High-voltage gel polymer electrolyte integrated laser-induced graphene flexible micro-supercapacitors for wearable and sustainable aerospace electronics.

Abstract

The global trend towards flexible, portable and wearable electronics, such as smartwatches, fitness trackers, and healthcare monitors etc., has intensified the demand for high-performance flexible energy storage systems. Supercapacitors (SCs) have recently emerged as promising, robust power management solutions for various space applications, including CubeSats, very low earth orbit (VLEO) satellites, electromechanical thrust vector actuation and interplanetary devices. However, their low energy density (<10 Wh kg-1) compared to current lithium-ion batteries (LIBs) and high self-discharge rate limit their widespread use. This work demonstrates the fabrication of high-voltage gel polymer electrolyte (GPE) and laser-induced graphene (LIG) electrode based flexible micro-supercapacitors (FMSCs) to address the current challenges. The GPE, designated as [EMIM][TFSI]/PPC/PC, is synthesized by entrapping the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][TFSI] into a matrix of polypropylene carbonate (PPC) and polycarbonates (PC). FMSCs (active device area: 1.6 cm2) are fabricated using interdigital LIG electrodes and the GPE, which demonstrated excellent electrochemical performance with an areal capacitance of 2.5 mF cm-2 at 3.2 V and 70 µA (0.04 mA cm-2), and an energy density of 3.5 µWh cm-2. Long-term charge-discharge stability was also evaluated up to 10 000 cycles at a fixed current of 100 µA and it also showed promising capacitance retention of more than 91%. This work presents a novel FMSC utilizing a high-voltage [EMIM][TFSI]/PPC/PC gel polymer electrolyte and LIG-interdigitated electrodes, engineered to address the stringent demand of space-terrestrial boundaries. The integrated gel polymer structure conceptually suppresses vacuum evaporation and eliminates phase separation under extreme vibrational or high-g loading, highlighting its future utility in unpressurized aerospace environments.

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