Cathode Material For Aqueous Zinc-ion Batteries Research Articles

Ammonium Ion and Structural Water Co‐Assisted Zn2+ Intercalation/De‐Intercalation in NH4V4O10∙0.28H2O†

Main observation and conclusionThe cathode material plays a crucial role in the performances of aqueous zinc‐ion batteries (ZIBs). Herein, we report an ammonium vanadate (NH4V4O10∙0.28H2O, NHVO) aqueous ZIB cathode material. The obtained NHVO microflowers manifest high discharge capacity (410 mA·h∙g–1 at 0.2 A∙g–1), long‐term durability (76% capacity retention over 500 cycles), as well as ideal rate performance (112 mA·h∙g–1 at 10 A∙g–1). The impressive electrochemical performance can be attributed to the ammonium ion and structural water co‐assisted Zn2+ intercalation/de‐intercalation, which has been demonstrated by various ex‐situ and in‐situ characterizations. The superior electrochemical performance makes the NHVO microflower an ideal candidate cathode material for aqueous ZIBs.

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−1 at 0.1 A g−1 and a stable rate capability of 348.2 mA h g−1 at 1 A g−1. Moreover, it exhibited a specific capacity of 202 mA h g−1 even 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−1 at 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.

Manganese oxides hierarchical microspheres as cathode material for high-performance aqueous zinc-ion batteries

For manganese-based oxides to be used as one of the most promising aqueous zinc-ion batteries (ZIBs) cathode materials, improvements in cycling stability are required. In this work, manganese oxides (MnOx) hierarchical microspheres, including MnO, γ-MnO2 (MnO2), Mn2O3 and Mn3O4, are prepared and their electrochemical performances are systematically investigated as cathode materials for aqueous ZIBs. The MnOx hierarchical structures can effectively shorten the diffusion pathway of Zn2+, tolerate the structural stress caused by Zn2+ insertion/extraction and restrain the self-aggregation of nanomaterials. Among MnOx, MnO hierarchical microspheres displays a high reversible capacity of 376.7 mAh g−1, good rate capability and excellent cycling stability with capacity retention of 99.37% over 1000 cycles. Finally, the zinc ion storage mechanism of MnO cathode is revealed. The results show that the remarkable electrochemical performance of MnO cathode is attributed to layered-type MnO2 structure formed during the initial few cycles, which is conducive to the insertion/extraction of zinc ions. This work is expected to deepen the understanding of the energy storage mechanism of MnO and helped to choose the ideal manganese-based cathode materials for aqueous ZIBs.

Crystal water assisting MoS2 nanoflowers for reversible zinc storage

As a special group of two-dimensional layered compounds, transition metal dichalcogenides (TMDs) have attracted great attentionfor rechargeable zinc ion batteries (ZIBs). However, the large zinc ion radius, the strong electrostatic interaction with the host material, and the slow dynamics of Zn2+ limit the application of TMDs in rechargeable aqueous ZIBs. Herein, MoS2·nH2O is synthesized through a facile hydrothermal reaction. The unique nanoscale flower structure combined with the introduction of crystal water can reduce the electrostatic interaction between zinc ion and skeleton, promote the diffusion of zinc ion, and effectively accelerate the reaction kinetics. Benefiting from the above advantages, the MoS2·nH2O electrode exhibits a high rate capacity and satisfactory cyclability (88% capacity retention after 800 cycles at 2 A g−1). The excellent performance of MoS2·nH2O proves that the introduction of crystal water is a practical strategy to promote the hydration kinetics of large-size multivalent ions, which may provide a viable and attractive solution for the synthesis of other cathode materials for aqueous ZIBs.

