A one-dimensional chain polymer as a dual-active-center cathode for aqueous zinc-ion batteries with air self-charging capability

Aqueous fibrous batteries with tiny volume, light weight and stretchability have furthered wearable smart textile systems like biocompatible electronics for a more efficient use of electricity. Challenges still faced by fibrous batteries include not only the deficient actual capacity but the cyclability on the cathode side. Herein, an in situ anodic oxidation strategy is reported to prepare 3D N-doped/defect-rich V2O5-x·nH2O nanosheets (DVOH@NC) as fibrous cathodes for aqueous zinc-ion batteries (AZIBs). Benefiting from the substantially abundant reaction sites, enhanced electrical conductivity, short electron/ion diffusion path and high mass loading, the newly designed DVOH@NC fibrous electrode delivers impressive capacity (711.9 mA h cm-3 at 0.3 A cm-3) and long-term durability (95.5% capacity retention after 3000 cycles), substantially outperforming previously reported fibrous vanadium-based cathodes. First-principles density functional theory (DFT) calculations further revealed that the oxygen vacancies can weaken the electrostatic interaction between Zn2+ and the host cathode accompanying the low Zn2+ diffusion energy barrier. To highlight the potential applications, a prototype wearable fiber-shaped AZIB (FAZIB) with remarkable flexibility and extraordinary weaving capability was demonstrated. More encouragingly, the resulting FAZIB could be charged with solar cells and power a pressure sensor. Thus, our work provides a promising strategy to rationally construct high-performance flexible vanadium-based cathodes for next-generation wearable AZIBs.

MOF-73 is explored as a novel cathode for aqueous zinc-ion batteries, and a co-contribution zinc ion storage mechanism is illustrated.

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

Conductive flower-like Ni-PTA-Mn as cathode for aqueous zinc-ion batteries

Na3V2(PO4)3 is a promising high-voltage cathode for aqueous zinc-ion batteries (ZIBs) and organic sodium-ion batteries (SIBs). However, the poor rate capability, specific capacity, and cycling stability severely hamper it from further development. In this work, Na3V2(PO4)3 (NVP) with vanadium nitride (VN) quantum dots encapsulated by nitrogen-doped carbon (NC) nanoflowers (NVP/VN@NC) are manufactured as cathode using in situ nitridation, carbon coating, and structural adjustment. The outer NC layer increases the higher electronic conductivity of NVP. Furthermore, VN quantum dots with high theoretical capacity not only improve the specific capacity of pristine NVP, but also serve as abundant "pins" between NVP and NC to strengthen the stability of NVP/VN@NC heterostructure. For Zn-ion storage, these essential characteristics allow NVP/VN@NC to attain a high reversible capacity of 135.4mAhg-1 at 0.1Ag-1, and a capacity retention of 91% after 2000 cycles at 5Ag-1. Meanwhile, NVP/VN@NC also demonstrates to be a stable cathode material for SIBs, which can reach a high reversible capacity of 124.5mAhg-1 at 0.1Ag-1, and maintain 92% of initial capacity after 11000 cycles at 5Ag-1. This work presents a feasible path to create innovative high-voltage cathodes with excellent reaction kinetics and structural stability.

Considering the high safety, low-cost and high capacity, aqueous zinc ion batteries have been a potential candidate for energy storage ensuring smooth electricity supply. Herein, we have synthesized inverse opal manganese dioxide constructed by few-layered ultrathin nanosheets by a solution template method at mild temperature. The ultrathin nanosheets with the thickness as small as 1 nm are well separated without obvious aggregation. Used as cathode material for aqueous zinc ion batteries, the few-layered ultrathin nanosheets combined with the inverse opal structure guarantee excellent performance. A high specific discharge capacity of 262.9 mAh·g−1 is retained for the 100th cycle at a current density of 300 mA·g−1 with a high capacity retention of 95.6%. A high specific discharge capacity of 121 mAh·g−1 at a high current density of 2,000 mA·g−1 is achieved even after 5,000 long-term cycles. The ex-situ X-ray diffraction (XRD) patterns, selected-area electron diffraction (SAED) patterns and high-resolution transmission electron microscopy (HRTEM) results demonstrate that the discharge/charge processes involve the reversible formation of zinc sulfate hydroxide hydrate on the cathode while in-plane crystal structure of the layered birnessite MnO2 could be maintained. This unique structured MnO2 is a promising candidate as cathode material for high capacity, high rate capability and long-term aqueous zinc-ion batteries.

