We retrospect recent advances in rechargeable aqueous zinc-ion batteries system and the facing challenges of aqueous zinc-ion batteries. Importantly, some concerns and feasible solutions for achieving practical aqueous zinc-ion batteries are discussed in detail.

We report the chemical intercalation of Li+ into the interlayer of V2O5·nH2O with enlarged layer spacing and fast Zn2+ diffusion, resulting in high rate capability and excellent long-term cycling performance.

Rechargeable aqueous zinc ion batteries (ZIBs) are highly desirable for large-scale energy storage due to their advantages of safety and low-cost. Development of advanced cathodes for use in aqueous ZIBs is urgently needed. Herein, we report a low-cost rechargeable aqueous Zn-V2O5 cell with 3 M ZnSO4 electrolyte that demonstrates high zinc storage capability. We also investigated the effect of different types/concentrations of the aqueous electrolytes on the performance of the Zn-V2O5 cells.

Rechargeable aqueous zinc‐ion batteries (ZIBs) with high safety and low‐cost are highly desirable for grid‐scale energy storage, yet the energy storage mechanisms in the current cathode materials are still complicated and unclear. Hence, several sodium vanadates with NaV3O8‐type layered structure (e.g., Na5V12O32 and HNaV6O16·4H2O) and β‐Na0.33V2O5‐type tunneled structure (e.g., Na0.76V6O15) are constructed and the storage/release behaviors of Zn2+ ions are deeply investigated in these two typical structures. It should be mentioned that the 2D layered Na5V12O32 and HNaV6O16·4H2O with more effective path for Zn2+ diffusion exhibit higher ion diffusion coefficients than that of tunneled Na0.76V6O15. As a result, Na5V12O32 delivers higher capacity than that of Na0.76V6O15, and a long‐term cyclic performance up to 2000 cycles at 4.0 A g−1 in spite of its capacity fading. This work provides a new perspective of Zn2+ storage mechanism in aqueous ZIB systems.

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Rechargeable aqueous Zn/manganese dioxide (Zn/MnO 2 ) batteries are attractive energy storage technology owing to their merits of low cost, high safety, and environmental friendliness. However, the b-MnO 2 cathode is still plagued by the sluggish ion insertion kinetics due to the relatively narrow tunneled pathway. Furthermore, the energy storage mechanism is under debate as well. Here, b-MnO 2 cathode with enhanced ion insertion kinetics is introduced by the efficient oxygen defect engineering strategy. Density functional theory computations show that the b-MnO 2 host structure is more likely for H + insertion rather than Zn 2+ , and the introduction of oxygen defects will facilitate the insertion of H + into b-MnO 2 . This theoretical conjecture is confirmed by the capacity of 302 mA h g À1 and capacity retention of 94% after 300 cycles in the assembled aqueous Zn/ b-MnO 2 cell. These results highlight the potentials of defect engineering as a strategy of improving the electrochemical performance of b-MnO 2 in aqueous rechargeable batteries.

The exploitation of cathode materials with high capacity as well as high operating voltage is extremely important for the development of aqueous zinc‐ion batteries (ZIBs). Yet, the classical high‐capacity materials (e.g., vanadium‐based materials) provide a low discharge voltage, while organic cathodes with high operating voltage generally suffer from a low capacity. In this work, organic (ethylenediamine)–inorganic (vanadium oxide) hybrid cathodes, that is, EDA‐VO, with a dual energy‐storage mechanism, are designed for ultrahigh‐rate and ultralong‐life ZIBs. The embedded ethylenediamine (EDA) can not only increase the layer spacing of the vanadium oxide, with improved mobility of Zn ions in the V–O layered structure, but also act as a bidentate chelating ligand participating in the storage of Zn ions. This hybrid provides a high specific capacity (382.6 mA h g−1 at 0.5 A g−1), elevated voltage (0.82 V) and excellent long‐term cycle stability (over 10 000 cycles at 5 A g−1). Assistant density functional theory (DFT) calculations indicate the cathode has remarkable electronic conductivity, with an ultralow diffusion barrier of 0.78 eV for an optimal Zn‐ion diffusion path in the EDA‐VO. This interesting idea of building organic–inorganic hybrid cathode materials with a dual energy‐storage mechanism opens a new research direction toward high‐energy secondary batteries.

Biphasic and multiphasic compounds have been well clarified to achieve extraordinary electrochemical properties as advanced energy storage materials. Yet the role of phase boundaries in improving the performance is remained to be illustrated. Herein, we reported the biphasic vanadate, that is, Na1.2V3O8/K2V6O16·1.5H2O (designated as Na0.5K0.5VO), and detected the novel interfacial adsorption–insertion mechanism induced by phase boundaries. First‐principles calculations indicated that large amount of Zn2+ and H+ ions would be absorbed by the phase boundaries and most of them would insert into the host structure, which not only promote the specific capacity, but also effectively reduce diffusion energy barrier toward faster reaction kinetics. Driven by this advanced interfacial adsorption–insertion mechanism, the aqueous Zn/Na0.5K0.5VO is able to perform excellent rate capability as well as long‐term cycling performance. A stable capacity of 267 mA h g−1 after 800 cycles at 5 A g−1 can be achieved. The discovery of this mechanism is beneficial to understand the performance enhancement mechanism of biphasic and multiphasic compounds as well as pave pathway for the strategic design of high‐performance energy storage materials.