Facile and Scalable Preparation of Ruthenium Oxide‐Based Flexible Micro‐Supercapacitors

Abstract

Tremendous efforts have been invested in the development of the internet of things during the past 10 years. Implantable sensors still need embedded miniaturized energy harvesting devices, since commercialized thin films and microbatteries do not provide sufficient power densities and suffer from limited lifetime. Therefore, micro‐supercapacitors are good candidates to store energy and deliver power pulses while providing non‐constant voltage output with time. However, multistep expensive protocols involving mask aligners and sophisticated cleanrooms are used to prepare these devices. Here, a simple and versatile laser‐writing procedure to integrate flexible micro‐supercapacitors and microbatteries on current‐collector‐free polyimide foils is reported, starting from commercial powders. Ruthenium oxide (RuO2)‐based micro‐supercapacitors are prepared by laser irradiation of a bilayered tetrachloroauric acid (HAuCl4 · 3H2O)–cellulose acetate/RuO2 film deposited by spin‐coating, which leads to adherent Au/RuO2 electrodes with a unique pillar morphology. The as‐prepared microdevices deliver 27 mF cm−2/540 F cm−3 in 1 m H2SO4 and retain 80% of the initial capacitance after 10 000 cycles. This simple process is applied to make carbon‐based micro‐supercapacitors, as well as metal oxide based pseudocapacitors and battery electrodes, thus offering a straightforward solution to prepare low‐cost flexible microdevices at a large scale.

Asymmetric micro-supercapacitors based on electrodeposited Ruo2 and sputtered VN films

“…Not surprisingly, the surface capacitance increases from 120 up to 220 mF.cm -2 when the thickness is increased from 300 nm (100 cycles) to 700 nm (600 cycles) thus indicating that more surface is available for the 700 nm film despite a higher thickness compared to the 300 nm film. These areal capacitances challenges the best values reported so far for planar electrodes of micro-supercapacitor [17,[33][34][35][36].Taking into account the potential windows used during the CV measurements (1 V), the corresponding areal capacities vary from 120 up to 220 mC.cm -2 . As already mentioned, to design an efficient asymmetric MSC with larger cell voltage than the symmetric one, it is crucial to balance the charge between the two electrodes.…”

“…Based on our last publications on VN films [10,20]], a 2.3 µm-thick sputtered VN film (negative electrode) is necessary to balance the charge stored on the hRuO 2 positive electrode in such a parallel plate configuration. Indeed, the capacitance value of such 2.3 µm-thick VN film is ~ 190 mF.cm -2 (operating potential windows = 0.6 V) [20] RuO 2 and VN materials were already used as efficient electrodes in micro-supercapacitor [10,33,35,43,44]. Direct Laser Writing method was achieved to produce symmetric RuO 2 / RuO 2 MSC on flexible substrate with good energy density (~ 3 µWh.cm -2 ) [33].…”

Hydrogel Cryo‐Microtomy Continuously Making Soft Electronic Devices

“…Soluble redox species of potassium iodide (KI) and vanadium sulfate (VOSO 4 ) were also added to the pristine PVA‐H 3 PO 4 gel electrolyte to improve the specific capacitance and energy density of supercapacitors (Figure S20, Supporting Information), as demonstrated in the literature. [ 26,27 ] The device areal capacitance increased from 7.3 mF cm −2 based on pristine electrolyte (Figure S16, Supporting Information) to 23.1 mF cm −2 based on modified electrolyte (Figure S20b, Supporting Information), much higher than many recently reported advanced supercapacitors (Table S2, Supporting Information) [ 28–34 ] . Furthermore, the modified device delivered a high areal energy density of 8.20 μWh cm −2 and power density of 2400 μW cm −2 , respectively, comparable with the reported state‐of‐the‐art supercapacitors (Table S3, Supporting Information).…”

Recent developments of advanced micro-supercapacitors: design, fabrication and applications

“…Such an integration provides a reference for the preparation of high performance MSCs. Figure 3f shows another example, in which Brousse et al 68 fabricated flexible MSCs based on ruthenium oxide (RuO 2 ) on PI foil using a simple approach by laser-writing of a bilayered film. Due to the pillar morphology of electrodes, the fabricated MSC delivered high capacitances of 27 mF cm −2 /540 F cm −3 in 1 M H 2 SO 4 , and it also presented high cycle performance, retaining 80% capacitance after 10,000 cycles.…”