Spontaneous knitting behavior of 6.7-nm thin (NH4)0.38V2O5 nano- ribbons for binder-free zinc-ion batteries

π-Conjugated N-heterocyclic compound with redox-active quinone and pyrazine moieties as a high-capacity organic cathode for aqueous zinc-ion batteries

Low-cost, safe, and environmental-friendly rechargeable aqueous zinc-ion batteries (ZIBs) are promising as next-generation energy storage devices for wearable electronics among other applications. However, sluggish ionic transport kinetics and the unstable electrode structure during ionic insertion/extraction hamper their deployment. Herein, a new cathode material based on a layered metal chalcogenide (LMC), bismuth telluride (Bi2 Te3 ), coated with polypyrrole (PPy) is proposed. Taking advantage of the PPy coating, the Bi2 Te3 @PPy composite presents strong ionic absorption affinity, high oxidation resistance, and high structural stability. The ZIBs based on Bi2 Te3 @PPy cathodes exhibit high capacities and ultra-long lifespans of over 5000 cycles. They also present outstanding stability even under bending. In addition, here the reaction mechanism is analyzed using in situ X-ray diffraction, X-ray photoelectron spectroscopy, and computational tools and it is demonstrated that, in the aqueous system, Zn2+ is not inserted into the cathode as previously assumed. In contrast, proton charge storage dominates the process. Overall, this work not only shows the great potential of LMCs as ZIB cathode materials and the advantages of PPy coating, but also clarifies the charge/discharge mechanism in rechargeable ZIBs based on LMCs.

Aqueous zinc-ion batteries (AZIBs), as one of the most promising energy storage devices, have attracted widespread attention owing to their abundant resources, environmental friendliness, and high safety. As a crucial component of AZIBs, the electrochemical performance of cathode materials plays a decisive role in battery performance, thus necessitating in-depth investigations into the structure and properties of cathode materials. Manganese dioxide (MnO2), as a cathode material for AZIBs, has garnered significant interest owing to advantages such as the low cost of manganese, stable structure, simple synthesis process, and abundant raw materials. Additionally, it exhibits high specific capacity and tunable cycling performance. However, MnO2 as a cathode in AZIBs is plagued by structural deformation, side reactions, and the Jahn-Teller effect during cycling. Therefore, it is essential to comprehensively review the research progress, reaction mechanisms, and optimization strategies of MnO2 in AZIBs. Herein, MnO2 is taken as the research focus. Firstly, we comprehensively summarize the development status and research progress of MnO2 materials as cathodes for AZIBs. Subsequently, we conduct an in-depth analysis of the structural evolution and Zn2+ storage mechanisms of MnO2 during cycling, including the conversion reaction mechanism, Zn2+ intercalation mechanism, dissolution-deposition mechanism, and H+/Zn2+ co-intercalation mechanism. Building on this, various optimization strategies such as structural control, morphological regulation, defect engineering, and electrolyte development are systematically reviewed. Finally, we outline future research directions for high-performance MnO2 cathodes, put forward a rational research roadmap to maximize the electrochemical properties of MnO2, and facilitate the construction of stable AZIBs.

