Highly Stretchable Microsupercapacitors Based on Hot-Press Transferred Single-Walled Carbon Nanotubes with a Hybrid Acid Electrolyte

Stretchable energy storage devices are highly demanded in wearable electronics. Herein, a high-performance stretchable microsupercapacitor (MSC) based on wrinkled hydroxylated single-walled carbon nanotubes (SWCNT–OH) with silicotungstic acid (SiWA) and phosphoric acid (H3PO4) hybrid electrolyte has been developed. The wrinkled SWCNT electrodes were constructed on prestretched thermoplastic polyurethane (TPU) fabric substrates by hot-pressing techniques. This endows the device with 100% uniaxial stretchability. Compared to the H3PO4 electrolyte, the SiWA electrolyte was found to broaden the voltage window (−0.8 to 0.8 V) and provide additional pseudocapacitance. A specific areal capacitance of 21.41 mF cm–2 can be achieved by MSCs featuring wrinkled SWCNTs and utilizing the SiWA–H3PO4 electrolyte at 5 mV s–1, being around 30 times higher than the MSCs solely using the H3PO4 electrolyte without a prestretching strategy. In addition, even after 10,000 charge/discharge cycles, the capacitor retains its capacity at a high level of 96.3%. Due to the robust adhesion between SWCNTs and the TPU substrate via hot-press transfer, the device maintained stable performance after undergoing water-washing and friction tests, demonstrating excellent mechanical durability and electrochemical reliability. This research provides a viable solution for wearable flexible energy storage devices, which creates possibilities for the evolution of energy storage technologies within next-generation flexible electronic devices.