Cathode For Aqueous Zinc-ion Batteries Research Articles

Flash Joule Heating Synthesis of Layer-Stacked Vanadium Oxide/Graphene Hybrids within Seconds for High-Performance Aqueous Zinc-Ion Batteries.

Vanadium oxides have been regarded as highly promising cathodes for aqueous zinc-ion batteries (ZIBs). However, obtaining high-performance vanadium oxide-based cathodes suitable for industrial application remains a significant challenge due to the need for cost-effective, straightforward, and efficient preparation methods. Herein, we present a facile and rapid synthesis of a composite cathode, consisting of layer-stacked VO2/V2O5 and graphene-like carbon nanosheets, in just 2.5 s by treating the commercial V2O5 powder via a flash Joule heating strategy. When employed as the cathode for ZIBs, the resulting composite delivers a comparable rate capacity of 459 mA h g-1 at 0.2 A g-1 and remarkable cycle stabilities of 355.5 mA h g-1 after 2500 cycles at 1.0 A g-1 and 169.5 mA h g-1 after 10,000 cycles at 10 A g-1, respectively. Further electrochemical analysis reveals that the impressive performance is attributed to the accelerated charge transfer and the alleviated structure degradation, facilitated by the abundant sites and a built-in electric field of the layer-stacked VO2/V2O5 heterostructure, as well as the excellent conductivity of graphene-like carbon nanosheets. This work introduces a unique approach for ultrafast and low-cost fabrication of high-performance vanadium oxide-based composite cathodes toward efficient ZIBs.

Poly(3,4-ethylenedioxythiophene)-Coated Vanadium-Doped MnO2 Nanorods for High-Performance Flexible Aqueous Zinc-Ion Battery Cathode.

Manganese-based aqueous zinc-ion batteries (AZIBs) are considered promising cathode materials for large-scale energy storage applications due to their low cost and high safety. However, the primary constraints on achieving high specific capacity and cycling stability are the inherent low conductivity and suboptimal structural stability of the AZIB cathodes. Herein, we report a high-performance poly(3,4-ethylenedioxythiophene) (PEDOT)-coated vanadium-doped MnO2 nanorod (NR) electrode for AZIBs. First, vanadium-doped MnO2 (V-MnO2) NRs were synthesized by a simple hydrothermal synthesis method. The V-MnO2 NRs were further encapsulated with a nanolayer of PEDOT through an in situ polymerization process, which was subsequently treated with sulfuric acid to achieve a smooth surface. The V doping creates oxygen vacancies within the MnO2, allowing for the rapid embedding and diffusion of Zn2+. The PEDOT nanolayer greatly enhances the conductivity and structural stability of the V-MnO2. Benefiting from the unique features, an optimal composite NRs electrode exhibits a high specific capacity of 250 mAh g-1 at 0.4 A g-1, a high energy density (388 Wh kg-1 at 151 W kg-1), and excellent stability over 5000 cycles at 3 A g-1. In addition, the flexible pouch cell assembled with the electrode shows good stability under bending. Given the positive outcomes, the material holds great potential for use as a cathode in next-generation flexible energy storage systems.

Vanadium-Based Cathodes for Aqueous Zinc-Ion Batteries: Mechanisms, Challenges, and Strategies.

