Developing High-Performance Flexible Zinc Ion Capacitors from Agricultural Waste-Derived Carbon Sheets

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.

Fabrication of an Energy-Dense, Binder-Free Zn//V5O12·6H2O Solid-State In-Plane Flexible Battery via a Rapid and Scalable Approach

“…If the value of b = 1, the process is completely dominated by the capacitive contribution and if the value of b = 0.5, then the process is dominated by the diffusion contribution. 8 The calculated b values for the fabricated Zn//V 5 O 12 •6H 2 O battery were found to be 0.55 and 0.60 for peak 1 and peak 2, respectively (Figure 3c). This indicates that the total capacity is a combined contribution by both the surface controlled and diffusioncontrolled processes, where the latter dominates.…”

“…These two components can be explained by the power law equation i = a v b where a and b are two adjustable parameters, and b represents the dominant component in these two. If the value of b = 1, the process is completely dominated by the capacitive contribution and if the value of b = 0.5, then the process is dominated by the diffusion contribution . The calculated b values for the fabricated Zn//V 5 O 12 ·6H 2 O battery were found to be 0.55 and 0.60 for peak 1 and peak 2, respectively (Figure c).…”

Developing High-Performance In-Plane Flexible Aqueous Zinc-Ion Batteries with Laser-Scribed Carbon-Supported All Electrodeposited Electrodes

“…Further, XRD (Figure c) was carried out for the three times scribed LSC (3T-LSC), which demonstrated the graphitic nature of the LSC, with a peak observed at 2θ of 25.96° and a hump around 45° corresponding to the (002) plane, representing the parallel stacking of carbon sheets, and the (100) plane corresponding to the sp 2 hybridized carbon, respectively . The additional peaks at 2θ of 14.79° and 21.98 ° can be ascribed to the characteristic peaks of polyimide. , The FESEM analysis of the three times scribed LSC (Figure d) shows interconnected graphitic carbon sheets forming 3D porous architecture. Such 3D porous carbon architecture is blessed with high conductivity and excellent mechanical flexibility, which make it suitable to act as a flexible current collector. ,,, …”

“…33 The additional peaks at 2θ of 14.79°and 21.98 °can be ascribed to the characteristic peaks of polyimide. 34,35 The FESEM analysis of the three times scribed LSC (Figure 1d) shows interconnected graphitic carbon sheets forming 3D porous architecture. Such 3D porous carbon architecture is blessed with high conductivity and excellent mechanical flexibility, which make it suitable to act as a flexible current collector.…”

Aging-Responsive Phase Transition of VOOH to V10O24·nH2O vs Zn2+ Storage Performance as a Rechargeable Aqueous Zn-Ion Battery Cathode

“…EIS was carried out within the frequency range of 100 kHz–0.1 Hz and has been represented in terms of Nyquist plots in Figure b. The impedance profiles had a starting depressed semicircle in the mid-frequency range, reflecting the diffusion of the Zn 2+ ions in the surface layer and charge transfer process followed by an approximate linear part in the low-frequency region, reflecting the solid-state diffusion of the ions. , The Nyquist plots were fitted with an equivalent electrical circuit (shown in the inset of Figure b), which consists of a resistor ( R s ) at high frequency, reflecting the total resistance of the electrolyte, separator, and electrical contacts, charge transfer resistance ( R ct ), a pair of constant phase elements corresponding to the surface film and double layer capacitance, and a Warburg impedance ( W ) arising from the Zn 2+ diffusion within the bulk electrode. Notably, all the cells had comparable R s values but had noticeable differences in the semicircle size, reflecting the difference in their interfacial charge transfer resistances.…”