Tuning the layer structure of molybdenum trioxide towards high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) have attracted significant attentions because of low cost and high reliability. However, conventional ZIBs are severely limited by the development of high energy density cathode materials with reversible Zn²⁺ insertion/extraction. Herein, a conducting polymer intercalated MoO₃ (PMO) with extensively extended interlayer spacing is developed as a high-performance ZIBs cathode material. The interlayer spacing of PMO is prominently increased which results in an improved Zn²⁺ mobility during charge and discharge process. More significantly, the electrochemical results reveals that the intercalation of PANI facilitates the charge storage and reinforces the layered structure of MoO₃, leading to a high capacity and good cycling stability. DFT calculation further reveals the intercalation of PANI into MoO₃ significantly lower Zn²⁺ diffusion barrier. Benefit from these advantages, the ZIBs based on PMO electrode delivers a considerable capacity of 157 mAh/g at 0.5 A/g and ameliorative stability with 63.4% capacity retention after 1000 cycles.     

Improved Reversible Zinc Storage Achieved in a Constitutionally Crystalline-Stable Mn(VO3)2 Nanobelts Cathode

Rechargeable zinc-ion batteries (ZIBs) are potential for grid-scale applications owing to their safety, low price, and available sources. The development of ZIBs cathode with high specific capacity, wide operating voltage window and stable cyclability is urgently needed in next-generation commercial batteries. Herein, we report a structurally crystalline-stable Mn(VO₃)₂ nanobelts cathode for ZIBs prepared via a facile hydrothermal method. The as-synthesized Mn(VO₃)₂ exhibited high specific capacity of 350 mAh g⁻¹ at 0.1 A g⁻¹, and maintained a capacity retention of 92 % after 10,000 cycles at 2 A g⁻¹. It also showed good rate performance and obtained a reversible capacity of up to 200 mAh g⁻¹ after 600 cycles at 0.2 A g⁻¹ under −20 °C. The electrochemical tests suggest that Mn(VO₃)₂ nanobelts impart fast Zn²⁺ ions migration, and the introduction of manganese atoms help make the structures more indestructible, leading to a good rate performance and prolonged cycle lifespan.     

A bi-component polyoxometalate-derivative cathode material showed impressive electrochemical performance for the aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries are recently gaining incremental attention because of low cost and material abundance, but their development is plagued by limited choices of cathode materials with satisfactory cycling performance. The polyoxometalates perform formidable redox stability and able to participate in multi-electron transfer, which was well-suited for energy storage. Herein, a bi-component polyoxometalate-derivative KNiVO (K₂[Ni(H₂O)₆]₂[V₁₀O₂₈]·4H₂O polyoxometalates after annealing) is firstly demonstrated as a cathode material for aqueous ZIBs. The layered KV₃O₈ (KVO) In the bi-component material constitutes Zn²⁺ migration and storage channels (K⁺ were substantially replaced by Zn²⁺ in the activation phase), and the three-dimensional NiV₃O₈ (NiVO) part acts as skeleton to stabilize the ion channels, which assist the cell to demonstrate a high-rate capacity and specific energy of 229.4 mAh/g and satisfactory cyclability (capacity retention of 99.1% after 4500 cycles at a current density of 4 A/g). These results prove the feasibility of POM as cathode materials precursor and put forward a novel pattern of the Zn²⁺ storage mechanism in the activated-KNiVO clusters, which also provide a new route for selecting or designing high-performance cathode for aqueous ZIBs and other advanced battery systems.     

A Long‐Cycling Aqueous Zinc‐Ion Pouch Cell: NASICON‐Type Material and Surface Modification

Aqueous zinc‐ion batteries (ZIBs) have become the highest potential energy storage system for large‐scale applications owing to the high specific capacity, good safety and low cost. In this work, a NASICON‐type Na₃V₂(PO₄)₃ cathode modified by a uniform carbon layer (NVP/C) has been synthesized via a facile solid‐state method and exhibited significantly improved electrochemical performance when working in an aqueous ZIB. Specifically, the NVP/C cathode shows an excellent rate capacity (e. g., 48 mAh g^?1 at 1.0 A g^?1). Good cycle stability is also achieved (e. g., showing a capacity retention of 88% after 2000 cycles at 1.0 A g^?1). Furthermore, the Zn²⁺ (de)intercalation mechanism in the NVP cathode has been determined by various ex‐situ techniques. In addition, a Zn||NVP/C pouch cell has been assembled, delivering a high capacity of 89 mAhg^?1 at 0.2 A g^?1 and exhibiting a superior long cycling stability.     