ConspectusZinc-ion batteries (ZIBs) are highly promising for large-scale energy storage because of their safety, high energy/power density, low cost, and eco-friendliness. Vanadium-based compounds are attractive cathodes because of their versatile structures and multielectron redox processes (+5 to +3), leading to high capacity. Layered structures or 3-dimensional open tunnel frameworks allow easy movement of zinc-ions without breaking the structure apart, offering superior rate-performance. However, challenges such as dissolution and phase transformation hinder the long-term stability of vanadium-based cathodes in ZIBs. Although significant research has been dedicated to understanding the mechanisms and developing high-performance vanadium-based cathodes, uncertainties still exist regarding the critical mechanisms of energy storage and dissolution, the actual active phase and the specific optimization strategy. For example, it is unclear whether materials such as α-V2O5, VO2, and V2O3 serve as the active phase or undergo phase transformations during cycling. Additionally, the root cause of V-dissolution and the role of byproducts such as Zn3(OH)2V2O7·2H2O in ZIBs are debated.In this account, we aim to outline a clear and comprehensive roadmap for V-based cathodes in ZIBs. On the basis of our studies, we analyzed intrinsic crystal structures and their correlation with performance to guide the design of V-based materials with high-capacity and high-stability for ZIBs. Then, we revealed the underlying mechanisms of energy storage and instability, enabling more effective design and optimization of V-based cathodes. After identifying the key challenges, we proposed effective design principles to achieve high cycling performance of V-based cathodes and outlined future development directions toward their practical application. Vanadium-based compounds include [VO4] tetrahedrons, [VO5] square pyramids, and [VO6] octahedra, which are connected through a cocorner, coedge and coplane. The [VO4] tetrahedron is inactive, and the [VO5] square pyramid is unstable in aqueous solutions because water attacks the exposed vanadium, whereas stable [VO6] octahedra are desirable because of their ability to reduce from +5 to +3 with minimal structural distortion. Therefore, high-performance vanadium-based oxides in ZIBs should maintain intact [VO6] octahedra while avoiding [VO4] tetrahedra or [VO5] square pyramids. The energy storage mechanism involves H2O/H+/Zn2+ coinsertion. The existence of interlayer water in V-based cathodes significantly improves the rate and cycling performance by expanding galleries, screening Zn2+ electrostatically via solvation, reducing ion diffusion energy barriers, and increasing layer flexibility. The insertion of H+/Zn2+ and the instability of V-based cathodes lead to the formation of byproducts such as basic zinc salts (i.e., Zn4SO4(OH)6·nH2O) and dead vanadium (Zn3(OH)2V2O7·2H2O), whose reversibility strongly affects long-term stability. To increase the cycling stability of vanadium-based cathodes, strategies such as electrolyte modulation and coating have been proposed to decrease water attack on the surface of V-oxides, thereby affecting the formation of byproducts. Additionally, in situ electrochemical transformation, ion preintercalation, and ion exchange were explored to prepare intrinsically stable V-based cathodes with enhanced performance. Furthermore, future research should focus on revealing atomic-scale mechanisms through advanced in situ characterization and theoretical calculations, enhancing rate-performance by facilitating ion/electron diffusion, promoting cycling stability by developing highly stable cathodes and refining interface engineering, and scaling up vanadium-based cathodes for practical ZIB applications.

Design and construction of V6O13/C nanorods as high-performance cathode material for aqueous zinc-ion batteries

As a candidate for commercial cathode material of aqueous zinc ion batteries (AZIBs), vanadium-based materials have attracted wide attention due to their unique layered structure and high specific capacity. However, the insertion/extraction process of Zn2+ can easily lead to the volume expansion of vanadium-based materials, resulting in battery failure. In addition, the inherent low conductivity and low diffusion kinetics of vanadium-based materials limiting their further development into high-performance cathode materials. Herein, a novel V6O13/N, O co-doped carbon (V6O13/C) nanorod electrode material has been successfully fabricated as a cathode for AZIBs. The N, O co-doped carbon can significantly improve the conductivity of materials and alleviate the volume change. The nanorod-like structure could enhance the structural stability during the Zn2+ insertion/extraction processes. Moreover, with N, O doped, the electrode can expose more reactive sites which is beneficial for promoting electrochemical processes. With the synergistic effort of the above optimization strategy, the as-obtained electrode delivers excellent long-term cycle stability of 151.7 mAh g−1 at 1 A g−1 after 1000 cycles.

