Human-friendly flexible solid-state biodegradable supercapacitor based on Ti3C2T MXene film without adhesive structure

With the rapid development of biomedical technology, biodegradable and implantable energy storage devices for biosensor and bioelectronics applications have attracted the great attention of scientists. However, the limited energy density, poor biocompatibility, and excessive space occupation of existing biodegradable energy storage devices pose major challenges to their application in the biomedical field. To address these challenges, in this work, flexible Ti3C2Tx film with an adhesive-free structure construction is proposed as electrode material for the flexible solid-state biodegradable supercapacitor (FSBSC). The morphology and structure of MXene films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A 0.9% NaCl saline, similar human body fluids was used as the electrolyte solution to construct symmetrical FSBSC (Ti3C2Tx//NaCl-PVA//Ti3C2Tx-FSBSC) Poly(vinyl alcohol) (PVA). The Ti3C2Tx//NaCl-PVA//Ti3C2Tx-FSBSC exhibits a high capacitance of 112 F/g at 1 A/g, excellent rate capability (73.2% at 20 A/g), long lifetime (81.6% after 10,000 cycles), and high specific energy/power (62.3 Wh/kg at 1000.8 W/kg). The charge storage mechanism was analyzed using ex situ XRD, TEM, and density function theory (DFT). DFT results show that the Ti3C2Tx (Tx = O)) electrode possesses metallic properties. The calculated adsorption energies (Eads) and smaller diffusion barriers of Na+ ions further proved the outstanding performance of the Ti3C2Tx electrode. Moreover, the apparatus is entirely biodegradable, thereby paving a promising path for the progression of bioelectronics and biomedical energy storage technologies.