Highly Ordered Graphene Polydopamine Composite Allowing Fast Motion of Cations: Toward a High‐Performance Microsupercapacitor

Abstract

The simple and eco‐friendly preparation of microsupercapacitor remains a great challenge. Here are presented the preparation and the characterizations of an all‐solid symmetric micro‐supercapacitor based on a new composite formed of highly ordered graphene sheets due to the presence of polydopamine between the layers, which present a d‐spacing of 0.356 nm. This graphene‐polydopamine composite is prepared by electroreduction of graphene oxide (GO) followed by the electrooxidation of dopamine added into the initial solution, i.e., after GO reduction. In Na2SO4 solution, this composite material shows excellent capacitance and stability even at a high scan rate (2 V s−1) and a very low relaxation time (τ0) of 62 ms. This value is in very good agreement with the high transfer kinetic and low transfer resistance values of the ions implied in the charge storage process (Na+·2H2O and Na+) determined by ac‐electrogravimetry. Finally, it is shown that the all‐solid micro‐supercapacitor (interdigitated electrodes obtained using a CO2 laser and Na2SO4/PVA hydrogel) prepared with this new composite delivers a remarkable energy density of 6.36 mWh cm−3 for a power density of 0.22 W cm−3 and exhibits excellent cycling stability (98% of retention after 10 000 cycles at 2 V s−1).

Current collector-free symmetric μ-supercapacitor based on a ternary composite of graphene, polydopamine and Co3O4

“…At a current density of 0.052 mA cm −2 , the rGO–PDA–Co 3 O 4 MSC achieves a capacitance of 180 F cm −3 , exceeding the capacitance values observed in MSCs utilizing capacitive materials under comparable current densities. 45,53 However, the capacitance of the rGO–PDA–Co 3 O 4 micro-device decreases significantly when the current density increases, reaching 41% of the initial capacitance (at 0.052 mA cm −2 ) for a current density 20 times greater (1 mA cm −2 ). This decline can be attributed to the sluggish kinetics of pseudocapacitive reactions involving Co 3 O 4 .…”

“…It is noted that rGO–PDA–Co 3 O 4 has been prepared in a hydrothermal route which facilitates the device fabrication. Since the electrode fabrication does not require a conducting substrate, unlike electrochemically prepared reduced graphene oxide and PDA based composites, 53 it is possible to fabricate a current-collector free symmetric μ-supercapacitor device. A slurry containing the rGO–PDA–Co 3 O 4 composite was deposited onto a plexiglass substrate which was then patterned into interdigitated electrodes by laser carving.…”

“…Remarkably, the current densities attained at a given scan rate surpass those of ERGO–PDA and rGO–PDA MSCs, reported in our previous work. 45,53 This elevated performance is attributed to the pseudocapacitive contribution arising from the presence of cobalt oxide (Co 3 O 4 ).…”

“…54–60 Indeed, at a power density of 0.26 W cm −3 , the rGO–PDA–Co 3 O 4 MSC developed in this work can provide an energy density of 12.25 mW h cm −3 . For high power densities, the volumetric energy densities delivered by the rGO–PDA–Co 3 O 4 MSC become comparable to those delivered by the MSCs based on ERGO–PDA and rGO–PDA, 45,53 due to the low kinetics of the pseudocapacitive reactions of Co 3 O 4 . These results indicate that the rGO–PDA–Co 3 O 4 MSC is rather suitable for applications that require moderate power densities with high energy densities.…”

Recent Advances in Functional Fabric‐Based Wearable Supercapacitors

“…Planar MSCs have garnered considerable attention owing to their thinner, lighter, and miniaturized nature. [129] The electrode materials are arranged within the same plane in a manner that a small gap is introduced, separating two electrodes and removing the possibility of a short circuit. The narrow interspaces between electrode arrays effectively shorten ion diffusion offering a high power output.…”