High-Performance Aqueous Zinc-Ion Battery Based on Layered H2 V3 O8 Nanowire Cathode

Layer-by-layer stacked vanadium nitride nanocrystals/N-doped carbon hybrid nanosheets toward high-performance aqueous zinc-ion batteries

Aqueous zinc ion batteries (AZIBs) hold great potential in large scale, low-cost energy storage. Unfortunately, their development is limited by the poor performing cathode materials due to their unstable structures and low capacities. Hence, we develop novel layer-by-layer stacked vanadium nitride nanocrystals/N-doped carbon hybrid nanosheets (VN/NC) as cathode materials by in situ thermal conversion of pyrolyzing pentyl viologen intercalated V₂O₅. The combination of a leaf-like morphology, the nano structure of vanadium nitride crystals and the conductive porous nitrogen-doped carbon nanosheets endow the VN/NC cathode with excellent electrochemical performance in AZIBs. Thus, it delivers a high discharge specific capacity of 566 mA h g^-1 at a current density of 0.2 A g^-1 and a superior rate capability. Most importantly, it exhibits a remarkable cyclic stability with capacity retention of 131 mA h g^-1 (85% of the initial capacity) after 1000 cycles at a current density of 10 A g^-1. The design of the unique VN/NC hybrid nano sheets offers a pathway towards developing high performance electrode materials for energy storage.

Electrochemical Activation of Oxygen Vacancy-Rich Nitrogen-Doped Manganese Carbonate Microspheres for High-Performance Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (ZIBs) are considered as one of the ideal devices for large-scale energy storage because of their safety, low cost, and nontoxicity. Unfortunately, the choice of cathode materials for ZIBs is still limited. Herein, a novel oxygen vacancy-rich nitrogen-doped MnCO₃ (MnCO₃@N) microsphere is reported as a cathode material for rechargeable ZIBs, which displays a relatively high reversible capacity of 171.6 mAh g^-1 at 100 mA g^-1, outstanding rate performance, and long-term cyclic stability up to 1000 cycles at 1000 mA g^-1. The better electrochemical performances of MnCO₃@N should be attributed to the introduction of oxygen vacancies in the MnCO₃ microcrystal by nitrogen doping, which not only improves the conductivity of MnCO₃ microspheres but also creates more active sites for zinc-ion diffusion. In addition, the energy storage mechanism of the MnCO₃@N microspheres is systematically investigated. During the initial charge process, the MnCO₃@N microspheres are activated to form MnO@N due to the insertion of Zn²⁺, and partial MnO@N is further oxidized into layered-type MnO₂@N, which becomes a part of the active material for subsequent energy storage. This work not only provides a new insight for the ZIB cathode but also deepens the understanding of the energy storage mechanism of carbonate materials.

Design Strategies for High-Energy-Density Aqueous Zinc Batteries

In recent years, the increasing demand for high-capacity and safe energy storage has focused attention on zinc batteries featuring high voltage, high capacity, or both. Despite extensive research progress, achieving high-energy-density zinc batteries remains challenging and requires the synergistic regulation of multiple factors including reaction mechanisms, electrodes, and electrolytes. In this Review, we comprehensively summarize the rational design strategies of high-energy-density zinc batteries and critically analyze the positive effects and potential issues of these strategies in optimizing the electrochemistry, cathode materials, electrolytes, and device architecture. Finally, the challenges and perspectives for the further development of high-energy-density zinc batteries are outlined to guide research towards new-generation batteries for household appliances, low-speed electric vehicles, and large-scale energy storage systems.

Molten Salt Thermal Treatment Synthesis of S-Doped V2CTx and Its Performance as a Cathode in Aqueous Zn-Ion Batteries

The lack of suitable cathode materials with a high capacity and good stability is a crucial problem affecting the development of aqueous Zn-ion batteries. Herein, a novel strategy for the modification of V₂CT_x through molten salt thermal treatment is proposed. In the novel route, S heteroatoms were introduced into V₂CT_x through a substitution reaction during the dissolution of Li₂S in LiCl-KCl molten salts. Then, surface V₂O₅ was obtained through the in situ electrochemical charging/discharging of the S-doped V₂CT_x (MS-S-V₂CT_x) cathode. The assembled Zn/MS-S-V₂CT_x battery showed a high reversible discharge capacity of 411.3 mAh g^-1 at a current density of 0.5 A g^-1, an 80% capacitance retention after long cycle stability tests at 10 A g^-1 for 3000 cycles, and a high energy density of 375.5 Wh kg^-1 in 2M ZnSO₄. Density functional theory calculations demonstrate that the improved electrochemical performance of the cathode can be attributed to the introduced S heteroatoms, which considerably reduced the ion diffusion energy barrier for Zn²⁺ ions and improved the stability of V₂O₅. This work provides a novel method to produce highly active and stable vanadium-based cathodes for aqueous Zn-ion batteries.

Achieving Stable Zinc-Ion Storage Performance of Manganese Oxides by Synergistic Engineering of the Interlayer Structure and Interface

Manganese oxide is a promising cathode material for rechargeable aqueous zinc-ion batteries (ZIBs). However, the low electronic conductivity and unstable structure evolution of manganese materials often result in poor rate performance and rapid capacity decay. Herein, we design N-doped Na₂Mn₃O₇ (N-NMO) by combining sodium preintercalation and nitridation treatment strategies to stabilize the crystalline structure and reaction interface. Sodium preintercalation not only enlarges the interlayer distance for fast Zn²⁺ ion diffusion but also serves as a robust pillar to stabilize the crystalline structure during cycling. Meanwhile, the nitridation layer on the surface of Na₂Mn₃O₇ particles is favorable for enhancing the electronic conductivity and inhibiting the cathode dissolution issue during repeated cycling. Consequently, the as-prepared N-NMO exhibits high reversible capacity (300 mAh g^-1 at 0.2 A g^-1), good rate capability (100 mAh g^-1 at 10 A g^-1), and outstanding long-term cycling stability (high capacity retention of 78.9% after 550 cycles at 2 A g^-1). Considering the facile and simple synthesizing methods, the synergistic engineering of the interlayer structure and interface is expected to provide new opportunities for the development of high-performance Mn-based cathode materials for aqueous ZIBs.

