Human-friendly flexible solid-state biodegradable supercapacitor based on Ti3C2Tx 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 Ti₃C₂T_x film with an adhesive-free structure constructed is proposed as electrode material for the flexible solid-state biodegradable supercapacitor (FSBSC). The morphology and structure of MXene films were characterized by XRD, XPS, Raman, SEM and TEM. A 0.9% NaCl saline, similar human body fluids was used as the electrolyte solution to construct symmetrical FSBSC (Ti₃C₂T_x//NaCl-PVA//Ti₃C₂T_x-FSBSC). The Ti₃C₂T_x//NaCl-PVA//Ti₃C₂T_x-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 1,000.8 W/kg). The charge storage mechanism was analyzed using ex-situ XRD, XPS and density function theory (DFT). DFT results show that the Ti₃C₂T_x (T_x = O)) electrode possesses metallic properties. The calculated adsorption energies (E_ads) and smaller diffusion barriers of Na⁺-ions further proved the outstanding performance of the Ti₃C₂T_x electrode. Moreover, the apparatus is entirely biodegradable, thereby paving a promising path for the progression of bioelectronics and biomedical energy storage technologies.