Unraveling the Anionic Redox Chemistry in Aqueous Zinc‐MnO2 Batteries

Activating anionic redox reaction (ARR) has attracted a great interest in Li/Na‐ion batteries owing to the fascinating extra‐capacity at high operating voltages. However, ARR has rarely been reported in aqueous zinc‐ion batteries (AZIBs) and its possibility in the popular MnO2‐based cathodes has not been explored. Herein, the novel manganese deficient MnO2 micro‐nano spheres with interlayer “Ca2+‐pillars” (CaMnO‐140) are prepared via a low‐temperature (140 °C) hydrothermal method, where the Mn vacancies can trigger ARR by creating non‐bonding O 2p states, the pre‐intercalated Ca2+ can reinforce the layered structure and suppress the lattice oxygen release by forming Ca−O configurations. The tailored CaMnO‐140 cathode demonstrates an unprecedentedly high rate capability (485.4 mAh g−1 at 0.1 A g−1 with 154.5 mAh g−1 at 10 A g−1) and a marvelous long‐term cycling durability (90.6% capacity retention over 5000 cycles) in AZIBs. The reversible oxygen redox chemistry accompanied by CF3SO3− (from the electrolyte) uptake/release, and the manganese redox accompanied by H+/Zn2+ co‐insertion/extraction, are elucidated by advanced synchrotron characterizations and theoretical computations. Finally, pouch‐type CaMnO‐140//Zn batteries manifest bright application prospects with high energy, long life, wide‐temperature adaptability, and high operating safety. This study provides new perspectives for developing high‐energy cathodes for AZIBs by initiating anionic redox chemistry.

Synergistic engineering of heterojunction and surface coating to boost Zn storage performance of V2O3-based microspheres as an advanced cathode for aqueous zinc-ion batteries

Vanadium-based compounds are highly regarded as potential cathodes for aqueous zinc-ion batteries (AZIBs) owing to the high theoretical capacity, diverse structural frameworks and abundant oxidation states. Nevertheless, the challenges such as slow diffusion kinetics, low electrical conductivity and inadequate structural stability restrict their further development. Herein, yolk shell-like SiO2-coated V2O3/VN heterojunction microspheres (VON@SiO2) are synthesized through a hydrothermal method followed by annealing and subsequent SiO2 coating. As an advanced cathode for AZIBs, the construction of V2O3/VN heterojunction effectively exposes reactive sites, leads to the reduction in interfacial charge transfer resistance, and thus improves the ion diffusion kinetics, while the surface coating of SiO2 is beneficial for enhancing the structural stability of the material and further reduces the capacity fading. Additionally, the micromorphology of porous yolk shell-like microspheres self-assembled by nanoparticles contributes to the complete penetration of electrolyte and greatly exposing reactive sites. Based on synergistic engineering of heterojunction, surface coating and porous shell-like micromorphology, the synthesized VON@SiO2 delivers excellent specific capacities of 483.5 mAh g−1 at 0.5 A g−1 and 294 mAh g−1 at 10 A g−1, and exhibits impressive cycling performance with 94 % of capacity retention after 1000 cycles at 10 A g−1. Further, in-situ XRD and ex-situ XPS reveals the mechanism of zinc ion storage. This work offers a valuable reference into the development of high-performance cathode materials for AZIBs by co-engineering of heterojunction, surface coating and micromorphology optimization.

K-ion modified V2O5 with abundant oxygen defects as cathode for aqueous zinc-ion battery

Aqueous zinc-ion batteries (ZIBs) are anticipated to be used for grid-scale energy storage because of their low cost, abundant resources, high safety, and non-toxicity. In this study, K-ion modified V2O5 with abundant oxygen defects (K0.1V2O5) was prepared using a one-step hydrothermal reaction followed by heat treatment. K0.1V2O5 showed remarkable specific capacity (307.9 mAhg−1 at 0.2 Ag−1), exceptional rate capability (184.3 mAhg−1 at 10 Ag−1), and good cycling stability (88.5 % capacity retention rate after 2000 cycles at 10 Ag−1). Furthermore, electrochemical kinetics revealed that the electrochemical process of the K0.1V2O5 electrode is governed by both ion diffusion and capacitive contribution, with the diffusion coefficient of Zn2+ ranging between 10−11 and 10−9 cm2 s−1. The exceptional performance of K0.1V2O5 makes it a promising candidate for cathode materials in zinc-ion batteries (ZIBs).