Controlling Vanadate Nanofiber Interlayer via Intercalation with Conducting Polymers: Cathode Material Design for Rechargeable Aqueous Zinc Ion Batteries

AbstractAqueous zinc ion batteries (ZIBs) are promising energy storage devices due to the high ionic conductivity of the aqueous electrolyte as well as the safety, eco‐friendliness, and low cost. Vanadium oxide‐based materials are attractive cathode materials for aqueous ZIBs because of their high capacity from their layered structure and multiple valences. However, it is difficult to achieve high cycle stability and rate capability due to the low electrical conductivity and trapping of diffused electrolyte cations within the crystal structure, limiting the commercialization of aqueous ZIBs. In this study, the authors propose a facile sonochemical method for controlling the interlayer of the vanadate nanofiber crystal structure using poly(3,4‐ethylene dioxythiophene) (PEDOT) to overcome the shortcomings of vanadium oxide‐based materials. In addition, the electrochemical correlation between the interplanar distance of the expanded vanadate layers by the insertion of PEDOT and the behavior of Zn2+ ions is investigated. As a result, the intercalation of the conducting polymer increases the electron pathway and extends the distance of the vanadate layers, which helps to increase the number of active sites inside the vanadate and accelerate the zinc ion intercalation/de‐intercalation process. Their findings may guide research on the next generation of ZIBs that can replace lithium ion batteries.

Three-dimensional hydrated vanadium pentoxide/MXene composite for high-rate zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) have been considered to be potential energy storage devices because of their cost-effectiveness and environmental friendliness. However, most of the cathode materials reported in ZIBs exhibit poor electrochemical performances like capacity fading during cycling and inferior performance at high current densities, which significantly hinder the further development of ZIBs. Here, we reported a novel three-dimensional hydrated vanadium pentoxide (V2O5·nH2O)/MXene composite via a simple one-step hydrothermal method. Owing to the unique structure and high electrical conductivity of MXene, V2O5·nH2O/Ti3C2Tx MXene shows a remarkable electrochemical performance with a reversible capacity of 323 mAh g−1 at 0.1 A g−1 and exceptional rate capability (262 mAh g−1 at 1 A g−1 and 225 mAh g−1 at 2 A g−1) when used as the cathode for aqueous ZIBs. This work offers a new insight into fabricating novel vanadium oxide-based cathode material for aqueous ZIBs.

Structural engineering of cathodes for improved Zn-ion batteries

A unique 3D flower-like zinc cobaltite (ZnCo 2 O 4- x ) with oxygen vacancies is designed and fabricated and a flexible solid-state ZIB was demonstrated, which delivers an extremely stable capacity under bending states. Aqueous zinc-ion batteries (ZIBs) are attracting considerable attention because of their low cost, high safety and abundant anode material resources. However, the major challenge faced by aqueous ZIBs is the lack of stable and high capacity cathode materials due to their complicated reaction mechanism and slow Zn-ion transport kinetics. This study reports a unique 3D ‘flower-like’ zinc cobaltite (ZnCo 2 O 4- x ) with enriched oxygen vacancies as a new cathode material for aqueous ZIBs. Computational calculations reveal that the presence of oxygen vacancies significantly enhances the electronic conductivity and accelerates Zn 2+ diffusion by providing enlarged channels. The as-fabricated batteries present an impressive specific capacity of 148.3 mAh g −1 at the current density of 0.05 A g −1 , high energy (2.8 Wh kg −1 ) and power densities (27.2 W kg −1 ) based on the whole device, which outperform most of the reported aqueous ZIBs. Moreover, a flexible solid-state pouch cell was demonstrated, which delivers an extremely stable capacity under bending states. This work demonstrates that the performance of Zn-ion storage can be effectively enhanced by tailoring the atomic structure of cathode materials, guiding the development of low-cost and eco-friendly energy storage materials.

Aluminium pre-intercalated orthorhombic V2O5 as high-performance cathode material for aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) are emerging as promising candidates for large-scale energy storage systems because of their low cost and high safety. However, the slow migration rate and strong electrostatic repulsion of divalent Zn2+ put forward many requirements for the properties of cathode materials. Herein, we present an aluminium pre-intercalated orthorhombic V2O5 (Al0.2V2O5) as a new cathode material for AZIBs. The analyses of GITT, ex-situ XRD, TEM and XPS indicate that the Al0.2V2O5 electrode possesses a higher Zn2+ diffusion coefficient than V2O5. And, the pre-intercalated Al3+ can stabilize the crystal structure and prevent Zn2+ from being trapped in the lattice. Because of the above advantages, Al0.2V2O5 shows much-enhanced electrochemical performance including a high capacity of 448.4 mA h g−1 at 0.1 A g−1, excellent rate capability of 143.9 mA h g−1 at 10 A g−1 and impressive long-term cycling stability with a capacity retention of 61.4% after 5000 cycles at 5 A g−1. Furthermore, the Al0.2V2O5/Zn battery can provide a high energy density of 327.1 W h kg−1 at 0.1 A g−1 and a high power density of 5491.8 W kg−1 at 10 A g−1, which shows great potential in the applications of large-scale energy storage.