Water-Processable and Multiscale-Designed Vanadium Oxide Cathodes with Predominant Zn2+ Intercalation Pseudocapacitance toward High Gravimetric/Areal/Volumetric Capacity

Layered vanadium oxides have great potential as cathode materials for recently surged aqueous zinc-ion batteries (AZIBs). However, achieving high energy/power densities simultaneously is challenging, and side reactions related to more frequently than disclosed Zn²⁺ /proton co-insertion mechanism aggravate stability concerns. Herein, an engineered binder-free cathode configuration based on water-processable and high packing-density sheet-shaped composites of carbon nanotubes network, surface poly(3,4-ethylenedioxythiophene) (PEDOT) bridging coating, and ultrasmall PEDOT-intercalated V₂ O₅ nanoflakes is developed, and therein, large pseudocapacitance via predominant (≈91%) Zn²⁺ intercalation is revealed. Besides competitive gravimetric/areal capacity, the binder-free cathodes exhibit high volumetric capacity of 1106.1 mAh cm^-3 and high-rate capability of 180.0 mA g^-1 at 30 A g^-1 as well as long-cycling stability. Such combined level of performance and unwanted reaction mechanism are attributed to the contained multiscale material/electrode design formula from crystal structure modification to 3D architecture construction of whole electrode, which endows the binder-free cathodes with abundant accessible sites for Zn²⁺ storage, but the least hydroxyl terminated surface for H⁺ insertion, as well as highly conductive network for electron transfer and fast Zn²⁺ diffusion kinetics throughout the electrode. Combined with scalable fabrication protocols, this study opens up great opportunities for high-performance vanadium oxide cathodes practically applicable to AZIBs.

Boosting Reversibility and Stability of Li Storage in SnO2 -Mo Multilayers: Introduction of Interfacial Oxygen Redistribution

Among the promising high-capacity anode materials, SnO₂ represents a classic and important candidate that involves both conversion and alloying reactions toward Li storage. However, the inferior reversibility of conversion reactions usually results in low initial Coulombic efficiency (ICE, ≈60%), small reversible capacity, and poor cycling stability. Here, it is demonstrated that by carefully designing the interface structure of SnO₂ -Mo, a breakthrough comprehensive performance with ultrahigh average ICE of 92.6%, large capacity of 1067 mA h g^-1 , and 100% capacity retention after 700 cycles can be realized in a multilayer Mo/SnO₂ /Mo electrode. Furthermore, high capacity retentions are also achieved in pouch-type Mo/SnO₂ /Mo||Li half cells and Mo/SnO₂ /Mo||LiFePO₄ full cells. The amorphous SnO₂ /Mo interfaces, which are induced by redistribution of oxygen between SnO₂ and Mo, can precisely adjust the reversible capacity and cycling stability of the multilayers, while the stable capacities are parabolic with the interfacial density. Theoretical calculations and in/ex situ investigation reveal that oxygen redistribution in SnO₂ /Mo heterointerfaces boosts Li-ion transport kinetics by inducing a built-in electric field and improves the reaction reversibility of SnO₂ . This work provides a new understanding of interface-performance relationship of metal-oxide hybrid electrodes and pivotal guidance for creating high-performance Li-ion batteries.

New Insight on K2 Zn2 V10 O28 as an Advanced Cathode for Rechargeable Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (ZIBs) have recently attracted people's extensive attention in their application in energy storage systems resulting from their exclusive characteristics of low cost and environmental compatibility. However, finding suitable cathode materials continues to be the major challenge. Polyoxovanadates (POVs), as an important branch of polyoxometalates (POMs), are considered as a promising electrode material for reversible aqueous ZIBs relying on the flexible valence state of V. Herein, POVs (K₂ Zn₂ V₁₀ O₂₈ : KZVO) are reported as an advanced cathode for storing Zn²⁺ , which delivers a high discharge capacity of 223.4 mAh g^-1 at 0.1 A g^-1 , considerable energy density (182.9 Wh kg^-1 ) and power density (40.38 W kg^-1 ), and robust cyclic performance. In addition, the dynamic properties of the KZVO/Zn battery are revealed by pseudocapacitance analysis and GITT tests. Meanwhile, the storage mechanism of Zn²⁺ is further analyzed by ex situ XRD, XPS, TEM, and HRTEM. Overall, this work not only draws up a cathode material for the POMs system in aqueous ZIBs, but also demonstrates that POMs are the rising star in energy storage and electric energy applications.

A Better Zn-Ion Storage Device: Recent Progress for Zn-Ion Hybrid Supercapacitors

As a new generation of Zn-ion storage systems, Zn-ion hybrid supercapacitors (ZHSCs) garner tremendous interests recently from researchers due to the perfect integration of batteries and supercapacitors. ZHSCs have excellent integration of high energy density and power density, which seamlessly bridges the gap between batteries and supercapacitors, becoming one of the most viable future options for large-scale equipment and portable electronic devices. However, the currently reported two configurations of ZHSCs and corresponding energy storage mechanisms still lack systematic analyses. Herein, this review will be prudently organized from the perspectives of design strategies, electrode configurations, energy storage mechanisms, recent advances in electrode materials, electrolyte behaviors and further applications (micro or flexible devices) of ZHSCs. The synthesis processes and electrochemical properties of well-designed Zn anodes, capacitor-type electrodes and novel Zn-ion battery-type cathodes are comprehensively discussed. Finally, a brief summary and outlook for the further development of ZHSCs are presented as well. This review will provide timely access for researchers to the recent works regarding ZHSCs.