Polyaniline-modified amorphous tin-based Prussian blue analogue as cathodes for long-life aqueous zinc ion batteries

Prussian blue analogs (PBAs) have emerged in the field of aqueous zinc ion batteries (AZIBs) owing to their simple synthesis method and three-dimensional open framework structure. Although PBAs have high redox potentials, the unsatisfactory specific capacity and poor electrical conductivity limit their development to some extent. In this work, amorphous tin hexacyanoferrate (SnHCF) and polyaniline (PANI) were combined to form SnHCF/PANI composite. The synergistic effect of the amorphous structure of SnHCF and PANI with good conductivity makes the SnHCF/PANI electrode exhibit excellent redox activity and achieve rapid ion/electron transfer. When used as a cathode in AZIBs, the SnHCF/PANI provides a high specific capacity (136.8 mAh g−1 at 0.5 A g−1) and excellent cycling stability (a discharge specific capacity of 54.3 mAh g−1 after 2500 cycles at 2 A g−1). This work offers a new idea for the development of PBAs-based composites as cathode materials for AZIBs.

Oxygen-deficient ZnVOH@CC as high-capacity and stable cathode for aqueous zinc-ion batteries

Vanadium oxides have become promising cathodes for aqueous zinc ion batteries (AZIBs) due to their low cost and high theoretical capacity. However, vanadium oxides suffer from the problems of low electrical conductivity and structural instability. To address the challenges, ZnxV2O5·nH2O with oxygen-rich vacancies was synthesized in situ on carbon cloth (ZnVOH@CC) via a one-step hydrothermal method. The introduction of Zn2+ and oxygen vacancies is beneficial to enhance the structural stability and improve the Zn2+ diffusion rate. The pre-intercalated Zn2+/H2O acts as “pillars” to increase the interlayer spacing of vanadium pentoxide (V2O5), weakening the electrostatic interactions between Zn2+ and the ZnVOH host lattice. Benefiting from the above advantages, the ZnVOH@CC composite was used as the cathode for AZIBs, which showed a high capacity of 464.9 mAh/g at 0.1 A/g, a large capacity of 208.1 mAh/g at 1.0 A/g after 1,000 cycles, and a good cycling stability at a high current density of 5.0 A/g after 10,000 cycles. In addition, the assembled ZnVOH@CC//Cu2Se full cell by matching ZnVOH@CC with Cu2Se also exhibits a high reversible capacity of 68 mAh/g at 1.0 A/g and 92.5 % capacity retention after 260 cycles.

Pre-removing partial ammonium ion induces vanadium vacancy assist NH4V4O10 as a high-performance aqueous zinc ion battery cathode

Ammonium vanadate (NH4V4O10) is regarded as a promising cathode material for aqueous zinc-ion batteries, given its considerable theoretical capacity and tunable interlayer spacing. However, due to its inherent low electrical conductivity and the excessive presence of ammonium ions between layers, NH4V4O10 exhibits unsatisfactory electrochemical performance. In this study, it is proposed that the electrochemical performance of NH4V4O10 can be significantly enhanced by removing part of the ammonium cation and increasing the vanadium vacancy. The decrease of ammonium further increases the layer spacing, reduces the irreversible deamination and accelerates the diffusion of Zn2+. Density functional theory (DFT) calculations reveal that increasing vanadium vacancies significantly diminishes the strong electrostatic interactions between the V-O layers and Zn2+, enhances the material’s electrical conductivity, and stabilizes the crystal structure during zinc ion (de)intercalation, thus obtaining excellent electrochemical properties. As a result, the Vd-NVO cathode demonstrates a high reversible capacity of 371 mAh g−1, excellent rate performance, and remarkable cyclic stability, maintaining a reversible capacity of 131 mAh g−1 even after 1000 cycles at 5 A g−1.