Low-current-density stability of vanadium-based cathodes for aqueous zinc-ion batteries

The electrochemical performance of α-MnO2 cathodes in aqueous zinc-ion batteries is limited by their low electronic conductivity, structural instability due to Jahn-Teller distortion, and slow Zn2+ diffusion kinetics. Although ion doping can alleviate these issues, conventional 3d transition metal dopants usually provide only modest improvement in electrochemical performance. In this work, we explore the possibility and demonstrate that ruthenium ions can act as an alternative dopant to address these challenges in a synergistic way. Ru3+/Ru4+ ions have highly delocalized 4d orbitals and high-bond-energy Ru-O bonds, which can modify the electronic structure of α-MnO2 effectively. As a result, the electrochemical performance of the ruthenium-doped α-MnO2 (RMO) cathode is enhanced showing a specific capacity of 360.1 mAh g-1 at 0.1 A g-1 and good cycling stability with 76.7% capacity retention after 5000 cycles at 3 A g-1, which is significantly higher than that of pristine α-MnO2. Density functional theory (DFT) calculations show that ruthenium doping can narrow the bandgap from 0.9296 eV to 0.6997 eV and decrease the Zn2+ diffusion energy barrier from 0.68 eV to 0.56 eV. This work demonstrates that 4d transition metal doping can fundamentally improve the physicochemical properties of MnO2 and enhance its potential as a cathode material in aqueous zinc-ion batteries.

Aqueous rechargeable zinc-ion batteries (AZIBs) are currently gaining traction as a potential successor to lithium-ion batteries for use in large-scale, stationary energy storage applications due to their inherent safety, low environmental impact, and low-cost. Recent advances have made breakthroughs in these anode and electrolyte stability; however, cathode development still lags preventing the commercial use of AZIBs. Vanadium pentoxide (V2O5) shows promise as a cathode material due to its low cost, environmental friendliness, and high specific capacity versus zinc (in excess of 400 mAh/g)1. V2O5 exhibits a single layer crystal structure which provides a large number of theoretical storage sites2. However, charge storage mechanisms and driving force behind the capacity fade in V2O5 are not well known yet. The lack of understanding surrounding insertion and storage mechanisms of zinc ions into V2O5 cathodes must be addressed to progress toward commercial viability.In this study, we aim to conduct in-operando stress and stress measurements in V2O5 during battery cycling. Curvature interferometry and digital image correlation techniques will be employed for in operando stress and strain measurements, respectively the composite V2O5 cathode will consist of a 7:2:1 ratio of active material, super P, and PVDF binder. By combining stress and strain measurements, coupled with spectroscopy studies, our goal is to identify the how interfacial stress and structural strains play a role on the charge storage mechanisms in V2O5.

We demonstrated the use of hydrated calcium vanadate (CaV6O16·3H2O, denoted as CaVO-2) as a cathode for aqueous zinc-ion batteries (AZIBs). Nanoribbons of hydrated calcium vanadate facilitated shortening of the Zn2+ transport distance and accelerated zinc-ion insertion. The introduction of interlayer structure water increased the interlayer spacing of calcium vanadate and as a "lubricant". Ca2+ insertion also expanded the interlayer spacing and further stabilized the interlayer structure of vanadium-based oxide. The density functional theory results showed that the introduction of Ca2+ and structured water could effectively improve the diffusion kinetics, resulting in the rapid transport of zinc ions. As a result, AZIBs based on the CaVO-2 cathode offered high specific capacity (329.6 mAh g-1 at 200 mA g-1) and fast charge/discharge capability (147 mAh g-1 at 10 A g-1). Impressively, quasi-solid-state zinc-ion batteries based on the CaVO-2 cathode and polyacrylamide-cellulose nanofiber hydrogel electrolytes maintained an outstanding specific capacity and long cycle life (162 mAh g-1 over 10 000 cycles at 5 A g-1). This study provided a reliable strategy for metal-ion insertion and the structural water introduction of oxides to produce a high-quality cathode for ZIBs. Meanwhile, it provides ideas for the combination of vanadium-based materials and gel electrolytes to construct solid-state zinc-ion batteries.

Synthesis of polycrystalline K0.25V2O5 nanoparticles as cathode for aqueous zinc-ion battery