A Comprehensive Understanding of Interlayer Engineering in Layered Manganese and Vanadium Cathodes for Aqueous Zn-ion Batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) hold a budding technology for large-scale stationary energy storage devices due to their inherent safety, cost-effectiveness, eco-friendly, and acceptable electrochemical performance. However, developing a cathode material with fast kinetics and durable structural stability for Zn 2+ intercalation is still an arduous challenge. Compared with other cathode materials, layered manganese/vanadium (Mn/V) oxides that feature merits of adjustable interlayer spacing and considerable specific capacity have attracted much interest in AZIBs. However, the intrinsic sluggish reaction kinetics, inferior electrical conductivity, and notorious dissolution of active materials still obstruct the realization of their full potentials. Interlayer engineering of pre-intercalation is regarded as an effective solution to overcome these problems. In this review, we start from the crystal structure and reaction mechanism of layered Mn/V oxide cathodes to critical issues and recent progress in interlayer engineering. Finally, some future perspectives are outlined for the development of high-performance AZIBs.

Boosting Zn2+ Diffusion via Tunnel-Type Hydrogen Vanadium Bronze for High-Performance Zinc Ion Batteries

Aqueous zinc ion batteries (ZIBs) are emerging as a promising candidate in the post-lithium ion battery era, while the limited choice of cathode materials plagues their further development, especially the tunnel-type cathode materials with high electrochemical performance. Here, a tunnel-type vanadium-based compound based on hydrogen vanadium bronze (H_xV₂O₅) microspheres has been fabricated and employed as the cathode for fast Zn²⁺ ions' intercalation/deintercalation, which delivers an excellent capacity (425 mAh g^-1 at 0.1 A g^-1), a remarkable cyclability (91.3% after 5000 cycles at 20 A g^-1), and a sufficient energy density (311.5 Wh kg^-1). As revealed by the experimental and theoretical results, such excellent electrochemical performance is confirmed to result from the fast ions/electrons diffusion kinetics promoted by the unique tunnel structure (3.7 × 4.22 Ų, along the c direction), which accomplishes a low Zn²⁺ ion diffusion barrier and the superior electron-transfer capability of H_xV₂O₅. These results shed light on designing tunnel-type vanadium-based compounds to boost the prosperous development of Zn²⁺ ion storage cathodes.

Connecting battery technologies for electric vehicles from battery materials to management

Vehicle electrification has always been a hot topic and gradually become a major role in the automobile manufacturing industry over the last two decades. This paper presented comprehensive discussions and insightful evaluations of both conventional electric vehicle (EV) batteries (such as lead-acid, nickel-based, lithium-ion batteries, etc.) and the state-of-the-art battery technologies (such as all-solid-state, silicon-based, lithium-sulphur, metal-air batteries, etc.). Battery major component materials, operating characteristics, theoretical models, manufacturing processes, and end-of-life management were thoroughly reviewed. Different from other reviews focusing on theoretical studies, this review emphasized the key aspects of battery technologies, commercial applications, and lifecycle management. Useful battery managing technologies such as health prediction, charging and discharging, as well as thermal runaway prevention were thoroughly discussed. Two novel hexagon radar charts of all-round evaluations of most reigning and potential EV battery technologies were created to predict the development trend of the EV battery technologies. It showed that lithium-ion batteries (3.9 points) would be still the dominant product for the current commercial EV power battery market in a short term. However, some cutting-edge technologies such as an all-solid-state battery (3.55 points) and silicon-based battery (3.3 points) are highly likely to be the next-generation EV onboard batteries with both higher specific power and better safety performance.

Zinc vacancy modulated quaternary metallic oxynitride GeZn1.7ON1.8: as a high-performance anode for lithium-ion storage

Zn-defected GeZn1.7ON1.8 (GeZn1.7−xON1.8) was successfully synthesized by a simple ammoniation and acid etching method. This well-designed Zn cation-deficient GeZn1.7−xON1.8 anode shows enhanced lithium-ion storage performance.

Mg ion pre-intercalated MnO2 nanospheres as high-performance cathode materials for aqueous Zn-ion batteries

Rechargeable Zn-MnO2 batteries with mild and nearly neutral aqueous electrolytes have shown great potential for large-scale energy storage because of their high safety, low cost, environmental friendliness and high energy...

Architecting a Hydrated Ca0.24V2O5 Cathode with a Facile Desolvation Interface for Superior-Performance Aqueous Zinc Ion Batteries

Vanadium-based materials are promising cathode candidates for low-cost and high-safety aqueous zinc-ion batteries (AZIBs). However, they suffer from inferior rate capability and undesirable capacity fading due to their intrinsic poor conductivity and structural instability. Herein, we synthesize hydrated Ca_0.24V₂O₅·0.75H₂O (CaVOH) nanoribbons with in situ incorporations of the carbon nanotubes via a one-step hydrothermal method, achieving an integrated architecture hybrid cathode (C/CaVOH) design. Benefitting from the robust structure and low desolvation interface, the prefabricated C/CaVOH cathodes deliver a high capacity of 384.2 mA h g^-1 at 0.5 A g^-1 with only 5.6% capacity decay over 300 cycles, enable an ultralong cycling life of 10,000 cycles at 20.0 A g^-1 with 80.2% capacity retention, and exhibit an impressive rate capability (165 mA h g^-1 at 40.0 A g^-1) with a high mass loading of ∼4 mg cm^-2. Moreover, through the theoretical calculations and a series of ex situ characterizations, we demonstrate the Zn²⁺/H⁺ co-intercalation storage mechanism, the key role of the gallery water, and the function of the induced C-O groups in promoting kinetics of the C/CaVOH electrode. This work highlights the strategy of in situ implanted high conductivity materials to engineer vanadium-based or other cathodes for high-performance AZIBs.