Modulating the Structure of Interlayer/Layer Matrix on δ‐MnO2 via Cerium Doping‐Engineering toward High‐Performance Aqueous Zinc Ion Batteries

Abstractδ‐MnO2 has been vigorously developed as an ideal cathode material for rechargeable aqueous zinc‐ion batteries (AZIBs) due to its spacious layer spacing suitable for ion storage. However, poor intrinsic conductivity, structural collapse, and sluggish reaction kinetics are major limitations restricting their battery performance. Doping engineering has been proven to be an effective strategy for modifying the structure, conductivity, and electronic properties of Mn‐based oxides. Here, a series of δ‐MnO2 hierarchical flowers with different cerium‐doped sites are proposed as high‐performance cathodes for AZIBs, revealing the effects of various Ce doping sites on the MnO2 layer‐by‐layer structure and battery performance. Chemical analysis and theoretical calculations indicate that δ‐MnO2 with both in‐layer and interlayer Ce doping (Cein/inter‐MnO2) allows for sufficient Zn2+ storage sites, higher conductivity, and enhanced reaction kinetics due to enlarged interlayer spacing, increased oxygen defects, and reduced Coulombic repulsion between zinc ions and manganese oxide hosts. As a result, Cein/inter‐MnO2 with extended ion transfer channels and sturdy structure delivers a superior capacity of 348.8 mAh g−1 at a current density of 300 mA g−1 over 100 cycles, and a high retention rate of ≈100% at a current density of 3000 mA g−1 over 2000 cycles.

Tailored crystal planes of VO2 cathode power fast Zn2+ storage

Vanadium dioxide (VO2) cathode with specific tunnel structure and favorable specific capacity is critical for developing aqueous zinc-ion batteries (AZIBs) with excellent electrochemical performance. However, sluggish electrochemical kinetics hampered its development in burgeoning energy storage devices. Herein, we tailored VO2 material with different exposed crystal planes and employed as cathodes for AZIBs. The comprehensive analyses indicate the exposed (201) and (001) crystal planes are favorable for fast electrochemical kinetics, high capacitance storage, and the smallest diffusion energy barrier, which guarantee electrodes with high discharge capacity (367 mA h/g at 0.1 A/g), excellent rate capability (281 mA h/g at 4 A/g) and cycling stability over 800 cycles. Besides, Ex-situ characterizations manifest VO2 cathode with specific exposed crystal planes easily transformed to Zn3+x(OH)2V2O7·2H2O in the first discharge process, hence allowing continuous embedding of Zn2+ in this layered structure, and the ex-situ scanning electron microscopy (SEM) analysis confirms the morphology change matched well with the structural transformation. This study may enlighten and promote the role of exposed crystal plane to develop high-performance rechargeable batteries.

Augmenting specific capacitance of ammonium vanadate cathode in aqueous zinc-ion batteries via barium doping directed by glutamic acid

Aqueous Zinc-Ion Batteries (AZIB), as a promising class of multivalent metal-ion batteries, have garnered attention for their exceptional safety and extremely high theoretical capacity. Despite these advantages, their adoption has been impeded by a notable capacity shortfall relative to Lithium-Ion Batteries (LIB). Addressing this challenge, our research leverages glutamic acid as a chelating agent to craft barium-doped ammonium vanadate nanoflowers through a hydrothermal approach, serving as an innovative AZIB cathode material. The incorporation of barium ions has notably expanded the doping distance from 9.817 Å to 12.900 Å, markedly diminishing the diffusion resistance of Zn2+ ions and unveiling a plethora of active sites. These structural enhancements have fostered accelerated ion transport and bolstered redox kinetics. Our fabricated cathode material exhibits exceptional reversibility during the redox transitions between V5+/V4+ and V3+ and the zinc ion doping process. Utilizing BNVO-3 as the cathode, which presents an ideal crystal configuration, the AZIB achieved near-perfect Coulombic efficiency. Impressively, at a current density of 0.1 A g-1, it achieved a remarkable peak discharge capacity of 384.91 mAh g-1. Furthermore, after 1500 cycles at 5A g−1, it maintained an impressive 92.9 % capacity retention. This study heralds a new era for barium-doped vanadium-based AZIB cathodes, characterized by their high stability, reversibility, and capacity.