High ionic conductive protection layer on Zn metal anode for enhanced aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) has been regarded as a promising energy storage system for large-scale application due to the advantages of low cost and high safety. However, the growth of Zn dendrite, hydrogen evolution and passivation issues induce the poor electrochemical performance of ZIBs. Herein, a Na₃Zr₂Si₂PO₁₂ (NZSP) protection layer with high ionic conductivity of 2.94 mS/cm on Zn metal anode was fabricated by drop casting approach. The protection layer prevents Zn dendrites formation, hydrogen evolution as well as passivation, and facilitates a fast Zn²⁺ transport. As a result, the symmetric cells based on NZSP-coated Zn show a stable cycling over 1360 h at 0.5 mA/cm² with 0.5 mAh/cm² and 1000 h even at a high current density of 5 mA/cm² with 2 mAh/cm². Moreover, the full cells combined with V₂O₅-based cathode displays high capacities and high rate capability. This work offers a facile and effective approach to stabilizing Zn metal anode for enhanced ZIBs.     

Cascading V2O3/N-doped carbon hybrid nanosheets as high-performance cathode materials for aqueous zinc-ion batteries

In recent years, especially when there is increasing concern about the safety issue of lithium-ion batteries（LIBs）, aqueous Zn-ion batteries（ZIBs） have been getting a lot of attention because of their costeffectiveness, materials abundance, high safety, and ecological friendliness. Their working voltage and specific capacity are mainly determined by their cathode materials. Vanadium oxides are promising cathode materials for aqueous ZIBs owing to their low cost, abundant resources, and multivale...     

Hybrid Superlattice-Triggered Selective Proton Grotthuss Intercalation in δ-MnO2 for High-Performance Zinc-Ion Battery

A great deal of attention has been paid on layered manganese dioxide (δ−MnO₂) as promising cathode candidate for aqueous zinc-ion battery (ZIB) due to the excellent theoretical capacity, high working voltage and Zn²⁺/H⁺ co-intercalation mechanism. However, caused by the insertion of Zn²⁺, the strong coulomb interaction and sluggish diffusion kinetics have resulted in significant structure deformation, insufficient cycle stability and limited rate capability. And it is still far from satisfactory to accurately modulate H⁺ intercalation for superior electrochemical kinetics. Herein, the terrace-shape δ−MnO₂ hybrid superlattice by polyvinylpyrrolidone (PVP) pre-intercalation (PVP−MnO₂) was proposed with the state-of-the-art ZIBs performance. Local atomic structure characterization and theoretical calculations have been pioneering in confirming the hybrid superlattice-triggered synergy of electron entropy stimulation and selective H⁺ Grotthuss intercalation. Accordingly, PVP−MnO₂ hybrid superlattice exhibits prominent specific capacity (317.2 mAh g⁻¹ at 0.125 A g⁻¹), significant rate performance (106.1 mAh g⁻¹ at 12.5 A g⁻¹), and remarkable cycle stability at high rate (≈100 % capacity retention after 20,000 cycles at 10 A g⁻¹). Therefore, rational design of interlayer configuration paves the pathways to the development of MnO₂ superlattice for advanced Zn−MnO₂ batteries.     

Hydrated ammonium manganese phosphates by electrochemically induced manganese-defect as cathode material for aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) with the merits of low cost, low toxicity, high safety, environmental benignity as well as multi-valence properties as the large-scale energy storage devices demonstrate tremendous application prospect. However, the explorations for the most competitive manganese-based cathode materials of AZIBs have been mainly limited to some known manganese oxides. Herein, we report a new type of cathode material NH₄MnPO₄·H₂O (abbreviated as AMPH) for rechargeable AZIBs synthesized through a simple hydrothermal method. An in-situ electrochemical strategy inducing Mn-defect has been used to unlock the electrochemical activity of AMPH through the initial charge process, which can convert poor electrochemical characteristic of AMPH towards Zn²⁺ and NH₄⁺ into great electrochemically active cathode for AZIBs. It still delivers a reversible discharge capacity up to 90.0 mAh/g at 0.5 A/g even after 1000^th cycles, which indicates a considerable capacity and an impressive cycle stability. Furthermore, this cathode reveals an (de)insertion mechanism of Zn²⁺ and NH₄⁺ without structural collapse during the charge/discharge process. The work not only supplements a new member for the family of manganese-based compound for AZIBs, but also provides a potential direction for developing novel cathode material for AZIBs by introducing defect chemistry.     