Unveiling the Reversibility and Stability Origin of the Aqueous V2 O5 -Zn Batteries with a ZnCl2 "Water-in-Salt" Electrolyte

Aqueous V2 O5 -Zn batteries, an alternative chemistry format that is inherently safer to operate than lithium-based batteries, illuminates the low-cost deployment of the stationary energy storage devices. However, the cathode structure collapse caused by H2 O co-insertion in aqueous solution dramatically deteriorates the electrochemical performance and hampers the operation reliability of V2 O5 -Zn batteries. The real-time phase tracking and the density functional theory (DFT) calculation prove the high energy barrier that inhibits the Zn2+ diffusion into the bulk V2 O5 , instead the ZnCl2 "water-in-salt electrolyte" (WiSE) can enable the dominant proton insertion with negligible lattice strain or particle fragment. Thus, ZnCl2 WiSE enables the enhanced reversibility and extended shelf life of the V2 O5 -Zn battery upon the high temperature storage. The improved electrochemical performance also benefits by the inhibition of vanadium cation dissolution, enlarged voltage window, as well as the suppression of the Zn dendrite protrusion. This study comprehensively elucidates the pivotal role of a concentrated ZnCl2 electrolyte to stabilize the aqueous batteries at both the static storage and dynamic operation scenarios.

A rechargeable aqueous manganese-ion battery based on intercalation chemistry

Aqueous rechargeable metal batteries are intrinsically safe due to the utilization of low-cost and non-flammable water-based electrolyte solutions. However, the discharge voltages of these electrochemical energy storage systems are often limited, thus, resulting in unsatisfactory energy density. Therefore, it is of paramount importance to investigate alternative aqueous metal battery systems to improve the discharge voltage. Herein, we report reversible manganese-ion intercalation chemistry in an aqueous electrolyte solution, where inorganic and organic compounds act as positive electrode active materials for Mn2+ storage when coupled with a Mn/carbon composite negative electrode. In one case, the layered Mn0.18V2O5·nH2O inorganic cathode demonstrates fast and reversible Mn2+ insertion/extraction due to the large lattice spacing, thus, enabling adequate power performances and stable cycling behavior. In the other case, the tetrachloro-1,4-benzoquinone organic cathode molecules undergo enolization during charge/discharge processes, thus, contributing to achieving a stable cell discharge plateau at about 1.37 V. Interestingly, the low redox potential of the Mn/Mn2+ redox couple vs. standard hydrogen electrode (i.e., -1.19 V) enables the production of aqueous manganese metal cells with operational voltages higher than their zinc metal counterparts.

High-performance reversible aqueous Zinc-Ion battery based on Zn2+ pre-intercalation alpha-manganese dioxide nanowires/carbon nanotubes

Rechargeable aqueous zinc ion batteries (ZIBs) have attracted more and more attention due to the advantages of high safety, low cost, and environmental friendly in recent years. However, the lack of high-performance cathode materials and uncertain reaction mechanisms hinder the large-scale application of ZIBs. Herein, a 1D structure interlaced by Zn_xMnO₂ nanowires and carbon nanotubes is synthesized as cathode material for ZIB. The Zn_xMnO₂/CNTs cathode exhibits excellent specific capacity of 400 mAh g^-1 at 100 mA g^-1 and outstanding long-cycle stability (with a capacity retention of 93% after 100 cycles at 1000 mA g^-1), which indicates the Zn²⁺ pre-intercalation and composite carbon nanotubes can effectively change the storage space of the tunnel structure and increase the electron transmission rate. In addition, the energy storage mechanism of the highly reversible co-insertion of H⁺ and Zn²⁺ is further elaborated. This work has enlightenment and promotion for the future research of ZIBs cathode materials. Moreover, the simple preparation method, low cost and excellent performance of Zn_xMnO₂/CNTs cathode material provide a new way for the practical application of ZIBs.

Reconstructing Vanadium Oxide with Anisotropic Pathways for a Durable and Fast Aqueous K-Ion Battery

Aqueous potassium-ion batteries are long-term pursued, due to their excellent performance and intrinsic superiority in safe, low-cost storage for portable and grid-scale applications. However, the notorious issues of K-ion battery chemistry are the inferior cycling stability and poor rate performance, due to the inevitably destabilization of the crystal structure caused by K-ions with pronouncedly large ionic radius. Here, we resolve such issues by reconstructing commercial vanadium oxide (α-V₂O₅) into the bronze form, i.e., δ-K_0.5V₂O₅ (KVO) nanobelts, as cathode materials with layered structure of enlarged space and anisotropic pathways for K-ion storage. Specifically, it can deliver a high capacity as 116 mAh g^-1 at the 1 C-rate, an outstanding rate capacity of 65 mAh g^-1 at 50 C, and a robust cyclic stability with 88.2% capacity retention after 1,000 cycles at 1 C. When coupled with organic anode in a full-cell configuration, the KVO electrodes can output 95 mAh g^-1 at 1 C and cyclic stability with 77.3% capacity retention after 20,000 cycles at 10 C. According to experimental and calculational results, the ultradurable cyclic performance is assigned to the robust structural reversibility of the KVO electrode, and the ultrahigh-rate capability is attributed to the anisotropic pathways with improved electrical conductivity in KVO nanobelts. In addition, applying a 22 M KCF₃SO₃ water-in-salt electrolyte can impede the dissolving issues of the KVO electrode and further stabilize the battery cyclic performance. Lastly, the as-designed AKIBs can operate with superior low-temperature adaptivity even at -30 °C. Overall, the KVO electrode can serve as a paradigm toward developing more suitable electrode materials for high-performance AKIBs.