Long‐Life Pillar[5]quinone Cathode for Aqueous Zinc‐Ion Batteries

AbstractAqueous zinc ion batteries (ZIBs) are currently gaining a significant amount of attention as a low‐cost and high safety energy storage option. While mostly inorganic structures are used as cathode materials in aqueous zinc batteries, these materials undergo structural degradation, therefore, alternative organic cathodes are expected to be developed to replace inorganic materials in aqueous zinc ion batteries (AZIBs). In this work, pillar[5]quinone (P5Q) is used as a cathode in AZIBs for the first time. Besides investigating the charge storage mechanism and interfacial property evolution of P5Q by various ex situ analyses, electrochemical quartz crystal microbalance (EQCM) and density functional theory (DFT) demonstrates both Zn2+ and H+ incorporation. The P5Q exhibits >99 % Coulombic efficiency through 10000 cycles at ultra‐fast (500 °C) current density, yielding a capacity value of approximately 120 mAh g−1 at the end of the cycle. When the current density is changed from 500 °C to 120 °C, an initial discharge capacity of approximately 182 mAh g−1 is achieved, demonstrating outstanding performance with over 80 % capacity retention for the subsequent 7000 cycles.

V2O3/VO2@NC@GO ultrathin nanosheets as a high-performance cathode for aqueous zinc-ion batteries

Recently, vanadium oxides have attracted much attention as advanced cathodes for aqueous zinc-ion batteries on account of their high theoretical specific capacity, multi-electron transfer and easy synthesis; however, structural instability and poor conductivity of the materials limit their practical application. Herein, N-doped carbon-coated V2O3/VO2 hybrid nanosheets were encapsulated into graphene oxide (V2O3/VO2@NC@GO) as an advanced cathode for aqueous zinc-ion batteries by the combined process of hydrothermal treatment, high-temperature annealing and freeze drying. The multi-valence of vanadium element activates diverse redox reactions and thus results in high specific capacity, while graphene oxide and N-doped carbon layer derived from polyvinyl pyrrolidone establish an efficient conductive network for electronic transfer and provide a rigid skeleton for enhancing the structural stability of the hybrid nanosheets. Benefiting from the above unique advantages of composition and micromorphology, the V2O3/VO2@NC@GO cathode exhibits excellent reaction dynamics and rapid electron transfer, generating high specific capacities of 493.0 mAh g−1 at 0.5 A g−1 and 411.9 mAh g−1 at 5 A g−1 and outstanding long-term cycling performance with a retention of 92.4 % after 1000 cycles at 5 A g−1. This work offers a viable approach for developing high-performance vanadium oxide-based cathodes for aqueous zinc-ion batteries by enriching the valence states of vanadium and encapsulating active materials into highly conductive carbon materials.

Manifesting the Carrier Behavior of a Vanadium Oxide/Carbon Composite Cathode in Aqueous Zinc-Ion Batteries

Manifesting the Carrier Behavior of a Vanadium Oxide/Carbon Composite Cathode in Aqueous Zinc-Ion Batteries

Exploring Zinc-Doped Manganese Hexacyanoferrate as Cathode for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZiBs) have emerged as a promising alternative to lithium-ion batteries as energy storage systems from renewable sources. Manganese hexacyanoferrate (MnHCF) is a Prussian Blue analogue that exhibits the ability to insert divalent ions such as Zn2+. However, in an aqueous environment, MnHCF presents weak structural stability and suffers from manganese dissolution. In this work, zinc doping is explored as a strategy to provide the structure with higher stability. Thus, through a simple and easy-to-implement approach, it has been possible to improve the stability and capacity retention of the cathode, although at the expense of reducing the specific capacity of the system. By correctly balancing the amount of zinc introduced into the MnHCF it is possible to reach a compromise in which the loss of capacity is not critical, while better cycling stability is obtained.