Water cointercalation for high-energy-density aqueous zinc-ion battery based potassium manganite cathode

Aqueous zinc-ion batteries (ZIBs) are gaining widespread attention owing to their intrinsic safety and low cost. However, it is still a challenge that finding robust cathode materials to build a high-energy-density aqueous ZIBs. Here, we synthesize a novel layered K0.41MnO2·0.5H2O (KMO) cathode material for aqueous ZIBs. The constructed Zn//KMO battery shows an ultrahigh discharge capacity of 425 mAh g−1 and a remarkable energy density of 503 Wh kg−1 at 175 mA g−1, as well as an good durability over 1500 cycles with no obvious capacity fading. A comprehensive study suggests that the water molecules can intercalate into layered KMO with H+ and Zn2+ ions during discharging process. The co-intercalating water not only facilitates ions insertion, but serves as pillars to stabilize the structure of KMO. This work demonstrates the mechanism about water cointercalation and provides a way for designing high-energy-density aqueous ZIBs.

Strongly coupled zinc manganate nanodots and graphene composite as an advanced cathode material for aqueous zinc ion batteries

Manganese-based oxides with high capacity and moderate operation voltage have been extensively studied as promising cathode materials for aqueous zinc ion batteries (ZIBs). However, the inherent poor electrical conductivity, sluggish reaction kinetics, huge volume expansion and dissolution of manganese species in electrolyte greatly restrict their practical applications. Herein, ultrasmall ZnMn2O4 nanodots uniformly anchored on reduced graphene oxide with strong interfacial interaction (ZnMn2O4 NDs/rGO composite) is synthesized. Compared with the pure ZnMn2O4 microspheres, the ZnMn2O4 NDs/rGO composite displays a much higher discharge capacity of 207.6 mA h g−1 at a current density of 0.2 A g−1, as well as better rate capability and long-term cycling stability. Impressively, the aqueous Zn//ZnMn2O4 NDs/rGO battery exhibits a high energy density of 266 W h kg−1 at a power density of 137 W kg−1, indicating great potential for practical applications. The excellent performance could be attributed to the abundant active sites, shortened ion diffusion pathway, improved electrical conductivity and good structure stability. Furthermore, electrochemical analyses reveal that favorable reaction kinetics towards efficient zinc ion storage is achieved in the composite. The present work might shed light on the rational design and synthesis of advanced strongly coupled graphene based composites as cathode materials for aqueous ZIBs.

Boosting the Cyclic Stability of Aqueous Zinc-Ion Battery Based on Al-Doped V10O24·12H2O Cathode Materials.

Rechargeable aqueous zinc-ion batteries (ZIBs) are considered an alternative energy storage system to lithium-ion battery because of its low price and high safety. However, the development of zinc-ion battery is limited by positive materials, which usually show poor cycling life because of the strong electrostatic interaction between divalent Zn2+ ions and crystal structure of materials. Developing a cathode material with a stable structure upon cycling is still a big challenge for researchers worldwide. Doping foreign elements, which can solidify the lattice, is an effective approach to improve the structural stability of materials. However, hardly any research based on the doping method for aqueous ZIBs has been reported. Here, we develop an Al-doped layer material of V10O24·12H2O as cathode material for aqueous ZIBs. Benefitting from the stable layered structure, the material exhibited an excellent cycling life with 98% capacity retention after 3000 cycles, which is much higher than the 65% in the pure V10O24·12H2O. The great enhancement on the cycle performance indicates that Al-doping can help build an advanced zinc-storage system.