This review presents the recent progress of mussel-inspired hydrogels from fundamental interaction mechanisms and design principles to promising applications.

As one of the most outstanding materials, the analysis of structure and function of hydrogels have been extensively carried out to tailor and adapt them to various fields of application....

safety issues of organic electrolyte, and lithium dendrites. [3][4][5][6] Alternatively, rechargeable aqueous zinc-ion batteries (ZIBs) are increasingly attracting attention owing to their straightforward processing, high capacity of Zn metal anode (820 mAh g −1 ), [7] excellent safety, cost effectiveness (US$65 kWh −1 ), [8] higher ionic conductivity of aqueous electrolytes (≈1 S cm −1 ) than non-aqueous electrolytes (1-10 mS cm −1 ), [8] and two-electron transfer mechanism. [9] However, previous works of ZIBs based on the alkaline electrolytes still retain formidable challenges, such as inferior cyclability (≤1000 cycles), low coulombic efficiency (≤90%), and limited capacity (≤400 mAh g −1 at 0.1 A g −1 ), [1] mainly caused by the byproducts and unstable cathodes.To solve the above issues, much attention has been devoted to exploring highcapacity, electron-ion conductive, and structurally stable cathode materials, such as manganese oxides, [10][11][12] Prussian blue analogues (e.g., Zn 3 [Fe(CN) 6 ] 2 ), [13] NASICON-type materials (e.g., Na 3 V 2 (PO 4 ) 3 ), [14] transition metal sulfide (e.g., VS 2, Mo 6 S 2 ), [15,16] polymer (e.g., pyrene-4,5,9,10-tetraone, [17] polyaniline, [18] ), and vanadium-based compounds. [19][20][21] Recently, layered vanadium-based materials, including Zn 0.25 V 2 O 5 ·nH 2 O, [8] [9] and zinc orthovanadate, [24] have been recognized as a very promising class for high-safety aqueous ZIBs with respectable Zn-storage capacity of 300-400 mAh g −1 and cyclability (>1000 cycles), [25] originating from multivalence nature of vanadium cations and superior stability of layered structure. [22,26,27] It is noteworthy that all of the layered vanadium-based materials reported are composed of crystalline frameworks with doped metal ion or structural water, which neither sufficiently accommodates the structural strain during the (de)intercalation process nor provides ample active sites for efficient charge storage. [28,29] In a sharp contrast, amorphous frameworks can not only provide more exposed ion channels, accelerate rapid charge transfer across the electrode/electrolyte interface, and further facilitate fast ion intercalation, but also offer low internal energy and outstanding chemical stability. [30,31] Moreover, 2D heterostructures by alternating stacking of two type different 2D nanosheets produce Rechargeable aqueous zinc-ion batteries (ZIBs) are appealing due to their high safety, zinc abundance, and low cost. However, developing suitable cathode materials remains a great challenge. Herein, a novel 2D heterostructure of ultrathin amorphous vanadium pentoxide uniformly grown on graphene (A-V 2 O 5 /G) with a very short ion diffusion pathway, abundant active sites, high electrical conductivity, and exceptional structural stability, is demonstrated for highly reversible aqueous ZIBs (A-V 2 O 5 /G-ZIBs), coupling with unprecedented high capacity, rate capability, long-term cyclability, and excellent safety. As a result, 2D A-V 2 O 5 /G heterostructures for stacked ZIBs at 0.1 A g −1 dis...