Polypyride intercalation boosting the kinetics and stability of V3O7·H2O cathodes for aqueous zinc-ion batteries

V3O7·H2O (VO) is a high capacity cathode material in the field of aqueous zinc ion batteries (AZIBs), but it is limited by slow ion migration and low electrical conductivity. In this paper, polypyridine (PPyd) intercalated VO with nanoribbon structure was prepared by a simple in-situ pre-intercalation, which is noted VO-PPyd. The total density of states (TDOS) shows that after the pre-intercalation of PPyd, an intermediate energy level appears between the valence band and conduction band, which provides a step that can effectively reduce the band gap and enhance the electron conductivity. Furthermore, the density functional theory (DFT) results found that Zn2+ is more easily de-intercalated from the V-O skeleton, which proves that the embeddedness of PPyd improves the diffusion kinetics of Zn2+. Electrochemical studies have shown that VO-PPyd cathode materials exhibit excellent rate performance (high specific capacity of 465 and 192 mA h g−1 at 0.2 and 10 A g−1, respectively) and long-term cycling performance (92.7% capacity retention rate after 5300 cycles), due to their advantages in structure and composition. More importantly, the energy density of VO-PPyd//Zn at 581 and 5806 W kg−1 is 375 and 247 W h kg−1, respectively. VO-PPyd exhibits excellent electrochemical properties compared to previously reported vanadium based cathodes, which makes it highly competitive in the field of high-performance cathode materials of AZIBs.

Using MXene as a Chemically Induced Initiator to Construct High-Performance Cathodes for Aqueous Zinc-Ion Batteries.

MXene usually exhibits weak pseudo-capacitance behavior in aqueous zinc-ion batteries, which cannot provide sufficient reversible capacity, resulting in the decline of overall capacity when used as the cathode materials. Taking inspiration from polymer electrolyte engineering, we have conceptualized an in situ induced growth strategy based on MXene materials. Herein, 5.25 % MXene was introduced into the nucleation and growth process of vanadium oxide (HVO), providing the heterogeneous nucleation site and serving as an initiator to regulate the morphology and structural of vanadium oxide (T-HVO). The resulted materials can significantly improve the capacity and rate performance of zinc-ion batteries. The growth mechanism of T-HVO was demonstrated by both characterizations and DFT simulations, and the improved performance was systematically investigated through a series of in situ experiments related to dynamic analysis steps. Finally, the evaluation and comparison of various defect introduction strategies revealed the efficient, safety, and high production output characteristics of the in situ induced growth strategy. This work proposes the concept of in situ induced growth strategy and discloses the induced chemical mechanism of MXene materials, which will aid the understanding, development, and application of cathode in aqueous zinc-ion batteries.

A Cu/MnOx Composite with Copper-Doping-Induced Oxygen Vacancies as a Cathode for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries are anticipated to be the next generation of important energy storage devices to replace lithium-ion batteries due to the ongoing use of lithium resources and the safety hazards associated with organic electrolytes in lithium-ion batteries. Manganese-based compounds, including MnOx materials, have prominent places among the many zinc-ion battery cathode materials. Additionally, Cu doping can cause the creation of an oxygen vacancy, which increases the material's internal electric field and enhances cycle stability. MnOx also has great cyclic stability and promotes ion transport. At a current density of 0.2 A g-1, the Cu/MnOx nanocomposite obtained a high specific capacitance of 304.4 mAh g-1. In addition, Cu/MnOx nanocomposites showed A high specific capacity of 198.9 mAh g-1 after 1000 cycles at a current density of 0.5 A g-1. Therefore, Cu/MnOx nanocomposites are expected to be a strong contender for the next generation of zinc-ion battery cathode materials in high energy density storage systems.