Highly Flexible and Tailorable Cobalt‐Doped Cross‐Linked Polyacrylamide‐Based Electrolytes for Use in High‐Performance Supercapacitors

Abstract

A novel hydrogel polymer electrolyte was prepared by incorporation of 1,4-butanediol diglycidyl ether (BG) to cross-linked polyacrylamide (PAM). The electrolyte (PAMBG) was modified with cobalt (II) sulfate with various doping ratios (PAMBGCoX) to increase the capacitance by increasing faradaic reactions. The supercapacitor device assembly was performed by using active carbon (AC) electrodes and hydrogel polymer electrolytes. The specific capacitance of the PAMBGCo5 device indicated 130 F g À 1 , which is at least a seven-fold improvement due to the insertion of Co as a redox component. The electrolyte device, PAMBGCo5, displays superior performance having an energy density of 38 Wh kg À 1 at a power density of 500 W kg À 1 . Additionally, with the same hydrogel, the device performed 10,000 galvanostatic chargedischarge cycles via retaining 91% of the initial capacitance. A cost-effective electrolyte, PAMBGCo5, was tested in a carbon-based supercapacitor under bent and twisted conditions at various angles, confirming the robustness of the device.

Synthesis of Boron-Doped Non-Flammable Anhydrous Electrolytes for Flexible Quasi-Solid-State Supercapacitor Applications

“…All curves had a straight line at a low frequency, indicating ion transport into the carbon electrode structure throughout the pores in the surface of the electrodes, known as Warburg impedance . This region demonstrates a characteristic performance of a double-layer reaction-based supercapacitor, which increases sharply and is almost parallel to the Z ″ axis, representing the dominance of double-layer reaction over pseudocapacitive capacitance . Thus, the charge–discharge performance of the device can be enhanced .…”

“…51 This region demonstrates a characteristic performance of a doublelayer reaction-based supercapacitor, which increases sharply and is almost parallel to the Z″ axis, representing the dominance of double-layer reaction over pseudocapacitive capacitance. 41 Thus, the charge−discharge performance of the device can be enhanced. 49 In the frequency region, the curves show a semi-circle, indicating the feature of a single "time constant" that can be attributed to charge-transfer resistance (R ct ) at the electrode/electrolyte interface, 52 which is obtained by fitting the equivalent circuit given in Figure S1.…”

“…The resulting quasi-solid-state gel electrolyte is abbreviated as Gly/xKOH/yBA with x = 1 and 3 M, y = 3 and 5% w/w. The electrode preparation was performed according to our previous work 41 where the content of the carbon slurry was arranged as CC, PVDF, and AC at a ratio of 1:1:8 (w/w) in NMP. Carbon composite electrodes containing active material of 1 mg 42,43 were produced by casting the slurry on an aluminum foil and cutting into circular shapes with a diameter of 1.5 cm.…”

The development of novel cost‐effective bio‐electrolyte with glycerol host for carbon‐based flexible supercapacitor applications

“…Although there are no redox peaks observed in the CV measurements, a strong EDLC formation which probably covers pseudocapacitive contributions by the Co ions. 35 It was noticed that further increasing the cobalt concentration in the electrolyte such as GlyP5Co10 do not enhance the capacitance of the supercapacitor. This may refer to accumulation of more free ions at the interface that might decrease the conductivity of the electrolyte leading a lower capacity.…”