Facile and effective defect engineering strategy boosting ammonium vanadate nanoribbon for high performance aqueous zinc-ion batteries

Coordination optimization of central V atoms induced by Cu2+ for enhanced Zn2+ storage in layered vanadium oxides

The development of cathode materials with fast kinetics and excellent cycling stability is essential to fully utilize the safety and economic advantages of aqueous zinc-ion batteries (AZIBs). In this study, a facile solvothermal route was designed to synthesize oxygen vacancy-rich CuxV10O24·nH2O (CVO-0.1) cathode materials. The introduction of Cu2+ into layered V10O24·nH2O induced oxygen vacancies and modulated the local coordination environment of V atoms, thereby optimizing the electronic structure, enhancing defect states, and improving electrical conductivity. This strategy effectively reduced the Zn2+ diffusion resistance while stabilizing the vanadium oxide framework. Owing to these structural merits, the CVO-0.1 cathode exhibited exceptional electrochemical performance, retaining 91.4 % capacity after 4,000 cycles. The reversible Zn2+ storage mechanism was further elucidated through in ex-situ characterization. This study provides new insights into the design of high-performance AZIBs cathode materials.

Regulating oxygen vacancies in ammonium vanadate electrode materials for advanced aqueous zinc ion batteries

In the past decade, vanadates have attracted one's attention as the electrode materials for aqueous zinc ion batteries (AZIBs). Nevertheless, their structural instability and sluggish ion/electron dynamics lead to an inevitable decline in the electrochemical performance. To address these issues, we introduce oxygen vacancies into NH4V4O10 nanosheets to improve the ion transport rate during the electrochemical reaction. The prepared NHVO-40 samples provide many active sites compared to NH4V4O10 materials. The assembled cell delivers a capacity of 452.03 mAh g-1 at a current density of 0.2 A g-1. It also presents a retention rate of 94.6% at 10 A g-1 after 4000 times cycling. In addition, they still possess an energy density of 332.5 Wh kg-1 at a power density of 70 W kg-1.

Supramolecular channels via crown ether functionalized polyaniline for proton-self-doped cathode in aqueous zinc-ion battery

Polyaniline (PANI) has been widely used as a cathode in aqueous zinc-ion batteries (AZIBs) because of its attractive conductivity and energy storage capability. However, the extensive application of PANI is limited by spontaneous deprotonation and slow diffusion kinetics. Herein, an 18-crown-6-functionalised PANI pseudorotaxane (18C6@PANI) cathode is successfully developed through a facile template-directed polymerisation reaction. The 18C6@PANI cathode exhibits a high specific capacity of 256 mAh g-1 at 0.2 A/g, excellent rate performance of 134 mAh g-1 at 6 A/g and outstanding cycle stability at a high current density of 3 A/g over 10,000 cycles. Experimental and theoretical analyses demonstrate the formation of the -N-Zn-O- structure. The abundant supramolecular channels in pseudorotaxane, induced by crown ether functional groups, are beneficial for achieving superior cyclability and rate capability. These encouraging results highlight the potential for designing more efficient PANI-based cathodes for high-performance AZIBs.

Two-dimensional/three-dimensional hierarchical self-supporting potassium ammonium vanadate@MXene hybrid film for superior performance aqueous zinc ion batteries

Currently, aqueous zinc ion batteries (AZIBs) have grown to be a good choice for large-scale energy storage systems due to their high theoretical specific capacity, low redox potential, low cost, and non-toxicity of the aqueous electrolyte. However, it is still challenging to obtain high specific capacity and stability suitable cathodes. Herein, hierarchical self-supporting potassium ammonium vanadate@MXene (KNVO@MXene) hybrid films were prepared by vacuum filtration method. Due to the three-dimensional nanoflower structure of KNVO with dual ions intercalation, high conductivity of two-dimensional Ti3C2Tx MXene, and the hierarchical self-supporting structure, the AZIB based on the KNVO@MXene hybrid film cathode possessed superior specific capacity (481 mAh/g at 0.3 A/g) and cycling stability (retaining 125 mAh/g after 1000 cycles at a high current density of 10 A/g). In addition, the storage mechanism was revealed by various ex-situ characterizations. Hence, a new viewpoint for the preparation of AZIB self-supporting cathode materials is presented.

Freestanding defective ammonium Vanadate@MXene hybrid films cathode for high performance aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) have gained extensive attention due to the numerous advantages of zinc, such as low redox potential, high abundance, low cost as well as high theoretical specific capacity. However, the development of AZIBs is still hampered due to the lack of suitable cathodes. In this work, the freestanding defective ammonium vanadate@MXene (d-NVO@MXene) hybrid film was synthesized by simple vacuum filtration strategy. Due to the presence of the hierarchical freestanding structure, outstanding MXene conductive networks and abundant oxygen vacancy (in the d-NVO nanoribbons), the d-NVO@MXene hybrid film can not only expose more active sites but also possess outstanding conductivity and kinetics of charge transfer/ion diffusion. When the d-NVO@MXene hybrid film was directly used as the cathode, it displayed a high specific capacity of 498 mAh/g at 0.5 A/g and superior cycling stability performance with near 100 % coulomb efficiency. Furthermore, the corresponding storage mechanism was elucidated by ex situ various characterizations. This work provides new ideas for the development of freestanding vanadium-based cathode materials for AZIBs.