In Situ Defect Induction in Close-Packed Lattice Plane for the Efficient Zinc Ion Storage

In situ electrochemical activation brings unexpected electrochemical performance improvements to electrode materials, but the mechanism behind it still needs further study. Herein, an electrochemically in situ defect induction in close-packed lattice plane of vanadium nitride oxide (VN_x O_y ) in aqueous zinc-ion battery is reported. It is verified by theoretical calculation and experiment that the original compact structure is not suitable for the insert of Zn²⁺ ion, while a highly active one after the initial electrochemical activization accompanied by the in situ defect induction in close-packed lattice plane of VN_x O_y exhibits efficient zinc ion storage. As expected, activated VN_x O_y can achieve very high reversible capacity of 231.4 mA h g^-1 at 1 A g^-1 and cycle stability upto 6000 cycles at 10 A g^-1 with a capacity retention of 94.3%. This work proposes a new insight for understanding the electrochemically in situ transformation to obtain highly active cathode materials for the aqueous zinc-ion batteries.

2,3-diaminophenazine as a high-rate rechargeable aqueous zinc-ion batteries cathode

Organic materials are attracting extensive attention as promising cathodes for rechargeable aqueous zinc-ion batteries (ZIBs). However, most of them fail to implement the requirement of batteries with combined high-rate and long-cycle performance. Herein, we report a flexible organic molecule 2,3-diaminophenazine (DAP) which exhibits ultrahigh rate performance up to 500C and high capacity retention of 80% after 10,000 cycles at 100C (25.5 A g^-1). Moreover, the Zn²⁺ storage mechanism in the DAP electrode is revealed by ex-situ characterization technologies and theoretical calculation, and the redox active centers CN participate in the reversible electrochemical reaction process. Furthermore, electrochemical analyses show that surface-controlled electrochemical behavior contributes to the high-rate performance of DAP cathodes. Besides, its excellent long-cycle performance can be ascribed to the suppressed DAP dissolubility by using a modified glass fiber separator with carbon nanotubes (CNT) film. Our work provides useful insight into the design of high-rate and long-life ZIBs.

Conductive copper glue constructs a reversible and stable zinc metal anode interface for advanced aqueous zinc ion battery

Aqueous zinc (Zn) ion battery (AZIB) has become one of the research hotspot in the field of energy storage due to its low cost, green environmental protection, high theoretical capacity, and high safety. However, the unrestrained growth of the dendrites leads to the occurrence of side reactions, such as corrosion of the electrodes and generation of hydrogen, which reduces the coulombic efficiency and performance of the battery. Herein, a simple method reports pasting a conductive copper glue (CCG) coating on the surface of Zn anode to improve the serious dendrite growth. The coating has strong intermolecular interaction and high conductivity, which not only avoids the occurrence of side reactions but also facilitates the uniform deposition of Zn²⁺ ions, preventing dendrite formation. The symmetrical battery assembled with Zn anode modified by CCG coating delivers longer cycle life (167 h) and lower voltage hysteresis (≈26 mV), which is much better than that of bare Zn symmetrical battery (30 h, ≈67 mV). Furthermore, the full battery assembly with modified Zn anode and stainless steel (SS) supported V₂O₅ nanospheres (VO-SS) cathode exhibit high capacity and long cycle life (113.5 mAh g^-1 after 4000 cycles at 4.8 A g^-1).

Stabilizing the Nanosurface of LiNiO2 Electrodes by Varying the Electrolyte Concentration: Correlation with Initial Electrochemical Behaviors for Use in Aqueous Li-Ion Batteries

This study attempted to stabilize the nanosurface of LiNiO₂ (LNO) electrodes by varying the electrolyte concentration, significantly influencing its initial electrochemical behaviors for use in aqueous lithium-ion batteries. The charge/discharge capacities, reversibility, and cyclability of LNO were improved during initial cycles with an increase in the concentration of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). As determined by the galvanostatic intermittent titration technique, the superior diffusivity of Li⁺ ions in the LNO electrode is also obtained in the concentrated electrolyte. Nanoscale observation of the LNO surface revealed that its morphology is maintained relatively well in the concentrated electrolyte while it is destroyed in dilute electrolytes after the initial electrochemical cycles. These results are considered to be attributable to the variation of the interface condition in the electrical double layer with an increase in the electrolyte concentration, thus stabilizing the nanosurface of LNO by suppressing the dissolution of Ni ions from the surface. Additionally, in situ X-ray diffraction analysis demonstrated that LNO shows more stable phase transitions and volume changes as the electrolyte concentration increases, indicating that its structural changes in bulk can be directly related to the state of the nanosurface, which has a positive impact on the initial electrochemical behaviors in this system.

Boosting the Electrochemical Performance of V2 O3 by Anchoring on Carbon Nanotube Microspheres with Macrovoids for Ultrafast and Long-Life Aqueous Zinc-Ion Batteries

Zinc-ion batteries (ZIBs) are next-generation energy storage systems with high safety and environmental friendliness because they can be operated in aqueous systems. However, the search for electrode materials with ideal nanostructures and compositions for aqueous ZIBs is in progress. Herein, the synthesis of porous microspheres, consisting of V₂ O₃ anchored on entangled carbon nanotubes (p-V₂ O₃ -CNT) and their application as cathode for ZIBs is reported. From various analyses, it is revealed that V₂ O₃ phase disappears after the initial charge process, and Zn_{3+ x} (OH)_{2+3 x} V_{2- x} O_{7-3 x} ∙2H₂ O and zinc vanadate (Zn_y VO_z ) phases undergo zinc-ion intercalation/deintercalation processes from the second cycle. Additionally, the electrochemical performances of p-V₂ O₃ -CNT, V₂ O₃ -CNT (without macrovoids), and porous V₂ O₃ (without CNTs) microspheres are compared to determine the effects of nanostructures and conductive carbonaceous matrix on the zinc-ion storage performance. p-V₂ O₃ -CNT exhibits a high reversible capacity of 237 mA h g^-1 after 5000 cycles at 10 A g^-1 . Furthermore, a reversible capacity of 211 mA h g^-1 is obtained at an extremely high current density of 50 A g^-1 . The macrovoids in V₂ O₃ nanostructure effectively alleviate the volume changes during cycling, and the entangled CNTs with high electrical conductivity assist in achieving fast electrochemical kinetics.