Reversible aqueous zinc-ion battery based on ferric vanadate cathode

Rechargeable aqueous zinc-ion batteries have attracted extensive interest because of low cost and high safety. However, the relationship between structure change of cathode and the zinc ion storage mechanism is still complex and challenging. Herein, open-structured ferric vanadate (Fe₂V₄O₁₃) has been developed as cathode material for aqueous zinc-ion batteries. Intriguingly, two zinc ion storage mechanism can be observed simultaneously for the Fe₂V₄O₁₃ electrode, i.e., classical intercalation/deintercalation storage mechanism in the tunnel structure of Fe₂V₄O₁₃, and reversible phase transformation from ferric vanadate to zinc vanadate, which is verified by combined studies using various in-situ and ex-situ techniques. As a result, the Fe₂V₄O₁₃ cathode delivers a high discharge capacity of 380 mAh/g at 0.2 A/g, and stable cyclic performance up to 1000 cycles at 10 A/g in the operating window of 0.2–1.6 V with 2 mol/L Zn(CF₃SO₃)₂ aqueous solution. Moreover, the assembled Fe₂V₄O₁₃//Zn flexible quasi-solid-state battery also exhibits a relatively high mechanical strength and good cycling stability. The findings reveal a new perspective of zinc ion storage mechanism for Fe₂V₄O₁₃, which may also be applicable to other vanadate cathodes, providing a new direction for the investigation and design of zinc-ion batteries.     

Highly Stable Aqueous Zinc‐Ion Storage Using a Layered Calcium Vanadium Oxide Bronze Cathode

Cost‐effective aqueous rechargeable batteries are attractive alternatives to non‐aqueous cells for stationary grid energy storage. Among different aqueous cells, zinc‐ion batteries (ZIBs), based on Zn²⁺ intercalation chemistry, stand out as they can employ high‐capacity Zn metal as the anode material. Herein, we report a layered calcium vanadium oxide bronze as the cathode material for aqueous Zn batteries. For the storage of the Zn²⁺ ions in the aqueous electrolyte, we demonstrate that the calcium‐based bronze structure can deliver a high capacity of 340 mA h g^?1 at 0.2 C, good rate capability, and very long cycling life (96 % retention after 3000 cycles at 80 C). Further, we investigate the Zn²⁺ storage mechanism, and the corresponding electrochemical kinetics in this bronze cathode. Finally, we show that our Zn cell delivers an energy density of 267 W h kg^?1 at a power density of 53.4 W kg^?1.     

Carbon Nitride Pillared Vanadate Via Chemical Pre-Intercalation Towards High-Performance Aqueous Zinc-Ion Batteries

Vanadium based compounds are promising cathode materials for aqueous zinc (Zn)-ion batteries (AZIBs) due to their high specific capacity. However, the narrow interlayer spacing, low intrinsic conductivity and the vanadium dissolution still restrict their further application. Herein, we present an oxygen-deficient vanadate pillared by carbon nitride (C₃N₄) as the cathode for AZIBs through a facile self-engaged hydrothermal strategy. Of note, C₃N₄ nanosheets can act as both the nitrogen source and pre-intercalation species to transform the orthorhombic V₂O₅ into layered NH₄V₄O₁₀ with expanded interlayer spacing. Owing to the pillared structure and abundant oxygen vacancies, both the Zn²⁺ ion (de)intercalation kinetics and the ionic conductivity in the NH₄V₄O₁₀ cathode are promoted. As a result, the NH₄V₄O₁₀ cathode delivers exceptional Zn-ion storage ability with a high specific capacity of about 370 mAh g⁻¹ at 0.5 A g⁻¹, a high-rate capability of 194.7 mAh g⁻¹ at 20 A g⁻¹ and a stable cycling performance of 10 000 cycles.     

Carbon-coated manganese dioxide nanoparticles and their enhanced electrochemical properties for zinc-ion battery applications

In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnO_2nanoparticles(α-MnO_2@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO_2@C was prepared via a gel formation, using maleic acid(C_4H_4O_4) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnO_2 nanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO_2@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO_2@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnO_2 electrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.     

