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.

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.

A zinc-ion battery (ZIB) employing an aqueous electrolyte, that is, an aqueous zinc-ion battery (AZIB), represents a unique combination of high energy and high power with much-desired safety. In this respect, vanadium oxide-based cathodes, with open frameworks and rich valence states, have shown promising characteristics toward hosting the Zn 2+ ions. Nevertheless, the degradation of the host during continuous (de-)intercalation and structural dissolution in the aqueous electrolyte affects the capacity and cycle life. Herein, we represent a high capacity and long cycle life AZIB based on an Ag 2 V 4 O 11 @reduced graphene oxide composite as a cathode in 1 M ZnSO 4 electrolyte. We demonstrate the combined effect of the intercalation−displacement mechanism and partially irreversible formation of zinc hydroxyl sulfate as the charge storage mechanism in 1 M ZnSO 4 electrolyte. We observed a comparatively quick capacity fading for the pristine Ag 2 V 4 O 11 ; however, the capacity, rate capability, and cycle stability could be dramatically improved when the Ag 2 V 4 O 11 was hydrothermally grown in situ in the presence of reduced graphene oxide (rGO). The charge storage mechanism, kinetics of charge storage, Zn 2+ diffusion coefficient, effect of cycling on the phase/crystallinity, and morphology of the electrode materials were investigated. A morphological transformation from nanorod to ultrathin sheet/micro-belt-type Ag 2 V 4 O 11 was observed with increasing rGO content. The rGO wrapped the Ag 2 V 4 O 11 sheets/microbelts and thus reduced the charge transfer resistance and provided structural integrity during continuous cycling. The favorable synergism between the Ag 2 V 4 O 11 and optimized rGO content could offer a high initial specific capacity of 328 mA h/g at 0.1 A/g, excellent rate capability with ∼150 mA h/g, specific capacity at 5 A/g, and long cycle stability with only 7% capacity loss over 3000 cycles.

Vanadium oxyhydroxide has been recently investigated as a starting material to synthesize different phases of vanadium oxides by electrochemical or thermal conversion and has been used as an aqueous zinc-ion battery (AZIB) cathode. However, the low-valent vanadium oxides have poor phase stability under ambient conditions. So far, there is no study on understanding the phase evolution of such low-valent vanadium oxides and their effect on the electrochemical performance toward hosting the Zn2+ ions. The primary goal of the work is to develop a high-performance AZIB cathode, and the highlight of the current work is the insight into the auto-oxidation-induced phase transition of VOOH to V10O24·nH2O under ambient conditions and Zn2+ intercalation behavior thereon as an aqueous zinc-ion battery cathode. Herein, we demonstrate that hydrothermally synthesized VOOH undergoes a phase transition to V10O24·nH2O during both the electrochemical cycling and aerial aging over 38–45 days. However, continued aging till 150 days at room temperature in an open atmosphere exhibited an increased interlayer water content in the V10O24·nH2O, which was associated with a morphological change with different surface area/porosity characteristics and notably reduced charge transfer/diffusion resistance as an aqueous zinc-ion battery cathode. Although the fresh VOOH cathode had impressive specific capacity at rate performance, (326 mAh/g capacity at 0.1 A/g current and 104 mAh/g capacity at 4 A/g current) the cathode suffered from a continuous capacity decay. Interestingly, the aged VOOH electrodes showed gradually decreasing specific capacity with aging at low current and however followed the reverse order at high current. At a comparable specific power of ∼64–66 W/kg, the fresh VOOH and aged VOOH after 60, 120, and 150 days of aging showed the respective energy densities of 208.3, 281.2, 269.2, and 240.6 Wh/kg. Among all the VOOH materials, the 150 day-aged VOOH cathode exhibited the highest energy density at a power density beyond 1000 W/kg. Thanks to the improved kinetics, the 150 day-aged VOOH cathode delivered a considerable energy density of 39.7 Wh/kg with a high specific power of 4466 W/kg. Also, it showed excellent cycling performance with only 0.002% capacity loss per cycle over 20 300 cycles at 10 A/g.

Developing high-performance, safer, and affordable flexible batteries is of urgent need to power the fast-growing flexible electronics market. In this respect, zinc-ion chemistry employing aqueous-based electrolytes represents a promising combination considering the safety, cost efficiency, and both high energy and high-power output. Herein, we represent a highperformance flexible in-plane aqueous zinc-ion miniaturized battery constructed with all electrodeposited electrodes, i.e., MnO 2 cathode and zinc anode with polyimide-derived interdigital patterned laser-scribed carbon (LSC) as the current collector as well as the template for electrodeposition. The LSC possesses a cross-linked network of graphitic carbon sheet, which offers large surface area over low footprint and ensures active materials loading with a robust conductive network. The LSC with high zincophilic characteristic also offers dendrite-free zinc deposition with very low Zn 2+ plating stripping overpotential. Benefitting from the Zn//MnO 2 -rich redox chemistry, the ability of the 3D LSC network to uniformly distribute reaction sites, and the architectural merits of in-plane interdigitated electrode configuration, we report very high capacity values of ∼549 mAh/g (or ∼523 μAh/cm 2 ) and 148 mAh/g (or 140 μAh/cm 2 ) at 0.1 A/g (0.095 mA/cm 2 ) and 2 A/g (1.9 mA/cm 2 ) currents, respectively. The device was also able to maintain a high capacity of 196 mAh/g (areal capacity of 76.19 μAh/cm 2 ) at 1 A/g (0.95 mA/cm 2 ) current after 1350 cycles. The flexibility of the device was demonstrated in polyacryl amide (PAM) gel polymer soaked with a 2 M ZnSO 4 and 0.2 M MnSO 4 electrolyte, which exhibited a comparable specific capacity of ∼102−110 mAh/g in flat condition and different bending (100°or 160°bending) conditions. The device does not use any conventional current collector, separator, and conductive or polymer additives. The overall process is highly scalable and can be completed in less than a couple of hours.