anchoring effect of plant roots. And the restoration of the surface vegetation on the slope promoted the photosynthesis and transpiration of plants and purifies the air quality along the highway. Ecological protection technology of highway slope could quickly restore the ecological balance, overall landscape and biodiversity of the region.

Redox flow batteries (RFBs) with decoupling energy and power, high safety, long durability and easy scalability have been considered as giant promising candidates for large-scale energy storage systems. As a key component of RFBs, the electrodes provide active sites for the conversion between electrical and chemical energies. Thus, the electrochemical properties of both the positive and negative electrodes are significantly important to the performance of batteries, especially the energy efficiency and the power. Therefore, improving the electrochemical performance of electrodes by effective modifications is essential for the advancements of RFBs. With high conductivity, high activity and stability, metal-based electrocatalysts have been widely used to modify and increase the electrochemical activities of electrodes in RFBs. This review summarizes and discusses the applications of metal-based electrocatalysts modified carbon-based electrodes of RFBs in a wide pH range (the acidic, alkaline and neutral electrolytes), including the characterizations of physicochemical and electrochemical properties of electrodes, the cell performance, the merits, and limitations.

Electrochemical CO

Recycling spent lithium-ion batteries (LIBs) is an urgent task in view of the resource shortage and environmental concerns. Here, a facile ternary molten salt approach is presented for efficiently regenerating the LiNi

Due to the pressing need for harnessing renewable energy, sizable energy storage technologies have become increasingly critical, among which vanadium redox flow batteries (VRFBs) are considered as one of the promising technologies. However, the lack of high-performance electrodes hinders the development of VRFBs. Herein, we report a new ammonia plasma-treated WO3@carbon felt as a high-performance electrode for VRFBs. The ammonia plasma introduces not only N-contained functional groups but also oxygen deficiencies on WO3, which provide additional active sites and improve the conductivity, leading to high catalysis for both cathodic and anodic vanadium redoxes. As a result, the energy efficiency and the power density of the VRFB increase from 78.9% to 86% and from 365.5 mWcm[Formula: see text] to 389.6 mWcm[Formula: see text], respectively. Moreover, the energy efficiency of composite electrodes remains stable for more than 300 cycles. This study provides a new strategy for designing cost-effective, environmentally friendly, and high-performance electrodes for future VRFBs.

Organic electrode materials offer a new opportunity to develop high energy/power density, low-cost, environmentally benign sodium ion batteries (SIBs). For many years this category of materials has not been considered as a potential electrode candidate for SIBs mainly because excessive research focused on inorganic materials due to their successful commercialization in the proven lithium ion battery (LIB) technologies. However, recently, many promising advancements have been made in the field of organic cathode and anode materials for SIB applications. This review for the first time consolidates and provides insights into the different sodium storage mechanisms observed in various categories of organic electrode materials. We believe that the fundamental understanding of the redox mechanisms that govern the electrochemical performances of SIBs is necessary to design new materials/electrodes and is beneficial for enhancing the existing properties of investigated compounds.

Seeking for suitable electrode materials and designing rational porous structures are great challenges for developing high performance supercapacitors. Herein, needle-like porous CoNi2S4-MnOOH (denoted as NCS-MO) were prepared via a simple two steps solvothermal method and used as battery-type electrode of supercapacitor for the first time. Owing to the multiple oxidation states of needle-like porous NCS-MO and the inherent porous structure, the electrode delivers outstanding electrochemical capacitive properties with a high gravimetric specific capacitance of 1267.7 F g−1 at the scan rate of 1 mV s−1. To further assess the practical electrochemical performances, we assembled a hybrid supercapacitor using the as-synthesized porous NCS-MO as cathode and active carbon as anode. The device exhibits excellent performance with a high energy density of 47.1 Wh kg−1 at the power density of 998 W kg−1 in an extended voltage range of 1.6 V and outstanding cycling stability. These results demonstrate that the needle-like porous NCS-MO could be promising potential electrode material for high performance supercapacitor.

Summary Defect sites are often proposed as key active sites in the design of catalysts. A promising strategy for improving activity is to achieve a high density of homogeneously dispersed atomic defects; however, this is seldom accomplished in metals. We hypothesize that vacancy-rich catalysts could be obtained through the synthesis of quantum dots (QDs) and their electrochemical reduction during the CO2 reduction reaction (CO2RR). Here, we report that QD-derived catalysts (QDDCs) with up to 20 vol % vacancies achieve record current densities of 16, 19, and 25 mAcm−2 with high faradic efficiencies in the electrosynthesis of formate, carbon monoxide, and ethylene at low potentials of –0.2, –0.3, and –0.9 V versus reversible hydrogen electrode (RHE), respectively. The materials are stable after 80 hr of CO2RR. These CO2RR performances in aqueous solution surpass those of previously reported catalysts by 2×. Together, X-ray absorption spectroscopy and computational studies reveal that the vacancies produce a local atomic and electronic structure that enhances CO2RR.