A Deep‐Cycle Aqueous Zinc‐Ion Battery Containing an Oxygen‐Deficient Vanadium Oxide Cathode

Rechargeable aqueous zinc‐ion batteries are attractive because of their inherent safety, low cost, and high energy density. However, viable cathode materials (such as vanadium oxides) suffer from strong Coulombic ion–lattice interactions with divalent Zn²⁺, thereby limiting stability when cycled at a high charge/discharge depth with high capacity. A synthetic strategy is reported for an oxygen‐deficient vanadium oxide cathode in which facilitated Zn²⁺ reaction kinetic enhance capacity and Zn²⁺ pathways for high reversibility. The benefits for the robust cathode are evident in its performance metrics; the aqueous Zn battery shows an unprecedented stability over 200 cycles with a high specific capacity of approximately 400 mAh g^?1, achieving 95 % utilization of its theoretical capacity, and a long cycle life up to 2 000 cycles at a high cathode utilization efficiency of 67 %. This work opens up a new avenue for synthesis of novel cathode materials with an oxygen‐deficient structure for use in advanced batteries.     

A Reversible Six-Electron Transfer Cathode for Advanced Aqueous Zinc Batteries

The electrochemical reactions for the storage of Zn²⁺ while embracing more electron transfer is a foundation of the future high-energy aqueous zinc batteries. Herein, we report a six-electron transfer electrochemistry of nano-sized TeO₂/C (n-TeO₂/C) cathode by facilitating the reversible conversion of TeO₂↔Te and Te↔ZnTe. Benefitting from the integrated conductive nanostructure and the proton-rich environment in providing optimized electrochemical kinetics (facilitated Zn²⁺ uptake and high electronic conductivity) and feasible thermodynamic process (low Gibbs free energy change), the as-prepared n-TeO₂/C with stable cycling performance exhibits a superior reversible capacity of over 800 mAh g⁻¹ at 0.1 A g⁻¹. A precise understanding of the reaction mechanism via ex situ and in situ characterizations presents that the reversible six-electron transfer reaction is proton-dependent, and a proton generating and consuming mechanism of three-phase conversion n-TeO₂/C in the weakly acidic electrolyte is thoroughly revealed.     

V-MOF@graphene derived two-dimensional hierarchical V2O5@graphene as high-performance cathode for aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) are attracting growing attention in the field of grid-scale energy storage systems due to their reliable safety and low cost. However, it is still hindered by the limited choices of suitable cathode materials with high performance for aqueous ZIBs. Herein, we developed a V-MOF@graphene derived two-dimensional hierarchical V₂O₅@graphene for the first time, where the porous V₂O₅ nanosheets are homogeneously attached to the 2D graphene substrate. Benefiting from the unique 2D composite structure with excellent electronic and ionic conductivity, adequate active sites, as well as the synergistic effect between the ultrathin V₂O₅ nanosheets and graphene, the V₂O₅@graphene here exhibits outstanding electrochemical performance in aqueous ZIBs. Particularly, it delivered an ultrahigh reversible capacity of 378 mAh/g at a current density of 2 A/g. What is more, a high specific capacity of 305 mAh/g after 100 cycles at 0.1 A/g and 200 mAh/g after 1,000 cycles at 1 A/g can be achieved. These ideal results suggest that the V₂O₅@graphene cathode hold great promise for high-performance aqueous zinc-ion batteries.     

NH4+ Charge Carrier Coordinated H-Bonded Organic Small Molecule for Fast and Superstable Rechargeable Zinc Batteries

Organic small molecules as high-capacity cathodes for Zn-organic batteries have inspired numerous interests, but are trapped by their easy-dissolution in electrolytes. Here we knit ultrastable lock-and-key hydrogen-bonding networks between 2, 7-dinitropyrene-4, 5, 9, 10-tetraone (DNPT) and NH₄⁺ charge carrier. DNPT with octuple-active carbonyl/nitro centers (H-bond acceptor) are redox-exclusively accessible for flexible tetrahedral NH₄⁺ ions (H-bond donator) but exclude larger and rigid Zn²⁺, due to a lower activation energy (0.14 vs. 0.31 eV). NH₄⁺ coordinated H-bonding chemistry conquers the stability barrier of DNPT in electrolyte, and gives fast diffusion kinetics of non-metallic charge carrier. A stable two-step 4e⁻ NH₄⁺ coordination with DNPT cathode harvests a high capacity (320 mAh g⁻¹), a high-rate capability (50 A g⁻¹) and an ultralong life (60,000 cycles). This finding points to a new paradigm for H-bond stabilized organic small molecules to design advanced zinc batteries.     

