Human friendly biodegradable supercapacitors utilizing water-soluble MoO_x@Mo-foil as electrode and normal saline as electrolyte

The rapid advancement of biomedical technology has sparked increasing interest in developing biodegradable implantable energy storage devices for applications in biosensors and bioelectronics. However, the limited energy density, biocompatibility, and degradability of existing materials have posed significant challenges to their widespread adoption in the biomedical field. In response, this study presents an electrode material for a solid-state biodegradable supercapacitor consisting of an array structure of molybdenum oxide (MoO_x) nanosheets in situ grown on water-soluble molybdenum foil (Mo-foil). The MoO_x@Mo-foil electrode exhibits exceptional electrochemical performance, suppressing previous designs. It demonstrated a high capacitance of 433.3 F/g at 1 A/g, and even at 10 A/g, it has a favorable rate capability of 48.9%. Furthermore, cycling stability test revealed an outstanding endurance, with an impressive retention of 88.0% after 5000 cycles. An symmetrical supercapacitor was assembled by combining two MoO_x@Mo-foil electrodes with remarkable energy storage capabilities and cycling stability of 94.3% over 5000 cycles. Additionally, the biodegradable supercapacitor exhibited a high energy density of 40.95 Wh/kg at 600.48 W/kg. Moreover, the device is fully biodegradable, which paves the way for advancing the field of bioelectronics and propelling the development of sustainable energy storage technologies for biomedical applications.