Cathode For Aqueous Zinc-ion Batteries Research Articles

Azopyridine Aqueous Electrochemistry Enables Superior Organic AZIBs.

Azo compounds (AZO), such as azobenzene, are classic organic electrode materials featuring a redox potential close to Zn/Zn2+. Recent studies show that azobenzene could work as a cathode in aqueous zinc-ion batteries (AZIBs), providing a voltage output of around 0.7 V. However, the energy storage mechanism of AZO cathodes in AZIBs remains unclear, and their practical usage in AZIBs is hindered by the low voltage. In this study, azopyridine isomers, the hydrophilic analogues of azobenzene, were adopted as cathodes for AZIBs, and the energy storage mechanism was unveiled through aqueous electrochemical studies. Through in situ electrochemical characterizations and theoretical computations, we reveal that both the electron-withdrawing effect of the pyridyl group and the H+-involved -N = N-/-NH-NH- redox reaction uplift the redox potential of the azopyridine cathodes. These findings led to the first AZO-based AZIB, providing a voltage output of 1.4 V. The proposed air-stable AZIBs deliver a high energy/power density and a capacity of around 200 mAh g-1. This work discovers different azopyridine electrochemistry in aqueous and organic electrolytes and enabling AZIBs to outperform its competitors from the AZO family.

Unveiling the Local Structure and the Ligand Field of Organic Cation Preintercalated Vanadate Cathode for Aqueous Zinc-Ion Batteries

Unveiling the Local Structure and the Ligand Field of Organic Cation Preintercalated Vanadate Cathode for Aqueous Zinc-Ion Batteries

Engineering Interlayer Space and Composite of Square-Shaped V2O5 by PVP-Assisted Polyaniline Intercalation and Graphene for Aqueous Zinc-Ion Batteries.

V2O5 undergoes irreversible phase transition and collapse of layered structure during the Zn2+ insertion/extraction, which severely limits its application as a cathode for aqueous zinc-ion batteries (AZIBs). Herein, a synergistic strategy of conductive polyaniline insertion and graphene composite was proposed to boost the Zn2+ storage performance of the V2O5 cathode. A square-shaped polyaniline (PANI)-intercalated and graphene-composited vanadium oxide (GO/PANI-PVP/V2O5) structure was successfully synthesized via an in situ oxidation/insertion polymerization combined with a hydrothermal method. The results showed that PANI intercalation and the composite of graphene combined with layered V2O5, enabling reversible intercalation of Zn2+/H+. The insertion of conjugated PANI not only increases the lattice spacing of V2O5, providing a channel for rapid transport of Zn2+, but also increases the storage sites for charges through doping/dedoping processes and redox conversion reactions. GO/PANI-PVP/V2O5 delivers an excellent specific capacity (495 mA h g-1 at 0.1 A g-1), wonderful rate capability (208 mA h g-1 at 30 A g-1), and good cycling stability (93% after 4000 cycles). Our results provide a new approach for adjusting the valence states, interlayer spacing, and rational design of organic-inorganic compound materials for different functional materials.

Unraveling the Anionic Redox Chemistry in Aqueous Zinc‐MnO2 Batteries

AbstractActivating 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.

Boosting the synergistic activation of δ-MnO2 as cathode for aqueous zinc-ion batteries through Ni, Co co-doping

Layered δ-MnO2 is regarded as a promising cathode material for high-performance aqueous zinc-ion batteries (AZIBs) due to the sufficient interlayer spacing for the accommodation and migration of charge carriers. However, the sluggish activation process limits the reversible capacity, thus prevent their application. In this study, Ni-Co co-doped layered δ-MnO2 was designed to enhance ion diffusion capability and cycling stability. The influencing mechanism of Ni and Co on the long activation process are proposed by a comparative analysis between single doping and co-doping approaches. Specifically, the optimized co-doped δ-MnO2 maintained a high specific capacity of 200.2 mAh·g−1 with a capacity retention of 97.40 % after 700 cycles at 1 A·g−1. The co-doping approach exhibited a synergistic effect in suppressing Mn dissolution and enhancing ion diffusion capability. These findings provide new directions on boosting the synergistic activation process of manganese oxide and shed lights on the rational design of low-cost and high-safe batteries.