Microwave-Assisted Rapid Synthesis of NH4V4O10 Layered Oxide: A High Energy Cathode for Aqueous Rechargeable Zinc Ion Batteries

Aqueous rechargeable zinc ion batteries (ARZIBs) have gained wide interest in recent years as prospective high power and high energy devices to meet the ever-rising commercial needs for large-scale eco-friendly energy storage applications. The advancement in the development of electrodes, especially cathodes for ARZIB, is faced with hurdles related to the shortage of host materials that support divalent zinc storage. Even the existing materials, mostly based on transition metal compounds, have limitations of poor electrochemical stability, low specific capacity, and hence apparently low specific energies. Herein, NH₄V₄O₁₀ (NHVO), a layered oxide electrode material with a uniquely mixed morphology of plate and belt-like particles is synthesized by a microwave method utilizing a short reaction time (~0.5 h) for use as a high energy cathode for ARZIB applications. The remarkable electrochemical reversibility of Zn²⁺/H⁺ intercalation in this layered electrode contributes to impressive specific capacity (417 mAh g⁻¹ at 0.25 A g⁻¹) and high rate performance (170 mAh g⁻¹ at 6.4 A g⁻¹) with almost 100% Coulombic efficiencies. Further, a very high specific energy of 306 Wh Kg⁻¹ at a specific power of 72 W Kg⁻¹ was achieved by the ARZIB using the present NHVO cathode. The present study thus facilitates the opportunity for developing high energy ARZIB electrodes even under short reaction time to explore potential materials for safe and sustainable green energy storage devices.

Polyaniline-expanded the interlayer spacing of hydrated vanadium pentoxide by the interface-intercalation for aqueous rechargeable Zn-ion batteries

The metal ions or conductive macromolecules intercalated hydrated vanadium oxides for aqueous Zn-ion batteries (AZIBs) have received increasing attention in recent years. The strategy for the preparation of the intercalated hydrated vanadium oxides has been achieved great advances but is still a huge challenge. In this contribution, we develop an interface-intercalation method to synthesize the polyaniline-intercalated hydrated vanadium pentoxide (V₂O₅·nH₂O), denoted as PANI-VOH, as the cathode materials for AZIBs. The prepared PANI-VOH exhibits a 3D sponge-like morphology and the surface area of 190 m²·g^-1. The interlayer spacing of VOH is expanded to be 14.1 Å, which provides a lot of channels for the rapidly reversible (de)intercalation of Zn²⁺ ions. The coin-typed Zn//PANI-VOH battery shows the specific discharge capacity of 363 mAh·g^-1 at 0.1 A·g^-1 and stable cycling performance. Furthermore, the specific capacity remains 131 mAh·g^-1 after 2000 cycles at 5 A·g^-1, and the energy density is calculated to be 275 Wh·kg^-1 at 78 W·kg^-1 on the mass of PANI-VOH. The achieved values are comparable to or even much higher than that of the most state-of-the-art V-based cathode materials for AZIBs. The PANI intercalation can shorten the pathways and facilitate the transports for the migration of ions and electrons. Our finding guides a novel strategy for the intercalation of PANI into the layered materials to adjust their interlayer spacing, which exhibits super ions migration efficiency, as the cathode materials for AZIBs and even other multivalent ions batteries.

Electrochemically Induced Phase Transition in V3 O7 · H2 O Nanobelts/Reduced Graphene Oxide Composites for Aqueous Zinc-Ion Batteries

V₃ O₇ ·H₂ O nanobelts/reduced graphene oxide (rGO) composites (weight ratio: 86%/14%) are synthesized by a microwave approach with a high yield (85%) through controlling pH with acids. The growth mechanisms of the highly crystalline nanobelts (average diameter: 25 nm; length: ≈20 µm; oriented along the [101] direction) have been thoroughly investigated, with the governing role of the acid upon the morphology and oxidation state of vanadium disclosed. When used as the ZIB cathode, the composite can deliver a high specific capacity of 410.7 and 385.7 mAh g^-1 at the current density of 0.5 and 4 A g^-1 , respectively, with a high retention of the capacity of 93%. The capacity of the composite is greater than those of V₃ O₇  · H₂ O, V₂ O₅ nanobelts, and V₅ O₁₂  · 6H₂ O film. Zinc ion storage in V₃ O₇ ·H₂ O/rGO is mainly a pseudocapacitive behavior rather than ion diffusion. The presence of rGO enables outstanding cycling stability of up to 1000 cycles with a capacity retention of 99.6%. Extended cycling shows a gradual phase transition, that is, from the original orthorhombic V₃ O₇  · H₂ O to a stable hexagonal Zn₃ (VO₄ )₂ (H₂ O)_2.93 phase, which is a new electrochemical route found in V₃ O₇ materials. This phase transition process provides new insight into the reactions of aqueous ZIBs.

