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.

No abstract

No abstract

A rechargeable zinc ion capacitor (ZIC) employing a metallic anode, nature-abundant materials-derived high-performance cathode, and an aqueous electrolyte represents an interesting combination of high capacitance, high power, safety operation, and overall a sustainable and economic system, which make them a leading power source to portable consumer electronics. However, it is often a challenge to fabricate a large-area flexible device with a metallic anode due to the characteristic rigidity of the metal. Herein we present a high-performance aqueous ZIC based on abundant agricultural waste biomass (Areca Catechu sheath)-derived highsurface-area (2760 m 2 /g) mesoporous multilayer-stacked carbon sheets as the capacitive electrode in 1 M ZnSO 4 electrolyte. In coin cell configuration, the ZIC showed a high specific capacitance of 208 F/g at 0.1 A/g, a good rate capability, and an outstanding cyclic stability with 84.5% capacitance retention after 10 000 cycles at a current density of 5 A/g. We also demonstrate an easy and scalable strategy to fabricate a large-area flexible zinc ion capacitor with laser-scribed carbon (LSC@PI), scribed on a polyimide film with customizable area as the flexible current collector for both anode and cathode. Electrodeposition of zinc onto LSC@PI as anode showed a very low plating stripping overpotential, and the flexible sandwich-type ZIC with an electrolyte-soaked paper separator exhibited excellent flexibility and a high areal capacitance of 128.7 mF/cm 2 at 100 mA/cm 2 current when bended at an angle of 110°, corresponding to an energy density of 32.6 μW h/cm 2 . When the current was increased by 20 times, the flexible device under bending condition could provide an energy density of 11 μW h/cm 2 at a high power density of 1.906 W/cm 2 . The synthesized materials were characterized by X-ray diffraction (XRD), RAMAN, Field Emission Scanning Electron Microscope (FESEM), and Brunauer−Emmett−Teller (BET) analysis, whereas the electrochemical performances were measured in terms of cyclic voltammetry (CV), galvanostatic charge−discharge (GCD), and Electrochemical impedance spectroscopy (EIS) analysis.

The past decade has witnessed a significant research interest on rechargeable Na-ion batteries (SIBs). Compared to Li-ion batteries, SIBs promise to be much more cost-effective, thanks to the high abundance...