Zinc–Organic Battery with a Wide Operation-Temperature Window from −70 to 150 °C

Aqueous zinc (Zn) batteries have been considered as promising candidates for grid-scale energy storage. However, their cycle stability is generally limited by the structure collapse of cathode materials and dendrite formation coupled with undesired hydrogen evolution on the Zn anode. Herein we propose a zinc–organic battery with a phenanthrenequinone macrocyclic trimer (PQ-MCT) cathode, a zinc-foil anode, and a non-aqueous electrolyte of a N,N-dimethylformamide (DMF) solution containing Zn²⁺. The non-aqueous nature of the system and the formation of a Zn²⁺–DMF complex can efficiently eliminate undesired hydrogen evolution and dendrite growth on the Zn anode, respectively. Furthermore, the organic cathode can store Zn²⁺ ions through a reversible coordination reaction with fast kinetics. Therefore, this battery can be cycled 20 000 times with negligible capacity fading. Surprisingly, this battery can even be operated in a wide temperature range from −70 to 150 °C.     

Bio-Inspired Polyanionic Electrolytes for Highly Stable Zinc-Ion Batteries

For zinc-ion batteries (ZIBs), the non-uniform Zn plating/stripping results in a high polarization and low Coulombic efficiency (CE), hindering the large-scale application of ZIBs. Here, inspired by biomass seaweed plants, an anionic polyelectrolyte alginate acid (SA) was used to initiate the in situ formation of the high-performance solid electrolyte interphase (SEI) layer on the Zn anode. Attribute to the anionic groups of −COO⁻, the affinity of Zn²⁺ ions to alginate acid induces a well-aligned accelerating channel for uniform plating. This SEI regulates the desolvation structure of Zn²⁺ and facilitates the formation of compact Zn (002) crystal planes. Even under high depth of discharge conditions (DOD), the SA-coated Zn anode still maintains a stable Zn stripping/plating behavior with a low potential difference (0.114 V). According to the classical nucleation theory, the nucleation energy for SA-coated Zn is 97 % less than that of bare Zn, resulting in a faster nucleation rate. The Zn||Cu cell assembled with the SA-coated electrode exhibits an outstanding average CE of 99.8 % over 1,400 cycles. The design is successfully demonstrated in pouch cells, where the SA-coated Zn exhibits capacity retention of 96.9 % compared to 59.1 % for bare Zn anode, even under the high cathode mass loading (>10 mg/cm²).     

Ethylene glycol-regulated ammonium vanadate with stable layered structure and favorable interplanar spacing as high-performance cathode for aqueous zinc ion batteries

Ammonium vanadate compounds featuring large capacity, superior rate capability and light weight are regarded as promising cathode materials for aqueous zinc ion batteries (AZIBs). However, the controllable synthesis of desired ammonium vanadates remains a challenge. Herein, various ammonium vanadate compounds were successfully prepared by taking advantage of ethylene glycol (EG) regulated polyol-reduction strategy and solvent effect via hydrothermal reaction. The morphology and crystalline phase of resultant products show an evolution from dendritic (NH₄)₂V₆O₁₆ to rod-like NH₄V₄O₁₀ and finally to lamellar (NH₄)₂V₄O₉ as increasing the amount of EG. Specifically, the NH₄V₄O₁₀ product exhibits a high initial capacity of 427.5 mAh/g at 0.1 A/g and stable cycling with a capacity retention of 90.4% after 5000 cycles at 10 A/g. The relatively excellent electrochemical performances of NH₄V₄O₁₀ can be ascribed to the stable open-framework layered structure, favorable (001) interplanar spacing, and peculiar rod-like morphology, which are beneficial to the highly reversible Zn²⁺ storage behaviors. This work offers a unique way for the rational design of high-performance cathode materials for AZIBs.     

Electrochemically Induced Metal–Organic-Framework-Derived Amorphous V2O5 for Superior Rate Aqueous Zinc-Ion Batteries

The electrochemical performance of vanadium-oxide-based cathodes in aqueous zinc-ion batteries (ZIBs) depends on their degree of crystallinity and composite state with carbon materials. An in situ electrochemical induction strategy was developed to fabricate a metal–organic-framework-derived composite of amorphous V₂O₅ and carbon materials (a-V₂O₅@C) for the first time, where V₂O₅ is in an amorphous state and uniformly distributed in the carbon framework. The amorphous structure endows V₂O₅ with more isotropic Zn²⁺ diffusion routes and active sites, resulting in fast Zn²⁺ transport and high specific capacity. The porous carbon framework provides a continuous electron transport pathway and ion diffusion channels. As a result, the a-V₂O₅@C composites display extraordinary electrochemical performance. This work will pave the way toward design of ZIB cathodes with superior rate performance.