Selenium Defect Boosted Electrochemical Performance of Binder-Free VSe2 Nanosheets for Aqueous Zinc-Ion Batteries

As a typical transition-metal dichalcogenides, vanadium diselenide (VSe₂) is a promising electrode material for aqueous zinc-ion batteries due to its metallic characteristics and excellent electronic conductivity. In this work, we propose a strategy of hydrothermal reduction synthesis of stainless-steel (SS)-supported VSe₂ nanosheets with defect (VSe_2-x-SS), thereby further improving the conductivity and activity of VSe_2-x-SS. Density functional theory calculations confirmed that Se defect can adjust the adsorption energy of Zn²⁺ ions. This means that the adsorption/desorption process of Zn²⁺ ions on VSe_2-x-SS is more reversible than that on pure SS-supported VSe₂ (VSe₂-SS). As a result, the Zn//VSe_2-x-SS battery showed more excellent electrochemical performance than Zn//VSe₂-SS. The VSe_2-x-SS electrode shows a good specific capacity of 265.2 mA h g^-1 (0.2 A g^-1 after 150 cycles), satisfactory rate performance, and impressive cyclic stability. In addition, we also have explored the energy-storage mechanism of Zn²⁺ ions in this VSe_2-x-SS electrode material. This study provides an effective strategy for the rational design of electrode materials for electrochemical energy-storage devices.

Novel aluminum vanadate as a cathode material for high-performance aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) have garnered widespread attention as a new large-scale energy storage candidate owing to their low cost and high theoretical capacity. Because of the unique divalent state of Zn²⁺and the existence of a strong electrostatic repulsion phenomenon, researchers are currently focusing on how to prepare high-performance cathode materials. In this study, we synthesized aluminum vanadate (AlV₃O₉) as a cathode material for AZIBs using a solvothermal method. Al³⁺acted as a pillar in the resultant structure and stabilized it. Furthermore, this large interlayer spacing enhanced the ion diffusion coefficient and accelerated the ion transport process. Because of these advantages, the AlV₃O₉(AVO) cathode exhibited excellent electrochemical performance, including a high capacity of 421.0 mA h g^-1at 0.1 A g^-1and a stable rate capability of 348.2 mA h g^-1at 1 A g^-1. Moreover, it exhibited a specific capacity of 202 mA h g^-1even at a high current density of 3 A g^-1(the capacity retention rate reached 84.38% after 1600 cycles). The prepared ZIBs presented a high power density of 366.6 W kg^-1at an energy density of 286 W h kg^-1. These extraordinary results indicate the great application potential of AVO as a cathode material for AZIBs.

An enhancement on supercapacitor properties of porous CoO nanowire arrays by microwave-assisted regulation of the precursor

A microwave-assisted hydrothermal approach with a follow up thermal treatment was employed to prepare 1D porous CoO nanowires, which is constructed by numerous high crystallinity nanoparticles. A significant change in crystal structure of the precursor were observed, as position shift and absence of some diffraction peaks, which was induced by the microwave-assistance during hydrothermal process. Moreover, the precursor's purity was also effectively improved. As a result, the as-synthesized CoO annealed from the microwave-assisted precursor exhibited a morphology and phase structure significantly different from that of without microwave involvement. Benefiting from the 'microwave effect', the microwave-assisted as-fabricated porous CoO nanowires showed an enhanced specific capacitance (728.8 versus 503.7 F g^-1 at 1 A g^-1 ), strengthened rate performance (70.0% versus 53.2% maintenance at 15 A g^-1), reduced charge transfer resistance (1.06 Ω versus 2.39 Ω), enlarged window voltage (0.85 versus 0.7 V) and enhanced cycle performance (82.3% versus 76.5% retention after 5000 cycles at 15 A g^-1), compared with that of sample without microwave assistance. In addition, the corresponding electrochemical properties are also higher than those reported CoO sample prepared by solvothermal method. In conclusion, this work provides a practical way for enhancing electrochemical properties of supercapacitor materials through adjusting the precursor by microwave assistance into hydrothermal process.

Aqueous Rechargeable Zn-ion Batteries: Strategies for Improving the Energy Storage Performance

The growing demand for the renewable energy storage technologies stimulated the quest for efficient energy storage devices. In recent years, the rechargeable aqueous zinc-based battery technologies are emerging as a compelling alternative to the lithium-based batteries owing to safety, eco-friendliness, and cost-effectiveness. Among the zinc-based energy devices, rechargeable zinc-ion batteries (ZIBs) are drawing considerable attention. However, they are plagued with several issues, including cathode dissolution, dendrite formation, etc.. Despite several efforts in the recent past, ZIBs are still in their infant stages and have yet to reach the stage of large-scale production. Finding stable Zn²⁺ intercalation cathode material with high operating voltage and long cycling stability as well as dendrite-free Zn anode is the main challenge in the development of efficient zinc-ion storage devices. This Review discusses the various strategies, in terms of the engineering of cathode, anode and electrolyte, adopted for improving the charge storage performance of ZIBs and highlights the recent ZIB technological innovations. A brief account on the history of zinc-based devices and various cathode materials tested for ZIB fabrication in the last five years are also included. The main focus of this Review is to provide a detailed account on the rational engineering of the electrodes, electrolytes, and separators for improving the charge storage performance with a future perspective to achieving high energy density and long cycling stability and large-scale production for practical application.

