Constructing a High-Performance Aqueous Rechargeable Zinc-Ion Battery Cathode with Self-Assembled Mat-like Packing of Intertwined Ag(I) Pre-Inserted V3O7·H2O Microbelts with Reduced Graphene Oxide Core

Abstract

Orthorhombic crystal structure of the V₃O₇·H₂O 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 V₃O₇·H₂O. We addressed this issue via a dual modification of the V₃O₇·H₂O material by pre-intercalation with Ag(I) inside the layers (henceforth will be mentioned as AgₓV₃O₇·H₂O) and simultaneous in situ composite formation with reduced graphene oxide (rGO). Computationally, we showed that Ag(I) pre-intercalation in V₃O₇ facilitates the Zn²⁺ intercalation process by thermodynamically stabilizing the material with an intercalation energy of −34.3 eV. The AgₓV₃O₇·H₂O cathode showed ∼1.44-fold improved capacity (270 mA h g–¹) with much improved rate capability, over the pristine V₃O₇·H₂O. 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 AgₓV₃O₇·H₂O microbelt mats with rGO core (AgₓV₃O₇·H₂O@rGO). The AgₓV₃O₇·H₂O@rGO cathode enabled a reversible Zn²⁺ 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 V₃O₇·H₂O 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 AgₓV₃O₇·H₂O@rGO before and after 1000 cycles reveals that, although the structural breakdown of the AgₓV₃O₇·H₂O is inevitable during repetitive cycling, the rGO support provides strong interaction with the AgₓV₃O₇·H₂O 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 V₃O₇·H₂O with only 0.028% capacity loss per cycle over 1000 cycles.