Multiwalled carbon nanotubes decorated ɛ-MnO2 nanoflowers cathode with oxygen defect for aqueous zinc-ion batteries

As a potential cathode for aqueous zinc-ion batteries, the low electrical conductivity and poor electrochemical kinetics of MnO2 limit its further development and application. Herein, multiwalled carbon nanotubes decorated MnO2 nanoflowers with hexagonal structure (ɛ-MnO2/MWCNTs) were synthesized by one-step co-precipitation method. The ɛ-MnO2/MWCNTs inherit the advantages of highly conductive MWCNTs and nanostructured MnO2, thus showing excellent zinc-ion storage capacity. The ɛ-MnO2/MWCNTs display high invertible capacity of 335.6 mAh/g at 0.2 A/g after 150 cycles, and long-term capacity of 115.7 mAh/g at 2.0 A/g after 4000 cycles. The results of kinetics tests further reveal that the MWCNTs decoration can reduce polarization of MnO2 and accelerate its reaction kinetics. Thanks to these merits, the ɛ-MnO2/MWCNTs hold great potential for high performance eco-friendly batteries cathode material.

Pre-inserting Mn2+/Zn2+ into NaV6O15 nanorods as high-stable and long lifespan cathodes for aqueous zinc-ion batteries

Vanadium-based compounds, characterized by diverse crystal structures, exhibit high theoretical capacities, and are regarded as potential cathode materials for aqueous zinc-ion batteries. Despite this, their development has been hindered by the sluggish diffusion of zinc ions and inadequate structural stability. In this study, we fabricated a stable monoclinic NaV6O15 nanorod via a simple hydrothermal synthesis. Mn2+ or Zn2+ ions are introduced into the crystal lattice to augment the interlayer spacing of NaV6O15, thereby enhancing the diffusion kinetics of Zn2+ ions. After pre-intercalating guest ions (Mn2+/Zn2+), the material experiences a morphological evolution from nanorods to nanobelts, which correlates with an expansion of the specific surface area and a proliferation of electrochemically active sites. This morphological alteration is associated with a marked enhancement in reversible capacity, reaching 278.1, 340.4, and 363.9 mAh/g for NVO, MNVO, and ZNVO, respectively, at 0.2 A/g. Furthermore, pre-intercalating guest ions not only expanded the interlayer spacing but also conferred structural robustness, leading to a pronounced enhancement in Zn2+ mobility and cyclability. Remarkably, the ZNVO cathode demonstrated a capacity retention of 118.4 % after 5000 cycles at a high current density of 5 A/g. Additionally, ex-situ XRD and XPS analyses elucidate that the Zn2+ storage in ZNVO is governed by the Zn2+ insertion/de-insertion mechanism. Our research offers a paradigm for the development of cathode materials for aqueous zinc-ion batteries.

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.

A fast-kinetics ternary composite cathode design for high-rate aqueous zinc-ion batteries

Aqueous zinc-ion battery (AZIB) attracts a great attention and becomes a hotspot due to its low cost and high safety in recent years. However, the sluggish transport kinetics of cathode materials is a significant drawback limiting their application. Herein, this work reports a novel VSe2/V2O5·nH2O/reduced graphene oxide ternary composite (VSe2/V2O5·nH2O/rGO) constructed with an anti-aggregation and porous 3D framework. The as-prepared ternary composite acting as cathode for AZIBs could provide a high capacity of 327.4 mA h g−1 at the current density of 0.2 A g−1. More importantly, it also possesses excellent rate capability and cyclic stability, which deliver a specific capacity of 254 mA h g−1 at a high current density of 5 A g−1. In addition, the structural evolution and transport kinetics of VSe2/V2O5·nH2O/rGO upon cycling are investigated. Benefiting from the high reversibility of phase evolution and the reduced graphene oxide (rGO) composition, the prepared VSe2/V2O5·nH2O/rGO can maintain a robust structure during cycling, improve the transport kinetics and thus displaying an outstanding electrochemical performance. This study offers a new route for designing cathode materials and promoting the development of high-performance AZIBs.

A Comprehensive Review of the Mechanism and Modification Strategies of V2O5 Cathodes for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) have attracted wide attention due to their affordability, inherent safety, and environmental friendliness, recognized as one of the most ideal next generation energy storage systems. Vanadium-based cathodes have garnered significant interest in the field of AZIBs, presenting vast application prospects in stationary energy storage. Among them, layered vanadium pentoxide (V2O5) stands out a promising material due to its high theoretical capacity, drawing extensive research efforts. However, the research on V2O5 is greatly hindered by issues such as cathode material dissolution, low conductivity, and byproduct formation. Therefore, this review starts from the characteristics of V2O5 materials, summarizes the energy storage mechanism of Zn2+, and elucidates the main challenges faced by V2O5. Subsequently, current modification strategies are summarized based on these challenges, along with the relationships between the issues and strategies. Finally, further challenges and directions faced by each modification strategy are proposed. It is expected to provide researchers with information to quickly familiarize themselves with the current applications and inspiring prospects of V2O5 in AZIBs.

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.

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.

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.