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3D micro-supercapacitors for embedded electronics

Periodic Reporting for period 2 - 3D-CAP (3D micro-supercapacitors for embedded electronics)

Reporting period: 2019-10-01 to 2021-03-31

The realization of high-performance micro-supercapacitors is currently a big challenge but the ineluctable applications requiring such miniaturized energy storage devices are continuously emerging, from wearable electronic gadgets to wireless sensor networks and the upcoming Internet of Things. Although they store less energy than micro-batteries, micro-supercapacitors can be charged and discharged very rapidly and exhibit a quasi-unlimited lifetime. The global scientific research is consequently largely focused on the improvement of their capacitance and energetic performances. However, to date, they are still far from being able to power sensors or electronic components.
In the 3D-CAP project, we propose a 3D paradigm shift of micro-supercapacitor design to ensure increased energy storage capacities. Hydrous ruthenium dioxide (RuO2) is a pseudocapacitive material for supercapacitor electrode well-known for its high capacitance. A thin-film of ruthenium oxide will be conformally deposited by atomic layer deposition (ALD) or by electrodeposition onto a high-surface-area 3D current collector prepared via an ingenious dynamic template built with hydrogen bubbles. The structural features of these 3D architectures will be controllably tailored by the processing methodologies. These electrodes will be combined with an innovative electrolyte in solid form (a protic ionogel) able to operate over an extended cell voltage. In a parallel investigation, we will develop a fundamental understanding of electrochemical reactions occurring in pseudocapacitive RuO2 electrodes. As a key achievement, prototypes will be designed using a new concept based on a self-adaptive micro-supercapacitors matrix, which arranges itself according to the global amount of energy stored.
The project is divided into 4 main tasks: the fabrication of 3D current collectors - the modeling and deposition of the pseudocapacitive material - the development of protic ionogel electrolyte - the realization of all-solid-state microsupercapacitor prototypes. All the workpackages have been implemented. Highy porous metallic current collectors have been obtained as well as 3D microsupercapacitor electrodes with high capacitance. Prototypes with different design are still in progress.
The resulting 3D micro-supercapacitors should display extremely high power, long lifetime and – for the first time – energy densities competing that of micro-batteries. Major breakthroughs with areal capacitances reaching 50 F/cm2 are expected, an improbable goal a couple of years ago.
Micro-supercapacitor device based on porous RuO2 for on-chip electronics