A High-Rate and Ultrastable Aqueous Zinc-Ion Battery with a Novel MgV2 O6 ·1.7H2 O Nanobelt Cathode

High-safety and low-cost aqueous Zn-ion batteries have triggered an astounding investigation surge in the last 5 years and are becoming competitive alternatives for grid-scale energy storage. However, the implementation of this promising technology is still plagued by the lack of effective and affordable cathode materials that can enable high energy densities and an exceptional cycling stability. Herein, a novel vanadium-based oxide cathode based on MgV₂ O₆ ·1.7H₂ O nanobelts, which delivers a high capacity (425.7 mAh g^-1 at 0.2 A g^-1 ), a robust rate capability (182.1 mAh g^-1 at 10 A g^-1 ), and an ultrastable cycle without any visible deterioration, as well as an adequate energy density (331.6 Wh kg^-1 ), is developed. Such excellent electrochemical Zn-ion storage performance is believed to result from the fast ion-diffusion kinetics boosted by a stable layered structure and an ultrahigh intercalation pseudocapacitance reaction, which are also benefited by a typical H⁺ /Zn²⁺ co-insertion mechanism, accompanied by an atypical Zn²⁺ intercalation chemistry with a partial but irreversible Mg²⁺ -Zn²⁺ ion-exchange reaction during the initial discharge. These results provide key and enlightening insights into the design of high-performance vanadium oxide cathode materials.

Facile and Scalable Synthesis of 3D Structures of V10O24·12H2O Nanosheets Coated with Carbon toward Ultrafast and Ultrastable Zinc Storage

Three-dimensional (3D) structures of V₁₀O₂₄·12H₂O nanosheets coated with carbon (denoted as V₁₀O₂₄@C) are facially and cost-effectively fabricated by reducing the V₂O₅-based aqueous solution with ethanol under hydrothermal conditions. By using the 3D V₁₀O₂₄@C as the cathode of zinc-ion batteries, the as-obtained 3D V₁₀O₂₄@C sample delivers excellent charge-discharge cycling capability, superior rate performance, and reasonable specific capacity, and a specific capacity of ca. 133.3 mA h g^-1 and a 94.1% capacity retention are achieved even after 10000 cycles at a high current density of 10 A g^-1 (∼80 C). Furthermore, it provides a facile and scalable approach to synthesize the 3D structures of pure-phased vanadium oxide nanosheets or other nanoscale metal oxides coated with carbon.

High-performance reversible aqueous zinc-ion battery based on iron-doped alpha-manganese dioxide coated by polypyrrole

The development of zinc-ion storage cathode materials for aqueous zinc-ion batteries (AZIBs) is a necessary step for the construction of large-scale electrochemical energy conversion and storage devices. Iron-doped alpha-manganese dioxide (α-MnO₂) nanocomposites were achieved in this study via pre-intercalation of Fe³⁺ during the formation of α-MnO₂ crystals. A polypyrrole (PPy) granular layer was fabricated on the surface of α-MnO₂ using acid-catalyzed polymerization of pyrroles. The pre-intercalation of Fe³⁺ effectively enlarges the lattice spacing of α-MnO₂ and consequently decreases the hindrance for Zn²⁺ insertion/extraction in the iron-doped α-MnO₂ coated by PPy (Fe/α-MnO₂@PPy) composite. Meanwhile, the PPy buffer layer can ameliorate electron and ion conductivity and prevent dissolution of α-MnO₂during the charge/discharge process. This unique structure makes the Fe/α-MnO₂@PPy composite an efficient zinc-ion storage cathode for AZIBs. The targeted Fe/α-MnO₂@PPy cathode achieves superior performance with reversible specific capacity (270 mA h g^-1 at 100 mA g^-1) and exhibits highdiffusioncoefficientof 10^-10-10^-14 cm^-2 s^-1. Therefore, a feasible approach is implemented on advanced electrode materials using in AZIBs for practical applications.

Water-Salt Oligomers Enable Supersoluble Electrolytes for High-Performance Aqueous Batteries

Aqueous rechargeable batteries are highly safe, low-cost, and environmentally friendly, but restricted by low energy density. One of the most efficient solutions is to improve the concentration of the aqueous electrolytes. However, each salt is limited by its physical solubility, generally below 21-32 mol kg^-1 (m). Here, a ZnCl₂ /ZnBr₂ /Zn(OAc)₂ aqueous electrolyte with a record super-solubility up to 75 m is reported, which breaks through the physical solubility limit. This is attributed to the formation of acetate-capped water-salt oligomers bridged by Br^- /Cl^- -H and Br^- /Cl^- /O-Zn²⁺ interactions. Mass spectrometry indicates that acetate anions containing nonpolarized protons prohibit the overgrowth and precipitation of ionic oligomers. The polymer-like glass transition temperature of such inorganic electrolytes is found at ≈-70 to -60 °C, without the observation of peaks for salt-crystallization and water-freezing from 40 to -80 °C. This supersoluble electrolyte enables high-performance aqueous dual-ion batteries that exhibit a reversible capacity of 605.7 mAh g^-1 , corresponding to an energy density of 908.5 Wh kg^-1 , with a coulombic efficiency of 98.07%. In situ X-ray diffraction and Raman technologies reveal that such high ionic concentrations of the supersoluble electrolyte enable a stage-1 intercalation of bromine into macroscopically assembled graphene cathode.

On-site building of a Zn2+-conductive interfacial layer via short-circuit energization for stable Zn anode

Aqueous zinc ion batteries (ZIBs) show great potential in large-scale energy storage systems for their advantages of high safety, low cost, high capacity, and environmental friendliness. However, the poor performance of Zn metal anode seriously hinders the application of ZIBs. Herein, we use the zinc-ion intercalatable V₂O₅·nH₂O (VO) as the interface modification material, for the first time, to on-site build a Zn²⁺-conductive Zn_xV₂O₅·nH₂O (ZnVO) interfacial layer via the spontaneous short-circuit reaction between the pre-fabricated VO film and Zn metal foil. Compared with the bare Zn, the ZnVO-coated Zn anode exhibits better electrochemical performances with dendrite-free Zn deposits, lower polarization, higher coulombic efficiency over 99% after long cycles and 10 times higher cycle life, which is confirmed by constructing Zn symmetrical cell and Zn|ZnSO₄ + Li₂SO₄|LiFePO₄ full cell.