Metal sulfides, known as being analogous to metal oxides, have emerged as a new class of materials for energy conversion and/or storage applications due to their low cost and high electrochemical activity.

Orthorhombic crystal structure of the V 3 O 7 •H 2 O material has large interlayer spacing with an open tunnel, making it promising as an intercalation-based cathode for aqueous zinc-ion batteries. However, structural degradation and dissolution cause quick capacity fading for V 3 O 7 •H 2 O. We addressed this issue via a dual modification of the V 3 O 7 •H 2 O material by pre-intercalation with Ag(I) inside the layers (henceforth will be mentioned as Ag x V 3 O 7 •H 2 O) and simultaneous in situ composite formation with reduced graphene oxide (rGO). Computationally, we showed that Ag(I) preintercalation in V 3 O 7 facilitates the Zn 2+ intercalation process by thermodynamically stabilizing the material with an intercalation energy of −34.3 eV. The Ag x V 3 O 7 •H 2 O cathode showed ∼1.44-fold improved capacity (270 mA h g −1 ) with much improved rate capability, over the pristine V 3 O 7 •H 2 O. The specific capacity and cycle stability was further significantly improved in the graphene constructed conductive flexible architecture with hydrothermally assisted self-assembled packing of several intertwined Ag x V 3 O 7 • H 2 O microbelt mats with rGO core (Ag x V 3 O 7 •H 2 O@rGO). The Ag x V 3 O 7 •H 2 O@rGO cathode enabled a reversible Zn 2+ insertion/ de-insertion process during charge/discharge (as observed in ex situ XRD study) and a significantly decreased (>27 times) charge transfer resistance over pristine V 3 O 7 •H 2 O to promote high specific capacity of 437 and 170 mA h g −1 at both low (100 mA g −1 ) and high (2000 mA g −1 ) current, respectively. The morphological analysis of the Ag x V 3 O 7 •H 2 O@rGO before and after 1000 cycles reveals that, although the structural breakdown of the Ag x V 3 O 7 •H 2 O is inevitable during repetitive cycling, the rGO support provides strong interaction with the Ag x V 3 O 7 •H 2 O mat and buffers the structural strain, prevents the agglomeration of the active material, and slows down the structural dissolution at the interface. The synergistic interaction enabled ∼2.3-fold improved cycle stability over the pristine V 3 O 7 •H 2 O with only 0.028% capacity loss per cycle over 1000 cycles.

Meeting the increasing global energy demand has pushed the energy storage research towards developing energy dense and safer electrochemical energy storage devices following sustainable and economic approach. In this regard,...

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