Summary Energy storage systems are crucial in the deployment of renewable energies. As one of the most promising solutions, redox flow batteries (RFBs) are still hindered for practical applications by low energy density, high cost, and environmental concerns. To breakthrough the fundamental solubility limit that restricts boosting energy density of the cell, we here demonstrate a new RFB system employing polysulfide and high concentrated ferricyanide (up to 1.6 M) species as reactants. The RFB cell exhibits high cell performances with capacity retention of 96.9% after 1,500 cycles and low reactant cost of $32.47/kWh. Moreover, neutral aqueous electrolytes are environmentally benign and cost-effective. A cell stack is assembled and exhibits low capacity fade rate of 0.021% per cycle over 642 charging-discharging steps (spans 60 days). This neutral polysulfide/ferricyanide RFB technology with high safety, long-duration, low cost, and feasibility of scale-up is an innovative design for storing massive energy., Graphical abstract, Highlights • A neutral polysulfide/ferricyanide flow battery (PFRFB) has been developed • The breakthrough of solubility limit of ferricyanide/ferrocyanide species to 1.6 M • The low-cost PFRFB system is ultra-high stable • The PFRFB cell stack shows low capacity fade rate of 0.021% per cycle (spans 60 days), Electrochemistry; Electrochemical energy storage; Energy materials

Slopes with carbonaceous mudstone (CM) are widely distributed in the southwest of China and have experienced numerous geological disasters in special climate, especially in rainfall conditions. Therefore, novel materials to stabilize CM slopes have attracted increasing interests. However, developing ultra-stable and cost-effective additives for CM slopes is still a great challenge. Herein, a hydrophobic polymeric material (polyvinylidene fluoride, PVDF) is investigated as an additive to enhance the mechanical strength and long-time stability of CM slopes. The PVDF is uniformly dispersed in CM matrix via interfacial interaction. The contact angle of the PVDF-modified carbonaceous mudstone (PVDF-MCM) can reach as high as 103.95°, indicating an excellent hydrophobicity. The unconfined compressive strength (UCS) and tensile strength (TS) of PVDF-MCM have been intensively enhanced to 4.07 MPa and 1.96 MPa, respectively, compared with ~0 MPa of pristine CM. Moreover, the UCS and TS of PVDF-MCM remain at 3.24 MPa and 1.03 MPa even after curing for 28 days in high humidity conditions. Our findings show that the PVDF can improve the hydrophobicity of CM significantly, which leads to super mechanical stability of PVDF-MCM. The excellent performance makes PVDF a promising additive for the development of ultra-stable, long-lifetime and cost-effective carbonaceous mudstone slopes.

Iontronics are effective in modulating electrical properties through the electric double layers (EDLs) assisted with ionic migration/arrangement, which are highly promising for unconventional electronics, ionic sensory devices, and flexible interactive interface. Proton conductors with the smallest and most abundant protons (H

A belt-like MnO2 nanomaterials is designed as cathode material to enable neutral aqueous, high energy density and ultra-long life asymmetric supercapacitor. The energy density and power density can reach as high as 33.8 Wh kg−1 and 5000 W kg−1 respectively even in the high-voltage region of 0–2 V. The asymmetric supercapacitor exhibits 91% capacity retention after 10,000 cycles indicating outstanding cycling property. The ultra-stability of the belt-like MnO2//activated carbon asymmetric supercapacitor makes it a promising device for large-scale applications.

The intrinsic poor electrical and large volume expansion upon cycling of ZnO raise up challenging kinetic issues. In this work, ZnO@TiO2 core/shell nanorod arrays heterostructure grown directly on carbon cloth is designed and fabricated. The atomic layer deposition coated TiO2 thin layer can not only function as an efficient stress buffer during electrochemical reaction, but also provide enhanced electronic conductivity by forming a heterostructure with ZnO. The ZnO@TiO2 nanorod arrays on carbon cloth can simultaneously achieve the high capacity and high-rate long cycle life (1000 mA h/g for 250 cycles at 1 A/g), which is far superior to that of bare ZnO nanorod arrays on carbon cloth without TiO2 shell. The density functional theory calculations reveal the strong chemical coupling between ZnO and TiO2, which realizes band gap tailoring and significant charge redistribution of both ZnO and TiO2. Such a unique structure endows the as prepared ZnO@TiO2 on carbon cloth great potential as high performance three-dimensional flexible electrode in Li-ion batteries.