Optimization of Laser-Induced Graphene Electrodes for High Voltage Micro-Supercapacitors

Abstract

With the development of grid-based distributed sensing with low-power electronics, the need for delocalized power supplies, Energy Storage Devices (ESDs) are moving toward miniaturized scales. Among ESDs, micro-supercapacitors (µSC) are currently under development as an alternative or complementary power supply/backup to batteries. Laser-induced graphene (LIG) is an emerging technology based on the laser conversion of polymers into graphene-based conductive materials. Polyimide (PI) is the most investigated polymer, moreover, it finds several applications in the electronics field. Laser scribing of polymers fastens the device processing reducing the number of wet chemistry steps carried out to fabricate micro-devices.PI Kapton foils of 125 µm thickness were used as substrate materials to produce LIG samples. A CO2 laser was exploited to convert polymeric samples and to pattern hard masks to print devices of optimized geometry and material properties. Further, electrodeposition processes can be used to increase the material capacity by depositing transition metal oxides with pseudocapacitive features. Among them, maganese oxide can be electrodeposited anodically without recurring to any thermal step. Tuning the LIG storage mechanism, and combining them, allows several degrees of freedom to design devices able to work in organic electrolyte environments in voltage windows ranging from 2.5 V up to 4.5 V. Moreover, optimization of electrode charges allows for improving the overall device lifetime and energetic efficiency.